U.S. patent application number 15/710020 was filed with the patent office on 2018-03-22 for systems, apparatuses and methods for improved rotating detonation engines.
This patent application is currently assigned to Board of Regents, The University of Texas System. The applicant listed for this patent is Board of Regents, The University of Texas System. Invention is credited to Frank K. Lu, Andrew R. Mizener.
Application Number | 20180080412 15/710020 |
Document ID | / |
Family ID | 61617926 |
Filed Date | 2018-03-22 |
United States Patent
Application |
20180080412 |
Kind Code |
A1 |
Mizener; Andrew R. ; et
al. |
March 22, 2018 |
SYSTEMS, APPARATUSES AND METHODS FOR IMPROVED ROTATING DETONATION
ENGINES
Abstract
Rotating detonation engines are provided with various
improvements pertaining to performance and reliability.
Improvements pertain to, for example, a fluidic valve/premixing
chamber, injection/swirl, flow control and turning, ignition, and
cooling.
Inventors: |
Mizener; Andrew R.; (Euless,
TX) ; Lu; Frank K.; (Arlington, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Board of Regents, The University of Texas System |
Austin |
TX |
US |
|
|
Assignee: |
Board of Regents, The University of
Texas System
Austin
TX
|
Family ID: |
61617926 |
Appl. No.: |
15/710020 |
Filed: |
September 20, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62398244 |
Sep 22, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23R 7/00 20130101; F02C
3/165 20130101; C23C 24/04 20130101; F02K 7/04 20130101; F02K 9/66
20130101; F02K 9/52 20130101; F02C 5/02 20130101 |
International
Class: |
F02K 9/52 20060101
F02K009/52; F02K 9/66 20060101 F02K009/66; F02K 3/04 20060101
F02K003/04; C23C 24/04 20060101 C23C024/04 |
Claims
1. A rotating detonation engine, comprising: a detonation chamber
configured to allow continuous detonation therein of a mixture of
fuel and oxidizer; and a fluidic valve upstream of the detonation
chamber, configured to convey at least one of the fuel and the
oxidizer into the detonation chamber.
2. The rotating detonation engine according to claim 1, further
comprising: a plurality of injection ports (a) disposed downstream
of the fluidic valve and upstream of the detonation chamber, and
(b) configured for receiving at least one of the fuel and the
oxidizer from the fluidic valve and injecting at least one of the
fuel and the oxidizer into the detonation chamber.
3. The rotating detonation engine according to claim 1, further
comprising: a plurality of injectors (a) disposed upstream of the
fluidic valve, and (b) configured for conveying at least one of the
fuel and the oxidizer into the fluidic valve.
4. The rotating detonation engine according to claim 1, wherein the
fluidic valve functions also as a premixing chamber for mixing the
fuel and the oxidizer prior to injection of the fuel and the
oxidizer into the detonation chamber
5. The rotating detonation engine according to claim 1, wherein the
fluidic valve is configured as an annular channel formed in a
structure upstream of the detonation chamber.
6. The rotating detonation engine according to claim 1, wherein the
fluidic valve comprises (a) an upstream portion and (b) a
downstream portion disposed downstream of the upstream portion, and
wherein the fluidic valve is configured such that a cross-sectional
area of the downstream portion exceeds a cross-sectional area of
the upstream portion.
7. The rotating detonation engine according to claim 1, further
comprising: a coolant channel configured to allow a fluid to flow
therethrough, wherein the coolant channel is disposed radially
inward of the detonation chamber.
8. The rotating detonation engine according to claim 7, wherein the
coolant channel is disposed adjacent a radially inner wall of the
detonation chamber.
9. A rotating detonation engine, comprising: a detonation chamber
comprising a longitudinal axis and a sidewall and configured to
allow continuous detonation in the detonation chamber of a mixture
of fuel and oxidizer; and a plurality of injection ports configured
for injecting at least one of the fuel and the oxidizer into the
detonation chamber, wherein each of the plurality of injection
ports comprises an upstream end and a downstream end, and wherein
the plurality of injection ports is characterized by one of the
following conditions: (1) all of the plurality of injection ports
are axial injection ports extending, at an angle greater than
0.degree. and less than 90.degree. relative to the longitudinal
axis of the detonation chamber, from the upstream end of the
respective injection port to the downstream end of the respective
injection port; (2) all of the plurality of injection ports are
sidewall injection ports extending in a curved manner from the
upstream end of the respective injection port to the downstream end
of the respective injection port; or (3) all of the plurality of
injection ports are sidewall injection ports extending from the
upstream end of the respective injection port to the downstream end
of the respective injection port at an angle greater than 0.degree.
and less than 90.degree. relative to the sidewall of the detonation
chamber or with an effective curvature, and one of the following
sub-conditions holds: (a) all of the plurality of injection ports
are disposed radially outward of the detonation chamber; (b) the
radial distance from the longitudinal axis of the detonation
chamber to a respective one of the injection ports is substantially
identical for all of the plurality of injection ports; and (c) the
effective curvature or the angle relative to the sidewall of the
detonation chamber is substantially identical for all of the
plurality of injection ports.
10. The rotating detonation engine according to claim 9, wherein
all of the plurality of injection ports are axial injection ports
extending, at an angle greater than 0.degree. and less than
90.degree. relative to the longitudinal axis of the detonation
chamber, from the upstream end of the respective injection port to
the downstream end of the respective injection port.
11. The rotating detonation engine according to claim 10, wherein
each of the plurality of injection ports is (1) straight, (2)
contoured converging-diverging, or (3) conical
converging-diverging.
12. The rotating detonation engine according to claim 9, wherein
all of the plurality of injection ports are sidewall injection
ports extending in a curved manner from the upstream end of the
respective injection port to the downstream end of the respective
injection port.
13. The rotating detonation engine according to claim 12, wherein
the sidewall of the detonation chamber is defined by a curvature,
and each of the plurality of injection ports has a curvature that
exceeds the curvature defining the sidewall of the detonation
chamber.
14. The rotating detonation engine according to claim 9, wherein
all of the plurality of injection ports are sidewall injection
ports extending from the upstream end of the respective injection
port to the downstream end of the respective injection port with an
effective curvature, or at an angle greater than 0.degree. and less
than 90.degree. relative to the sidewall of the detonation chamber,
and one of the following conditions holds: (a) all of the plurality
of injection ports are disposed radially outward of the detonation
chamber; (b) the radial distance from the longitudinal axis of the
detonation chamber to a respective one of the injection ports is
substantially identical for all of the plurality of injection
ports; and (c) the effective curvature or the angle relative to the
sidewall of the detonation chamber is substantially identical for
all of the plurality of injection ports.
15. A rotating detonation engine, comprising: a detonation chamber
configured to allow continuous detonation therein of a mixture of
fuel and oxidizer; and flow turning vanes installed at or near a
downstream end of the detonation chamber, configured to change a
direction of an exit flow from the detonation chamber.
16. The rotating detonation engine (RDE), according to claim 15,
wherein the flow turning vanes are fixed in position or
adjustable.
17. A rotating detonation engine, comprising: a detonation chamber
configured to allow continuous detonation therein of a mixture of
fuel and oxidizer; and an igniter configured to ignite the fuel and
the oxidizer so as to initiate the continuous detonation of the
mixture of fuel and oxidizer, wherein the igniter comprises a pulse
detonation engine coupled to the detonation chamber.
18. The rotating detonation engine according to claim 17, wherein
the pulse detonation engine extends in a direction tangential to
the detonation chamber.
19. The rotating detonation engine according to claim 17, wherein
the pulse detonation engine extends in a direction parallel to the
detonation chamber and is coupled to the detonation chamber by a
coupling extending in a direction tangential to the detonation
chamber, and wherein the pulse detonation engine extends from a
position upstream or downstream of the detonation chamber to the
coupling.
20. The rotating detonation engine according to claim 17, wherein
the pulse detonation engine extends in a direction around the
detonation chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/398,244, entitled "Systems, Apparatuses
and Methods for Improved Rotating Detonation Engines," which was
filed on Sep. 22, 2016 and is hereby incorporated herein by
reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not applicable.
TECHNICAL FIELD OF THE INVENTION
[0003] The present disclosure relates generally to rotating
detonation engines (RDEs), methods of operating the same, and
systems including the same. More particularly, the disclosure
relates to improvements in performance, efficiency, reliability and
various other aspects of RDEs.
BACKGROUND
[0004] In a conventional combustion engine, energy from fuel is
converted to useful work by a subsonic, approximately isobaric
combustion process, referred to as deflagration. In contrast, a
detonation wave engine such as an RDE operates by means of a
supersonic, pressure-gain combustion process, referred to as
detonation. The detonation may be initiated, for example, by
igniting a mixture of fuel and oxidizer (e.g., air) in a detonation
chamber.
[0005] Compared to conventional combustion engines, detonation wave
engines have higher thermodynamic efficiencies and fewer moving
parts, among other advantages. Nonetheless, challenges remain in
improving RDEs for various practical applications.
SUMMARY
[0006] According to a first aspect of the invention, there is
provided a rotating detonation engine (RDE) including (1) a
detonation chamber configured to allow continuous detonation
therein of a mixture of fuel and oxidizer, and (2) a fluidic valve
upstream of the detonation chamber, configured to convey at least
one of the fuel and the oxidizer into the detonation chamber.
[0007] According to a second aspect of the invention, there is
provided an RDE including (1) a detonation chamber comprising a
longitudinal axis and a sidewall and configured to allow continuous
detonation in the detonation chamber of a mixture of fuel and
oxidizer, and (2) a plurality of injection ports configured for
injecting at least one of the fuel and the oxidizer into the
detonation chamber. Each of the plurality of injection ports
comprises an upstream end and a downstream end, and the plurality
of injection ports is characterized by one of the following three
conditions: (1) all of the plurality of injection ports are axial
injection ports extending, at an angle greater than 0.degree. and
less than 90.degree. relative to the longitudinal axis of the
detonation chamber, from the upstream end of the respective
injection port to the downstream end of the respective injection
port; (2) all of the plurality of injection ports are sidewall
injection ports extending in a curved manner from the upstream end
of the respective injection port to the downstream end of the
respective injection port; or (3) all of the plurality of injection
ports are sidewall injection ports extending from the upstream end
of the respective injection port to the downstream end of the
respective injection port at an angle greater than 0.degree. and
less than 90.degree. relative to the sidewall of the detonation
chamber or with an effective curvature, and one of the following
three sub-conditions holds: (a) all of the plurality of injection
ports are disposed radially outward of the detonation chamber; (b)
the radial distance from the longitudinal axis of the detonation
chamber to a respective one of the injection ports is substantially
identical for all of the plurality of injection ports; and (c) the
effective curvature or the angle relative to the sidewall of the
detonation chamber is substantially identical for all of the
plurality of injection ports.
[0008] According to an third aspect of the invention, there is
provided an RDE including (1) a detonation chamber configured to
allow continuous detonation therein of a mixture of fuel and
oxidizer, and (2) flow turning vanes installed at or near a
downstream end of the detonation chamber, configured to change a
direction of an exit flow from the detonation chamber.
[0009] According to a fourth aspect of the invention, there is
provided an RDE including (1) a detonation chamber configured to
allow continuous detonation therein of a mixture of fuel and
oxidizer, and (2) an igniter configured to ignite the fuel and the
oxidizer so as to initiate the continuous detonation of the mixture
of fuel and oxidizer. The igniter comprises a pulse detonation
engine coupled to the detonation chamber.
[0010] Other aspects of the embodiments described herein will
become apparent from the following description and the accompanying
drawings, illustrating the principles of the embodiments by way of
example only.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The following figures form part of the present specification
and are included to further demonstrate certain aspects of the
present claimed subject matter, and should not be used to limit or
define the present claimed subject matter. The present claimed
subject matter may be better understood by reference to one or more
of these drawings in combination with the description of
embodiments presented herein. Consequently, a more complete
understanding of the present embodiments and further features and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals may identify like elements,
wherein:
[0012] FIG. 1 is a schematic view of an RDE;
[0013] FIG. 2 is a schematic, perspective view of an RDE with a PDE
igniter disposed in a tangential configuration relative to the RDE,
in accordance with some embodiments;
[0014] FIG. 3 is a schematic, perspective view of an RDE with a PDE
igniter disposed in a parallel configuration relative to the RDE
and disposed upstream of the RDE, in accordance with some
embodiments;
[0015] FIG. 4 is a schematic, perspective view of an RDE with a PDE
igniter disposed in a parallel configuration relative to the RDE
and disposed downstream of the RDE, in accordance with some
embodiments;
[0016] FIG. 5 is a schematic, perspective view of an RDE with a PDE
igniter disposed in a coiled configuration relative to the RDE, in
accordance with some embodiments;
[0017] FIG. 6 is an enlarged perspective view of the coupling of
FIG. 2, in accordance with some embodiments;
[0018] FIGS. 7A-7G are schematic views of an RDE or portions
thereof, in accordance with some embodiments, with FIG. 7A being an
exploded, perspective view thereof and further including the
coupling of FIGS. 2 and 6, FIG. 7B being a perspective view of the
housing thereof, FIG. 7C being a perspective view of the head mount
(downstream face) thereof, FIG. 7D being a perspective view of the
centerbody endcap (upstream face, with gasket) thereof, FIG. 7E
being a perspective view of the core assembly (without centerbody
endcap) thereof, FIG. 7F being a longitudinal cross-sectional view
thereof, taken along the line A-A in FIG. 7A, and FIG. 7G being an
axial cross-sectional view thereof or equivalently an elevational
view thereof taken from the rear, with the centerbody endcap and
housing endcap removed;
[0019] FIG. 8 is a schematic, axial cross-sectional view showing
fins on the surface of an annular coolant channel of an RDE, in
accordance with some embodiments;
[0020] FIGS. 9A-9C are schematic plan views showing arrangements of
surface projections for use in a coolant channel of an RDE, in
accordance with some embodiments, with FIG. 9A showing the fins of
FIG. 8, FIG. 9B showing fins configured as cylindrical posts
arranged in an aligned arrangement, and FIG. 9C showing fins
configured as cylindrical posts arranged in an offset
arrangement;
[0021] FIG. 10 is a schematic, fragmentary, longitudinal
cross-sectional view of an RDE, illustrating transpiration cooling,
in accordance with some embodiments;
[0022] FIGS. 11A-11D are schematic, longitudinal cross-sectional
views of injection port configurations with converging-diverging or
simple diverging sections, in accordance with some embodiments,
with FIG. 11A showing a contoured converging-diverging
configuration, FIG. 11B showing a conical converging-diverging
configuration, FIG. 11C showing a contoured diverging
configuration, and FIG. 11D showing a conical diverging
configuration;
[0023] FIGS. 12A-12C are schematic longitudinal cross-sectional
views of angled injection port configurations, in accordance with
some embodiments, with FIG. 12A showing a straight, angled
configuration, FIG. 12B showing a contoured converging-diverging,
angled configuration, and FIG. 12C showing a conical
converging-diverging, angled configuration;
[0024] FIG. 13 is a perspective view of an injector plate, showing
the upstream face of the injector plate (with radially inner and
outer copper sealing gaskets), the injector plate having the
straight, angled injection ports of FIG. 12A, in accordance with
some embodiments;
[0025] FIG. 14A is a schematic, axial cross-sectional view of an
RDE with curved sidewall injection ports, for providing swirled
sidewall injection, in accordance with some embodiments, and FIG.
14B is a schematic, axial cross-sectional view of an RDE with
straight sidewall injection ports, for providing swirled sidewall
injection, in accordance with some embodiments;
[0026] FIG. 15 is a schematic perspective view of an RDE (with the
housing, housing endcap, and gaskets removed) and the coupling of
FIGS. 2 and 6, the RDE having flow turning vanes installed therein,
in accordance with some embodiments;
[0027] FIGS. 16A and 16B are schematic views of an arrangement of
multiple concentric annular RDEs/detonation chambers, in accordance
with some embodiments, with FIG. 16A being a longitudinal
cross-sectional view, and FIG. 16B an axial cross-sectional
view;
[0028] FIG. 17 is a schematic view of an arrangement of multiple
concentric RDEs/detonation chambers that are not annular in shape,
in accordance with some embodiments; and
[0029] FIG. 18 is a schematic view of an arrangement including a
main RDE/detonation chamber and multiple secondary RDEs/detonation
chambers housed within the annular central region of the main
RDE/detonation chamber, in accordance with some embodiments.
NOTATION AND NOMENCLATURE
[0030] Certain terms are used throughout the following description
and claims to refer to particular system components and
configurations. As one skilled in the art will appreciate, the same
component may be referred to by different names. This document does
not intend to distinguish between components that differ in name
but not function. In the following discussion and in the claims,
the terms "including" and "comprising" are used in an open-ended
fashion, and thus should be interpreted to mean "including, but not
limited to . . . ."
DETAILED DESCRIPTION
[0031] The foregoing description of the figures is provided for the
convenience of the reader. It should be understood, however, that
the embodiments are not limited to the precise arrangements and
configurations shown in the figures. Also, the figures are not
necessarily drawn to scale, and certain features may be shown
exaggerated in scale or in generalized or schematic form, in the
interest of clarity and conciseness. Relatedly, certain features
may be omitted in certain figures, and this may not be explicitly
noted in all cases.
[0032] While various embodiments are described herein, it should be
appreciated that the present invention encompasses many inventive
concepts that may be embodied in a wide variety of contexts. The
following detailed description of exemplary embodiments, read in
conjunction with the accompanying drawings, is merely illustrative
and is not to be taken as limiting the scope of the invention, as
it would be impossible or impractical to include all of the
possible embodiments and contexts of the invention in this
disclosure. Upon reading this disclosure, many alternative
embodiments of the present invention will be apparent to persons of
ordinary skill in the art. The scope of the invention is defined by
the appended claims and equivalents thereof.
[0033] Illustrative embodiments of the invention are described
below. In the interest of clarity, not all features of an actual
implementation are necessarily described or illustrated for each
embodiment disclosed in this specification. In the development of
any such actual embodiment, numerous implementation-specific
decisions may need to be made to achieve the design-specific goals,
which may vary from one implementation to another. It will be
appreciated that such a development effort, while possibly complex
and time-consuming, would nevertheless be a routine undertaking for
persons of ordinary skill in the art having the benefit of this
disclosure.
[0034] Detonation engines include pulse detonation engines (PDEs)
and RDEs. A PDE operates by means of a series of consecutive
detonations. Each detonation cycle may be referred to as a pulse.
In contrast, an RDE operates by means of a continuously propagating
detonation wave, described below. The basic structure and operation
of PDEs and RDEs are known to one of ordinary skill in the art, and
hence are not described herein in detail or comprehensively.
Further description of the structure and operation of PDEs and RDEs
may be found, e.g., in "Rotating Detonation-Wave Engines" by D. A.
Schwer and K. Kailasanath (2011 NRL Review, pages 89-94; also
available at http://www.nrl.navy.mil/content_images/11_FA2.pdf) and
"Detonation Engines" by Piotr Wola ski (Journal of KONES Powertrain
and Transport, Vol. 18, No. 3, 2011, pages 515-521; also available
at:
http://ilot.edu.pl/kones/2011/3_2011/2011_wolanski_detonation_engines.pdf-
), both of which articles are hereby incorporated herein by
reference.
[0035] RDEs may also be referred to as "Rotating Detonation Wave
Engines," "Continuous Detonation Wave Engines," and "Continuous
Detonation Engines." These terms are used interchangeably herein.
In addition, although the term "rotating" may be understood as
connoting circular motion, the term "RDE" and its equivalents as
used herein do not require circular (annular) configurations of
detonation chambers and corresponding circular motion of a
detonation wave. Rather, the RDEs described herein include
embodiments having annular detonation chambers as well as
embodiments having non-annular detonation chambers (with motion of
the continuous detonation wave corresponding to the configuration
of the detonation chamber, in either case).
[0036] FIG. 1 is a schematic and simplified diagram of an RDE (with
various, e.g., internal, components omitted). As seen in FIG. 1,
RDE 100 includes a detonation chamber 102, a means 104 for
injection of fuel and oxidizer (injection means) and an igniter (or
initiator) 106. The terms "propellants" and "reactants" may also be
used herein to refer to fuel and oxidizer. RDE 100 may be defined
by a head (or upstream) end 111 and an exit (or downstream end)
113. RDE 100 may include a nozzle (not shown) at the downstream end
113.
[0037] As shown in FIG. 1, RDE 100 is cylindrical. The axis of the
cylinder (shown by the dashed line) may be referred to as the
cylindrical axis, the axis, or the longitudinal axis. The
longitudinal extent of RDE 100 is the extent along the longitudinal
axis. (This terminology, namely, "longitudinal axis," "cylindrical
axis," etc., is used for any cylindrical shape/structure in this
disclosure, e.g., a cylindrical hole.) The head (upstream) end 111
and exit (downstream end) 113 of RDE 100 may be referred to as the
two axial ends of RDE 100. Detonation chamber 102 is defined by an
outer cylindrical wall 107 (which is the inner wall of the housing
108) and an inner cylindrical wall 109 (which is the outer wall of
the centerbody 110). Accordingly, detonation chamber 102 has an
annular cross section. However, as mentioned, it is possible for
RDE 100 to have a shape other than a cylinder and for detonation
chamber 102 to have a cross section other than annular (and hence
for the continuous detonation wave to traverse a path that is other
than circular), and specific embodiments with these other
configurations are described below. Nonetheless, for simplicity,
RDEs described herein will generally be described as cylindrical
with annular detonation chambers (and hence with the continuous
detonation wave propagating in a circumferential direction, or
circular path, around the detonation chamber). It will be
understood that any feature or embodiment described herein,
although described in the context of a cylindrical RDE with annular
detonation chamber, may be instantiated in a non-cylindrical RDE
with non-annular detonation chamber, unless specifically indicated
to the contrary.
[0038] In operation, once a detonation wave is ignited or initiated
in RDE 100, the detonation wave continues in a circumferential
direction around the annular detonation chamber 102, as shown by
the large arrow (oriented in a generally upward direction) in FIG.
1. Fuel and oxidizer are continually injected into detonation
chamber 102 in order to sustain the detonation wave. The detonation
products are ejected or exhausted out of the exit 113 (as indicated
by the generally horizontal, rightward pointing arrows shown at the
right side of FIG. 1) to produce thrust or extract work.
[0039] Detonation is a combustion process consisting of a shock
wave coupled to and sustained by a trailing combustion front. The
wave speed is on the order of thousands of meters per second,
compared with a flame speed on the order of tens of meters per
second for deflagration. This built-in compression and rapid heat
release of detonation result in lower entropy gain, and thus higher
thermodynamic efficiency, as compared to deflagration, given the
same initial conditions.
[0040] It should be noted that the use of the term "detonation
chamber" does not mean that no non-detonative combustion ever
occurs therein. Rather, non-detonative combustion may occur, and
may regularly occur, in a detonation chamber of an RDE. The term
"combustion chamber" may also be used in this disclosure to refer
to a detonation chamber of an RDE.
[0041] In addition to the aforementioned variability of the shape
or configuration of the RDE 100/housing 108 and detonation chamber
102, numerous other variations in RDE 100 are possible. For
example, injection means 104 is shown as including a series of
holes 114 arranged circumferentially around detonation chamber 102
at/near head end 111 for injection of fuel, and an annular slit 115
at the head end of the detonation chamber 102 for injection of air
(the injection of air being indicated by the generally horizontal,
rightward pointing arrows shown at the left side of FIG. 1). In
other embodiments, both fuel and air (or other oxidizer) may be
injected through holes 114 (and slit 115 may not be provided). For
example, alternating holes may be used for fuel and oxidizer, that
is, a first hole may be used for fuel, a second hole next to the
first hole may be used for oxidizer, a third hole next to the
second hole may be used for fuel, a fourth hole next to the third
hole may be used for oxidizer, and so on. In other cases, the same
holes may be used for both fuel and oxidizer; for example, fuel and
oxidizer may be mixed in a premixing chamber (not shown in FIG. 1)
upstream of injection holes 114, and then the premixed combined
fuel and oxidizer mixture may be injected into all the holes 114.
Examples of this arrangement are shown in FIGS. 7F (seventh set of
embodiments, pertaining to fluidic valve, described below) and 16A
(ninth set of embodiments pertaining to multiple concentric RDEs,
described below) (note, however, that injection holes 114 are
disposed in the sidewall while the injection ports in FIGS. 7F and
16A are disposed axially; the distinction between sidewall and
axial injection is clarified below). It should be understood that
this arrangement (namely, premixing of fuel and oxidizer and
injection of the fuel/oxidizer mixture into the same injection
ports) is not limited to application with the specific features of
those embodiments, but may generally be used in any embodiment in
this disclosure, unless indicated to the contrary. This arrangement
may be understood as comprising multiple stages (both structural
and temporal stages): first, fuel and oxidizer are injected (first
temporal stage) via an inlet (first structural stage) into a
premixing chamber or manifold (second structural stage), where they
are mixed (second temporal stage), then the mixture of fuel and
oxidizer is injected (third temporal stage) via injection ports
(third structural stage) into the detonation chamber.
[0042] Further to the above-described possible variations of holes
114, whether used for injecting fuel and/or air, the location of
holes 114 may vary from that illustrated. For example, while holes
114 are illustrated as being disposed circumferentially around the
RDE (which is referred to as sidewall injection, discussed below),
it is also possible to dispose holes 114 at a head end 111 of the
RDE, e.g., on head mount A (as described below for many of the
embodiments in this disclosure; see FIG. 7A for head mount A). In
other cases, holes 114 may be located farther downstream, farther
away from head end 111 (e.g., on a sidewall of the RDE 100). While
holes 114 are illustrated as supplying fuel from locations radially
interior of detonation chamber 102, in other embodiments fuel
and/or oxidizer may be delivered via holes from locations radially
exterior to detonation chamber 102 (e.g., on a sidewall of the RDE
100). Further, while holes 114 are illustrated as cylindrical
(having a uniform circular cross section throughout their
longitudinal extent), they may be formed in another shape (see,
e.g., the fifth set of embodiments described below). In addition,
conduits other than holes may be used as injection means. The
examples of variation of injection means 104 are not intended to be
exhaustive. Some other variations are described in specific
embodiments below. Holes 114, slit 115, and/or variations thereof
such as mentioned here, may be referred to, either individually or
collectively, as injectors.
[0043] As for igniter 106, some conventional RDEs have used a spark
plug. Other RDEs have used a single-shot detonation tube together
with a diaphragm for separating the single-shot detonation tube
from the detonation chamber. Neither of these mechanisms can
reliably re-start an RDE quickly. A spark plug is unpredictable. (A
spark plug has the additional disadvantage of its
omnidirectionality/random directionality of ignition, described
below.) With the single-shot detonation tube, the diaphragm must be
replaced manually after each start. As the fuel and oxidizer are
injected separately in the single-shot detonation tube by low speed
or manual valves, the use of the diaphragm is necessary in order to
provide time for the fuel and the oxidizer to mix fully before
detonation and to keep these reactants separate from the RDE during
the mixing process. Accordingly, the spark plug and single-shot
detonation tube are not able to provide quick and reliable
re-starting of the RDE, whereas the ability to provide for quick
and reliable re-starting of the RDE is important in practical
applications.
[0044] RDE 100 may also include one or more pressure transducer
ports 116 (one shown). Pressure transducer port 116 may accommodate
a pressure transducer (not shown) for measuring pressure in the
detonation chamber 102.
[0045] According to a first set of embodiments, instead of a
conventional spark plug or single-shot detonation tube, the igniter
may include a PDE. Unlike a conventional spark plug or single-shot
detonation tube, a PDE (which is equipped with appropriate
ignition, valving, injection, and timing systems) is able to send
multiple ignition pulses back-to-back in rapid succession, thus
permitting high-frequency operation of the RDE and quick and
reliable re-starting (and without manual intervention). A PDE is
configured as a tube that can be repeatedly (i.e., as needed)
filled with a detonable gas and ignited. In operation of a PDE,
combustion transitions from deflagration at the head end (upstream
end) of the PDE to detonation at the exit (downstream end). For
this transition to occur, the PDE must have a certain minimum
length (which may vary depending on the parameters of the PDE
arrangement). The PDE may be coupled to the detonation chamber 102
by a direct coupling (conduit) without a diaphragm. A diaphragm is
not required with the PDE, as the PDE uses precise flow rate
controls and ignition timing mechanisms to ensure that the PDE
fills with fuel and oxidizer rapidly and to the proper amount, and
the PDE's injection systems promote rapid mixing of the
reactants.
[0046] FIGS. 2-5 illustrate variations of a PDE igniter coupled to
the detonation chamber of an RDE. (The PDE igniter may be referred
to simply as a PDE. For simplicity, the coupling of the PDE to the
detonation chamber of the RDE may be described as the coupling of
the PDE to the RDE.) Variations of the arrangement of a PDE igniter
coupled to an RDE, other than those illustrated in FIGS. 2-5, are
also possible. As for the scale of these figures, the PDE may be 35
inches in length, and the RDE may be 6 inches in diameter. Other
dimensions are also possible. As mentioned, in operation a
detonation wave exits from the downstream end of the PDE. In the
embodiments of FIGS. 2-5, this detonation wave is conducted (via a
coupling, described below) to the detonation chamber of the RDE.
Entering the detonation chamber of the RDE, the detonation wave
triggers detonation of the reactants (fuel and oxidizer) in the
detonation chamber of the RDE. As described above, once a
detonation wave is ignited or initiated in the RDE, the detonation
wave continues in a circumferential direction around the detonation
chamber.
[0047] FIG. 2 is a three-dimensional perspective view of an RDE,
with a PDE igniter in a tangential configuration relative to the
RDE.
[0048] As seen in FIG. 2, RDE 200 is coupled to PDE igniter 206 by
a coupling 205. PDE 206 and coupling 205 may be formed together as
a single integral element or as two physically distinct and
separate elements that are joined together. Coupling 205 is
connected to PDE 206 at a distal end (or PDE interface end) 221 of
coupling 205, and coupling 205 is connected to (the detonation
chamber of) RDE 200, at or near the upstream end of the detonation
chamber, at a proximal end (or RDE interface end) 222 of coupling
205. (The upstream end of RDE 200, and hence of the detonation
chamber thereof, is the end shown in the foreground in FIG. 2; the
downstream end of RDE 200 is in the background of the figure and is
not visible to the viewer.) Coupling 205 may have any length (i.e.,
distance between the distal end 221 and the proximal end 222
thereof).
[0049] As mentioned, PDE igniter 206 has a tangential configuration
relative to RDE 200. By "tangential" configuration is understood a
configuration in which PDE igniter 206 is disposed in a tangential
position relative to the (detonation chamber of) RDE 200. That is,
if PDE igniter 206 were to extend all the way to RDE 200 (e.g., in
the absence of coupling 205), it would contact or intersect with
the (detonation chamber of) RDE 200. While FIG. 2 shows PDE 206 as
lying in a direction perpendicular to (or disposed at an angle of
90 degrees relative to) RDE 200, the tangential configuration does
not require this perpendicularity relative to RDE 200. For example,
PDE 206 could be disposed at a different angle (e.g., >0
degrees, <180 degrees, and not equal to 90 degrees) relative to
RDE 200. The tangential configuration contrasts with the parallel
and coiled configurations described below with reference to FIGS.
3-5.
[0050] FIG. 3 is a three-dimensional perspective view of an RDE
300, with a PDE igniter 306 in a parallel configuration relative to
RDE 300 and disposed upstream of RDE 300.
[0051] By "parallel" configuration is understood a configuration in
which PDE igniter 306 is disposed parallel to the (detonation
chamber of) RDE 300. Thus, if PDE igniter 306 were extended farther
downstream relative to RDE 300, it would remain parallel to RDE 300
and would not contact or intersect with the RDE 300.
[0052] As seen in FIG. 3, RDE 300 is coupled to PDE igniter 306 by
a coupling 305. The above description of coupling 205 applies also
to coupling 305. But, as seen in FIGS. 2 and 3, while coupling 205
is straight and tangential (indeed, perpendicular) to RDE 200,
coupling 305 has a curved elbow configuration such as to effect a
90 degree turn from the direction of PDE 306, so as to connect to
RDE 300 tangentially (indeed, perpendicularly). Thus, both coupling
205 and coupling 305 connect with respective RDEs 200 and 300
tangentially, indeed, perpendicularly. This tangential connection
of the coupling 205, 305 with the RDE 200, 300 is desirable, as the
injection of the detonation wave from the PDE 206, 306 into the RDE
200, 300 in the tangential direction helps direct the detonation
being initiated in the RDE 200, 300 to propagate in the desired
direction, that is, circumferentially around the detonation
chamber. Propagation in the circumferential direction is necessary
to sustain a continuous detonation wave in the RDE 200, 300. Thus,
the tangential coupling with the RDE is advantageous compared,
e.g., to prior art spark plug ignition, in which the spark ignition
is omnidirectional (and the resulting direction of detonation
propagation appears to be a matter of chance) and hence does not
generally assist in directing the detonation wave in the desired,
circumferential direction.
[0053] FIG. 4 is a three-dimensional perspective view of an RDE
400, with a PDE igniter 406 in a parallel configuration relative to
RDE 400 and disposed downstream of RDE 400.
[0054] The embodiments of FIG. 4 are the same as the embodiments of
FIG. 3, and the foregoing description of the latter applies also to
the former, except that in FIG. 4 the PDE 406 is downstream of the
RDE 400 while in FIG. 3 the PDE 306 is upstream of the RDE 300
(and, concomitantly, the curved elbow couplings 305 and 405 effect
right-angle turns in directions opposite to each other in order to
couple with the respective RDE 300 or 400; if coupling 305 is
deemed to effect a 90 degree turn, coupling 405 would be deemed to
effect a 270 turn).
[0055] FIG. 5 is a three-dimensional perspective view of an RDE
500, with a PDE igniter 506 in a coiled configuration relative to
RDE 500.
[0056] By "coiled" configuration is understood a configuration in
which PDE igniter 506 is coiled around the (detonation chamber of)
RDE 500 concentrically therewith, as illustrated. The above
description of the embodiments of FIG. 2 applies to the embodiments
of FIG. 5, except for the fact that PDE 506 is coiled whereas PDE
206 is tangential, and the concomitant difference between coupling
505 and coupling 205. Coupling 505 effects a 90 degree turn so as
to couple with RDE 500, like couplings 305 and 405, but the turn is
in a plane parallel to an axial cross section of RDE 500 (i.e., a
cross section perpendicular to the cylindrical axis of RDE 500),
whereas in the case of couplings 305 and 405 the 90 degree turn is
in a plane perpendicular to an axial cross section of RDE 300, 400,
as seen in FIGS. 3-5. At the proximal end of coupling 505 (i.e.,
the end at which it couples to RDE 500), it is tangential (and
perpendicular) to RDE 500, like couplings 205, 305 and 405. As will
be understood by one of ordinary skill in the art, the curvature of
the coiled PDE 506 should not exceed a certain maximum, as
discussed, e.g., in "Stable Detonation Wave Propagation in
Rectangular-Cross-Section Curved Channels," by H. Nakayama, T.
Moriya, J. Kasahara, A. Matsuo, Y. Sasamoto, and I. Funaki
(Combustion and Flame, Vol. 159, Iss. 2, 2012, pages 859-869),
which article is hereby incorporated herein by reference.
[0057] The different variations, such as the tangential, parallel
(upstream), parallel (downstream), and coiled configurations,
facilitate use of a PDE igniter with an RDE in different
applications. The PDE requires a relatively long length in order to
achieve the deflagration to detonation transition. In some
operational environments, it may not be feasible to accommodate the
full length of the PDE in a certain direction/position relative to
the RDE. Accordingly, the other configurations described here are
available for use. For example, where the available space is very
limited and inadequate to accommodate the fully extended length of
the PDE in any direction, the coiled configuration may be used.
Thus, depending on the spatial requirements, etc. of the RDE
application, one or more of the different PDE configurations or any
variation described here may be suitable for use with the RDE.
[0058] FIG. 6 is an enlarged, close up, perspective view of
coupling 205 showing more detail than FIG. 2. As seen in FIG. 6,
coupling 205 may have multiple mounting or connection holes 625 at
distal end (PDE interface end) 221 for mounting or connecting to
PDE 206 and multiple mounting or connection holes 626 at proximal
end (RDE interface end) 222 for mounting or connecting to RDE 200.
The number and arrangement of holes may vary. Any suitable one or
more connection means may be used for connecting to PDE 206 and RDE
200, as will be appreciated by one of ordinary skill in the art;
such means need not include holes such as 625 and 626. The long
main body portion of coupling 205 may be tubular, serving as a
conduit for the detonation wave from the PDE 206 to the RDE 200, as
described above. The hole 627 at the proximal end 222 of this
tubular portion is seen in FIG. 6, disposed in the center of the
four illustrated mounting holes 626. The hole at the distal end 221
of this tubular portion is not visible in FIG. 6, being located
underneath proximal end 222 (given the orientation of proximal end
222 in FIG. 6); however, this hole is similarly located at the
center of mounting holes 625. Proximal end 222 is curved so as to
fit on the cylindrical (surface of the) housing of the RDE 200,
which is equipped with holes corresponding to holes 626 and 627 for
communicating with holes 626 and 627, respectively, for the purpose
of physical connection and inflow of the detonation wave to the RDE
200, respectively. Likewise PDE 206 is equipped with holes
corresponding to holes 625 and the hole at the distal end 221 of
the tubular portion of coupling 205, for the purpose of physical
connection and inflow of the detonation wave from the PDE 206,
respectively. Gasket 627-G, surrounding hole 627, is discussed
below.
[0059] According to a second set of embodiments, the engine core or
centerbody region of the RDE (i.e., the center region, radially
inward of the annular detonation chamber) is used for active
cooling of the radially inner annular wall of the detonation
chamber. Due to the tremendous heat release in operation, RDEs are
understood not to permit being operated for long durations of time
such as are suitable for real world applications. For example, the
radially inner annular wall of the detonation chamber can become
very hot and fail, since in operation of the RDE the centerbody
(i.e., the portion radially inward of the detonation chamber) is
understood to become a heat sink, that is, heat from operation of
the RDE (i.e., heat from the detonation chamber) is continuously
directed through the radially inner annular wall of the detonation
chamber into the centerbody. Providing cooling in the region
radially inward of the detonation chamber is therefore useful to
mitigate this problem.
[0060] A general description of this second set of embodiments is
as follows. An RDE includes a detonation chamber configured to
allow continuous detonation therein of a mixture of fuel and
oxidizer, and a coolant channel configured to allow a fluid to flow
therethrough. The coolant channel is disposed radially inward of
the detonation chamber. More specifically, the coolant channel is
disposed adjacent a radially inner wall of the detonation chamber.
Still more specifically, the RDE may further include a coolant
inlet configured to allow coolant to enter the coolant channel, and
a coolant outlet configured to allow coolant to exit the coolant
channel. More specifically, the coolant channel may include a
coolant supply channel disposed adjacent a radially inner wall of
the detonation chamber, the coolant supply channel configured to
allow the fluid to flow from the coolant inlet through the coolant
supply channel to cool the detonation chamber, and a coolant return
channel disposed radially inward of the coolant supply channel, the
coolant return channel configured to allow the fluid, after having
flown through the coolant supply channel, to flow through the
coolant return channel to the coolant outlet.
[0061] A more detailed description of this second set of
embodiments will be provided with reference to FIGS. 7A-7G. In the
discussion below, initially, each of FIGS. 7A-7G will be described
simply so as to enumerate the components shown therein. Afterward,
aspects of the operation of RDE 700, including further detail of
its components, will be described with reference to various ones of
FIGS. 7A-7G.
[0062] FIG. 7A is an exploded, three-dimensional perspective view
of an RDE. Each of FIGS. 7B-7G is a view of a portion of RDE 700 of
FIG. 7A.
[0063] FIG. 7A shows RDE 700 and coupling 205. One difference
between RDE 700 and RDE 100 is that RDE 700 has axial injection
ports 714 (FIG. 7C) for fuel and oxidizer while RDE 100 has axial
injection slit 115 for oxidizer and sidewall injection ports 114
for fuel. As seen from left to right in the exploded view of FIG.
7A, RDE 700 includes the following components: head mount 703;
outer injector gasket 704-GI; inner injector gasket 704-GO;
injector plate 704; housing 708; outer exhaust end gasket 713-GO;
centerbody outer shell 710-SO; centerbody inner shell 710-SI; inner
exhaust end gasket 713-GI; centerbody endcap 710-E; housing endcap
708-E. Coupling gasket 627-G seals the interface between coupling
205 and RDE 700. It is noted that the centerbody 710 of the RDE 700
may be understood as including centerbody outer shell 710-SO,
centerbody inner shell 710-SI, and centerbody endcap 710-E.
[0064] As used in this disclosure, the terms "axial injection,"
"axial injection ports" and the like refer to injection/injection
ports in which the fuel and/or oxidizer is injected into the RDE at
the upstream axial end of the RDE (i.e., at the front face of head
mount 703) or at a plane (planar surface) substantially parallel to
the upstream axial end. The upstream axial end of the RDE or a
plane parallel thereto is perpendicular to the
longitudinal/cylindrical axis of the RDE. In axial injection the
fuel and/or oxidizer is injected into the RDE in a direction that
may be axial (i.e., coincident with or parallel to the
longitudinal/cylindrical axis of the RDE), substantially axial, or
including an axial component. Axial injection ports may but need
not be located at the upstream end of the RDE, where they are
injecting fuel and/or oxidizer into the RDE from outside the RDE;
in some cases, axial injection ports may be located within the RDE.
In contrast to axial injection/injection ports, the terms "sidewall
injection," "sidewall injection ports" and the like refer to
injection/injection ports in which the fuel and/or oxidizer is
injected into the RDE at a sidewall of the RDE (e.g., along the
long, annular portion of housing 708, not the upstream or
downstream end of housing 708) or a surface substantially parallel
thereto. The sidewall of the RDE or a plane parallel thereto is
parallel to the longitudinal/cylindrical axis of the RDE; the
sidewall of the RDE refers generally to the portion of the exterior
of the RDE that is not the upstream or downstream end of the RDE.
(In the terminology of geometry with regard to a cylinder, the
circular bases of the cylinder would correspond to the upstream and
downstream ends of the RDE, and the annular surface extending along
the height or length of the cylinder would correspond to the
sidewall of the RDE; as noted, an RDE need not be cylindrical.) In
sidewall injection the fuel and/or oxidizer is injected into the
RDE in a direction that may be radial (i.e., perpendicular to the
longitudinal/cylindrical axis of the RDE), substantially radial, or
including a radial component. Sidewall injection ports may but need
not be located at the exterior surface of the side (e.g., housing
708) of the RDE, where they are injecting fuel and/or oxidizer into
the RDE from outside the RDE; in some cases, sidewall injection
ports may be located within the RDE. Examples of the distinction
between axial and sidewall injection/injection ports may be seen,
inter alia, in the sixth set of embodiments discussed below, where
FIGS. 12A-12D and 13 illustrate axial injection/injection ports and
FIGS. 14A and 14B illustrate sidewall injection/injection ports.
FIG. 7C illustrates another example of axial injection/injection
ports.
[0065] FIG. 7B is a a perspective view of housing 708. Housing 708
includes four PDE-coupling mounting holes 726 for mounting
(physically connecting) coupling 205 to housing 708, and ignition
hole 727, centered between PDE-coupling mounting holes 726, for
inflow of the detonation wave from (PDE 206 via) coupling 205.
Consistent with the above discussion with reference to FIG. 6,
PDE-coupling mounting holes 726 on RDE 700 interface with holes 626
(FIG. 6) on coupling 205, and ignition hole 727 on RDE 700
interfaces with hole 627 (FIG. 6) on coupling 205. As further seen
in FIG. 7B, an annular gasket groove 727-GG is provided around
ignition hole 727 for mounting therein sealing gasket 627-G (FIGS.
6 and 7A), for sealing this junction point between coupling 205 and
RDE 700. (Sealing gasket 627-G is discussed in the fourth set of
embodiments below.) Housing 708 further includes two coolant holes
708-HC, one for inlet to the auxiliary coolant channel and one for
outlet from the auxiliary coolant channel. The two holes 708-HC are
interchangeable: the assignment of one for inlet and the other for
outlet may be reversed. Housing 708 further includes four
head-mount-housing mounting holes 708-HH for mounting the head
mount 703 to the housing 708. Housing 708 further includes eight
pressure transducer holes 716 (four shown) for interface with a
pressure transducer (not shown). Unless indicated to the contrary,
the locations and numbers of the various holes in RDE 700 (as
illustrated in FIG. 7B or other figures) may differ from what is
illustrated, as will be understood by one of ordinary skill in the
art.
[0066] FIG. 7C is a perspective view of the head mount 703, looking
at the downstream face thereof. Head mount 703 includes a fluidic
valve/mixing chamber 712 (discussed below), which appears as an
annular channel or trough. Fuel and oxygen is conveyed into fluidic
valve/mixing chamber 712 by eight propellant injection holes 714 in
head mount 703 (in FIG. 7C, the lower five holes 714 are shown, and
the upper three are hidden from view due to the orientation of the
perspective view). Head mount 703 further includes eight (four
pairs of) coolant inflow holes 703-HCI and one coolant outflow hole
703-HCO. Head mount 703 further includes four head-mount-housing
mounting holes 703-HH for mounting the head mount 703 to the
housing 708. Head-mount-housing mounting holes 703-HH interface
with head-mount-housing mounting holes 708-HH of housing 708,
described above with reference to FIG. 7B, to achieve the physical
connection between head mount 703 and housing 708. Head mount 703
includes four centerbody-outer-shell-head mount mounting holes
703-HSO for mounting (physically connecting) head mount 703 to
centerbody outer shell 710-SO, and four centerbody-inner-shell-head
mount mounting holes 703-HSI for mounting (physically connecting)
head mount 703 to centerbody inner shell 710-SI.
[0067] FIG. 7D is a perspective view of the centerbody endcap
710-E, looking at the upstream face thereof. The upstream face of
centerbody endcap 710-E includes a recessed circumferential annular
region 710-ER (recessed into the surface of endcap 710-E and hence
recessed into the plane of the page), which mates with a
corresponding region of centerbody outer shell 710-SO for mounting
thereon. Furthermore, the radially outermost portion of recessed
circumferential annular region 710-ER includes a groove (not shown,
which is recessed into the surface of region 710-ER and hence
further recessed into the plane of the page), on which a mating
(e.g., copper) gasket 710-G is seated. When so seated, the upstream
surface (appearing in the foreground in the figure) of copper
gasket 710-G is raised above the surface of recessed
circumferential annular region 710-ER. Copper gasket 710-G serves
to seal the interface between centerbody outer shell 710-SO and
centerbody endcap 710-E. Centerbody endcap 710-E also includes four
centerbody-outer-shell-centerbody-endcap mounting holes 710-EHSO
for mounting (physically connecting) centerbody endcap 710-E to
centerbody outer shell 710-SO, and four
centerbody-inner-shell-centerbody-endcap mounting holes 710-EHSI
for mounting (physically connecting) centerbody endcap 710-E to
centerbody inner shell 710-SI.
Centerbody-inner-shell-centerbody-endcap mounting holes 710-EHSI
are disposed in respective recesses 710-EHSIR that fit and mate
with centerbody inner shell 710-SI, for mounting centerbody endcap
710-E to centerbody inner shell 710-SI.
[0068] FIG. 7E is a perspective view of the core assembly 700-CA of
RDE 700, but without the centerbody endcap 710-E. The core assembly
700-CA as shown includes head mount 703, outer injector gasket
704-GO; inner injector gasket 704-GI (not visible in the figure);
injector plate 704; centerbody outer shell 710-SO; and centerbody
inner shell 710-SI. Injector plate 704 includes injector holes
704-H for injection of propellant into the detonation chamber
(annular region radially between housing 708 and centerbody outer
shell 710-SO). Centerbody outer shell 710-SO includes four
centerbody-outer-shell-centerbody-endcap mounting holes 710-SOH for
mounting (physically connecting) centerbody endcap 710-E to
centerbody outer shell 710-SO. Similarly, centerbody inner shell
710-SI includes four centerbody-inner-shell-centerbody-endcap
mounting holes 710-SIH for mounting (physically connecting)
centerbody endcap 710-E to centerbody inner shell 710-SI.
Centerbody outer shell 710-SO also includes a circumferential
annular region 710-SOA for mating with recessed circumferential
annular region 710-ER of centerbody endcap 710-E, and with gasket
710-G which is seated in region 710-ER, gasket 710-G serving to
seal the interface between centerbody outer shell 710-SO and
centerbody endcap 710-E. As for the mating, circumferential annular
region 710-SOA is recessed over an annular subregion thereof
including the circumference of centerbody outer shell 710-SO, and
unrecessed over an annular subregion thereof radially inward of the
recessed annular subregion. The unrecessed annular subregion mates
with recessed circumferential annular region 710-ER of centerbody
endcap 710-E, while the recessed annular subregion mates with
gasket 710-G, which rises above the surface of recessed
circumferential annular region 710-ER. Coolant recirculation ports
790 (discussed below) are seen between the legs 710-SIL of
centerbody inner shell 710-SI, one port 790 between each pair of
adjacent legs 710-SIL. Also seen in FIG. 7E are head-mount-housing
mounting holes 703-HH, described above with reference to FIG.
7C.
[0069] FIG. 7F is a longitudinal cross-sectional view of RDE 700,
taken along the line A-A in FIG. 7A (of course, in FIG. 7F, RDE 700
is assembled, in contrast to the exploded view of FIG. 7A). FIG. 7F
shows the following components of RDE 700 already mentioned with
reference to FIGS. 7A-7E: head mount 703, propellant injector holes
714, coolant inflow hole 703-HCI, coolant outflow hole 703-HCO,
fluidic valve/mixing chamber 712, injector plate 704, ignition hole
727, housing 708, centerbody outer shell 710-SO, centerbody inner
shell 710-SI, centerbody endcap 710-E, housing endcap 708-E, and
pressure transducer holes 716. In addition, FIG. 7F shows
detonation chamber 702, coolant supply channel 791 and coolant
return channel 792 (discussed below), and a spark plug hole 718 for
a spark plug, which serves as a backup ignition means.
[0070] FIG. 7G is an elevational view of RDE 700 taken from the
rear, with the centerbody endcap 710-E and housing endcap 708-E
(see FIG. 7A) removed. FIG. 7G shows the following components of
RDE 700 already mentioned with reference to FIGS. 7A-7F: housing
708, detonation chamber 702, injection holes 704-H, centerbody
outer shell 710-SO, centerbody inner shell 710-SI, (four) coolant
supply channels 791, (eight) coolant inlet holes 703-HCI, coolant
return channel 792, and (four) coolant recirculation ports 790. In
addition, FIG. 7G shows (four) auxiliary coolant channels 793.
Coolant supply channel 791 and coolant return channel 792 may also
be referred to as central or inner coolant (supply and return)
channels, as they are located radially within detonation chamber
702, as described above and as seen in FIG. 7G, while auxiliary
coolant channels 793 may also be referred to as outer or peripheral
coolant channels, as they are located radially outward of
detonation chamber 702, as seen in FIG. 7G. While injection holes
704-H are of course located upstream of detonation chamber 702,
nonetheless detonation chamber 702 is indicated here to facilitate
understanding of the radial relationship between detonation chamber
702 and coolant channels 791, 792 and 793. It is also understood
that coolant inlet holes 703-HCI are of course upstream of supply
channel 791; it will be noted that in the embodiment here
illustrated each (non-circular cross section) supply channel 791
has two (circular cross section) inlet holes 703-HCI. The number of
channels may be varied.
[0071] As seen in FIGS. 7C and 7F, coolant enters RDE 700 through
coolant inlet holes 703-HCI and exits RDE 700 through a single
coolant outlet hole 703-HCO, both the coolant inlet holes 703-HCI
and the coolant outlet hole 703-HCO being disposed in the head
mount 703. The coolant inlet holes 703-HCI are arranged in a
circular pattern that is radially in between the center and the
circumference of the circularly shaped head mount 703. The coolant
outlet hole 703-HCO is located at the center of the circularly
shaped head mount 703. The number and arrangement pattern of the
inlet holes 703-HCI and the outlet holes 703-HCO may differ from
that illustrated. As mentioned, in other embodiments, the RDE, and
hence the head mount, need not be circular (cylindrical) in
shape.
[0072] As seen in FIG. 7F and in part in FIG. 7G, the coolant,
supplied through the coolant inlet holes 703-HCI, travels
downstream (rightward in FIG. 7F) through the annular gap between
the centerbody outer shell 710-SO and the centerbody inner shell
710-SI, all or most of the longitudinal extent of the centerbody
710 and detonation chamber 702, and then returns upstream (leftward
in FIG. 7F) through the hollow center (tubular portion) of the
centerbody inner shell 710-SI to the coolant outlet hole 703-HCO in
the head mount 703, where it exits the RDE 700. The annular gap
between the centerbody outer shell 710-SO and the centerbody inner
shell 710-SI may be referred to as the aforementioned coolant
supply channel 791, and the hollow center (tubular portion) of the
centerbody inner shell 710-SI may be referred to as the
aforementioned coolant return channel 792.
[0073] The return upstream of the inflow coolant is achieved via
coolant recirculation ports 790. As shown in FIG. 7E and 7G, the
coolant recirculation ports 790 may be understood as the gaps
between the legs 710-SIL of centerbody inner shell 710-SI (these
gaps and the four legs 710-SIL together, circumferentially along
their radially outward faces, define a circle in FIG. 7G, which
circle is the circumference of centerbody inner shell 710-SIH).
Restating the flow of coolant in terms of FIG. 7E, the coolant
flows in to RDE 700 from head mount 703, travels downstream (upward
in FIG. 7E) through the coolant supply channel 791 (mostly not
visible in FIG. 7E), i.e., the annular gap between centerbody outer
shell 710-SO and centerbody inner shell 710-SI, is redirected 180
degrees at the coolant recirculation ports 790, and then flows
upstream (downward in FIG. 7E) through the coolant return channel
792 (mostly not visible in FIG. 7E), i.e., through the hollow
center of centerbody inner shell 710-SI, back to the head mount
703. The annular gap between centerbody outer shell 710-SO and
centerbody inner shell 710-SI is visible in FIG. 7E as the annular
gap between the legs 710-SIL of centerbody inner shell 710-SI and
the centerbody outer shell 710-SO.
[0074] Note that the annular region between the centerbody outer
shell 710-SO and the housing 708 is the detonation chamber 702, as
seen in FIGS. 7F and 7G. Accordingly, the centerbody outer shell
710-SO is the radially inner annular wall of the detonation chamber
702. Since the coolant inflow flows along the centerbody outer
shell 710-SO (specifically, between the centerbody outer shell
710-SO and the centerbody inner shell 710-SI), the coolant serves
to cool the radially inner annular wall of the detonation chamber
702, and hence the detonation chamber 702 and the RDE 700.
[0075] As further seen in FIG. 7G, RDE 700 may be provided with one
or more auxiliary coolant channels 793 disposed radially outward of
detonation chamber 702. Specifically, as illustrated, four
additional coolant channels 793 may be provided in housing 708. The
numbers and arrangement of the additional coolant channels 793 may
vary from what is illustrated. The name "auxiliary" given to
coolant channels 793 is not to be taken as limiting the structure
or functioning of these elements. Auxiliary coolant channels 793
may but need not be secondary in function to coolant channels 791
and 792; auxiliary coolant channels 793 may also be referred to as
"additional" coolant channels. Auxiliary coolant channels 793 may
extend from a position at, near, or toward the front (upstream end)
to a position at, near, or toward the back (downstream end) of the
RDE 700 or of the detonation chamber 702. Each of these additional
coolant channels 793 is provided with two ports (referred to above
as coolant holes) 708-HC (FIG. 7B), one at the aforementioned
upstream position and one at the aforementioned downstream
position. These ports 708-HC may be disposed on the outer wall of
the housing 708, as illustrated in FIG. 7B. The two ports 708-HC
for a given channel 793 are used as inlet and outlet ports,
respectively, that is, one port 708-HC is used for inlet and the
other port 708-HC is used for outlet (at any given time). The two
ports 708-HC for a given channel 793 are interchangeable between
inlet and outlet functionality. That is, coolant may be flowed in
at the upstream port 708-HC (which is thus used as an inlet), run
downstream, and flowed out at the downstream port 708-HC (which is
thus used as an outlet), or coolant may be flowed in at the
downstream port 708-HC (which is thus used as an inlet), run
upstream, and flowed out at the upstream port 708-HC (which is thus
used as an outlet). As these additional coolant channels 793 run
inside of housing 708 along a wall of housing 708 that separates
housing 708 from the detonation chamber 702, these additional
coolant channels 793 may be used (in addition to or instead of the
above-described coolant channels 791 and 792 that are disposed
radially inward of the detonation chamber 702) to cool the
detonation chamber 702. These additional coolant channels 793 may
also be used to cool pressure sensors (not shown) disposed in the
housing 708 (if pressure sensors are used in the given RDE
application). Holes 716 for accommodating such pressure sensors are
illustrated in FIGS. 7B and 7F. Note that FIG. 7F does not show the
additional coolant channels 793 disposed in housing 708 because the
section illustrated in FIG. 7F goes through the pressure sensor
holes 716 and not through the additional coolant channels 793.
[0076] The coolant may be any suitable fluid as would be understood
by one of ordinary skill in the art, for example, a gaseous or
liquid propellant (including cryogenic propellants), water, or a
dedicated refrigerant. Preferably, the coolant should be able to
cool the detonation chamber 702 without igniting, corroding the
walls, or having another destructive effect. The coolant may start
cold (i.e., by cryogenics or some other method of precooling) or at
room temperature, as long as it has the capacity to absorb heat.
High thermal conductivity and low initial temperature are
preferred, as they aid in heat transfer. In some embodiments, if
cooling of the radially inner annular wall of the detonation
chamber 702 is not required (e.g., if alternative cooling of the
detonation chamber 702 is provided), or if the above-described
portion of the cooling system that is radially inward of the
detonation chamber 702 does not take up all of the space available
inside the centerbody 710, the space available in the centerbody
710 may be used to store propellant (fuel and/or oxidizer), to
house electronics, avionics, sensors, etc., to preheat the
reactants, or for any number of other productive uses.
[0077] A third set of embodiments provides techniques and
structures for cooling the detonation chamber 702, further to the
use of coolant described in the second set of embodiments. These
techniques and structures generally serve to enhance heat transfer.
Some of these techniques and structures involve modifications or
treatment of a cold-side surface of a wall (or the like) across
which heat transfer occurs, a cooler fluid flowing on the cold-side
of the wall to effect heat transfer from a hotter region of the RDE
on the other side of the wall. In this case, the wall across which
heat transfer occurs is a wall of the detonation chamber 702, which
may be either the radially outer or radially inner wall. As one
example, the wall may be the radially inner wall and/or the
radially outer wall of the detonation chamber, and the heat
transfer effected by the coolant of the second set of embodiments
may be enhanced by techniques and structures of the third set of
embodiments.
[0078] A more detailed description of this third set of embodiments
will be provided with reference to FIGS. 8-10.
[0079] According to a first subset of the third set of embodiments,
a cold-side surface across which heat transfer occurs in the RDE
may be treated in such a manner that the surface is rendered rough,
not smooth. The surface may be a surface of a wall of the
detonation chamber, e.g., a cold-side surface of the radially outer
wall or radially inner wall of an annular detonation chamber. For
example, the heat transfer effected by the coolant of the second
set of embodiments may be enhanced by rendering the surface of the
radially inner side (cold side) of the radially inner wall
(centerbody outer shell 710-SO) of the detonation chamber 702
(i.e., the radially inner one of the two exterior (cold) sides of
the annular detonation chamber 702) rough. In other embodiments the
surface of another wall, e.g., the cold-side surface of the
radially outer wall of the detonation chamber 702 (i.e., the
radially outer one of the two exterior (cold) sides of the annular
detonation chamber 702), may be made rough (the effectiveness of
this assumes that the surface in question is in contact with a
fluid that effects heat transfer from the detonation chamber
702).
[0080] Increasing surface roughness enhances the heat transfer
(achieved by the coolant that is flowing in contact with the
surface) in two ways. First, surface roughness increases the
surface area of the cold-side wall that is in contact with the
coolant, so there is at any time a greater area over which heat
transfer occurs. Second, surface roughness promotes the transition
of the flow of the coolant from laminar to turbulent flow.
Turbulent flow provides for significantly improved heat transfer as
compared to the more orderly laminar flow. Surface roughness is
relatively easy to implement in a narrow confined space, such as in
the cooling section of the centerbody, and surface roughness does
not significantly impede flow. Finally, surface roughness is
well-suited to any type of cooling fluid, e.g., a gaseous or liquid
propellant (including cryogenic propellants), water, or a dedicated
refrigerant.
[0081] According to a second subset of the third set of
embodiments, a cold-side surface across which heat transfer occurs
in the RDE may be provided with fins, vanes, or other
surface-area-increasing structures. More generally, all of these
structures may be referred to as projections (projecting outward
from the surface), although it is also possible to increase the
surface area with depressions or indentations (projecting inward
into the surface). The cold-side surface in question may be a
cold-side surface of a wall of the detonation chamber 702, as
described above with respect to the surface roughness
embodiments.
[0082] Compared to surface roughness, the projections mentioned
here are very large, greatly increasing the surface area. There are
innumerable possible configurations/shapes and arrangements of the
projections, examples of which are illustrated in FIGS. 8 and
9A-9C. FIG. 8 shows an axial cross section of a cylindrical
structure 830, including an annular region 831 through which
coolant flows (perpendicularly to the plane of the page), with fins
832 on the radially inner wall or surface 833 of the two annular
walls or surfaces (833, 835) defining annular region 831. In this
arrangement, the region 834, which is radially inward of region
831, may be the detonation chamber 702 and the region 831 may be
comparable to the above-described additional cooling channel 793 in
the housing 708. In other embodiments, fins 832 may be applied to
the radially outer surface (i.e., the surface closest to the
detonation chamber 702) of the above-described coolant supply
channel 791, which is radially inward of the detonation chamber
702. In either case, the cooling of the detonation chamber 702 by
heat transfer to the coolant flowing through the radially adjacent
coolant channel (e.g., 793 or 791) provided with fins 832 is
enhanced by the fins 832. In other embodiments, the outer periphery
wall 835 could be omitted, the radially inner wall or surface 833
could be the exterior wall/surface of the housing 708, the region
834 could be the detonation chamber 702, and vanes 832 could serve
to enhance the heat transfer achieved by the flow of ambient air
over the exterior wall/surface 833 of the housing 708 (or by the
exposure of the housing 708 to outer space).
[0083] Fins 832 may be configured as vertical walls relative to the
annular wall or surface 833 from which they project, as illustrated
in FIG. 8. Given the annular configuration of region 831 and
wall/surface 833, the fins 832 extend radially outward from
wall/surface 833. Though not visible due to the cross-sectional
nature of the FIG. 8, fins 832 also extend in the direction
into/out of the plane of the page. FIG. 9A is a plan view of vanes
932 comparable to vanes 832 but not formed around an annular
wall/surface such as wall/surface 833, the view looking down on the
vanes 932 from above. The long direction (indicated by the
double-headed arrow) of vanes 932 in FIG. 9A corresponds to the
direction into/out of the plane of the paper in FIG. 8. With this
signification, the double-headed arrow applies also to FIGS. 9B and
9C, which are plan views, like FIG. 9A, but of other types and
arrangements of projections. Specifically, these two figures show
projections 936 configured as vertical cylindrical posts relative
to the surface from which they project. In FIG. 9B, these
projections 936 are arranged in rows and columns, all of the rows,
columns, and projections 936 aligned with one another,
respectively. In FIG. 9C, these projections 936 are arranged in
rows and columns, such that every other row is aligned with one
another and the two rows in any pair of adjacent rows are offset
with respect to one another, and the columns are arranged in the
same manner. The arrangement of FIG. 9B may be referred to as an
"aligned" arrangement, while that of FIG. 9C may be referred to as
an "offset" arrangement, even though in some sense the arrangement
of FIG. 9C is still aligned or regular. It is also possible to
provide projections that are arranged in irregular arrangements.
Also, shapes of projections other than those illustrated are
possible. (To be sure, the axial cross-sectional view of FIG. 8 may
also be understood as depicting the vertical posts 936 as arranged
in FIGS. 9B or 9C.)
[0084] Projections such as those discussed here, in addition to
increasing surface area, may generally cause the flow of the
coolant to transition from a laminar flow to a turbulent flow.
While these projections may be substantially more effective in
these respects than surface roughness, such individual projections
may also cause blockage of the coolant flow and thus may not be
optimal for tightly enclosed spaces. These projections are
well-suited to any type of cooling fluid, and especially
well-suited to gaseous flows. While these projections can be used
with liquids, both room-temperature and cryogenic, greater spacing
between the individual projections may be preferable (in view of
the possibility of flow blockage) when used with liquids as
compared to gases, due to the higher viscosity of liquids.
[0085] The structures and techniques of the first and second
subsets of the third set of embodiments (namely, surface roughness
and surface projections) may be referred to generally as surface
modifications, surface treatments, or surface-area-increasing
structures.
[0086] According to a third subset of the third set of embodiments,
there is provided a feature called transpiration cooling, which is
described with reference to FIG. 10. FIG. 10 is a longitudinal
cross-sectional view (i.e., taken parallel to the longitudinal or
cylindrical axis of the RDE) of a portion of an RDE, showing
portions of the annular detonation chamber 1002, the walls 1007,
1009 of the annular detonation chamber 1002, and the injector
cavity 1004, upstream of detonation chamber 1002. The wall 1007 is
radially outward of the annular detonation chamber 1002 (and
corresponds to the radially inner wall of housing 708 of FIG. 7A;
see FIG. 7G, discussed above, where the additional coolant channel
793 that goes through housing 708 effectively splits housing 708
into radially inner and radially outer walls), and the wall 1009 is
radially inward of the annular detonation chamber 1002 (and
corresponds to centerbody outer shell 710-SO of FIG. 7A). As
further seen in FIG. 10, the walls 1007, 1009 separate the
detonation chamber 1002 from inner coolant channel 1041 and outer
coolant channel 1042, respectively. Thus, the inner coolant channel
1041 lies radially inward of the annular detonation chamber 1002
(and corresponds to the coolant supply channel 791, between the
centerbody outer shell 710-SO and the centerbody inner shell
710-SI, described above in the second set of embodiments), and the
outer coolant channel 1042 lies radially outward of the annular
detonation chamber 1002 (and corresponds to the additional coolant
channel 793 seen in FIG. 7G and described above in the second set
of embodiments). Transpiration cooling is achieved by machining
many small holes or pores 1017, 1019 in walls 1007, 1009,
respectively, as illustrated. Transpiration cooling is the process
of bleeding coolant flow through the small holes 1017, 1019 in the
walls 1007, 1009 separating the detonation chamber 1002 from the
coolant channels 1042, 1041, respectively. That is, coolant fluid
from the coolant channels 1041, 1042 will be caused to travel
through the holes 1017, 1019 and onto the adjacent
detonation-chamber-side surface of the walls 1007, 1009 by
capillary action. As seen in FIG. 10, this bleed flow through holes
1017 and 1019, respectively, forms respective thin films or a
cool(er) barrier layers 1027 and 1029 on the respective hot-side
walls of the detonation chamber 1002. Thus, this thin film/barrier
layer 1027, 1029 is inside the detonation chamber 1002, between the
respective detonation chamber wall 1007 or 1009 and the hot
combusted flow (generated from detonation/combustion of fuel and
oxidizer) that flows inside the detonation chamber 1002. The thin
film/barrier layers 1027, 1029 may achieve very significant heat
reduction, e.g., by reducing the local equivalence ratio or by
absorbing energy. Transpiration cooling is often used with oxidizer
flow, e.g., oxygen (though an inert gas like nitrogen or argon is
also possible), and can be used with either gaseous or cryogenic
liquid fluids as coolant. (It is also possible to provide and use
holes in only one of the walls 1007, 1009 for transpiration
cooling.)
[0087] According to a fourth subset of the third set of
embodiments, an ablative lining is provided on an interior wall of
the detonation chamber. The ablative lining is a coating provided
on the interior wall of the detonation chamber, which is designed
to burn away (as a sacrificial material) at a controlled rate
during operation of the RDE so as to protect the wall from
damage.
[0088] The ablative lining may prevent the wall from melting by
serving as a buffer layer and burning away. The ablative lining may
be composed of materials comprising high-temperature, high-strength
fibers impregnated with resin, or other materials as will be
understood by one of skill in the art. A discussion of materials
suitable for the ablative lining is found in "Rocket Propulsion
Elements," by G. P. Sutton and 0. Biblarz (7th Edition, John Wiley
& Sons, New York, 2001), which is hereby incorporated herein by
reference. How the ablative lining is applied to the detonation
chamber wall surface is also known to one of ordinary skill in the
art. Since the ablative lining burns off after a limited period of
time, use of an ablative lining is suitable only for finite burn
times. Also, where an ablative lining is used on the walls of a
detonation chamber, either the detonation chamber is not reusable,
or the ablative lining must be reapplied or replaced after every
use, depending on the circumstances.
[0089] Although ablative linings and transpiration cooling are
generally not used in combination for the same component (e.g.,
detonation chamber wall), otherwise the cooling techniques and
structures of the first through fourth subsets of the third set of
embodiments can be used in any combination of one or more of them.
An example of an ablative lining is illustrated in FIG. 8. As
described above, in the structure 830 annular region 834
corresponds to the detonation chamber 702. The annular region 834
(detonation chamber) is bounded/defined by wall 833, which is
radially outward of region 834, and wall 837, which is radially
inward of region 834. On the radially inner surface of wall 833,
that is, the surface adjacent the region 834 (detonation chamber),
an ablative lining 838 is provided. While this is an example of an
ablative lining employed in combination with another cooling
technique/structure, namely, fins 832, an ablative lining may be
used on its own without one of the other cooling
techniques/structures described here.
[0090] According to a fourth set of embodiments, copper or other
soft metal sealing gaskets are provided in an RDE, as described
below. In an RDE, there are various interfaces or connections
between parts where it is necessary to seal the
interface/connection to prevent materials (e.g., fuel, oxidizer,
coolant) from bleeding to locations where they are not supposed to
be, e.g., to bleed from one stage to the subsequent or previous
stage of the RDE. In this regard, conventional rubber or silicone
seals may not adequately withstand the extreme heat generated in
the RDE, e.g., hot-side temperatures in excess of 1500.degree. F.
Even ultra-high-temperature gaskets are only suitable for
temperature loads of approximately 700.degree. F., and only for
intermittent use with such loads.
[0091] According to the fourth set of embodiments, sealing gaskets
formed of copper, bronze, or any relatively soft metal may be used
to seal these interfaces in an RDE. Copper is a relatively soft
metal with an extremely high thermal conductivity. Also, the
relative softness means that copper can deform slightly when put
under load, which can aid with sealing. For example, in some cases,
a copper gasket may be machined to be slightly larger than the
tolerance allows, so that it deforms to fill gaps when tightened
into place. Further, copper has a coefficient of thermal expansion
greater than or approximately equal to most varieties of stainless
steel, a material commonly used for fabrication of RDEs. This means
that copper gaskets have an added benefit that, at high
temperatures, the copper gaskets may expand slightly more than the
stainless steel hardware, thus again aiding with sealing at high
temperatures. The above features of copper also hold for other
relatively soft metals. (It will be understood by one of ordinary
skill in the art that materials other than stainless steel may be
used for fabricating an RDE. Non-limiting examples of such
materials include various alloys made by Haynes International.)
[0092] Examples of the use of such sealing gaskets, at the fore end
of the centerbody 710 where it interfaces with the injector plate
704 and at the aft end of the centerbody 710 where it interfaces
with the centerbody endcap 710-E, are described with reference to
FIGS. 6, 7D, 7E, and 13.
[0093] In FIG. 6, the (e.g., copper) sealing gasket 627-G is shown
around hole 627, which is located at the proximal (RDE interface)
end 222 of the tubular portion of coupling 205. The combustion
products from the PDE igniter 206 (having entered the coupling 205)
travel from coupling 205 into the detonation chamber 702 (FIGS. 7F
and 7G) of the RDE 700 through hole 627. As discussed above with
reference to FIG. 7B, hole 627 interfaces and communicates with the
ignition hole 727 in FIG. 7B, and annular gasket groove 727-GG is
provided around the ignition hole 727 for mounting therein the
sealing gasket 627-G for sealing this junction point between
coupling 205 and RDE 700. Sealing gasket 627-G around hole 627 is
also shown in an unassembled position in FIG. 7A.
[0094] FIG. 7D shows the upstream side of the centerbody endcap
710-E (see FIG. 7A). Centerbody endcap 710-E has an annular groove
around its circumference but this annular groove is not visible
because a (e.g., copper) sealing gasket 710-EG is seated in it.
Sealing gasket 710-EG is for sealing the junction between the
(upstream side of) centerbody endcap 710-E and the (downstream side
of) centerbody outer shell 710-SO (see FIG. 7A). Just radially
inward of the annular groove/sealing gasket 710-EG is an annular
recess 710-ER for mounting (interfacing, connecting) the upstream
side of the centerbody endcap 710-E on (with) the downstream side
of the centerbody outer shell 710-SO.
[0095] FIG. 7E shows, at the top of the figure, the downstream side
of both the centerbody outer shell 710-SO and the centerbody inner
shell 710-SI (see FIG. 7A). As described immediately above with
reference to FIG. 7D, the downstream side of the centerbody outer
shell 710-SO connects with the (upstream side of) centerbody endcap
710-E, and the sealing gasket 710-EG (FIG. 7D; not shown in FIG.
7E) serves to seal the junction therebetween. As seen in FIG. 7E,
the downstream side of the centerbody outer shell 710-SO has an
annular groove 710-SOG for interfacing with sealing gasket 710-EG
at the circumference of centerbody outer shell 710-SO.
[0096] FIG. 13 shows (e.g., copper) sealing gaskets 704-GO and
704-GI around the outer circumference and the inner circumference,
respectively, of the injector plate 704. Injector plate 704 and
sealing gaskets 704-GO and 704-GI are also shown in FIG. 7A. As
seen in FIGS. 7A and 7E, the injector plate 704 interfaces, at its
upstream face, with the head mount 703 and, at its downstream face,
with the centerbody outer shell 710-SO. The outer sealing gasket
704-GO serves to seal the interface of the injector plate 704 with
the head mount 703, as seen in FIG. 7E, and the inner copper
sealing gasket 704-GI serves to seal the interface of the injector
plate 704 with the centerbody outer shell 710-SO.
[0097] According to a fifth set of embodiments,
converging-diverging injection ports or diverging injection ports
are provided. Examples of injection ports (also referred to as
injection holes or the like) are seen in FIG. 1 (element 114), FIG.
7D (element 714 in head mount 704; only four of eight holes 714 are
visible due to the perspective of the figure), FIG. 7E (element
704-H in injector plate 704), and FIG. 13 (element 704-H in
injector plate 704). It will be understood that various different
designs (e.g., configurations/shapes, locations, arrangements) of
the injection holes are possible, including combinations of the
designs of the fifth set of embodiments illustrated herein, as well
as other designs different from those illustrated herein. Examples
of such different designs were discussed above with reference to
(holes 114 shown in) FIG. 1. Accordingly, the injection holes
described herein may be used for fuel and/or oxidizer, or for a
premixed fuel/oxidizer mixture. The fifth set of embodiments,
providing converging-diverging or diverging injection ports, thus
deals with various different shapes or configurations of injection
ports. The converging-diverging or diverging configurations
described below may be applied to any of the injection ports
described throughout this disclosure, such as those mentioned
above. In some embodiments, the converging-diverging and diverging
configurations described below are applied to the injection ports
704-H of the injector plate 704 shown in FIGS. 7E. Injection ports
704-H are axial (i.e., they enter the detonation chamber 702 at an
axial end thereof, specifically, the head end; they are disposed on
a surface perpendicular to the longitudinal axis of the RDE
700/detonation chamber 702), rather than sidewall.
[0098] One rationale for providing converging-diverging or
diverging injection ports is described as follows. The pressure
distribution behind a detonation wave is well-described in the
literature, and consists of three regions:
[0099] 1. P.sub.inj<P.sub.ch: Blocked flow. In this region, the
injection pressure (P.sub.inj) is less than the chamber pressure
(P.sub.ch), so there is no flow into the annulus (in fact, the
opposite occurs: there is backflow into the injectors).
[0100] 2. P.sub.ch<P.sub.inj<P.sub.cr: Subsonic flow. In this
region, the injection pressure is greater than the chamber
pressure, but less than the critical pressure (P.sub.cr) for sonic
flow. Inflow is subsonic, and occurs at the injector pressure. The
critical pressure for sonic flow is a function of the injection
flow stagnation pressure T.sub.0,inj and the propellant ratio of
specific heats .gamma..sub.inj and is given by Equation (1) shown
below.
[0101] 3. P.sub.inj>P.sub.cr: Sonic flow. In this region, the
injection pressure is greater than the critical pressure; injection
is sonic, and occurs at the critical pressure.
P cr = T 0 , inj ( 2 .gamma. inj - 1 ) .gamma. inj .gamma. inj - 1
( 1 ) ##EQU00001##
[0102] The third region identified above may benefit by
converging-diverging injection ports. The injection flow pressure
(which dictates the detonation wave pressure) in straight (i.e.,
not converging or diverging) or purely converging injection ports
is limited to the critical pressure. Straight or converging
injection ports may suffer from choked flow for a significant
portion of the annular region behind the detonation wave. The
addition of a diverging section in the injection port increases
pressure recovery beyond the critical pressure limit. This enables
lower injection pressure requirements to achieve a desired
detonation chamber pressure condition (and with it an attendant
decrease in weight of the RDE due to reduced structural and pumping
requirements), or it increases the detonation chamber pressure for
a given injection pressure condition (with a corresponding increase
in performance). If the sonic condition is provided at the upstream
face of the injector plate, a converging section may not be
necessary, in which case a simple (solely) diverging section may be
used.
[0103] FIGS. 11A-11D show examples of possible injection port
configurations with converging-diverging or simple diverging
sections. Other configurations are possible. Each of FIGS. 11A-11D
shows a series of adjacent injection holes, shown in a flat planar
projection (even though in an actual RDE the injection holes may be
arranged in a circumferential arrangement, such as illustrated,
e.g., in FIGS. 1, 7C and 7E). Further, FIGS. 11A-11D show the holes
in longitudinal cross section, the cross section being taken along
the longitudinal (cylindrical) axis of the holes. (Even though, due
to the converging and diverging sections, the injection holes are,
strictly speaking, not cylinders, the terminology "longitudinal
axis," "cylindrical axis," etc. is used as if the injection holes
were cylindrical, along the lines noted above in the description of
embodiments with reference to FIG. 1.)
[0104] FIG. 11A shows a contoured converging-diverging
configuration. In this configuration, each of the holes 1114A
converges from its (upstream) entrance to its midpoint 1114A-M
(i.e., halfway between its (upstream) entrance and its (downstream)
exit), and then diverges from its midpoint 1114A-M to its
(downstream) exit. As illustrated, the convergence and divergence
occur in a contoured (curved) manner. FIG. 11B shows a conical
converging-diverging configuration. In this configuration, as with
FIG. 11A, each of the holes 1114B converges from its (upstream)
entrance to its midpoint 1114B-M, and then diverges from its
midpoint 1114B-M to its (downstream) exit. However, in contrast to
FIG. 11A, as illustrated, the convergence and divergence occur in a
conical (straight line) manner.
[0105] FIG. 11C shows a contoured diverging configuration. In this
configuration, each of the holes 1111C diverges from its (upstream)
entrance to its (downstream) exit. As illustrated, the divergence
occurs in a contoured (curved) manner. FIG. 11D shows a conical
diverging configuration. In this configuration, as with FIG. 11C,
each of the holes 1111D diverges from its (upstream) entrance to
its (downstream) exit. However, in contrast to FIG. 11C, as
illustrated, the divergence occurs in a conical (straight line)
manner.
[0106] A sixth set of embodiments provides for swirled injection of
propellants. As discussed above with respect to the second set of
embodiments, since the detonation wave needs to propagate in the
circumferential direction in order to sustain a continuous
detonation wave, it is desirable that the detonation wave be
initiated in the circumferential direction (or in a direction
approaching the circumferential direction). One way to so control
the direction of propagation is by tangential injection of a
detonation wave (from a PDE), as described above in the second set
of embodiments (FIGS. 2-5). A second method is by the use of
swirled injection of propellants, described here in the sixth set
of embodiments. That is, by imparting a circumferential velocity
component to the injection flow (flow of injected propellants), it
is possible to predispose the detonation wave to travel in the
desired (i.e., circumferential) direction.
[0107] A first way to produce swirled injection is to use axial
injection holes that are angled along their axial (longitudinal)
extent. These injection holes may be disposed at or near the
upstream axial end of the detonation chamber. Also, they may be
oriented so as to extend (from upstream entrance to downstream exit
of the hole) in a direction at an angle of greater than 0.degree.
and less than 90.degree. relative to the longitudinal axis of the
detonation chamber (here, an angle of 0.degree. means the
downstream direction along or parallel to the longitudinal axis of
the detonation chamber/RDE, an angle of 180.degree. means the
upstream direction along or parallel to the longitudinal axis of
the detonation chamber/RDE, and angles of 90.degree. and
270.degree. are in respective radial directions perpendicular to
the longitudinal axis of the detonation chamber/RDE). (Note that,
with such angled injection ports, the upstream-to-downstream
direction of the injection port is not the same as the
upstream-to-downstream direction of the detonation chamber/RDE. The
upstream-to-downstream direction of the injection port is a
direction at an angle of greater than 0.degree. and less than
90.degree. relative to the longitudinal axis of the detonation
chamber, while the upstream-to-downstream direction of the
detonation chamber/RDE is the direction of the longitudinal axis of
the detonation chamber/RDE).
[0108] Examples of these angled injection ports are shown in FIGS.
12A-12C and 13. Configurations other than those illustrated are
possible.
[0109] Like FIGS. 11A-11D, each of FIGS. 12A-12C shows a series of
adjacent injection holes, shown in a flat planar projection. Also,
FIGS. 12A-12C show the holes in longitudinal cross section, the
cross section being taken along the longitudinal (cylindrical) axis
of the holes. (Again, even though, due to the converging and
diverging sections, the injection holes are, strictly speaking, not
cylinders, the terminology "longitudinal axis," "cylindrical axis,"
etc. is used as if the injection holes were cylindrical, along the
lines noted above in the description of embodiments with reference
to FIG. 1.)
[0110] FIG. 12A shows a straight, angled configuration. In this
configuration, each of the holes 1214A is angled in its extent from
its (upstream) entrance to its (downstream) exit: as illustrated,
each hole 1214A extends from its upstream entrance (at a lower,
relatively left location in FIG. 12A) to its downstream exit (at an
upper, relatively right location in FIG. 12A). Further, the hole
1214A is straight (i.e., not converging and not diverging) in the
sense that the illustrated longitudinal cross section of the hole
1214A shows straight lines defining the sidewalls 1214A-SW of the
hole 1214A.
[0111] FIG. 12B shows a contoured converging-diverging, angled
configuration. In this configuration, as with FIG. 12A, each of the
holes 1214B is angled in its extent from its (upstream) entrance to
its (downstream) exit: as illustrated, each hole 1214B extends from
its upstream entrance (at a lower, relatively left location in FIG.
12B) to its downstream exit (at an upper, relatively right location
in FIG. 12B). However, in contrast to FIG. 12A, the hole 1214B is
contoured converging-diverging (as in FIG. 11A), as seen in the
illustrated longitudinal cross section of the hole 1214B.
[0112] FIG. 12C shows a conical converging-diverging, angled
configuration. In this configuration, as with FIGS. 12A and 12B,
each of the holes 1214C is angled in its extent from its (upstream)
entrance to its (downstream) exit: as illustrated, each hole 1214C
extends from its upstream entrance (at a lower, relatively left
location in FIG. 12C) to its downstream exit (at an upper,
relatively right location in FIG. 12C). However, in contrast to
FIGS. 12A and 12B, the hole 1214C is conical converging-diverging
(as in FIG. 11B), as seen in the illustrated longitudinal cross
section of the hole 1214C.
[0113] FIG. 13 shows a three-dimensional perspective view of an
injector plate 1304 having injection ports 1304-H characterized by
the straight, angled configuration as in FIG. 12A. These injection
ports 1304-H are angled at an angle of 30.degree.. The injection
ports 1304-H are arranged circumferentially around the injector
plate 1304 (corresponding to injector plate 704 in FIG. 7A). The
figure shows the upstream face of the injector plate 1304 (with the
aforementioned (e.g., copper) outer and inner sealing gaskets
704-GO and 704-GI (shown also in FIG. 7A).
[0114] The angled configurations such as those discussed here may
be applied to any of the injection ports described throughout this
disclosure, such as those mentioned in the fifth set of embodiments
above. In some embodiments, the angled configurations described
here are applied to the injection ports 704-H of the injector plate
704 shown in FIG. 7E. These injection ports 704-H are axial (i.e.,
they enter the detonation chamber 702 (FIGS. 7F and 7G) at an axial
end thereof, specifically, the head end; they are disposed on a
surface perpendicular to the longitudinal axis of the RDE
700/detonation chamber 702), rather than sidewall.
[0115] A second way to produce swirled injection is by swirled
sidewall injection. In this case, in contrast to the first way
discussed above, the injection ports are disposed on the
cylindrical sidewall of the detonation chamber, rather than in an
axial injection arrangement at or near the upstream axial end
thereof (the injection ports also enter the detonation chamber from
the sidewall thereof and hence, even if they are located near the
head end, they do not enter the detonation chamber, strictly
speaking, at or from an axial end thereof). Also, the swirled
sidewall injection ports may extend (from upstream entrance to
downstream exit of the hole) in a circumferential direction
(described specifically, below), rather than in a direction at an
angle of greater than 0.degree. and less than 90.degree. relative
to the longitudinal axis of the annular detonation chamber. Put
another way, the center line of each of the swirled sidewall
injection ports may be curved. (Note that, again, with such curved
injection ports, the upstream-to-downstream direction of the
injection port is not the same as the upstream-to-downstream
direction of the detonation chamber/RDE. The upstream-to-downstream
direction of the injection port is a circumferential direction
(described specifically, below) similar to that of the annular
detonation chamber, while the upstream-to-downstream direction of
the detonation chamber/RDE is the longitudinal direction of the
detonation chamber/RDE).
[0116] FIG. 14A shows an axial cross section (i.e., a cross section
perpendicular to the longitudinal axis) of an RDE 1400A with curved
sidewall injection ports 1424A for providing swirled sidewall
injection. As illustrated, a plurality of ports 1424A may be
arranged in a circumferential arrangement around the detonation
chamber 1402A. Each port 1424A (e.g., the center line thereof)
extends in a circumferential direction (or in a curved manner) from
port entrance (located radially outside of the detonation chamber
1402A) to port exit (which goes into the detonation chamber 1402A).
The center line of the port 1424A (or the circumferential direction
in which the port 1424A extends) is defined by a curve that has a
greater curvature than the curvature of the annular detonation
chamber 1402A. This greater curvature permits the ports 1424A to
start at a radially exterior position (radially outside of the
detonation chamber 1402A) and end at a radially interior position
(at the radially outer boundary of the detonation chamber 1402A).
However, the curvature of the center line of the port 1424A, while
greater than the curvature of the annular detonation chamber 1402A,
exceeds the curvature of the annular detonation chamber 1402A by
only a limited extent, such that the injection flow exits the port
1424A with a positive (non-zero) component of velocity in the
(clockwise) circumferential direction of the annular detonation
chamber 1402A. If the curvature of the port 1424A were too great,
the injection flow could enter the detonation chamber 1402A in a
radial direction (i.e., toward the center of the circle, in FIG.
14A) or even in an opposite (i.e., counterclockwise)
circumferential direction.
[0117] Summing up the above description, swirled sidewall injection
provided by curved sidewall injection ports (e.g., 1424A) may be
described as follows: each of the plurality of injection ports
(e.g., 1424A) is disposed on a sidewall of the detonation chamber
(e.g., 1402A) and is characterized by (its centerline having) a
curvature as it extends from an upstream end of the injection port
configured for receiving the fuel and/or the oxidizer to a
downstream end of the injection port configured for injecting the
fuel and/or the oxidizer into the detonation chamber, wherein the
curvature is in a circumferential direction and is greater than the
curvature of the sidewall of the detonation chamber (or put another
way, greater than the curvature of the annulus defining the annular
shape of the detonation chamber).
[0118] As discussed above, e.g., with reference to FIG. 1, sidewall
injection may be used with standard or other kinds of injection
ports, and it is not restricted to use with
curved/circumferentially extending injection ports or with swirled
injection. While FIG. 14A shows curved/circumferentially extending
injection ports 1424A, FIG. 14B illustrates RDE 1400B according to
another embodiment, in which swirled sidewall injection is provided
using angled straight-line (rather than curved/circumferentially
extending) injection ports 1424B. In such embodiments, the
straight-line injection ports 1424B enter the wall of the
detonation chamber 1402B at an angle relative to the radial
direction and at an angle relative to the tangential direction,
specifically, at an angle greater than 0.degree. and less than
90.degree. relative to the sidewall of the detonation chamber
1402B. (In this context, entering the wall of the detonation
chamber at an angle of 90.degree. means entering the wall of the
detonation chamber in a radial direction; injection ports 114 in
FIG. 1 enter the wall of the detonation chamber 102 at an angle of
90.degree.. An angle of 0.degree. refers to a line tangent to the
circle defining the annular wall of detonation chamber; as a line
tangent to the circle never enters the circle, a hypothetical
injection port at an angle of 0.degree. would never enter the
detonation chamber.) Accordingly, injection ports 1424B may also be
described as: (a) entering the detonation chamber 1402B at an angle
other than 90.degree.; (b) not entering the detonation chamber
1402B at an angle of 90.degree.; (c) entering the detonation
chamber 1402B at an angle other than 0.degree.; (d) etc.
[0119] Injection ports 1424B may also be characterized as having an
"effective curvature" in the circumferential direction of (or
around) the annular detonation chamber 1402B, the effective
curvature being greater than the curvature of the sidewall of the
detonation chamber (or the effective curvature being greater than
the curvature of the annulus defining the annular shape of the
detonation chamber). The term "effective curvature" is to be
understood in terms of the relative positions of the upstream end
and the downstream end of the injection port. Note that a curved
sidewall injection port such as 1424A and an angled straight-line
injection port such as 1424B may have their respective upstream
ends at the same location (on the exterior of the detonation
chamber sidewall) and their respective downstream ends at the same
location (on the interior of the detonation chamber sidewall). In
such a case, the angled straight-line injection port 1424B would be
said to have an effective curvature equal or equivalent to the
curvature of the curved sidewall injection port 1424A.
[0120] Similarly, curved sidewall injection ports 1424A may be said
to be "effectively oriented" or "effectively angled" at an angle
greater than 0.degree. and less than 90.degree. relative to the
sidewall of the detonation chamber 1402A. With the same meaning,
curved sidewall injection ports 1424A may be said to "effectively
enter" the detonation chamber 1402A at an angle greater than
0.degree. and less than 90.degree. relative to the sidewall of the
detonation chamber 1402B (hence at an angle relative to the radial
direction and at an angle relative to the tangential
direction).
[0121] With respect to swirled sidewall injection as here
described, it is noted that, as illustrated in FIGS. 14A and 14B,
the sidewall injection ports (e.g., 1424A or 1424B) may be located
all on one side of the detonation chamber (1402A or 1402B), more
specifically, on the radially outer side of the detonation chamber
and not on the radially inner side of the detonation chamber. Also,
the sidewall injection ports may all be located at the same radial
position relative to (or same radial distance from the center of)
the RDE, detonation chamber, or other cylindrical (or other
symmetrical closed-shape) component of the RDE. It may also be
noted that, as illustrated in FIGS. 14A and 14B, the sidewall
injection ports (e.g., 1424A or 1424B) may all be angled or
effectively angled at an angle greater than 0.degree. and less than
90.degree. relative to the sidewall of the detonation chamber, and
may all have a curvature or an effective curvature greater than the
curvature of the sidewall of the detonation chamber (it will be
understood that various equivalent formulations of these
descriptions, along the lines described above, may be stated).
Also, the sidewall injection ports may all be angled or effectively
angled at the same angle, and may all have the same curvature or
effective curvature. While FIGS. 14A and 14B show detonation
chambers 1402A and 1402B configured for travel of the detonation
wave in the clockwise direction, it will be understood that, where
the detonation chamber is configured for travel of the detonation
wave in the counterclockwise direction, the orientation (angles,
curvatures) of the sidewall injection ports may be modified
accordingly. It will be understand that, in such case, the
descriptions of the sidewall injection ports given here in terms of
the language "at an angle greater than 0.degree. and less than
90.degree. relative to the sidewall of the detonation chamber"
would still apply.
[0122] A seventh set of embodiments provides for use of a fluidic
valve in an RDE. In some of these embodiments, a fluidic valve is
coupled to an injector of the RDE. In others of these embodiments,
a fluidic valve and a premixing chamber are combined as a single
element of an RDE.
[0123] The use of a fluidic valve to reduce the interruption time
of an injector in a high-frequency detonation application was
proposed in "Experimental Study of a High-Frequency Fluidic Valve
Fuel Injector" by E. M. Braun, T. S. Balcazar, D. R. Wilson, and F.
K. Lu (Journal of Propulsion and Power, 28(5):1121-1125, 2012).
Additional description of fluidic valves can be found in U.S.
Provisional Patent Application No. 61/513,484 by Braun et al. filed
on Jul. 29, 2011. Both this article and this provisional patent
application are hereby incorporated herein by reference.
[0124] One of the characteristics of an RDE is the region behind
the detonation wave for which the detonation chamber pressure is
greater than the injector plenum pressure. It is beneficial to
reduce the length of this region as much as possible, so as to
limit backflow from the detonation chamber into the injectors. Such
backflow interrupts injection and accordingly reduces the frequency
of injection and hence the frequency of operation of the RDE. A
fluidic valve may serve to mitigate this backflow and to increase
the propellant mass flow per cycle. A fluidic valve generally has
no moving parts and operates by using the natural behavior of the
fluid based on the principles of fluid dynamics that govern fluid
flow, in contrast to a mechanical or other valve that has moving
parts.
[0125] In some embodiments, separate fluidic valves may be coupled
to each of the fuel and oxidizer flows, e.g., just downstream of
the initial injection of fuel and oxidizer in the head mount. In
other embodiments, fluidic valves may be coupled to an upstream
premixing chamber to receive therefrom premixed (combined fuel and
oxidizer) flow. In still other embodiments, as illustrated in FIGS.
7C and 7F (described below), the fluidic valve and premixing
chamber are combined into a single element. In these embodiments,
fuel and oxidizer are each injected at several points around the
annulus, and the complex flow dynamics inside the injector are
harnessed to enhance propellant mixing. Combining the fluidic valve
and the premixing chamber into a single element (thereby
eliminating the need for a separate premixing chamber) decreases
the overall size and weight of the RDE, which aids practical
operational utility.
[0126] As seen in FIG. 7C, injectors for fuel and/or oxidizer
(propellant injection holes 714) are provided in head mount 703
(FIG. 7A), and the propellants entering these injectors 714 flow
out of them into a combined fluidic valve and premixing chamber 712
immediately downstream of and in fluid communication with the
injectors 714. As further seen in FIG. 7C, the fluidic
valve-premixing chamber 712 is configured as an annular channel or
recess formed in the rear (downstream) face of head mount 703; the
annular channel is rather deep relative to the total depth
(longitudinal extent) of head mount 703. While FIG. 7C offers a
three-dimensional perspective view of the fluidic valve-premixing
chamber 712, FIG. 7F shows a longitudinal cross-sectional view of
the fluidic valve-premixing chamber 712. As also seen in FIG. 7F,
the outflow from the fluidic valve-premixing chamber 712 flows
downstream into the injector plate 704 (injector plate 704 is shown
also in FIGS. 7A, 7E and 13). Accordingly, this arrangement may be
understood to contain different stages of injectors/injection, as
described above. First, fuel and oxidizer is injected into head
mount 703 by injectors (propellant injection holes 714, FIG. 7C).
Then, the fuel and oxidizer flow from these injectors 714 into the
fluidic valve-premixing chamber 712, where they are mixed. Finally,
the premixed combination of fuel and oxidizer flows into the
injection ports 704-H in the injector plate 704 and from there into
the detonation chamber 702. To describe the operation of the
fluidic valve-premixing chamber 712 in more detail, it is noted
that the fluidic valve-premixing chamber 712 may have a generally
rectangular cross-section plenum cavity which, as indicated, is
disposed between the detonation chamber 702 and the injectors 714.
The configuration of the fluidic valve-premixing chamber 712 is
further characterized in that its cross-sectional area increases
suddenly shortly downstream of the injectors 714. This sudden
increase in area attenuates the shock wave entering the cavity,
allowing the supply pressure of the propellants (mixed fuel and
oxidizer) to more quickly push the contact surface between
combustion products and propellants back out of the igniters and
refuel the RDE.
[0127] In the following, alternate descriptions of some of the
embodiments and aspects of the seventh set of embodiments are
presented.
[0128] According to a first given embodiment, an RDE may comprise a
detonation chamber configured to allow continuous detonation
therein of a mixture of fuel and oxidizer, and a fluidic valve
upstream of the detonation chamber, configured to convey at least
one of the fuel and the oxidizer into the detonation chamber. (The
at least one of the fuel and the oxidizer need not be conveyed
directly into the detonation chamber; that is, the at least one of
the fuel and the oxidizer may be convey from the fluidic valve via
another element (e.g., injection ports 704-H) into the detonation
chamber.)
[0129] The RDE according to the first given embodiment may further
comprise a plurality of injection ports (e.g., 704-H) (a) disposed
downstream of the fluidic valve and upstream of the detonation
chamber, and (b) configured for receiving at least one of the fuel
and the oxidizer from the fluidic valve and injecting at least one
of the fuel and the oxidizer into the detonation chamber.
[0130] The RDE according to the first given embodiment may further
comprise a plurality of injectors (e.g., 714) (a) disposed upstream
of the fluidic valve, and (b) configured for conveying at least one
of the fuel and the oxidizer into the fluidic valve.
[0131] In the RDE according to the first given embodiment, the
fluidic valve may function also as a premixing chamber for mixing
the fuel and the oxidizer prior to injection of the fuel and the
oxidizer into the detonation chamber.
[0132] In the RDE according to the first given embodiment, the
fluidic valve may be configured as an annular channel formed in a
structure (e.g., head mount 703) upstream of the detonation
chamber.
[0133] In the RDE according to the first given embodiment, the
fluidic valve may comprise (a) an upstream portion and (b) a
downstream portion disposed downstream of the upstream portion, and
the fluidic valve may be configured such that a cross-sectional
area of the downstream portion exceeds a cross-sectional area of
the upstream portion. Put in other words, as the fluidic valve
extends (in the) downstream (direction), the cross-sectional area
of the fluidic valve may increase. This increase may be sudden as
described above.
[0134] The RDE according to the first given embodiment may be
characterized by any one or more of the above descriptions.
[0135] While the illustrations of the seventh set of embodiments
show axial injection, it is also possible to use sidewall injection
with a fluidic valve.
[0136] The specific configurations and arrangements of fluidic
valves described and illustrated here are just examples; many
different configurations and arrangements are possible.
[0137] According to an eighth set of embodiments, an RDE is
provided with flow turning vanes at or near the exit plane of the
RDE. (The language "at or near the exit plane of the RDE" should be
understood to encompass both cases where the flow turning vanes are
within the RDE and those where the flow turning vanes are outside
e.g., downstream, of the RDE, as described below.) Since the
detonation wave travels in a circumferential direction in the
detonation chamber, it is understood that there may be a degree of
swirl (that is, flow in a direction other than the axial direction)
in the exit flow (that is, the flow that exits the downstream end
of the RDE). This is particularly true if swirled injection (e.g.,
as described above in sixth set of the embodiments) is used. As a
component of velocity not aligned with the RDE axis, swirl
represents a potentially significant reduction in performance. In
addition, conservation of angular momentum dictates that any swirl
present in the exit flow will cause a force (torque) on the RDE
opposing the thrust. This torque also affects in many ways the
design of systems to which the RDE is mounted.
[0138] To counteract the effect of this unwanted torque and to
reduce the afore-mentioned performance loss, flow turning vanes can
be installed at or near the exit plane of the RDE to de-swirl the
exhaust flow, that is, to change the direction of the exit flow to
a direction more aligned with the axial direction. Put in other
words, the flow turning vanes may reduce a component of the flow
velocity that is not in the axial direction. These vanes can be
fixed in position or adjustable (movable, repositionable), with the
latter providing greater operational flexibility. For example, with
adjustable vanes, the orientation or angle of the vane (e.g.,
relative to the longitudinal axis of the RDE) could be varied so as
to appropriately compensate for the particular swirl angle, as the
swirl angle of the flow may vary over time, over different
operating conditions, over different injection port configurations
(e.g., injection port angle; injection port location (sidewall
versus axial)), etc. In addition, these flow turning vanes can be
used as thrust vectoring devices (see tenth set of embodiments,
below), particularly if adjustable and if independently
controllable.
[0139] FIG. 15 shows an example configuration of fixed position
flow turning vanes 1540 installed in an RDE 1500. Except for vanes
1540, RDE 1500 is the same as RDE 700 depicted in FIG. 7A, but RDE
1500 is assembled, not exploded, and in FIG. 15 the housing 708 and
associated elements have been removed in order to show the vanes
1540. As illustrated in FIG. 15, the flow turning vanes 1540 may be
mounted on the outer surfaces of centerbody outer shell 710-SO and
centerbody endcap 710-E, hence inside the detonation chamber 702
(see FIGS. 7F and 7G), at the downstream end thereof. The
configuration/shape, orientation, position, and arrangement of
vanes 1540 may vary from what is illustrated. For example, vanes
1540 may be flat plates, curved airfoil shapes, or other
configurations. Vanes 1540 may also be located outside of the RDE
1500, downstream of the RDE 1500, e.g., immediately downstream of
the exit so that the exhaust flow leaves the detonation chamber 702
and directly encounters the flow turning vanes 1540. In terms of
FIG. 15, where the flow heading toward the exit has a component in
the clockwise circumferential direction, when the flow strikes the
flow turning vanes 1540, the vanes 1540 will serve to deflect the
flow to a more axial direction. In some embodiments, in addition to
or instead of flow turning vanes, where angled injection ports
(sixth set of embodiments) are used, the angle of the injection
ports can be adjusted to affect or limit the swirl of the exit
flow.
[0140] According to a ninth set of embodiments, there is provided
an arrangement (RDE system) comprising multiple concentric (or
nested) RDEs/detonation chambers. The annular configuration of an
RDE lends itself to arrangements of multiple concentric RDEs or
detonation chambers. For example, one or more smaller RDEs (or
detonation chambers) could be fitted inside the centerbody inner
shell 710-SI (FIG. 7A) of RDE 700, with all of the RDEs being
concentric. In this way, the otherwise empty and unused radially
interior region inside centerbody inner shell 710-SI could be
filled with one or more additional RDE/detonation chamber(s),
providing additional thrust, power, etc. in an engine of the same
volume. As described here in the ninth set of embodiments, multiple
concentric RDEs/detonation chambers may be used in airbreathing
modes and/or conventional rocket modes.
[0141] FIGS. 16A and 16B illustrate an example arrangement of
multiple concentric annular RDEs. FIG. 16A is a longitudinal
cross-sectional view extending the length of the engine, while FIG.
16B is an axial cross-sectional view, the cross section taken at a
position downstream of the injector ports and upstream of the
aerospike nozzles. As seen in FIG. 16A, the engine 1600 includes
(in order from upstream to downstream, i.e., going from left to
right in the figure), a propellant inlet 1614 for propellant
injection, a propellant manifold 1612, which could serve as a
premixing chamber, injector ports 1604-H, detonation chambers 1602,
and toroidal aerospike nozzles 1613-N at the exhaust end or exit.
While in this depiction, each annular detonation chamber 1602 is
equipped with a partial aerospike (plug) nozzle 1613-N, the entire
nozzle configuration need not be so restricted For example, in some
other embodiments, the concentric RDEs/detonation chambers may
exhaust into a common bell nozzle. While FIGS. 16A and 16B show an
engine 1600 having three concentric RDEs/detonation chambers 1602,
there is no theoretical upper limit to the number of concentric
RDEs/detonation chambers that may be mounted concentrically,
although practical considerations may impose an upper limit.
[0142] Again, as mentioned in describing other embodiments, the
RDEs or detonation chambers need not be annular (circular). It is
sufficient if they have a curved closed shape, e.g., any generally
rounded or curved shape that is closed, such as a ring, loop, or
sleeve, whether it be circular, oval, elliptical, or another
generally curved shape, and regardless of whether or not the shape
is uniform or regular along its perimeter. Further, the curved
closed shape need not be continuously curved; it may be partly
curved and partly not curved (e.g., partly straight), e.g., a
partial (e.g., half) annulus whose two ends are connected by a
straight portion; or two parallel straight portions connected by
two half-annuli, as shown in FIG. 17. As long as multiple
RDEs/detonation chambers have substantially the same closed curved
shape (whether continuously curved or not), they may be efficiently
nested concentrically to form an engine containing multiple
RDEs/detonation chambers. FIG. 17 shows an example of an engine
1700 including three concentric RDEs/detonation chambers 1702.
[0143] A tenth set of embodiments provides various arrangements to
achieve thrust vectoring, which is changing the direction of the
thrust. Thrust vectoring can be used, e.g., to steer or turn a
vehicle (e.g., aircraft, spacecraft, ship) that is powered by the
RDE. Thrust vectoring can also serve to counteract undesired torque
generated due to the swirl of the exit flow.
[0144] FIG. 18 illustrates an arrangement for achieving thrust
vectoring. Specifically, FIG. 18 shows an RDE 1800 including a main
engine (primary detonation chamber) 1850 and multiple subengines
(smaller, secondary detonation chambers) 1860 housed within the
annular central region (e.g., within centerbody inner shell
1810-SI) of the main engine 1850. While four subengines 1860 are
shown, another number of subengines could be used. In some
embodiments, RDE 1800 includes only the subengines 1860, without a
main engine 1850. While FIG. 18 shows the subengines 1860 arranged
parallel to the centerline (cylindrical/longitudinal axis) of the
main engine 1850, this is not required and other arrangements are
possible. For example, subengines 1850 may be canted or angled
relative to the centerline.
[0145] Since each subengine 1860 is located in a position that is
not centered/symmetric about the centerline of engine 1850/RDE
1800, each subengine 1860 will produce off-centerline thrust (which
may also be referred to as offline thrust). In operation, thrust
vectoring may be achieved by generating different thrusts in one or
more of the subengines 1860 (if the same thrust were generated in
all of the subengines 1860, thrust vectoring would not be
achieved). For example, increasing (or decreasing) the thrust in
any one subengine 1860, relative to the others, would produce
off-centerline thrust. Changing the thrust in a given subengine
1860 may be achieved in different ways, e.g., by changing the
equivalence ratio or fuel-to-oxidizer ratio, or by changing the
injection pressure, in that subengine 1860. Accordingly, the
injection system (valving, timing mechanisms, etc.) of each one of
the primary engine 1850 and the secondary engines 1860 may be
individually controllable. Thus, RDE 1800 may have a primary
injection means for the primary detonation chamber 1850 and
respective secondary injection means for each of the secondary
detonation chambers 1860, such that the primary and multiple
respective secondary injection means are collectively configured to
permit the primary detonation chamber and each of the secondary
detonation chambers to be independently controlled. For example,
the primary injection means may be configured to permit the primary
detonation chamber to be controlled independently of the secondary
detonation chambers, and each of the secondary injection means may
be configured to permit the respective secondary detonation chamber
to be controlled independently of the primary detonation chamber
and independently of the other secondary detonation chambers. In
various embodiments, RDE 1800 may be provided with one or more of
various other features (components or functionalities of an
apparatus or method of use thereof) that may facilitate the thrust
vectoring described here, which is achieved by generating different
thrusts in one or more subengines 1860. One example of such a
feature would be separate pressurization and/or pumping systems,
configured to adjust the chamber pressure inside each subengine
1860, so that the chamber pressure of each subengine 1860 may be
individually controlled, independently of the other subengines
1860. Another example of such a feature would be the use of
multiple different propellants for different engines/subengines,
for example, a large engine could use a low-detonability fuel
(e.g., propane), and the smaller engines could use a
higher-detonability one (e.g., hydrogen).
[0146] If a subengine 1860 is canted or angled relative to the
centerline of the main engine 1850/RDE 1800, that in itself would
cause the thrust generated by that subengine 1860 to have a
component directed at an angle relative to the centerline. This may
be used to enhance thrust vectoring and/or provide for
redundancy.
[0147] Thrust vectoring, or generating offline thrust, reduces the
aerodynamic load on selected control surfaces of the vehicle being
powered. This allows the vehicle to turn more tightly (smaller
turning radius) than it would otherwise be able to, or to effect
the same degree of directional control while using smaller, lighter
control surfaces (or in some cases without certain control
surfaces).
[0148] Flow turning vanes (eighth set of embodiments, discussed
above) may also be used to achieve thrust vectoring, inasmuch as
these vanes can change the direction of the exit flow. While flow
turning vanes can be used to de-swirl the exhaust flow, e.g., so as
to align the flow with the centerline (as discussed above in the
eighth set of embodiments), flow turning vanes can also be used to
change the direction of the flow so that it is not aligned with the
centerline (e.g., so that it is directed at an angle relative to
the centerline).
[0149] In some embodiments, RDE 1800 may have counter-rotating
multiple subengines 1860. That is, for example, RDE 1800 could have
a total of two subengines 1860, one in which the detonation flow
rotates in a clockwise direction, and another in which the
detonation flow rotates in a counterclockwise direction. These two
subengines 1860 would thus generate torque in directions opposite
to one another. Thus, the torque generated by the first subengine
1860 would tend to counteract the torque generated by the second
subengine 1860. The respective torques produced by the two
subengines 1860 would tend to cancel each other out, and thus to
eliminate the undesired torque altogether and its negative effect
on performance. Variations of this arrangement are possible. For
example, the number of subengines 1860 may be varied. The
subengines could be arranged side by side or concentrically.
[0150] As noted below, any embodiment referenced herein is freely
combinable with any one or more of the other embodiments referenced
herein, and any number of features of different embodiments is
combinable with one another, unless indicated otherwise or so
dictated by the description herein. One example of combining
embodiments is a combination of the second set of embodiments
(using the engine core or centerbody region of the RDE for active
cooling of the radially inner annular wall of the detonation
chamber) and the ninth set of embodiments (multiple concentric
RDEs). In such a combination, one or more concentric RDEs may be
contained within the centerbody region of the main or outermost
RDE, and the coolant channel, comprising coolant supply and coolant
return channels, may cool both the outermost RDE and the inner
RDE(s). Another example of combining embodiments is a combination
of the second set of embodiments and the tenth set of embodiments
(thrust vectoring using, e.g., a main engine and a plurality of
subengines). In such a combination, one or more subengines may be
contained within the centerbody region of the main or outermost
RDE, and the coolant channel, comprising coolant supply and coolant
return channels, may cool both the outermost RDE and the
subengines.
[0151] With regard to the second, ninth and tenth sets of
embodiments, the instant inventors understand that the centerbody
of the RDE has not heretofore been used to house such functional
components (i.e., coolant channels, concentric engines, or
subengines). Conventionally, RDEs have not been built large enough
to feasibly accommodate such functional components within the
centerbody. With regard to the eighth set of embodiments (flow
turning vanes, to counteract swirl in the exit flow), it will be
understood that past research has not definitively determined
whether swirl exists in the exit flow of an RDE. Accordingly, the
underlying problem of exit swirl, and hence the need for a
solution, has not necessarily been appreciated.
[0152] In light of the principles and example embodiments described
and illustrated herein, it will be recognized that the example
embodiments can be modified in arrangement and detail without
departing from such principles. Also, the foregoing discussion has
focused on particular embodiments, but other configurations are
also contemplated. In particular, even though expressions such as
"in one embodiment," "in another embodiment," or the like are used
herein, these phrases are meant to generally reference embodiment
possibilities, and are not intended to limit the invention to
particular embodiment configurations. As used herein, these terms
may reference the same or different embodiments that are combinable
into other embodiments. As a rule, any embodiment referenced herein
is freely combinable with any one or more of the other embodiments
referenced herein, and any number of features of different
embodiments is combinable with one another, unless indicated
otherwise or so dictated by the description herein.
[0153] Similarly, although example processes have been described
with regard to particular operations performed in a particular
sequence, numerous modifications could be applied to those
processes to derive numerous alternative embodiments of the present
invention. For example, alternative embodiments may include
processes that use fewer than all of the disclosed operations,
processes that use additional operations, and processes in which
the individual operations disclosed herein are combined,
subdivided, rearranged (including, e.g., steps re-ordered), or
otherwise altered.
[0154] This disclosure may include descriptions of various benefits
and advantages that may be provided by various embodiments. One,
some, all, or different benefits or advantages may be provided by
different embodiments.
[0155] In view of the wide variety of useful permutations that may
be readily derived from the example embodiments described herein,
this detailed description is intended to be illustrative only, and
should not be taken as limiting the scope of the invention. What is
claimed as the invention, therefore, are all implementations that
come within the scope of the following claims, and all equivalents
to such implementations.
* * * * *
References