U.S. patent application number 11/333691 was filed with the patent office on 2009-07-09 for piezo-resonance igniter and ignition method for propellant liquid rocket engine.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Mark D. Horn, Thomas M. Walczuk.
Application Number | 20090173321 11/333691 |
Document ID | / |
Family ID | 40843582 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090173321 |
Kind Code |
A1 |
Horn; Mark D. ; et
al. |
July 9, 2009 |
PIEZO-RESONANCE IGNITER AND IGNITION METHOD FOR PROPELLANT LIQUID
ROCKET ENGINE
Abstract
An ignition system for a rocket engine utilizes the pressure
energy in a propellant flow. The propellant flow generates an
oscillating pressure force in a resonance system which is then
transmitted to a piezoelectric system. The electrical pulses are
utilized to generate a spark in an igniter system spark gap,
resulting in ignition. Since the spark energy production is driven
by the resonance of the propellant flow, a fully passive
auto-ignition system is provided. Once ignition occurs, the
resultant backpressure in the combustion chamber "detunes" the
resonance phenomena and spark production stops. Furthermore, should
the engine flame out, spark production would automatically resume
as the propellant valves remain open thereby providing relight
capability.
Inventors: |
Horn; Mark D.; (Granada
Hills, CA) ; Walczuk; Thomas M.; (Oak Park,
CA) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Assignee: |
United Technologies
Corporation
|
Family ID: |
40843582 |
Appl. No.: |
11/333691 |
Filed: |
January 17, 2006 |
Current U.S.
Class: |
123/642 |
Current CPC
Class: |
F02P 15/003 20130101;
F02K 9/95 20130101; F02P 3/12 20130101 |
Class at
Publication: |
123/642 |
International
Class: |
F02P 3/12 20060101
F02P003/12 |
Claims
1. An ignition system for a combustor comprising: a resonance
system; a piezoelectric system driven by said resonance system; and
an igniter powered by said piezoelectric system.
2. The ignition system as recited in claim 1, wherein said
resonance system is in communication with said piezoelectric system
through a gas resonance tube.
3. The ignition system as recited in claim 2, further comprising a
working fluid inlet to said resonance system, said working fluid
inlet generally opposite said gas resonance tube.
4. The ignition system as recited in claim 3, wherein said working
fluid is a gas.
5. The ignition system as recited in claim 4, wherein said working
fluid is an inert pressurant.
6. The ignition system as recited in claim 4, wherein said working
fluid is GOx.
7. The ignition system as recited in claim 3, wherein said working
fluid is an incompressible fluid.
8. The ignition system as recited in claim 2, wherein said gas
resonance tube is sealed with a force transmission diaphragm.
9. The ignition system as recited in claim 8, wherein said force
transmission diaphragm includes a relief feature, said force
transfer member contacts said force transmission diaphragm within
said relief feature.
10. The ignition system as recited in claim 8, further comprising a
force transfer member in contact with said force transmission
diaphragm.
11. The ignition system as recited in claim 10, wherein said force
transfer member includes a force transfer rod and a force transfer
platen, said force transfer platen in contact with said force
transmission diaphragm.
12. The ignition system as recited in claim 11, wherein said force
transfer platen is of a larger diameter than said force transfer
rod and the force transfer diaphragm is of larger diameter than
resonance tube.
13. The ignition system as recited in claim 11, wherein said force
transfer rod is in contact with a piezoelectric crystal stack.
14. The ignition system as recited in claim 13, wherein said
piezoelectric crystal stack is in electrical communication with
said igniter.
15. The ignition system as recited in claim 10, wherein said force
transfer member includes a frustro-conical member.
16. The ignition system as recited in claim 8, further comprising a
relieved area adjacent said force transfer diaphragm adjacent an
end of said gas resonance tube.
17. A combustor device comprising: a combustor; a working fluid
system in communication with said combustor; a resonance system in
communication with said working fluid system; a piezoelectric
system driven by said resonance system; and an igniter system
powered by said piezoelectric system to ignite a working fluid from
said working fluid system.
18. The combustor device as recited in claim 17, further
comprising: a force transfer member in communication with said
resonance system, said force transfer member driven by an
oscillating pressure force within said resonance system; a force
transmission diaphragm in contact with said force transfer member;
and a piezoelectric crystal stack in contact with said force
transfer member.
19. The combustor device as recited in claim 18, wherein said
piezoelectric system includes a force transfer member in
communication with said resonance system, said force transfer
member including a frustro-conical member.
20. The combustor device as recited in claim 17, wherein said
igniter system includes an electrode in direct communication with
combustor.
21. The combustor device as recited in claim 17, wherein said
resonance system includes a resonance cavity in communication with
said working fluid.
22. The combustor device as recited in claim 17, wherein said
resonance system includes a split leg fluidic resonator.
23. A method of igniting a combustion device comprising the steps
of: (A) communicating a working fluid to a resonance system to
generate a resonance; (B) driving a piezoelectric system with the
resonance generated in said step (A); and (C) powering an igniter
with the piezoelectric system.
24. A method as recited in claim 23, wherein said step (B) further
comprises: (a) driving a force transmission diaphragm with the
resonance; (b) driving a force transfer member in contact with the
force transmission diaphragm; and (c) driving a piezoelectric
crystal stack with the force transfer member.
25. A method as recited in claim 23, further comprising the step
of: (D) detuning the resonance in response to ignition of the
combustion device to deactivate the igniter.
26. The ignition system as recited in claim 1, wherein said
resonance system communicates an oscillating pressure into a gas
resonance tube.
27. The ignition system as recited in claim 26, wherein said force
transmission diaphragm seals said gas resonance tube, said force
transmission diaphragm operable to react pressure loads from said
oscillating pressure in said gas resonance tube.
28. The combustor device as recited in claim 17, wherein said
combustor is a thrust chamber assembly combustor.
29. The combustor device as recited in claim 17, wherein said
resonance system communicates an oscillating pressure into a gas
resonance tube.
30. The combustor device as recited in claim 29, wherein said force
transmission diaphragm seals said gas resonance tube, said force
transmission diaphragm operable to react pressure loads from said
oscillating pressure in said gas resonance tube.
31. The ignition system as recited in claim 1, wherein said
resonance system is in communication with said piezoelectric system
through a gas resonance tube, an oscillation pressure caused by a
resonant flow interaction between a jet flow into said gas
resonance tube.
32. The ignition system as recited in claim 1, wherein said
resonance system generates an oscillation pressure force by a
resonant flow interaction between two parallel interconnected flow
passages which carry an incompressible flow.
33. The ignition system as recited in claim 32, wherein said two
parallel interconnected flow passages are separated by a split leg
resonator having a first leg and a second leg which form a
generally triangular relationship.
34. The ignition system as recited in claim 33, wherein a gas
resonance tube is in communication with said first leg of said
split leg resonator to generate said oscillating pressure force
within said gas resonance tube.
35. The ignition system as recited in claim 34, wherein said gas
resonance tube is sealed with a force transmission diaphragm, a
force transfer member in contact with said force transmission
diaphragm.
36. The ignition system as recited in claim 35, wherein said force
transfer member includes a force transfer rod and a force transfer
platen, said force transfer platen in contact with said force
transmission diaphragm.
37. The ignition system as recited in claim 36, wherein said force
transfer platen is of a larger diameter than said force transfer
rod and the force transfer diaphragm is of larger diameter than
said resonance tube.
38. The ignition system as recited in claim 37 wherein said force
transfer rod is in contact with a piezoelectric crystal stack of
said piezoelectric system.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a piezo-resonance igniter
system for passive auto ignition of a rocket engine, and more
particularly to a method which utilizes the pressure energy in the
propellants themselves to excite piezoelectric crystals such that
high voltage electrical pulses are created to generate a spark in
an igniter system.
[0002] Various conventional ignition systems have been used for
ignition of a propellant mixture in a combustion chamber of a
rocket engine. These ignition systems generally employed a spark
induced by an electrical current from a source of electricity and a
control for sensing when to supply and discontinue the spark. These
conventional systems, although effective, tend to be relatively
complex, heavy, and may not provide restart capability.
[0003] With the increasing need for safe storable propellant
systems such as Gaseous Oxygen (GOx) and Methane combinations, an
uncomplicated fully passive auto ignition system is desired to
complement the advantages of the safe storable propellants by
reducing ignition system complexity, weight, and cost while
increasing safety and reliability.
[0004] Accordingly, it is desirable to provide an uncomplicated,
lightweight passive auto ignition system with restart capability
that eliminates separate spark exciter electronics, vehicle
electrical power requirements for ignition and ignition control and
monitoring systems.
SUMMARY OF THE INVENTION
[0005] The ignition system according to the present invention
generally includes a resonance system in communication with a
propellant system, a piezoelectric system, and an electrical
conditioning system to power an igniter and ignite a propellant
flow. The resonance system is in communication with the
piezoelectric system through a gas resonance tube which is sealed
with a force transmission diaphragm. A force transfer member
increases the surface area in contact with the force transmission
diaphragm to react pressure loads from an oscillating flow within
the resonance tube. The sizing of the diaphragm allows the
resonance pressure pulses to act over a relatively large effective
area to increase a net force output for a given resonance gas
resonance tube diameter and supply pressure.
[0006] The oscillating pressure force from the oscillating flow is
transmitted to the piezoelectric crystal stack to generate
electrical pulses and power the ignition system. The oscillating
force can provide for direct spark ignition in which each pressure
pulse results in a spark. Alternatively, the electrical pulses
generated may be stored then metered out at various schedules to
provide the desired spark repetition rate and spark power per
pulse.
[0007] Since the spark energy production is driven by the resonance
of the propellant flow, a passive auto-ignition system is provided.
When the propellant valves are opened, flow through the resonance
system is such that resonance occurs and spark energy is generated.
Once ignition occurs, the resultant backpressure in the combustion
chamber reduces the pressure drop across the resonance system and
"detunes" the resonance phenomena, such that spark production
stops. Furthermore, should the engine flame out causing combustion
chamber pressure to drop again, spark production automatically
resumes as long as the propellant valves remain open. Control and
operation of the rocket engine is considerably simplified through
elimination of the heretofore necessity of an electrical power
supply and separate switching commands and monitoring of the
ignition system such that the otherwise typical uncertainties in
setting spark timing and duration are obviated. Significant
advantages are thereby provided for distributed multi-thruster
systems, such as an Attitude Control System (ACS), where the
characteristics of a conventional ignition system are multiplied by
a significant number of thrusters.
[0008] The present invention therefore provides an uncomplicated,
lightweight passive auto ignition system with restart capability
that eliminates separate spark exciter electronics and switching
command systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The various features and advantages of this invention will
become apparent to those skilled in the art from the following
detailed description of the currently preferred embodiment. The
drawings that accompany the detailed description can be briefly
described as follows:
[0010] FIG. 1 is a general perspective view an exemplary of rocket
engine embodiment for use with the present invention;
[0011] FIG. 2A is a schematic view of an ignition system of the
present invention;
[0012] FIG. 2B is an expanded view of the ignition system
components illustrated in FIG. 2A;
[0013] FIG. 3 is a schematic view of a flight ready ignition system
of the present invention with an indirect piezo-resonance
module;
[0014] FIG. 4 is a schematic view of a flight ready piezo-resonance
module ignition system of the present invention utilizing a direct
spark torch approach mounted directly within a combustion chamber;
and
[0015] FIG. 5 is a schematic view of a flight ready piezo-resonance
module ignition system of the present invention for use with an
incompressible fluid flow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] FIG. 1 illustrates a general schematic view of a rocket
engine 10. The engine 10 generally includes a thrust chamber
assembly 12, a fuel system 14, an oxidizer system 16 and an
ignition system 18. The fuel system 14 and the oxidizer system 16
preferably provide a gaseous propellant system of the rocket engine
10, however, other propellant systems such as liquid will also be
usable with the present invention.
[0017] A combustion chamber wall 20 about a thrust axis A defines
the nozzle assembly 12. The combustion chamber wall 20 defines a
thrust chamber 22, a combustion chamber 24 upstream of the thrust
chamber 22, and a combustion chamber throat 26 therebetween. The
thrust chamber assembly 12 includes an injector 12A with an
injector face 28 which contains a multitude of fuel/oxidizer
injector elements 30 (shown somewhat schematically) which receive
fuel which passes first through the fuel cooled combustion chamber
wall 20 fed via fuel supply line 14a of the fuel system 14 and an
oxidizer such as Gaseous Oxygen (GOx) through an oxidizer supply
line 16a of the oxidizer system 16.
[0018] The ignition system 18 generally includes a resonance system
36 in communication with one of the propellants such as the
oxidizer system 16, a piezoelectric system 38, and an electrical
conditioning system 40 to power an igniter 42 mounted within the
injector 12A to ignite the fuel/oxidizer propellant flow from the
fuel/oxidizer injector elements 30. The oxidizer is fed to the
igniter via a dedicated line 16b in this embodiment, and the fuel
is also fed to the igniter torch via a dedicated line 14b. It
should be understood that various propellant flow paths may be
usable with the present invention so long as at least one
propellant flow is in communication with the resonance system 36.
Ignition of the fuel/oxidizer propellant flow from the
fuel/oxidizer injector elements 30 with the igniter 42 is
conventional and need not be described in further detail herein. It
should also be understood that while the current focus of this
invention is a rocket ignition, other applications for power
generation and ignition of other combustion based devices will also
be usable with the present invention.
[0019] Referring to FIG. 2A, one ignition system 18 includes a
housing 32 which defines a resonance cavity 44 having an inlet 34
incorporating a supersonic inlet nozzle 46 to receive a flow of
propellant such as the oxidizer from the oxidizer supply line 16c
of the oxidizer system 16. An outlet 16a from the resonance system
36 includes an outlet nozzle 50 to maintain pressure in the cavity
44 at a predetermined level. Although the illustrated embodiment of
the oxidizer is a gaseous propellant (compressible flow) resonance
configuration, it should be understood that resonant pressure
pulses from incompressible liquid flow as well as from other
propellant sources will likewise be usable with the present
invention.
[0020] The resonance system 36 is in communication with the
piezoelectric system 38 through a gas resonance tube 52. It should
be understood that in FIG. 2A the piezoelectric system 38 is
illustrated in a schematic form in what may be considered a ground
based configuration which may include adjustment features that may
or may not be required. That is, other even less complicated
piezoelectric systems are achievable as illustrated in the
following embodiments.
[0021] The gas resonance tube 52 is located through an opening 54
in the resonance cavity 44 opposite the supersonic inlet nozzle 46.
The oxidizer entering through the supersonic inlet nozzle 46 as
underexpanded flow is directed at the gas resonance tube 52 causing
an oscillating detached shock 56 to form upstream of the entrance
56N to the gas resonance tube 52. Reflected shocks within the gas
resonance tube 52 couple and reinforce the detached shock 56 and
interact with the flow within the gas resonance tube 52 such that
the successive cycles of shocks cause the formation of a series of
unstable zones of elevated pressure within the gas resonance tube
52. Physical criteria for the interaction may be defined by: "d"
the diameter of the supersonic inlet nozzle 46N; "G" the distance
between the inlet nozzle 46N throat and the entrance 56N of the gas
resonance tube 52; "Dtube" the internal diameter of resonance tube
52 and "DMC" which is the throat diameter of the outlet nozzle 50.
A constant diameter resonance tube 52 is depicted; however, it is
understood that stepped, conical or other shaped resonance tubes
may alternatively be utilized with the present invention.
[0022] The gas resonance tube 52 is sealed at an end opposite the
entrance 56N with a force transmission diaphragm 58 (also
illustrated in FIG. 2B). A force transfer member 60 includes a
force transfer rod 62 and a force transfer platen 64 in contact
with the force transmission diaphragm 58. The force transfer platen
64 is of a larger diameter than the force transfer rod 62 so as to
increase the surface area in contact with the force transmission
diaphragm 58 and react pressure loads from the oscillating
pressures in the resonance tube 52. The sizing of the force
transmission diaphragm 58 allows the resonance pressure pulses to
act over a relatively large effective area, increasing the net
force output for a given gas tube 52 diameter (Dtube) and supply
pressure. Flow relief passages 52a (FIG. 2B) may be incorporated
into the mating faces of the resonance tube 52 and the force
transmission diaphragm 58 to increase working fluid transfer across
the face of the force transmission diaphragm 58 during the
relatively short resonant pressure pulses in the resonance tube
52.
[0023] The force transfer rod 62 is received within a guide sleeve
65. The guide sleeve 65 contains a piezoelectric crystal stack 66
mounted in contact with the force transfer rod 62. The oscillating
pressure force in the gas resonance tube 52 is transmitted to the
piezoelectric crystal stack 66 through the force transfer member 60
to generate electrical pulses. The wire harness 67 is connected
directly to the igniter 42, eliminating the electrical conditioning
system 40. The oscillating force drives the direct spark ignition,
in which each pressure pulse results in a spark, offering a
persistent source of ignition.
[0024] Alternatively or in addition thereto, the electrical pulses
are communicated to the igniter 42 through a wire harness 67 and
the electrical conditioning system 40. An energy storage system 68A
(illustrated schematically) such as an electrical capacitor or
battery and a voltage multiplier system 68B (illustrated
schematically) within the electrical condition system 40 conditions
the spark to a desired spark output energy and frequency
independent of the crystal output. This permits the system to be
sized to suit any application. In other words, the electrical
condition system 40 may include various electrical subsystems such
as storage capacitors or voltage amplifiers to specifically tailor
the ignition system to provide various outputs.
[0025] Since the spark energy production is driven by the resonance
of the propellant flow, a fully passive auto-ignition system is
provided. When the propellant valves are open, flow through the
resonance system 36 is such that resonance occurs and spark energy
is created. Once ignition occurs, the resultant backpressure within
the combustion chamber 24 (FIG. 1) "detunes" the resonance
phenomena and spark production stops. Furthermore, should the
engine flame out, spark production automatically resumes as the
propellant valves remain open. Control and operation of the rocket
engine is considerably simplified by the elimination of separate
power supply and switching command systems in the igniter system
such that the heretofore typical uncertainties in the spark
duration control are obviated. This provides significant advantages
for distributed multi-thruster systems, such as an attitude control
system (ACS).
[0026] Referring to FIG. 2B, the force transmission diaphragm 58 is
preferably sandwiched between an end segment 70 of the gas
resonance tube 52 and a diaphragm support ring 72 which may be
welded together through a weld W or other attachment. The force
transmission diaphragm 58 preferably includes a relief feature 74
located between the diaphragm support ring 72 and the force
transfer platen 64. The relief feature 74 is preferably a circular
flexed portion of the force transmission diaphragm 58 within which
the force transfer platen 64 is received. The relief feature 74
minimizes tensile load losses on the force transmission diaphragm
58 thereby enhancing flexibility to maximize transfer of the
oscillating pressure force to the force transfer platen 64 and
thence to the piezoelectric crystal stack 66 through the force
transfer rod 62.
[0027] Applicant has demonstrated relatively short ignition delay
times of approximately 18 mseconds utilizing a gaseous propellant
(compressible flow) resonance configuration. However, multiple
approaches exist to achieve the resonant pressure pulses from
incompressible liquid flow as well such that the present invention
is adaptable to any propellants.
[0028] Referring to FIG. 3, another ignition system 18B is
illustrated. The resonance system 36A includes a more compact
flight-ready piezoelectric system 38A integrated with the resonance
system 36A. Such a system is readily mounted anywhere within the
communicating conduits of a working fluid system such as embodied
by the oxidizer system or fuel system (FIG. 1).
[0029] The piezoelectric system 38A includes an electrical
condition system 90A to remotely power the igniter system 92
(illustrated schematically) mounted within a piezoelectric housing
80. The resonance system 36A includes a resonance housing 82 which
defines the resonance cavity 44 therein. Preferably, the resonance
housing 82 is threaded to the piezoelectric housing 80 to provide
an exceedingly compact and robust system which is readily
maintained.
[0030] A piezoelectric guide sleeve 84 is interfit with an
insulator load reaction interface sleeve 86 and both are mounted
within the piezoelectric housing 80 against a stop 88. The force
transmission diaphragm 58 is preferably sandwiched between and end
segment 82a of the resonance housing 82 which defines the gas
resonance tube 52 and the piezoelectric guide sleeve 84. The force
transmission diaphragm 58 preferably includes a relief feature 74
as illustrated in FIG. 2B.
[0031] A force transfer member 90 is mounted within the
piezoelectric guide sleeve 84 adjacent the force transmission
diaphragm 58. The force transfer member 90 is preferably a
frustro-conical member in which an apex 92 thereof is located in
contact and preferably interfits with the piezoelectric crystal
stack 66. That is, the force transfer member 90 essentially
combines the force transfer rod 62 and a force transfer platen 64
of the above embodiment, however operation is generally equivalent
as the apex 92 is in contact with the piezoelectric crystal stack
66. The oscillating pressure force in the gas resonance tube 52 is
transmitted to the piezoelectric crystal stack 66 through the force
transfer member 90 to generate electrical pulses in an electrode 94
opposite the piezoelectric crystal stack 66. The electrical pulses
from the electrode are communicated to the igniter system 42
through the electrical conditioning system 90A via a wire harness
96. The wire harness preferably terminates in a connector 98 which
permits removable attachment to a spark power cable 99 such that
the system 36A, 38A may be readily replaced during maintenance. As
discussed above, since the spark energy production is driven by the
resonance of the propellant flow, a fully passive auto-ignition
system is provided which is "detuned" when ignition occurs such
that spark production automatically stops.
[0032] Referring to FIG. 4, another ignition system 18c is
illustrated. The resonance system 36B and piezoelectric system 38B
are integrated within a combustion chamber 24B as would be
preferred for a thruster system as each individual thruster system
thereby includes an essentially self-contained ignition system. The
resonance system 36B is preferably defined by a resonance housing
12B which defines the resonance cavity 44 therein. The resonance
housing 12B is attached directly to the injector 12A through
fasteners such as bolts b or the like.
[0033] As the FIG. 4 embodiment generally includes components
common to that of the previous embodiments, consistent reference
numeral usage will be utilized while components more specific to
the FIG. 4 embodiment will be described in detail. It will be
understood that operation of the FIG. 4 embodiment is generally as
the FIG. 3 embodiment, however, the electrode 100 of the FIG. 4
embodiment is mounted to provide a direct spark torch approach.
That is, the electrode directly communicates with the combustion
chamber 24 through the injector face 28 which contains the
multitude of fuel/oxidizer injector elements 30 (shown
schematically) which receive fuel from the fuel cooled combustion
chamber wall 20 which is fed via fuel supply line 19a of the fuel
system 14 and an oxidizer such as Gaseous Oxygen (GOx) through an
oxidizer supply line 36a of the oxidizer system 16 (also
illustrated in FIG. 1).
[0034] The electrode 100 extends through an oxidizer manifold 102
and a fuel manifold 103 to generate a spark within the combustion
chamber 24. The electrode 100 is mounted within an insulator load
reaction interface 104 which extends along a significant length of
the electrode 100. The insulator load reaction interface 104 is
interfit with the piezoelectric guide sleeve 84 and retained within
the injector 12A. A torch housing 106 is defined about the
electrode and the insulator load reaction interface 104 to define a
torch oxidizer feed annulus 108.
[0035] Oxidizer is communicated form the oxidizer manifold 102
through torch oxidizer inlet ports 110 through the torch housing
106. A multitude of fuel injection ports 112 in communication with
the fuel manifold 103 communicate fuel toward the distal end of the
electrode 100. Oxidizer and fuel is thereby injected adjacent a
distal end of the electrode 100 from which the ignition spark is
generated to thereby ignite the mixture within the combustion
chamber 24B. As discussed above, since the spark energy production
is driven by the resonance of the propellant flow, a fully passive
auto-ignition system is provided which is "detuned" when ignition
occurs such that spark production automatically stops.
[0036] Referring to FIG. 5, another ignition system 18D that
utilizes an incompressible working fluid such as a liquid
propellant is illustrated. The resonance system 36C includes an
incompressible fluid resonance housing 120 which defines a
resonance cavity 122 therein. Preferably, the resonance housing 120
includes a threaded portion 120A such that a piezoelectric housing
80 and associated piezoelectric system (as disclosed in FIG. 3) is
threaded thereto. In other words, the piezoelectric housing 80 and
associated piezoelectric system (as disclosed in FIG. 3) is a
common system which may be driven by, for example only, either the
resonance housing 82 illustrated of FIG. 3 or the incompressible
fluid resonance housing 120 illustrated in FIG. 5 to provide an
exceedingly compact and robust system.
[0037] The incompressible fluid resonance housing 120 includes a
split leg resonator 124 having a first leg 126a and a second leg
126b. The legs 126a, 126b split off from an incompressible fluid
inlet 128 and rejoin at a common leg 126c which form a generally
triangular relationship. It should be understood that other paths
will also be usable with the present invention. The common leg 126C
includes an incompressible fluid outlet 132 which is in
communication with a combustion chamber as illustrated in FIG. 1. A
gas resonance tube 130 is in communication with the first leg 126a
of the split leg resonator 124 to generate an oscillating pressure
force within the gas resonance tube 130 due to the unstable flow
oscillations between the parallel flowpaths in legs 126A and 126B.
The oscillating pressure force generated within the gas resonance
tube 130 may then utilized to drive the piezoelectric system as
described above.
[0038] As discussed above, since the spark energy production is
driven by the resonance of the propellant flow, a fully passive
auto-ignition system is provided which is "detuned" when ignition
occurs such that spark production automatically stops.
[0039] It should be understood that relative positional terms such
as "forward," "aft," "upper," "lower," "above," "below," and the
like are with reference to the normal operational attitude of the
vehicle and should not be considered otherwise limiting.
[0040] It should be understood that although a particular component
arrangement is disclosed in the illustrated embodiment, other
arrangements will benefit from the instant invention.
[0041] Although particular step sequences are shown, described, and
claimed, it should be understood that steps may be performed in any
order, separated or combined unless otherwise indicated and will
still benefit from the present invention.
[0042] The foregoing description is exemplary rather than defined
by the limitations within. Many modifications and variations of the
present invention are possible in light of the above teachings. The
preferred embodiments of this invention have been disclosed,
however, one of ordinary skill in the art would recognize that
certain modifications would come within the scope of this
invention. It is, therefore, to be understood that within the scope
of the appended claims, the invention may be practiced otherwise
than as specifically described. For that reason the following
claims should be studied to determine the true scope and content of
this invention.
* * * * *