U.S. patent number 3,685,740 [Application Number 04/872,171] was granted by the patent office on 1972-08-22 for rocket burner with flame pattern control.
This patent grant is currently assigned to Air Reduction Company, Incorporated. Invention is credited to Thomas L. Shepherd.
United States Patent |
3,685,740 |
Shepherd |
August 22, 1972 |
ROCKET BURNER WITH FLAME PATTERN CONTROL
Abstract
An oxygen-fuel burner of the rocker burner type comprising a
cylindrical combustion chamber having an open discharge end and a
burner plate with separate oxygen and fuel ports constituting the
opposite end of the chamber; the projected longitudinal axes of the
oxygen ports extending in converging directions towards the
longitudinal axis of the chamber but in off-set, non-intersecting
relation thereto, so that points on the respective axis that most
closely approach the chamber axis define a transversely positioned
plane between the burner plate and the chamber exhaust; the
projected longitudinal axes of the fuel ports being substantially
parallel to the chamber axis for mixing of oxygen and fuel at and
beyond the plane of closest approach, and means for adjusting the
longitudinal position of the burner plate on the chamber axis and
thereby locating the plane of closet approach in relation to the
chamber exhaust for determining the pattern of the burner discharge
flames.
Inventors: |
Shepherd; Thomas L. (Essex
Fells, NJ) |
Assignee: |
Air Reduction Company,
Incorporated (New York, NY)
|
Family
ID: |
25358989 |
Appl.
No.: |
04/872,171 |
Filed: |
October 29, 1969 |
Current U.S.
Class: |
239/400; 239/424;
431/351; 239/132.3; 239/430; 431/353 |
Current CPC
Class: |
F02K
9/52 (20130101); F23D 14/32 (20130101); F23D
14/78 (20130101) |
Current International
Class: |
F23D
14/72 (20060101); F23D 14/78 (20060101); F23D
14/32 (20060101); F23D 14/00 (20060101); F02K
9/00 (20060101); F02K 9/52 (20060101); B05b
007/10 () |
Field of
Search: |
;239/399,402.5,403,405,432,400,422X,43X,433,428,132.3
;266/34,DIG.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: King; Lloyd L.
Claims
I claim:
1. An oxygen-fuel burner of the rocket-burner type having a
combustion chamber wherein a plurality of oxygen and fuel streams
are fed into one end of the chamber and the opposite end is open
for combustion flame discharge, comprising:
a. means for directing separate streams of fuel into the chamber
and toward the discharge end,
b. means for directing separate streams of oxygen into the chamber
for converging flow, the respective projected axes of the oxygen
streams being in off-set, non-intersecting relation to the
longitudinal axis of the chamber,
c. means for directing a comparatively small amount of the fuel
flow into the converging oxygen flow for establishing a primary
stabilizing combustion region,
d. the diverging oxygen flow beyond the primary combustion region
traversing and mixing with the main amount of the fuel flow for
establishing a secondary combustion region,
e. and means for varying the traversing location of the oxygen and
fuel with respect to the discharge end of the combustion chamber
for controlling the discharge pattern of the secondary combustion
flames.
2. An oxygen-fuel burner as specified in claim 1 wherein the oxygen
and fuel stream directing means consists of a burner plate having a
plurality of ports for the respective streams, and control means
produce relative movement between the burner plate and combustion
chamber along the longitudinal axis of the chamber for varying the
traversing location of the oxygen and fuel.
3. An oxygen-fuel burner as specified in claim 2 wherein the oxygen
ports are radially spaced from the center of the burner plate, and
the projected longitudinal axes thereof are inclined in generally
converging, non-intersecting relation to the longitudinal axis of
the chamber.
4. An oxygen-fuel burner as specified in claim 2 wherein ports for
the main fuel flow are located along the peripheral portion of the
burner plate, and ports for the primary fuel are located centrally
of the burner plate in general alignment with the primary
combustion region.
5. An oxygen-fuel burner as specified in claim 4 wherein the
projected longitudinal axes of the fuel ports are generally
parallel to the longitudinal axis of the chamber.
6. An oxygen-fuel burner as specified in claim 3 wherein the
projected longitudinal axes of the oxygen ports at the respective
points closest to the chamber axis define a transverse plane
determining the location of the primary gas mixing zone.
7. An oxygen-fuel burner as specified in claim 2 wherein the main
fuel streams form a secondary fuel envelope within the combustion
chamber in surrounding relation to the oxygen and primary fuel
streams.
8. An oxygen-fuel burner as specified in claim 7 wherein the
projected axes of the oxygen ports diverge beyond the primary
combustion region toward the side wall of the combustion chamber
for traversing and mixing with the enveloping fuel flow.
9. An oxygen-fuel burner as specified in claim 8 having an adjusted
position of the burner plate representing divergence of the oxygen
port axes beyond the discharge end of the chamber, wherein a
radially expanding flame region is formed for producing short,
spreading flames in a generally mushrooming pattern.
10. An oxygen-fuel burner as specified in claim 8 having an
adjusted position of the burner plate representing intersection of
the diverging axes with the chamber side wall in a comparatively
long combustion chamber, wherein confined mixing and interaction of
the oxygen and fuel streams produce an elongated, needle-type flame
discharge from the combustion chamber.
11. An oxygen-fuel burner of the rocket-burner type having a
combustion chamber wherein a plurality of oxygen and fuel streams
are fed into one end of the chamber and the opposite end is open
for combustion flame discharge, comprising:
a. means for directing separate streams of oxygen into the chamber
for converging flow, the respective projected axes of the oxygen
streams being in off-set, non-intersecting relation to the
longitudinal axis of the chamber,
b. means for directing a portion of the fuel flow into the
converging oxygen flow for establishing a primary stabilizing
combustion region remote from the feed end of the chamber,
c. and means for directing the main portion of fuel flow along the
chamber wall so as to envelop the oxygen streams and primary
combustion region,
d. the diverging oxygen streams beyond the primary combustion
region traversing and mixing with the fuel envelope for
establishing a secondary combustion region.
12. An oxygen-fuel burner comprising housing means having a
discharge end for projecting an oxy-fuel flame, a burner element in
said housing means, said element including a plurality of fuel gas
ports for projecting a plurality of streams of fuel gas from said
element, said element further including a plurality of oxygen ports
for projecting separate streams of oxygen for converging flow about
a longitudinal axis, the respective projected axes of the said
oxygen ports being in off-set, non-intersecting relation with
respect to the longitudinal axis, certain of the fuel gas ports
being positioned centrally with respect to the oxygen ports for
establishing with said oxygen streams a primary stabilizing
combustion region, other of said fuel gas ports being positioned to
form a fuel gas envelope surrounding the oxygen streams.
13. A burner as set forth in claim 12, further including means to
adjust the position of said burner element relative to the
discharge end of the burner.
14. A burner as set forth in claim 12, wherein the longitudinal
axis of each certain fuel gas port intersects with the projected
axis of a respective oxygen port for insuring mixing of the
respective streams.
15. A burner as set forth in claim 12, wherein the oxygen ports
form a vortex about said longitudinal axis.
Description
BACKGROUND OF THE INVENTION
The invention concerns burners for space heating, heat working, and
the like, and especially burners of the oxygen-fuel type wherein
oxygen and fuel respectively are fed as required to the burner for
combustion and projection of heating flames. Control of the
physical size and shape, i.e. pattern or configuration, of the
burner flames is essential for many applications, such as for
example where short, bushy or spreading flames best serve the
heating purpose; in other applications, a long slender, needle-type
flame may be indicated.
Although flame pattern control for oxygen-fuel burners has
heretofore been proposed and practiced, it has not been
satisfactorily achieved insofar as known, in modern acceptable
burner equipment. For example, a prior art device known as the
"shell-type" burner utilized the needle valve principle for
changing the flame pattern. In this burner the oxygen is fed
through a cylindrical housing or shell and mixed with fuel gas from
a feeder that is axially adjustable in the shell for defining an
annular nozzle type opening, constituting the adjustable burner
passage. The burner also includes a so-called "bluff body" flame
stabilizer and spreader that is in direct contact with the
oxygen-fuel flame at the point of mixing. As indicated above,
control of the flame pattern of the shell burner is accomplished by
axial movement of the central fuel feeder for varying in the manner
of needle valve control, the annular passage for directing an
oxygen-fuel mixture into the combustion region at the bluff
body.
Serious difficulties and disadvantages were encountered in the
operation of the shell burner. Premature ignition of the highly
combustible oxygen-fuel mixtures within the burner itself created a
dangerous explosion hazard; also excessive maintenance was involved
due to the difficulty of properly cooling the burner parts in
direct contact with the hot oxygen-fuel flames. For these reasons
general use of the shell type oxygen-fuel burner has greatly
declined.
A more acceptable oxygen-fuel burner now in common use is known as
the "rocket burner," a typical example being shown by U.S. Pat. No.
3,135,626 granted June 2, 1964 to Moen and Shepherd. Briefly, the
rocket burner comprises a cylindrical combustion chamber open at
the discharge end and having a multi-port burner plate forming the
opposite end of the chamber. Fuel gas and oxygen are separately fed
in closely grouped parallel streams through respective ports in the
burner plate for mixing and burning in the combustion chamber.
Initially, this is accompanied by establishment of low velocity
anchoring flames as gases along the peripheries of adjacent fuel
and oxygen streams mingle after passing through the burner plate
ports.
In the rocket burner, a limited degree of flame pattern control can
of course, be achieved by valve regulation of the amounts,
pressures and ratios of the oxygen and fuel fed to the burner; also
by locating the burner plate selected distances from the burner
exhaust, an elongated "stiff" flame or a comparatively short, fat
flame can be produced. However, regulation of the oxygen and fuel
burner input does not provide for flexibility in varying the flame
pattern for a given BTU burner output. Location of the burner plate
at different distances from the burner exhaust also does not
achieve the desired control of flame pattern as the closely grouped
parallel gas streams from the conventional burner plate ordinarily
start mixing and burning well within the combustion chamber near
the burner plate and tend to diverge downstream. Where the burner
plate is comparatively close to the exhaust of the combustion
chamber, bushy type flames naturally result; however, a
widespreading umbrella-shaped flame is not possible with the
conventional rocket burner.
The invention therefore is concerned with providing an improved
rocket burner having flexible flame pattern control over a wide
range for a given BTU burner output.
SUMMARY OF THE INVENTION
In accordance with the invention in its broader aspects, a rocket
type oxygen-fuel burner is provided with a specially designed
multiple-port burner plate for so directing respective streams of
fuel gas and oxygen into the cylindrical combustion chamber of the
burner, that initial mixing of the gases for combustion occurs
within a region spaced from the burner plate; furthermore for a
given BTU output of the burner, this region can be shifted toward
or away from the exhaust end of the combustion chamber by
corresponding relative longitudinal movement of the burner plate
with respect to the combustion chamber for changing throughout a
wide range the pattern of the discharge flames.
In a preferred form of the invention, the region of initial gas
mixing is determined by interaction of a plurality of the fuel gas
streams that flow from the burner plate generally parallel to the
longitudinal or central axis of the chamber, with a plurality of
oxygen streams that flow angularly from the burner plate so as to
converge toward the chamber axis, but in off-set or tangential,
non-intersecting relation thereto. Accordingly, the points on the
respective converging axes that are closest to the chamber axis
define a plane that is transverse to this axis. The plane, herein
called the "plane of closest approach," is the general locator of
the region of gas mixing and primary combustion.
Since the projected longitudinal axes of the oxygen ports start to
diverge beyond the plane of closest approach, the momentum of high
velocity oxygen streams tends to produce bushy, wide-spreading
flames where the burner is adjusted for axes divergence beyond the
chamber exhaust; conversely where the adjustment is such that the
diverging streams are confined by the chamber walls, an elongated
sharp and jet-like high velocity flame is produced. Variation of
the flame discharge pattern within the limits indicated above is
achieved in accordance with the invention by relative longitudinal
movement between the burner plate and the combustion chamber, and
hence variation of the position of the plane of closest approach
with respect to the chamber exhaust for controlling divergence of
the mixed combustion gases.
A principal object of the invention therefore is to provide an
improved oxygen-fuel burner of the rocket burner type with flame
pattern control wherein the mixing of oxygen and fuel gas occurs
within a region of the combustion chamber remote from the burner
plate, and the distance between the mixing region and the chamber
exhaust is made variable for varying within a wide range the
pattern of the chamber exhaust flames.
A further and related object is to provide an improved burner of
the character described above wherein the projected longitudinal
axes of the oxygen and fuel ports of the burner plate are angularly
related for defining the remotely spaced gas mixing region, and the
burner plate is movable relative to the chamber exhaust for varying
the location of the mixing region and so controlling the pattern of
the exhaust flames.
A further object of the invention is to provide an improved burner
of the type described above that achieves efficient use of heat
output for variable flame pattern control, that is easily
adjustable for a given BTU burner output within a wide range of
flame pattern control, and that has low maintenance cost and is
free of preignition hazard.
Other objects, features and advantages will appear from the
following description with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, partly in section, of a rocket type
oxygen-fuel burner embodying the invention;
FIG. 2 is a plan view of the multi-port burner element of the
rocket burner shown in FIG. 1;
FIG. 3 is a sectional view taken along the line 3--3 of FIG. 2;
FIG. 4 is a diagrammatic view of the burner element and combustion
chamber indicating convergence of two oxygen streams toward the
chamber axis;
FIG. 5 is a diagrammatic plan view indicating the relation of the
oxygen streams to the chamber axis at the plane of closest approach
along line 5--5 of FIG. 4; and
FIGS. 6, 7, and 8 are diagrammatic views illustrating respectively,
different positions of the burner plate with respect to the
combustion chamber exhaust for achieving different patterns of the
exhaust flames.
DESCRIPTION OF PREFERRED EMBODIMENT
The oxygen-fuel rocket burner 10 shown by way of example in FIG. 1,
comprises a tubular or cylindrical housing 12 within which a burner
element 14 defines one end of a combustion chamber 16. The open end
of the housing at 18 defines the opposite or discharge end of the
chamber from which heating flames are projected for heat working,
space heating, etc. As the combustion chamber is subject to the
high temperatures encountered in the operation of oxygen-fuel
burners, the housing 12 includes a water-cooled jacket 20 that
extends throughout the length of the combustion chamber and most of
the housing for effective heat dissipation.
The burner element 14, herein for convenience termed "burner
plate," constitutes in effect a flow divider for separately feeding
a plurality of oxygen and fuel-gas streams respectively into the
combustion chamber. In the present example, the burner plate is
formed as an apertured disc-like cylinder that is concentrically
mounted within the combustion chamber and serves as a partition
between the combustion chamber and an elongated plenum chamber 22
for the fuel gas. The plenum chamber extends from the burner plate
to the opposite end of the housing where it is connected to a fuel
gas supply conduit at 23, that conveniently may be utility natural
gas.
Certain of the burner plate apertures or ports are centered as at
24 for example, and extend through the burner plate for directly
communicating with the fuel gas plenum chamber 22. A plurality of
other ports 26 for supplying oxygen to the combustion chamber are
arranged in a circle, preferably concentric with the longitudinal
axis of the combustion chamber (and burner plate), around the
smaller centrally grouped fuel ports 24. Additional fuel ports 28
in the burner plate, also communicating with the fuel chamber 22,
are disposed in a circle around the outer peripheral area of the
oxygen ports 26. The central fuel ports 24, shown as 6 in number,
and the outer fuel ports 28, also 6 in number, extend transversely
through the burner plate; i.e., the axes of the respective ports
extend generally parallel to the longitudinal axis of the
combustion chamber. The oxygen ports 26, however, are angularly
disposed with respect to the chamber axis, the projected
longitudinal axes of which converge toward the chamber exhaust in
off-set, tangential relation to the chamber axis so as to be in
non-intersecting relation therewith. That is, the longitudinal axes
of the oxygen ports are inclined toward and skewed somewhat with
respect to the chamber axis as indicated in FIG. 2 for establishing
the geometric relation described above.
The oxygen ports 26 are connected to an oxygen supply through a
manifold arrangement that comprises a plurality of tubes 30
interconnecting the corresponding oxygen ports and a header 32. The
header in turn, is fed by a conduit 34 that extends longitudinally
through the chamber 22 and the housing to the exterior for
connection as indicated with a source of pressurized oxygen.
It will be apparent that in the apparatus so far described,
separate supplies of oxygen and fuel-gas are fed to the
corresponding ports in the burner plate, the oxygen from the
conduit 34 and manifold to the ports 6, and the fuel-gas from the
supply line at 23 and plenum chamber 22 directly to the burner
plate ports 24 and 28. Accordingly, the burner plate ports direct
as indicated above, separate streams of oxygen and fuel-gas
respectively into the combustion chamber 16 for mixture beyond the
burner plate and subsequent burning as more fully described
below.
The combustion chamber walls as mentioned above are protected from
overheating by a water-cooled jacket 20 constituting part of the
housing 12 and consisting of concentric tubular walls 36, 38, and
40 that are spaced in the usual manner for defining annular,
reverse-flow cooling paths. As shown, the cooling path extends from
the cooling water inlet 42 through the annular passage 44 defined
by walls 38 and 40 to the burner exhaust end, where the flow
reverses into the annular passage 46 formed between the walls 36
and 38, and thence to the cooling water outlet 48.
The materials of construction for the present burner may conform in
general to those used in previous rocket burners; i.e., the burner
plate may be made of copper or tellurium copper, and the cylinders
of the housing, cooling jacket and combustion chamber made of brass
or stainless steel, according to required thermal conductivity,
flame-corrosion resistance, etc.
In practicing the invention, the position of the burner plate 14 is
adjustable along the longitudinal axis of the combustion chamber
with respect to the chamber exhaust; i.e., the burner plate can be
moved toward or away from the chamber exhaust for in effect
changing the length of the combustion chamber, and thereby the
pattern of the exhaust flames. To this end, the burner plate 14,
manifold 30-32, and conduit 34 are integrated as a structural unit
for relative movement with respect to the housing 12. The burner
plate has a sliding fit with the inner cylinder wall 40
constituting the combustion chamber wall, and the conduit 34 is
guided for longitudinal movement by a sealing bushing 50 through
the end wall 52 of the housing. Relative movement between the
burner plate assembly and the housing can be achieved in any
suitable manner; for example, a gear rack 54 that is connected to
the conduit, is engaged by a coacting pinion 56 that in turn is
manually operated at 58 for moving the conduit (and the burner
plate) longitudinally in either direction.
Reference is now made to FIGS. 2 and 3 for illustrating the
specific arrangement of the burner plate ports for directing
interacting streams of oxygen and fuel-gas respectively into the
combustion chamber. Taking for example the oxygen port 26a, it will
be noted that the longitudinal axis 26' thereof is skewed with
respect to the center of the burner plate, i.e., the longitudinal
axis of the combustion chamber, so that intersection of the port
axis 26' with the chamber axis 16' is not possible. It will also be
noted that the oxygen port axis 26' intersects with the
longitudinal axis of one of the centrally located small fuel ports
24b, hereinafter referred to as "primary fuel" ports, for ensuring
mixing of these two streams. Moving clockwise, it will also be seen
that the other oxygen ports 26b, 26c, etc., are similarly skewed
with respect to the chamber axis and have their respective
longitudinal axes oriented for intersecting with corresponding axes
of primary fuel ports 24c, 24d, etc.
FIG. 3 illustrates the angular direction of the oxygen ports 26a
and 26d for directing oxygen streams in converging direction toward
the chamber axis 16', but in tangential off-set, non-intersecting
relation thereto as best illustrated in FIG. 2. The oxygen streams
from the 6 ports shown in FIG. 2 therefore tend to form a clockwise
vortex around the chamber axis at a region remote from the burner
plate.
FIGS. 4 and 5 which diagrammatically supplement FIGS. 2 and 3,
indicate the relationship between the projected longitudinal axes
of the oxygen ports and the extension of the chamber axis 16'. In
the partly sectional view of the combustion chamber and burner
plate shown by FIG. 4, the burner plate is in a similar position to
that shown in FIG. 3. The oxygen streams from the ports 26a and 26d
are represented for convenience in illustration, as straight high
velocity jets or stream cores 0-1 and 0-4, disregarding for the
moment any modifying effects of the fuel-gas streams (not shown)
from the primary fuel ports 24a and 24d, etc. Although the axes of
the two skewed streams appear in FIG. 4 to intersect each other and
the chamber axis 16' at some point beyond the section line 5--5,
their closest approach to the axis actually occurs at the section
line. Accordingly, the transverse plane or region determined by the
section line 5--5 is referred to herein as the "plane of closest
approach." FIG. 5 taken along this section line shows the skewing
angle .alpha. of the oxygen streams 0-1 and 0-4 as about 60.degree.
in clockwise direction from the initial positions of FIG. 3 as
represented by the horizontal or transverse burner plate axis 14'.
The other oxygen streams 0-2 and 0-3, etc., are assumed to be
skewed uniformly in the same direction as best shown in FIG. 2.
Between the plane of closest approach and the chamber exhaust, the
oxygen streams begin to diverge toward the combustion chamber wall.
FIG. 6 illustrates schematically this divergence for a given
advanced position of the burner plate wherein the combustion
chamber is comparatively short. In this example, divergence of the
oxygen port axes extends beyond the chamber exhaust.
Returning briefly to FIG. 2, it will be seen that the additional or
secondary fuel gas ports 28 along the peripheral area of the burner
plate are designed to supply the main volume of comparatively low
velocity fuel to the combustion chamber. As the axes of these
ports, as in the case of the central or primary fuel-gas ports 24a,
24b, etc., extend generally parallel to the chamber axis, the
secondary fuel gas streams form in effect a low velocity gas
envelope at the chamber periphery surrounding the oxygen and the
primary fuel streams.
In FIG. 6, the sectional view is intended to indicate the
interaction of the oxygen and fuel streams in and beyond the
combustion chamber, rather than the precise scalar relationship of
the axes in FIGS. 2, 3, and 4. It was found in developing the
present invention that a wide spreading, bushy or "umbrella" type
flame for the rocket burner as represented by FIG. 6 is best
achieved by using the momentum of high velocity oxygen streams
directed in both converging and tangential (or skewed) directions
with respect to the combustion chamber axis for locating the plane
of closest approach sufficiently near the chamber exhaust that the
divergence of the high velocity stream is not confined by the
chamber walls. By avoiding convergence carried to actual
intersection of the oxygen stream axes, as at some common point on
the chamber axis, serious problems involving limitation of flame
length, combustion chamber cooling, etc., are avoided and the
advantages of free gas and flame divergence beyond the plane of
closest approach for producing the desired umbrella-type flame are
retained.
Referring more specifically to the burner operation, the primary
combustion mechanism in the present invention, while somewhat
similar to that described in the Moen and Shepherd patent above,
wherein holding flames for stabilizing the main combustion chamber
flames are established in a low velocity region near the discharge
side of the burner plate, actually differs materially therefrom by
establishing primary combustion for the stabilizing flames in a
chamber-centered region a material distance from the burner plate.
This is achieved by feeding the comparatively small primary supply
of fuel gas from the burner ports 24a, 24b, etc., directly into the
converging oxygen streams entering the region of closest approach,
FIGS. 2 and 6. As the oxygen and primary fuel streams gradually
converge, the respective streams mix and provide as schematically
indicated at 25 low velocity holding flames.
This introduction of a comparatively small amount of fuel into the
oxygen streams at the plane of closest approach, produces a
transversely extending region for the primary and stabilizing
combustion. This region is in a gas mixture zone of relatively low
velocity, extending to the enveloping fuel streams F.sub.s.
Secondary combustion is therefore effectively stabilized by direct
communication with the primary combustion zone. The size and spread
of this zone, referring to FIG. 5, is readily controlled in the
design, according to the convergence and skewing angles of the
oxygen port axes. As the diverging oxygen streams from the region
of closest approach continue to diverge toward the chamber exhaust
and mix with the enveloping main supply of secondary fuel gas from
the ports 28, combustion of the mixed gases is ensured by the
primary combustion or holding flames at the region of closest
approach as indicated in FIG. 6.
The secondary combustion region, i.e., where combustion of the
spreading mixed oxygen and fuel gases is completed, extends beyond
the chamber exhaust as indicated and is determined generally by the
velocity and divergence of the oxygen streams with respect to the
chamber exhaust and the amount of fuel gas from the ports 28. It
will be seen from FIG. 6 that the main or secondary fuel supply
envelope from the ports 28 is traversed by and mixed with the
stronger high velocity diverging oxygen streams 0-1 and 0-4, etc.,
with consequent spreading or mushrooming of the mixed burning gases
beyond the chamber exhaust. Accordingly, a secondary combustion or
flame region having the desired wide-spreading umbrella type
pattern is established.
The degree of flame spread for a given burner plate adjustment can
of course be further varied by empirical adjustment of the supply
pressures for the oxygen and fuel gas streams. Variation of the
oxygen-fuel ratio affects flame spread to the extent that a ratio
giving an optimum fuel supply for producing combustible mixtures
for the main combustion flame system, results in a larger secondary
combustion region. Although the term "oxygen" as used herein
generally refers to the preferred use of commercially pure oxygen,
it is also intended to include oxygen enriched gases in
applications where the higher combustion temperatures obtainable by
pure oxygen are not required.
Where the burner plate and plane of closest approach are located as
illustrated in FIG. 7, so that the projected diverging axes 26' of
the oxygen stream cores intersect the combustion chamber wall, as
distinguished from FIG. 6 wherein divergence of the axes beyond the
plane of closest approach is not restricted by the chamber wall,
mixing and initial secondary combustion of the enveloping fuel
streams F.sub.s and the oxygen streams 0-1 and 0-4, etc., are
confined to a greater extent within the now elongated combustion
chamber 16. That is, as the chamber wall is now effective to
deflect the oxygen streams generally along and into the enveloping
fuel stream, mixing of the oxygen and secondary fuel tends to take
place mainly within the combustion chamber. The momentum of the
oxygen streams, combined with the chamber pressure incident to
secondary combustion, produces a stiff, sharp and elongated flame
at the combustion chamber exhaust. It is believed that this effect
is due in part to the energy of the deflected oxygen cores, that
tend to reconverge, somewhat as a tapering cone, on the chamber
axis. Secondary fuel is during this process mixed with the oxygen
and carried along toward the central axis of the chamber, where
secondary combustion continues as the mixed gases and combustion
flames are discharged at high velocity from the burner exhaust to
form a long, needle-type flame.
FIG. 8 illustrates an intermediate adjustment of the burner plate
for obtaining a flame pattern that represents a moderately bushy
flame, materially longer than the umbrella type flame of FIG. 6. In
this flame pattern adjustment the projected longitudinal axes 26'
of the oxygen stream cores barely clear the chamber exhaust so that
part of the oxygen stream is deflected inwardly by the chamber
wall. Accordingly, but part of the oxygen stream energy is
available to spread the mixed gases and flame in divergent
directions at the exhaust so that a modified bushy flame of
moderate length is produced. It will be apparent from the
descriptions of FIGS. 6-8, that a wide range of graduated flame
pattern control can be achieved by corresponding adjustment of the
burner plate (and plane of closest approach) with respect to the
chamber exhaust.
Summarizing briefly, it will be seen that the invention avoids
certain prior art difficulties by the use of aerodynamic
flame-holding for establishing an oxygen-fuel mixing region remote
from any part of the burner plate, thereby isolating the movable
burner plate from any contact with flame or combustible oxygen-fuel
mixtures.
In practice, the rocket burner of the invention is flexible in
scope of operation; all gaseous, atomizable or vaporizable fuels
can be burned at high efficiency without major design changes, and
optimum conditions for a given fuel can be obtained by adjustment
of design parameters. Basic variable factors of the burner include
the burner BTU output that is determined by the amounts of oxygen
and fuel supplied, the angle of exhaust flame divergence determined
by the position of the burner plate (and the diverging and skewing
angles of the oxygen stream cores), and the "turn-down ratio." The
latter is defined in terms of the full range of burner operation
for a stable flame situation. This can be quantitatively expressed
as a ratio
Conventional commercial burners have in general a narrow range
within which stable flame operation can be obtained, whereas rocket
burners of the present invention may have, for example, a turn-down
ratio of about 1,000:1, that is determined by the burner
dimensions, principally the diameters of the respective oxygen and
fuel ports, and the angular relation of the port axes to the
chamber axis.
Practical advantages of the invention also include improved flame
stability by reason of the low velocity, centered primary
combustion region, improved turn-down ratio, simplicity of design
wherein a flame stabilizing bluff body or the like, in the flame is
not needed, and greatly improved safety with practical elimination
of preignition and explosion hazard.
Having set forth the invention in what is considered to be the best
embodiment thereof, it will be understood that changes may be made
in the system and apparatus as above set forth without departing
from the spirit of the invention or exceeding the scope thereof as
defined in the following claims.
* * * * *