US2860483A - Apparatus for burning fluid fuel in a high velocity air stream with addition of lower velocity air during said burning - Google Patents

Description

4 Sheets-Sheet 1 FOX Nov. 18, 1958 APPARATUS FOR BURNING FLUID FUEL IN A HIGH VELOCITY AIR STREAM WITH ADDITION OF LOWER VELOCITY AIR DURING SAID BURNING Filed Jan. 2. 1953 ATTORNEYS H. M. FOX

APPARATUS FOR BURNING FLUID FUEL IN A HIGH VELOCITY AIR STREAM WITH ADDITION OF LOWER VELOCITY AIR DURING SAID BURNING Filed Jan. 2. 1953 I INVENTOR. H. M. FOX

ATTORNEYS Nov. 18, 1958 ox 2,860,483 APPARATUS FOR BURNING FLUID FUEL IN A HIGH VELOCITY AIR STREAM WITH ADDITION OF LOWER VELOCITY AIR DURING SAID BURNING Filed Jan. 2. 1953 4 Sheets-Sheet 3 ATTORNEYS DYNAMIC PRESSURE (P TOTAL- PSTATIC)IN INCHES H O NOV. 18, 1958 ox APPARATUS FOR BURNING FLUID FUEL IN A HIGH VELOCITY I AIR STREAM WITH ADDITION OF LOWER VELOCITY AIR DURING SAID BURNING Filed Jan. 2. 1953 4 Sheets-Sheet 4 MPLE FLAMEHOLDER PRESENT INVENTION WA 0.2 #/sc. WA=O.2#/SEC.

SIMPLE FLAMEHOLDER I wA=o.oae=lk/szc. I I

I V o I I 4 DISTANCE FROM BAFFLE IN INCHES INVENTOR. H. M. FOX

ATTORNEYS Application January 2, 1953, Serial N 0. 329,296

4 (Ilaims. (Cl. oil-39.65)

This invention relates to combustion apparatus for a "propulsive gaseous stream. Inone aspect it relates to combustion apparatus useful in gas-turbine engines. In another aspect it relates to combustion apparatus useful in jet engines, or the ram jet type, or of the gas-turbine jet engine type.

In combustion apparatus of the prior art for use in propulsive gaseous streams considerable ditficulty has been experienced in obtaining thorough and continuous mixing of fuel and air, with the result that burning is erratic and the flame goes out, orextends further than desired and comes into contact with turbine blades or other parts of the apparatus, which should not be so exposed to flame. "As a result the rate of heat release is not high enough and there is too great a drop of pressure through the combustion apparatus which impairs the com bustor efficiency and tends to promote instability as well as reduce the efiiciency of the entire device.

One object of thepresent invention is to provide an apparatus which will producefcontinuous combustion at a high rate of heat release. a v

Another object is ,to provide an apparatus in which there is a low pressure drop with improved combustion efliciency and stability. t

' Another object is to provide improved combustion apparatus for propulsive gaseous streams. I t

A further object is to provide improved gas-turbine engines, ram jet engines, and similar devices, useful in fixed power installations, jet engines for the propulsion of vehicles, and the like.

Numerous other objects and advantages will'be apparpanying specification, claims and drawings.

Figure 1 is an elevational view with parts broken away to show details of construction of a gas-turbine jet engine embodying the present invention. Figure 2 is a cross-sectional view of the device shown in Figure 1 taken along. a line 22 thereof, looking in the direction indicated. t

Figure 3 is a cross-sectional elevational view of one of the burner tubes shownin Figure '1, taken along the line 3-3 of Figures 4 and 5 looking in the direction ent to those skilled in the art upon reading the accomindicated, which is? also suitable for use alone as a ramjet engine. H a

Figure. 4 is a cross-sectional view of the apparatus shown in Figure 3 taken along the line 4-4 looking in the direction indicated.

Figure 5 is a cross-sectional view of the device shown in Figure 3 taken along the line 5-5 looking in the-direction indicated.

Figure 6 is a cross-sectional view similar to Figure 4 i of a modified second species of the invention in which the cylindrical elements of Figure 4 have arcuate and cannular in Figure 6.

Figure 7 is a view-corresponding to Figure 5 of the been made modification of the invention shown in Figure 6. 1' A .4

Figure 8 is an elevational cross-sectional view of a modified third species of the combustion apparatus in which the'baflle and all of the passages' are annular.

' Figure 9 is a cross-sectional view of the device shown'in Figure 8 taken indicated. a i

Figure 10 is a graphical representation of the results of tests made with the present invention (as shown in Figure 3) and with a simple flame holder. I

Figure 1. illustrates the embodiment of the presentinvention ina gas-tm bin'e jet engine generallyitdesignated as 12. Engine 12has a housing 13 forminga chamber 14, with an inlet 161and an outlet 17 for air from/the atmosphere. While the invention 'is illustrated as applied to a-gas-turbine jet. engine.for-propelling vehicles,-such as. aircraft (not shown), itshouldbenoted that in one aspect the invention isthe subcombination of a combustion-apparatus for a-propulsive gaseous stream and in another aspect relates tov processes of burning fuel inamovv ing airQstream to produce a propulsive gaseousstream', as well as the jet engine combinationshown; In chamber 14 there are connected in series an air compressorilsg a. combustion apparatus;19, and a gas turbine 2 1;: al1.bcing generally design'atedby'the numerals listed and lying in the order describedbetween inlet 16 and outlet 17;;

Gas-turbine 21 preferably comprises .arotor having slanted. propeller blades 22 anda stator-having suitable slanted guidingvanes 23 to provide a turbine with one or more stages of power output tall of .which;.is ell known in fthe of turbinesg R otor 22 and shaft 24 are journaled into suitablebearings. (notjshown) andyian along the line 9 9 looking in the direction nular outlet 17 maybe provided with a central conoidal secured therebetween.,,Air compressor 18 comprises a rotor havingslantingfair-propelling blades 27 and a stator having slanting air directing blades 2.8,,all arranged in a manner Well-known to those skilledin. the air compressor art. A roundedcentml nose 2 9,may beprovided in inlet 16 to help. direct the airinto the compressor 18. The journals for shaft 24 n1ay be located in nose and tailfi piece 26, which are in turn supported' in housin'g'13'by radial struts, or fins, 3 1 and 3;2.respectively, orsome similarsupporting-elements. I A .In' asimilar manner the .unitcomprising combustion apparatus 19. may. be supported from housing13 by.lon-. gitudin'al radial fins; 33 itbeing desirable to leave some space 34 betweenf saidhousing and the'bnrner tube, or wall, 3 of the combustion unitl? in most instances, although space 34 can be entirely eliminated if desired and apparat'us19 besupported by direct contact withsaid housing. Flow of air through space 34 is reduced, cone, trolled, or prevented entirely by means of baffie plate, or wall, 37. The combustion apparatus 19 in Figure 1 is formed from an ,annularly disposed set of parallel burner-- device 19 may be replaced by the annular deviceishown in;

Figures 8 and 9.

- Figure '2 is a cross section of Figure 1' taken along the" line 2-2'looking* in thedirection indicated arid shows the gas-turbine jet engine-12comp'rising a housing lfiandi six burners disposed in a circle around shaft :24, ".tl'f'e passage'of air around burner tubes 36 being regulated or I eliminated by baffle 37, and each of burner tubes 36 hav L ing an inlet 39 with ailaring mouth 38 in the form of an I arcuate cannular opening at its-inlet end, funneling down to fit the circular inlet opening 39 of the burner.

Figure 3 shows the burner which was used to obtain the data charted-on the graph in Figure 1-0 with the"-dashdot-dot 'line having the'legend present invention. Figure 3 also shows the internal construction 'of combustion apparatus 19-01? Figure 1. Combustionapparatus'19, as shown in Figure 3, however, may be used in other combinations-andsubcombinations than that shown'in Figure 1, foreexample, the combustion apparatus of Figure 3 is suitable for use in a ram-jet engine which does not have a compressor 18 or' turbine 21 as shown in Figure 1-, but instead relies on'its velocity'through-the atmosphere'to 'pacl -air inithrough circular inlet opening 39 in a' sufficientamou'nt'to operate as a ram-jet. Bu'rner 19 is also adaptedto be used in anye'ngine in which a continuouscombustion apparatus for creating a propulsive gaseous streamjis of value,'snch as a turboprop-engine (not shown) which'wouldbe like Figure 1 except thab'shaft 24 would extend axially out of either or both en'ds 16 'and 26 and have one or'more screw pro- 'pellers attached thereto'ateither 'or' both 'ends' for creating a propulsive slipstream in the atmosphere exterior of 1 housing'l3.

- In Figure '3, burner l9-comprises a'burner tube, or housing, 36 having' a conduit 41"with' opening 39 disposed-to supply a moving air stream 44 as indicated'by the arrow. -'Mounte'd in housing 36is a ba'fiie '42- having a stream-lined end 43 disposed upstream of said moving air stream 44, and an abruptlyterminating'non-streamlined end-"46 disposeddownstream of'said moving air stream. nr housing 36-is disposed'axially a duct 47 with its leading edge 48' preferably extendinginto inlet '39 before-'any'enla'rgement of 39has occurred. Duct 47 is disposed totake the first portion of said air 44 from said first conduit 41 and'direct the'samethroughnozzleor orifice 49 against the nose 43 of baflie 42 as indicated by dotted' lines 51. g Y

While results ofvalue can be bbtain'ed' witha' uniform diameter nozzle "49 (not shown), in which case the velocity of the air stream '44-'in conduit 41 is merely maintained and not increased inthe gas stream 51, it is preferable to construct nozzle- 49 with a converging entry portion 52. By employing a nozzle with a well rounded entry-48, or a converging nozzle'orifice 521it is possible to increase the velocity of airstream 51 over that of 44 and thereby'augment the efl ects that occur'when' stream 51 strikes nose 43 of bafile 42. It is preferred to have a reduction in area between the cross-sectional area of entrance 48 and exit "49 ofatleast three to one. This same reduction in the case of the burneractually used'to obtain-the data of Figure l was between four to one and five to'o'ne. It is preferred to limit the reduction in area to not more than twenty to one, however.

'That portion of air stream 44 which .does not enter the duct 48 passes through an annular bypass duct 53, which may have constant area throughout (not shown) but preferably expandsin area as itproceeds downstream. Nozzle 47 is provided with a skirt 54 protecting bafiie 42 and the area in its immediate neighborhood from contact with the air coming through passage 53, andthe portion of passingthrough 53is reunited with the air coming through nozzle49-downstream of terminal edge 56 of skirt" 54. This reuniting of thestreams of airmaybe accomplished in a single step with-valuable results, but I prefer to divide the=stream of air in passage 53 by two or more cylindrical concentric sleeves 57 and '58 and return the air from. space 53 in a; series of annular sheets through A fuel injection line 67 connected to housing 36 by suitable connection means 68 may be disposed toact both as a support for baffle 42 and as a means to feed fuel downstream of said baflie, for example by atomizing the same, or spraying the same, through a nozzle 69 of a type well known in the prior art. Fuel nozzle 69 may be either the pressure-ato'mizing type shown, or may be any type known to the prior art, provided the fuel is sprayed into the flame space outlined by dotted line 64. In order to ignite the fuel-air mixture in the turbulent flame 64 any suitable ignition mechanism of the prior art may be employed, such as a spark plug 71 having electrical leads 72 secured in place by securing means 73. Either a continuous, or intermittent, spark may be employed, or the spark plug need only be actuated at times of igniting the burner.

Figure 4 is a cross-section of Figure 3 looking downstream as indicated and needs no further description. The construction and disposition of lugs or blocks 74 which hold the concentriccylinders 54, 57 and 58 will be evident from a comparison of Figures 3 and 4.

Figure 5"is the same as Figure 4 except looking upstream and needs no further description.

Figure 6 is a cross-sectional view similar to Figure 4, and Figure 7 is a cross-sectional view similar to Figure 5. Figures 6 and 7 are views similar to Figures 4 and 5 respectively, showing howthe device of Figure 3 can be easily modified into an arcuate, cannular form, thereby utilizing all of the space available so as to leave no space between cylinders 36 which is represented by baflle 37 in Figure 2. Parts in Figures 6 and 7 corresponding to those in Figures 4 and 5 have'been given the same numbers, the numerals'being primed when they differ by'being arcuate and cannular in shape. No further description is believed necessary.

Figures 8 and 9 show another modification in which waste space 37 shown in Figure 2 isutilized by making all the parts and spaces annular and continuous around a central tube 3613 which may be placed around a shaft similar to shaft 24 shown in Figure 1, except of course such parts as the single fuel line 67, which can supply a plurality of nozzles 69 spaced around-the annular baifle 42A, and spark plug 71, as one can ignite a flame all around the annulus without having more than one'spark plug.

The parts in Figures 8 and 9 whichcorrespond in functions with like parts in the preceding figures have been given the same numerals with the letter'A added, and

when a further corresponding concentric part is needed to carry out that function, it'has also been given the same numeral with the letter B added.

In'Figure 8 the air enters through annulus 39A and a portion is taken through annulus 49A lying between annulus members 47A and 47B. Annular space 49A may be cylindrical throughout (not shown) but preferably-said annularspace converges as shown'to concentrate the air into annular jet 51A which impinges on the streamlined face 43A of annular bafile 42A. The remaining portion of the air is carried through two annular spaces 53A and 53B and is reunited with the other air in annular space 63A after passing through the annular Spacesbetween cylinders 54A, 57A, 58A and 36A and between cylinders 54B, 57B, 58B and 36B. Fuel coming in line 67 is distributed and spread through a plurality of nozzles 69into annular space 63A to form a turbulent flame downstream of baflle 42A.v

Figure 10 is 'a graphical representation of comparative data obtained while testing the burner of Figure 3, and a simple flame holder of the prior art comprising a bafiie like '42 of Figure 3 with a fuel injector like 69 of said figure placed inside a single cylindrical tube, and both devices tested under similar conditions. The pressure readings were obtained by moving the dynamic entrance to a Pitot tube at different distances from the baflie indicated in Figure 10.

to accelerate the air and a hemispherical baffle.

The readings in FigurelO were made along the'axis of the burner and show that much greater turbulence of mixing occurs in the present invention than in a simple flame holder. These readings show that turbulence exists for a greater distance in back of the baffle of this invention than in back of the baffle of the simple flame holder.

Downstream of baflle 42 in the present invention there is negative velocity, or backflow, for some four and one-third inches in the small model tested, as shown in Figure 10.

Operation The present invention provides for the continuous combustion of fuel with a fuel pressure drop to produce propulsive gaseous streams whereby under relatively severe inlet conditions for combustion, a combustion efliciency of 92 to 98 percent is often obtained, combustion stability is improved, and a maximum stable temperature rise higher than the temperature rise in conventional combustion apparatus, and therefore higher heat release, is developed.

The improved performance of the combustion apparatus of this invention is believed to be the result of the formation of a long and turbulent quiescent zone in which the reverse axial air currents recycle and carry the activated fuel particles back to the combustion zone, which thereby increases the overall velocity of the combustion reaction. The large volume of the quiescent zone obtained in the combustion apparatus of the present invention also permits more complete combustion of the fuel particles.

The radial spacing of cylindrical tubes 57 and 58 is such that sheaths of high velocity air, as is emitted by a jet ejector, are formed around the quiescent zone and reduce its tendency to collapse. Although only three secondary air passages are shown in this embodiment, any number of such passages may be used and also different velocities of air flow from each passage may be provided.

The baifle 42 is mounted in spaced relationship to air nozzle 49 and the discharge of secondary air passages 59, 61 and 62 so that a direct stream or jet of high speed air from air nozzle 49 strikes baflle 42 and expands around its surface, only partially filling the annulus between the baffle and the inner surface of flame tube 54, and leaves the downstream edge of baflle 42 as a tube of air traveling at high speed. The sheaths of high speed secondary air discharged from passages 59, 61 and 62 promote the formation of this quiescent zone and help to prevent its collapse. In Figure is shown a comparison of the quiescent zones obtained in a conventional low pressure-drop combustion chamber consisting of a conical flame holder in a tube of constant cross-sectional area and the combustion chamber of Figure 3 of this invention employing an air nozzlg Wit the chambers operating at 50 pounds per square inch absolute pressure and mass air flow of 0.2 pound per second, the region of backflow was found to extend only two inches from the downstream edge of the flame holder of the conventional combustion chamber as com- L pared to a region of backflow of over four inches in the 1 sion of fuel may be made in other localities.

' in Figure 3, the fuel nozzle 69 may be placed on the downstream side of baflie 42 and the fuel line utilized as a support for baffle 42 in the combustion space. Fuel nozzle 69 may be either of the pressure-atomizing or gas-assist type. Various designs of batlies may be used and preferably the baffle should be one which progressively increases in cross-sectionalarea from the upstream to the downstream end of said baflie so as to impart a high kinetic energy to the stream of air leaving the downstream edges of the balfle. In the design showri in Figure 3 the upstream surface of the baffle is a hemisphere.

While certain specific embodiments of the invention have been shown for purposes of illustration, the invention is not limited thereto.

Having described my invention, I claim:

1. Combustion apparatus for burning a fluid fuel in a moving stream of a combustion supporting gas comprising in combination a body having a conduit therethrough provided with an inlet and an outlet for said gas, a baifle disposed in said conduit having a streamlined end disposed toward said inlet and an abruptly terminating non-streamline end disposed toward said outlet, a plurality of spaced concentric tubes surrounding and spaced from said baflle and disposed in and spaced from the walls of said conduit, said tubes overlapping in longitudinal extent along the axis of said conduit with the tubes terminating progressively closer to said outlet in the same order as their distance from said baffle, a converging nozzle with an inlet disposed in the inlet end portion of said conduit and with an outlet disposed to discharge a reduced area stream of said gas of higher velocity than enters said nozzle against said streamlined end of said baflie, means sealing off the space between said nozzle and the wall of the tube adjacent said baffle upstream of said bafiie, said conduit enlarging in area downstream of the inlet of said nozzle, and said tubes and conduit being disposed in said enlarged portion to lower the velocity of said gas passing around said nozzle and reunite the same downstream of said baffle with the gas that has passed through said nozzle, means for injecting said fluid fuel into the space downstream of and adjacent to said baffle, and means to burn said fuel and said combustion supporting gas in said body downstream of said baflle.

2. The combination of claim 1 in which the tubes are imperforate.

3. Combustion apparatus for burning a fluid fuel in an annular moving stream of a combustion supporting gas comprising in combination a body having an annular conduit therethrough provided with an annular inlet and an annular outlet for said gas, an annular baffle disposed in said conduit having an annular streamlined end disposed toward said inlet and an abruptly terminating annular non-streamline end disposed toward said outlet, a plurality of spaced concentric tubes surrounding and spaced from said baffle and disposed in and spaced from the walls of said conduit, said tubes overlapping in longitudinal extent along the axis of said conduit with the tubes terminating progressively closer to said outlet in the same order as their distance from said baflle, an annular converging nozzle with an annular inlet disposed in the inlet end portion of said conduit and with an annular outlet disposed to discharge a reduced area annular stream of said gas of higher velocity than enters said nozzle against said annular streamlined end of said baifle, means sealing off the space between said nozzle and the wall of the tube adjacent said baffle upstream of said baflle, said conduit enlarging in area downstream of the inlet of said nozzle, and said tubes and conduit being disposed in saidenlarged portion to lower the velocity of said gas passing around said nozzle and reunite the same downstream of said baflie with the gas that has passed through said nozzle, means for injecting said fluid fuel into the annular space downstream of and adjacent to said annular baffle, and means to burn said fuel and said combustion supporting gas in said body downstream of saidbaflie.

4. The combination of claim 3 in which the tubes are imperforate.

(References on following page) References Cited in the file of this patent UNlTED STATES PATENTS Christensen ...-2 Ian. 9, 1951 Redding Feb. 13, 1951 5 Sforzini Mar. 2 0, 1951 Christensen et a1. May 22, 1951 De Zubay et al. Nov. 6, 1951 Hundstad Mar. 11, 1952 8 Clarke et a1. 5 May 6, 1952 Buckland et a1. July 8, 1952 Leduc .2. -2 Aug. 4, 1953 Probe'rt May 25, 1954 Collins Feb. 12, 1957 FOREIGN PATENTS Great Britain Aug. 27, 1941 Canada June 3, 1952

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