US2629225A

US2629225A - Pulse flow fuel injection system for turbojet engines

Info

Publication number: US2629225A
Application number: US13733A
Authority: US
Inventors: Rolf M Ammann
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-03-08
Filing date: 1948-03-08
Publication date: 1953-02-24
Anticipated expiration: 1970-02-24

Description

Feb. 24, 1953' AMMANN 2,629,225

PULSE FLOW FUEL INJECTION SYSTEM FOR TURBOJET ENGINES Filed March 8, 1948 5 Sheets-Shet 1 24 22 z/ 23' 1'15 1 25 /f 26 30 3/ y IN V EN TOR.

Feb. 24, 1953 R. M. AMMANN 2,629,225

' PULSE FLOW FUEL INJECTION SYSTEM FOR TURBbJET ENGINES Filed March 8, 1948 3 Sheets-Sheet 2 x & Q

& I I 5 El Jjj 49 43 z j .56 zV Pal/f1? fflfleff I INVENZJTE R. M. AMMANN Feb. 24, 1953 PULSE FLOW FUEL INJECTION SYSTEM FOR TURBOJET ENGINES 3 Sheets-Sheet 5 Filed March 8, 1948 3 99%? Q m 9 W w 1 patented Feb. 24, 1953 UNITED STATES PATENT OFFICE PULSE FLOW FUEL INJEc'rIoN SYSTEM FOR TURBOJET ENGINES Rolf Ammann, Patterson- Field, Ohio Appetite-ion March 's, 1948, Serial No. 13,733.

(Granted under Title 35, U. s. Code (1952);

See. 266') 3 Claims.

The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

The present invention relates to a fuel injection system or apparatus for use with jet engines and combustion turbines;

The primary object of the invention is more-- vide a fuel. injection system. of" apparatus for operative association with a turbojet engine wherein the injection apparatus provides means to force the: fuel through thS'fllEl feed pipes and injection nozzles and means to distribute the fuel. intermittently to" the" various injection nozzles, and wherein the latter means operates in a predetermined cyclic manner to effect fuel distribution according to" a definite pattern or plan depending. on the type of engine, number of fuel injection nozzles and power outputdesired;

A secondary object of the invention is to provide a: fuel injection system for use in atturbojet engine wherein the fuel injection nozzles are of a type having. a self-cleaning action when actuated intermittently by fuel flowing: therethrough in surges: or impulses.

A further object of the invention'is to provide a fuel injection system for use ina turbojet engine. wherein there is provided a combined fuel pump and fuel distributor havingf drive means which is capable of substantial speed regulation and. wherein the fuel distributor is adapted to supply uniform'quantities of :fuel toa plurality of fuel nozzles in an intermittent and predetermined manner. v

A further object of-the invention is. to provide a. fuel injection. system for asturbojet engine" in which saidsystem includes a'wmultiplicity of intermittently" actuatedfuelinjection nozzles which are supplied with fuelin a predetermined sequence. and at pressures which will ensure proper atomization of the fuel in spite of variae' tions' in the: power settingtof the fuelinject'ion pump-orenginewpower selector. 7

Another object:- ofu'ther invention is to provide an improved .turbojets. enginesuitable for use on" high speed aircraft and characterized by a fuel injection: system which is reliableim operation and which requiresi'aiminimum of maintenanceservice jover. long" periods Ofoperation.

Another object? of the jection systems therefor; l

The above and other objects of the invention will become apparent'upon reading the following detailed description in conjunction with the drawings; in which:

Fig. 1 is a longitudinal side elevation view partly in cross section; of turbojet engine provided with afuel injection apparatus embodying the principles I of the Dmsentainventien.

Fig.- 2- is a diagrammatic view of the fuel in jection system asused with the" engine of Fig. 1.

Fig. 3 is aschematicview partly in cross sec: tion and-showing the principal operating components of the present fuel injection and dis-. tribution system.

Fig. 4 is an interior view of the combined pump and distributor component of the fuel injection and distribution system.

Fig. 5 is a longitudinal cross section of a fuel injection nozzle adapted for use in the present fuel injection system;

Fig. 6 is a diagrammatic view of the fuel injection system as applied to" a turbojet engine. having a single annular combustion chamber provided with a' plurality ofuniformlyspaced fuel injection nozzles;

Inturbojet engines and combustion turbines there: 15 normally provided one or more combustion chambers. equipped with fuel injection: nozzles which are adaptedto atorhize a liquid fueldelivered under pressure toithe nozzles. The

fuel; is usually kerosene, which requires fairly high pressure for. proper atomization. In 6111-. playing. open nozzles. a high pressure should: be

maintained onthe fuel at all times, since the invention isto generally improve the dependability and operating characteristics of turboj'et engines and fuel in'- the engine is cold when starting. Efiicient performance of the engine at moderate rates of fuel flow is important, because in cruising at high altitudes the turbojet engine may run for long periods at moderate power output. Also in gliding from high altitudes the engine may be at idling speed for some time and if combustion is inefficient the combustion chambers may be cooled to such an extent as to cause cessation of combustion, thus stalling the engine.

Various solutions for the above stated difficulties have been proposed. As an example it has been proposed to use nozzles having two or three fuel openings of different size with means.

to select a fuel opening consistentwith the power setting of the fuel pump. An alternative arrangement is the provision of two or more fuel injection nozzles in a group with an automatic selector valve to allow operation of as many nozzles simultaneously as required for the instant power setting of the fuel pump or fuel throttle valve. Thus it may be possible to operate each nozzle at an optimum injection-pressure to avoid incomplete atomization of the liquid fuel. It has also been found that the open type of injection nozzle is often subject to coking u and thus becomes clogged as thecarbon accumulations build up around the fuel opening. This is especially apt to occur at low rates of flow of the fuel, when there is little chance for the fuel itself to blow the carbon out of the way.

Fuel injection system m use onengine having multiple combustion chambers .plece rotor ZIl-of' duplex design and capable of drawing air from outside the' engine according to the 'direction'of the arrows and. thus build: ing up air pressure in the annular pressure 2 the nozzles may be denoted L-2 and Rr-2 for example. The pump and distributor unit 21 is provided with six fuel outlets A to F which are active one at a time in rotation as indicated by the arrow, to supply fuel to the chambers I to S in clockwise rotation as shown by the arrow. The fuel lines A to F each connect to groups of three nozzles which are tabulated as follows:

Fuel Line Nozzles A L-l, L-4, L-7 B L-2, L-5, L-S O. L-3, L-6, L-9 'D R-l, 3-4, R-7 E R-2, R-5, R-S F R-S, R-6, R-Q

. if desired, although the speed relation may vary order to open the fuel nozzle.

I tion 7 chamber. 4o

considerably in various engine designs. The spaced fuel injections in the chambers provide by combustion a continuous series of expansion waves following so closely on one another as to preclude the possibility of the spaced injections failing to ignite. At the beginning of each injection the fuel pressure builds up rapidly in When the nozzle opens the fuel is under high pressure and is therefore projected far enough to ensure ignition by the previously injected fuel charge as well as by radiation from the heated combus- Of course each chamber is provided with .a spark igniter for starting the engine, but this feature is not illustrated because it is so well known. By using a plurality of fuel nozzles in each combustion chamber the reliability of the engine is increased and furthermore chamber 2|. 'Leading from the outer edge of the chamber 2| there are a number of combustion chambers 22, each of which encloses a retort or muffle chamber 23 havingi'air inlet and outlet passages at the opposite ends thereof. At the air inlet end of the retort 23 there is provided a pair of fuel injection nozzles, indicated at 24, which dischargeliquid fuel; in the direction of the'airflo-w and which are supplied with fuel oil by means of a pair of

fuel lines

25 and 26. The fuel lines'extend to'a centrally located fuel distributing and pumpingunit forming part of the accessory section I. .This unitwill be described in detail below but its function is to supply fuelto the various fuel. lines in high pres sure surges or pulses in a-predetermined cyclic manner. One possible arrangement or plan for. the firing cycle is shown in'Fig; .2, where the zles are indicated by the letters L and R. meaning left and right. Thus the nozzles for cham-. b l y be. e d, L and Rel. for chambe this arrangement permits the separate nozzles to completely close between fuel injections. By the firing plan used in the diagram of Fig. 2, each fuel nozzle is operated only once while the combustion chambers are going through two complete injection or firing cycles. Each cycle may be considered a firing sequence beginning with the firing of chamber l and ending with the firing of chamber 9. Since the rapid action of the fuel distributor provides an ebb and flow of fuel pressure in the separate fuel lines A to F, the present system may be aptly termed a pulse flow fuel injection system. The fuel feed lines connecting groups of three nozzles in three spaced combustion chambers and supplyin fuel thereto simultaneously may be termed common rail fuel distributing conduits.

The combustion waves starting in the chambers .l to 9 proceed toward the outlet ends of the chambers (see Fig. l), and pass between guide vanes 30 of the turbine section IV. These vanes give the hot gases the proper direction so that they may act with greatest effect on the blades 3| of turbine wheel 3|. The turbine wheel is mounted rigidly on a central shaft 32 which drives the compressor rotor 20 and also the units of the accessory section I. The rapid expansion of air and products of combustion in the combustion chambers, and also rearwardly thereof, to some extent, provides a reaction efzfect todriveizthecngine. in a direction opposite seems connected to lever 61 becomes a relatively fixed point and the lever 61 turnsslightly in response to movement of the eccentric 63 by link 69 and bellows HI.

Considering the action of differential 56 more in detail, it will be seen that the power shaft 51 rotates in a clockwise direction thus turning the carrier plate 58 at the same speed and in the same direction. The planetary gears 59 are of course carried aroundwith the plate 58 and are adapted to rotate on their own pivots by reason of their engagement with the ring gear 6|. Now with the ring gear 6! tationary the pinions 59 will be driven in a counterclockwise direction about their own pivot shafts, looking at the lower side of the differential. The pinions 59 will in turn cause the shaft 43. to turn clockwise by their driving engagement with sun gear 60. However looking at the upper side of the pump and distributor unit, as in Fig. 2, the shaft 43 and rotor 45 will be rotating in a counterclockwise direction; Now if the control motor 65 is turned on and acts through

gears

62 and 64 to rotate the ring gear 6| in the same direction as the power shaft 51 and pump shaft 43, the planetary pinions 59 will be speeded up thus increasing the rotative speed of gear 60 and shaft 43, As the value of the armature resistance 66 is decreased the motor 65 Will go faster and the pump shaft 43 will also be rotated faster to step up the fuel injection pressure and the amount of fuel injected in the combustion chambers at each actuation of the fuel nozzles. Expansion of the bellows by the effect of increased altitude or movement of the manual lever 12 to the right will increase the instant value of resistance 66 to reduce the speed of motor 65 and also reduce the speed of the fuel pump. The speed control means for the pump and distributor involving a differential gearing assembly is shown by way of example, it being understood that other types of variable speed transmissions may be substituted as desired.

Fuelinjection nozzle The various fuel lines A to F terminate in fuel injection nozzles of the spring-closed type, such as shown in Fig.6. Each fuel injection nozzle 24 is threaded as at 80 to engage similar threads formed internally of a member 8| which is flanged at 8| to retain the fuel line 82 in connected relation to the nozzle. The hollow nozzle is provided with a transverse wall 83 centrally apertured to provide a valve seat engaged by a ball valve member 84. On the opposite side of the ball there is a spring retainer 85 having a coil spring 86 seated therein. Extending within the spring 86 is a valve stem 81 having a flange 88 thereon adapted tobe engaged by the upper end of spring 86. Secured within the nozzle is a plug member 89 having a number --of fuel passages 90 arranged in circular manner about the valve stem 87. Seated betweenthe plug member 8t and the flange .88 is a coil spring 9i, which acts to hold the nozzle closed as will be explained below. As the fuelfl-ows outward under pressure through the fuel passages, it impinges on a series of swirl fins 92 to give the fuel a definite rotary motion before it leaves the nozzle and .thus assist in more thorough atomization of the fuel. The outer end of the hollownozzle is closed by an end closure 93 screw threaded-into secured position as shown. The closure 93 is provided with a conical valve seat to. receive the conical head portion 94 on the valve stem 81 in closely engag ing relation.

The action of the fuel injection nozzle is fairly obvious but it is noted that the liquid fuel always fills the interior spaces of the nozzle. When pressure is put on the fuelby the action of the fuel pump and distributor, the fuel displaces the ball check member 84 and also forces the stem 81 outwardly against the compression of coil spring 9!. Thus the valve stem head portion is lifted off its seat and the fuel is forced out in a swirling spray until the fuel pressure again falls to zero by action of the fuel distributor. The exact structure or formation of the valve stem head portion 94 and seat therefor may be varied considerably. For instance the parts may have curved mating faces, with the head portion 94 ap-' proximating a hemisphere. This will prevent the spray of fuel from spreading out too much as it enters the combustion chamber. It is seen also that the nozzle 26 is threaded at 95 to permit easy securing thereof in the combustion chamber wall.

The self-closing fuel injection nozzle as used in the present invention is a vital part of the fuel injection system. Even though carbon may collect on the end portions of the nozzle in the combustion chamber, the valve seat and comple mental closure therefor are protected from the action of combustion except when the valve is open. At that time however the outflow of liquid fuel under high pressure effectively prevent any combustion products from reaching the valve seat or closure 54. Also any crust or particles around the edges of these parts are blown off by the flowing liquid fuel when the valve opens under fuel pressure. As explained previously the spraying or atomizing action of fuel nozzle is always eflici-ent, because the nozzle does not open until substantial pressure is put on the fuel entering the nozzle. Since the fuel pump and fuel distributor are engine driven the supply of fuel for combus- 7 tion will always keep pace with engine speed. By providing a variable speed transmission between the engine and the fuel pump and distributor unit, the fuel quantities delivered to the combustion chambers may be varied sufficiently to provide flexible operation and precise engine control.

The fuel nozzle design as shown and described is only one example of a self-closing fuel injection valve. Other types and constructionsmay be substituted according to performance requirements. For instance a number of present day fuel nozzles for diesel engines'would be suitable in many instances. One such fuel injection nozzle is shown on page 66 of Diesel Fuel Injection Systems by Louis R. Ford (1945). Others are shown on pages 119 to 122 of Gemischbildung und Verbrennung im Dieselmotor by Anton Pischinger and Otto Cordier.

Fuel injection system for use on engine having an annular combustion chamber tribution of. liquid fuel to a plurality of springclosed fuel injection nozzles regardless of the type of combustion chamber. In Fig. 6 there is shown in diagrammatic form a possible arrangement of fuel nozzle and fuel distribution plaul for use with a turbojet engine having a single annular combustion chamber 100 and central' engine shaft- NH; The constructional details of such an engine may be found on page 117 of Gas Turbines and Jet Propulsion for Aircraft 'by G. Geoffrey Smith (fourth edition-4946) For purposes of illustration the engine combustion chamber 100 is provided with evenly-spaced fuel injection nozzles N-l to N-IO all of which discharge into the same combustion'chamber H19 in a direction more or less from the air inlet end to the gas outlet end. In some "engines of this type there may be twice as 'many nozzles as shown in Fig. 6, since increase in the number of such nozzles gives more uniform distribution of heat and smoother gas flow to the turbine located just behind the combustion chamber. It is understood that the fuel injection nozzles N- to N-| inclusive are of the self-closing type discussed hereinabove. V

In the fuel distribution plan as shown in Fig. 6 the nozzles are combined in opposite pairs and supplied by fuel lines G to K The fuel lines connect to the fuel pump and distributor unit [2! at the fuel outlets G to'K arranged in circular manner to receive fuel one at a time, in the same way as described with respect to Figs. 2 and 4. In this case the fuel distribution is in a clockwise direction as shown by the arrow on the unit 121. Also the fuel lines are connected so that the fuel nozzles are supplied in this same direction of rotation. The fuel lines G to K connect to pairs of nozzles as'tabulated thus:

The firing plan of the combustion process becomes obvious from the table and from an inspection of Fig. 6. Just as in the first described embodiment of the invention the fuel pump and distributor unit I21 is controlled by a differential mechanism, but is driven by power from the engine main shaft I 0! through a reducing gear.

All the essential details of the fuel injection apparatus are the same in both examples. However with an annular combustion chamber the sequential combustion waves tend to cause a rotative effect on the products of combustion as the fuel injections proceed around the chamber in the same direction. This will obviate the necessity of mixing vanes in the chamber and will also result in slightly higher turbine speeds for the same flow of fuel. While there may be the usual flame anchors or dividing walls between the fuel injection nozzles, these will not extend more than a few inches rearwardly of the nozzles. As in the construction of Figs. 1 and 2, the turbine will be so built as to produce rotation of the turbine wheel and shaft in the same direction as the sequence of injection of fuel and order of firing of the nozzles. This direction is indicated by an arrow between the shaft ml and the annular combustion chamber I00.

The present pulse flow fuel injection system for turbojet engines provides a controllable means to meter liquid fuel to a plurality of fuel injection nozzles in an orderly and ositive manner. Moreover it is emphasized that the fuel injection nozzles require a positive fuel pressure starting and-idling the engine.

for actuation ana this pressure gua rantee's adequate fuel'injection pressure capable of atomizing the fuel even at low rates of fuel fiowras' in The self-closing fuel nozzles are also less subject to clogging by carbon-accumulations, as explained above. The invention is not limited to the use of the specific fuel distribution apparatus shown, but may be practiced with various types of sequentially operated fuel 'injectorscapable of forcing liquid fuel through the injection nozzles in a predetermined cyclic manner. The injection pattern to provide a logical firing sequence may be planned according to the particular engine and power requirements. The differences in cyclic firing order in the two illustrated embodiment demonstrate the possible wide variations in the specific details of the system.

The embodiments of the invention here shown and described are to be regarded as illustrative only and it is to be understood that the invention is susceptible to variations, modifications and changes within the scope of the appended claims.

Icla ini: q

l 1. A fuelinjection system for use in a-turbojet engine having in consecutive series an air compressor section," a combustion chamber section including a plurality of combustion oham bers circumferentially' arranged aroundthe central aX-is'of'said engine, a turbine section for supplyingpower through a central shaft to said air compressor section, and an'exhaust section to conduct the exhaust-gases from said turbine to the atmosphere, said fuel injection system comprising a pair: of adjacent fuel injection nozzles extending into each combustion chamber at the tip-stream end thereof, each of said nozzles ineluding a tubular body having an injection aperture at the end of said body within said chamber and a spring-actuated member in said body to close said aperture when the pressure of the fuel 7 within said body is reduced below the counterpressure exerted by said spring-actuated memher, a fuel distributor having a rotatably mounted member provided with a fuel distributing passage therethrough, mean to continuously connect said fuel distributing passage to a source of liquid fuel under pressure, a relatively stationary fuel distributing plate contiguous to said rotatably mounted member and provided with a plurality of fuel passages equidistant from the center of rotation of said rotatably mounted member adapted to connect in consecutive order with said fuel distributing passage, and fuel conduits connecting said fuel passages and said nozzles to provide for sequential injection of fuel through one nozzle of the combustion chambers proceeding around the engine in one direction before sequential injection of fuel through the other nozzle of the combustion chambers proceeding around the engine in said one direction, the firing sequence in said combustion chambers being so rapid as to maintain continuous combustion in each chamber whereby there is a continuing series of expansion waves moving through each chamber toward the turbine section of said turbojet engine to produce rotation of the turbine and air compressor thereof.

2. A fuel injection system for use in a turbojet engine having in consecutive series an air compressor section, a combustion chamber section including a plurality of combustion chambers circumferentially arranged around the cen- .tral axis of said engine, a turbine section for supplying power through a central shaft to said air compressor section, and an exhaust section to conduct the exhaust gases from said turbine to the atmosphere, said fuel injection system comprising a pair of adjacent fuel injection nozzles extending into each combustion chamber at the up-stream end thereof, each of said nozzles including a tubular body having an injection aperture at the end of said body within said chamber and a spring actuated member in said body to close said aperture when the pressure of the fuel within said body is reduced below the counter pressure exerted by said spring-actuated member, a fuel distributor having a rotatably mounted member provided with a fuel distributing passage therethrough, means to continuous- 1y connect said fuel distributing passage to a source of liquid fuel under pressure, a relatively stationary fuel distributing plate contiguous to said rotatably mounted member and provided with a. plurality of fuel passages equidistant from the center of rotation of said rotatably mounted member adapted to connect in consecutive order with said fuel distributing passage as said member is rotated in one direction about its center of rotation, a plurality of common rail fuel distributing conduits each connected to a separate fuel passage and also connected to a separate group of single nozzles of at least two spaced combustion chambers, with said fuel passages being thus connected in the order of their connection with said fuel distributing passage to successive groups of nozzles proceeding around the engine in one direction, whereby to complete fuel injection through all nozzles only after two complete injection cycles wherein the first cycle covers injection through one nozzle of each chamher, and the second cycle covers injection through the other nozzle of each chamber. q, 3. A fuel injection system for use in a turbojet engine having a plurality of combustion chambers therein comprising a plurality of fuel injection nozzles extending into each combustion chamber at the upstream end thereof, each of said nozzleshaving an injection aperture and a spring biased member normally closing the aperture, a fuel distributor operatively associated with said injection nozzles and having a rotatably mounted member with a fuel distributing passage therethrough, means providing a continuous connection between said passage and a source of liquid fuel under pressure, a relatively stationary distributing plate arranged contiguous to said rotatably mounted member and having a plurality of passages therethrough each adapted to be consecutively aligned with the fuel distributing passage, fuel distributing conduits, each connecting one of said plurality of passages and a plurality of single nozzles, each in separate spaced combustion chambers whereby the respective connected nozzles will be simultaneously and sequentially operated to maintain continuous combustion.

ROLF M. AMMANN.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name Date 1 1,690,893 Dorner Nov. 6, 1928 1,854,615 Lasley Apr. 19, 1932 2,157,284 Egersdorfer May 9, 1939 2,365,636 Hedges Dec. 19, 1944 2,397,357 Kundig Mar. 26, 1946 2,427,845 Forsyth Sept. 23, 1947 2,514,513 v Price July 11, 1950 I FOREIGN PATENTS Number Country Date 251,677 Italy Jan. 26, 1927