US2609868A - Fuel supply control for gas turbines - Google Patents

Description

Sept. 9, 1952 F. H. CAREY FUEL SUPPLY CONTROL FOR GAS TURBINES 2 SHEETS-SHEET 1 Filed Aug. 4, 1947 g mm g 3 mm 4 mm g E E B m o 0 a O m o a canon- Sept. 9, 1952 F. H. CAREY 2,609,868

FUEL SUPPLY CONTROL FOR GAS TURBINES Filed Aug. 4, 1947 2 SHEETS-SHEET 2 79 J 117 L I L11I 60 11? 11p:

8 i 74 701 I 0- i I i y f I 54 J 58 Fig.2

Patented Sept. 9, 1952 2,609,868 V FUELjsUee Y, comrnonroa GAS immerses {Frederick H; Carey, Cheltenha'm, England, assiin'or to r Dowty -iEquipment Limited; 'Ch'elte'nham, England epxilicatjic e g sm, 1947, "Serial No.1 66,003 njfi rs in itai rcsrr rlw" te h esw 1 5 36 This invention consistseina fuel sunply YS6IT for an aircraft internal combustion turbine power unit in which a control gnemberresponsive to .controllable variable-speed motor meansibut totally unresponsive to ambientconditions suchas pressure changes due to altitude difierencea. and a follower member responsive ,to engine-speed are so associated with one anothery.andawith means by which fuel is supplied to'theengineatavariable rate, that when; either of said members tends to lag behind or? over-ride the movement of the other, the rate of tuel- :supply. is correspondingly varied to cause the engine to assumea speed dictated by the speed of said motor means.

If the operatortwishes .tospeed up. the, en ine he will movehis leveror other-actuatorfto.selectively increase the speed-ofothe variablefspeed motor means. Thisf'will calwe' thecontrol member to tend to over-ride ,the follower member with the result that-the rate-of liuelsupply will be increased, which will increase thespee'd-ot the engine until the follower member is in synchronism with the control; member Tat the selected increased speed. 'I f,"onfthe -othemhandgthe operator wishes toslow down the enginehe will slow down the variable .-spe6d mdwlt-meanawhich will cause the control memberitottendf'to Jagbehind the follower memberan'dso'bring aboutfa reduction in the rate oitlieljsupflyan'cl hence acorresponding reduction in the enginegspeed. In other circumstances, assumln'g the operator wishes the engine togcontinue to, operate at a selected speed, it maybe (jand isfth rcasej in aircraft internal combustio'nturbine. power units) that the engine fuel requirementsat the selected speed may vary owing, for examplatovariation in altitude orambient temperature. Insnch an event the unaltered rate'of fuel;supply lwill,'with the changing conditions, cause the engine speed to increase or decreasefas'thecasernay be. This, according to the present invention will react through the control and follower members "to bring about the appropriate variation in the rate of fuel supply until'the engineisrunnim atjthe selected speed but in the changed conditions. From the above it will be seen that any position of the operatorslever or'other'actuatoriwill correspond to a definiteR-P. M, ortheengin'e irrespective of influences such asfchanges' in'altitude or ambient temperature whlchtendgtoyal't'er the engine speed.

The control and follower members may directly operate means for metering the iuel'flowwhether in a delivery line or in a spill returnline, Torjthey may control ,someintcrmlelliate. .j en b whit the fuelmay bec'ontrolled. As'an' ei'cample 'of h t mm o t t'm i th a t u i st r ablejldelivery pump; Iorjthje setting ofanieterin 'orifice'jmay be co ntrolledbynuid pressure means thejsense of operation of wliich isldeterminedby the r l ti n hip 1 fthegcpntrolian fi llciver ber's.

i jd ihe 'itmay bei l erl pdereflood ea r t t r am neinv nt bn ne be 6; scribed with ref erencetojthe accompanying dia rammatic drawings, foilwhich:

Figure l .i's a ."schehfiaticilayout diagram of a Figure'2 is a section through'the c m ensating means embodied in the Figure 1 game ment, and

.F llles :3, 4 "and-5 are sections taken respec- Ei t m l flfhesystem now-to be'described hasbeen dejternal combustion, reaction turbine as aircraft propulsion. In Figured, the reference numeral gtfi'represents a variable delivery purnpi In this case,"the pump is o'fthe radial cylinder type with plungers'L-SG operating n the radial-bores 31 0f the rotorwhich is driven for rotation by an externaldziye conneetion. The' cylinder assembly rotates, about the stationary spindle '38', which incorporates the' inlet port 39 and' the outlet port is'in a minimum -eccentricity condition at' wlilc'h the delivery is' at itsminimum." --"Ihe pump takes liduid fuel -fromthe 'iuel supply tanks along" the condiiit] M and -i:ue1 'fe'ds into the inletport Sil afidis-thenfIi'ui'npeH v'i'al jthe pistons through the 'oL 1tlet port- {4flof the p1iri1p for delivery" past} the-emergency fuel control-cock 45 along the conduit-433150 the" burner ring IT. The burner rin :is provided with a Qnu'in ber ol burners 92, atfl least one 'tor each mmeasam chamber of the turbine. Foi detai1 er: rich burnersand the fuel supply "s'ystefrr'iwhereinlthy may 'be er'nployed, reference is-made tofiny copending estim tion-seem N6. $2343, filed January raises; rr ie'r eleeiiv ry Cancun; as run h s s r n :qmi le c; L whi iee is ;wetnes 'fimltml ml ll lib max mu s e d fx hei r ineiami s sta n J mu 'st lflel if ed nt th oiu fl lire i e duit'lG. p

"In the case of the arrangement shown in Figure sembly 52 and the piston operates in the cylinder 53 with fluid supply conduits 54. and 55 respec-,.

tively running to each end of the cylinder. Fluid supplied for track ring eccentricity variation is tapped oif the fuel supply conduit 44 running be.- tween the tanks and the pump through the actuating system supply conduit 56 leadin into the auxiliary pump 51, which in this case is a gear pump. The conduit 58 leads from the pressure 4 flow metering purposes is thus controlled by rela-: tive rotary displacement of the inner and outer sleeves, which can rotate relatively to a limited extent. Fluid flows to theinterior-of the control valve through the auxiliary"pressuresupply conduit 58 into the annulus 59 and therefrom through the centre ports 14 of the outer sleeve into an annulus 15 between the inner and outer sleeves and from" the annulus 15 through the outlet of the auxiliary pump 51 into the central annulus 59 of a rotary control valve 60, the details of which will later be described, but, for the time being, it suffices to explain that according to whether the electric motor 6! tends to be driven at a higher or lower speed than the speed of rotation of the engine driven shaft 62, actuating fluid is metered by the valve to flow either along the conduit 54 or along the conduit 55. The arrangement is in fact such that'delivery of actuating fluid along the conduit 55 into the cylinder 53, moves the track ring control plunger 50 leftwardly for reduction of eccentricity of the track ring whereby to reduce the quantity of fuel delivered along the fuel delivery conduit 46 to the burner ring. Conversely, actuating fluid supplied at pressure along the conduit 54 increases track ring eccentricity.

A drive to the engine speed responsive shaft 62 is picked up through the pinion '63 and the elec .current lead 61. The speed of rotation of the motor which is designed so .as to be capable of exceeding the intended maximum speed of rotation of the engine speed responsive shaft 62 can thus be varied by manipulation of the engine sped control lever 66. The purpose of theresistance box 90 will presently appear,. and can be disregarded at this stage. A f I Dealing now with the detail construction of the rotary valve, the details are best seen with reference to Figures 2, 3, 4 and 5, through the main parts are shown; in the schematic layout of Figure 1. The basic elements of the valve are two-ported rotary sleeves, the inner sleeve Bil-of which is revealed in Figure 1 by breaking away of the ends of the outer sleeve 69. Both sleeves have co-operating ports, of which the ports iii and II of the outer sleeve are visible in Figure 1, whereas the ports of the inner sleeve which cooperate with the ports 10 and H are seen respectivelyin Figures 4 and 6. It is convenient to refer to theports which operate for metering the flow, as control ports. Thus the ports 10 and H of the outer sleeve are the control ports of the outer sleeve and, correspondingly, the control ports of the inner sleeve which co-operate with the control ports 10 of the outer sleeve are designated by the reference numeral 12. Likewise, the control ports 13 of the inner sleeve cooperate with the control ports H of the outer sleeve. The orifice area which is variable for centre ports; 75 of'the inner sleeve to pressurize the'spaces.,,71 def 1ned between the inner sleeve and a centre. piece 18 fixed therein to extend throughoutthe length of the inner sleeve 68. It thus follows that the spaces 11 are pressurized to the pressure at the output of the auxiliary pump '5! at all times when the system is working.

At this point in the description, it is believed that it Will facilitate matters if the auxiliary system flow be traced through the valve, having particular reference tothe sectional Figures 3, 4 and 5. In that respect, Figure 4 is basic in that it'deals withthe pressurization of the spaces 71, from which it follows, if reference be directed to Figure 3, that, if the'inner sleeve 68 be rotated clockwise, as viewed on the section, relative to outer sleeve 69, how will be permitted from the port I! through'the control port 13 of the inner sleeve and out through the control port H of the outer sleeve into the annulus 79 from which actuatingfiuid can flow along the conduit 55 to the cylinder 53 to operate the plunger 50 to reduce track ring eccentricity, and therefore to reduce the amount of fuel supplied. "The inner sleeve 68 is rotated by the electric motor 6|, and such a movement corresponds to a decrease of the speed of'th eelectric motor in relation to the engine speed responsiveshaft'BZ from which the outer sleeve is driven. 7 Movement of the stroke control plunger 50f'clisp1aces liquid from the other end of the cylinder 53 alongthe conduit 54 into the annulus 80 '(see Figure: 5) and the corresponding relative, clockwise movement of the inner sleeve 6 8,fwhich brings the control ports ii and I3 of Figure 3 into register, also brings the ports 10 of the outer sleeve into register with the ports'lZaof the inner-sleeve which lead'into the exhaust 'spaces 8! which, like the pressure spaces '11, extend throughout the length of the inner sleeve. The exhaust space 8| are in communication with the centralexhaust duct 82 through the transverse port'83. seen in Figure 4 and, in dotted lines, in Figures 3 and 5, and the exhaust from the j central exhaust duct 82 is piped away back into'the fuel supply reservoir. 7 If, on the other hand, it isrequired to increase the speed of the turbine,'theispeed of the electric motor is correspondingly increased to bring about COUIltGIFClQCKWlSG movement, of the inner sleeve 68 with respect to they outer sleeve 69 and the valve operatesexactly as, before except with flow reversed, so that auxiliary fluid passes along the conduit 54 to thecylinder 53 with return flow along the conduit 55, and the strokeof the pump and the volume of fuel supply is' correspondinglyincreased; N of In operation,offthefiystem, starting up'from cold, the valve 45" is. first operatedlto open the pump deliveryoutput into the fuel delivery conduit 46 and the engine is 'run up on'the'starter. The track ring 42 of the fuel pump is loaded by the spring assembly 52 to a maximum eccentricity position 'Whichensures'an adequate supply of fuel for starting, QFuel'is piped along the conduit 45 through the'governor controlled valve which, be it' remembered, operatesonly as a max El imam speed governor'. =As'is usual inigas turbines used for aircraft propulsion, the burners incorpo rate relief valves which open only when a predetermined'pressure has been reached inf'a fuel upply sys'terh.- such an expedient is to ensure a predetermined and adequate delivery of fuel and to prevent burner trouble which might otherwise result in unsatisfactory combustion. By reason of the fact that the valves are operating in the initial stages of running up the engine, fuel is delivered into the small starting accumulator 49 in which compression pressure is built up against resilience in some form until'the starting pressure is reached and, at that stage, the re- 1ief valves on the burners areopenea and a steady delivery of fuel ensues at the burners. Ifhe fuel is quickly ignited by the usual electrical igniting ineans'andthen very quickly burns continuously. For starting purposes, of course, the engine speed. "control levertifi will have been-set to the required starting speed which thus limits the driven-speed of the electric motor SI and the result is that, once having started, the engine quickly begins to race so that the inner sleeve 58, driven as it is by 'theelectric motor, immediately tends to lag with respect to the engine speed responsive outer sleeve and fuel is delivered through the conduit 55to the cylinder 53 to operate the strokecontrol plunger 50 for reductionof track ring eccentricity against the spring loading 52. Thus, idling speed is achieved almost instantaneously on starting up.

Once having started, any increase dictated by the engine speed control lever "65, speedsup the electric'motor until the inner sleeve 68 driven thereby is rotating at such a speed that the engine speed responsive sleeve 09 is the laggard and actuating fluid is delivered to the other end of the cylinder 53 to operate the stroke control plunger 50 for increase of eccentricity of the track ring.

When operating under ideal conditions at a steady settin of the engine speed control lever, the speed of rotation of the sleeves 68 and 69 is identical and once the sleeves 68 and 69 have settled down after the last previous adjustment of the engine speed control lever they will theoretically blank oh the pipe lines 54 and 55, though in actual practice it is believed that such an ideal theoretical set up will rarely prevail. The fact that the sleeves 68 and 69 rarely stabilize so precisely does not introduce hunting of the speed of the turbine because the response to speed changes is practically instantaneous.

It must be appreciated that the relative movement provided for between the inner and outer sleeves G8 and 69 respectively must be limited to such an extent that at one limit the cooperating ports I0, 12 and 1 l, 13 are fully in register, whereas in the other limits they are blanked off. To provide such limited relative movement, it suffices to provide co-operating dog and slot projections between the two drives, the one respectively operating between the electric motor driven shaft and the inner sleeve 68 and the other between the engine speed responsive shaft 62 and the outer sleeve 69.

The governor controlled valve 48 has governor weights 85 which are driven for rotation from a suitably arranged auxiliary drive shaft through the pinion 84. Increasing engine speed swings the governor weights 85 out against the loading exerted by the compression spring 86 and, if a predetermined maximum speed is achieved, the upper land 81 of the governor controlled valve 48 opens pump delivery into i the relief passage 08. The fuel flowing to the burner rin is thus cut down to effectually limit the maximum speed, excess fuel being returned back to the inlet of the' pump 35.

It will appreciated that numerous modificationsjmaybe incorporated without departing from then'ature of the-invention; thus the motor til, which is the actual speed controlling means, might conceivably be a hydraulic motor or air r'notdr but, in that respect, it should be stated thatan electric' -motor-"presents many points or advantage. One "such advantage has in tact been s'ubject'to corisiderationih the preseh-t system where specifically adapted for supplying fuel to a gas turbine ro'r aircraft propulsion on "the jet reaction principle. In such'installation's, surner ranures have introduced difficulties because of disproportioned metering "of the fuel'to the-remaining burnersshould one or more burners fail. To avoidoverheating of the remaining burners, a thermo-couple is fitted to each burner, viz. the thermo-cou'ple '5! fitted to the burner 92 in Figure 1. The thermo couple 9 l -is connected by a current lead 93 to an amplifying stage 94 which is in turn connected by the current lead 89 to the resistanc'ebox 90.. If the burner 92 fails, the thermo-couple 9! acts through the amplifyin stage 94 upon tappings "in the resistance box 90 to increase the resistance in the motor current leadtl. The speed of the electric motor BI is thereby reduced, and consequently the total "fuel supply to the remaining burners is proportionately cut down.

It isa'n important feature of the present invention that speed compensation throughout the whole speed range can be achieved without the necessity for an over-ride barometric control such as has hitherto been regarded as necessary in aircraft which may be called to operate at any altitude from sea level to 40,000 or 50,000 feet, at the present stage of development.

The fuel control cook 45 serves a dual purpose. On the one hand it operates as a shut-off cock when the system is not operating, in which event the delivery is opened back into the relief port 83 so that the pumps or the system will not be injured should the starter be operated with the fuel delivery conduit 46 shut off, whereas, on the other hand, it can be used in emergency should the automatic compensating side of the system fail, in which event the pilot can still land in emergency by manual manipulation of the control cock 45.

It is believed that the only other item which is seen in the drawings and which has not so far been referred to is the relief valve 9| which operates to relieve any excessive pressure which may be developed in the auxiliary system. To that end, the spring loaded relief valve 92 can be blown open against the loading exerted by the compression spring 93 to give relief into the pump casing and therefrom into the inlet side of the pump.

It will be appreciated that the rotary form of control valve of Figure 1 might be employed equally well as a variable restriction directly metering the fuel supply, or the spill return line from the burners, in which event the pump 35 could be replaced by a constant delivery pump.

I claim:

1. A control valve for use in a fuel system for an aircraft internal combustion turbine engine, in which fuel system a pressure-fluid operable shifter is operatively connected to decrease or increase the effective fuel supply, said valve comprising two concentric, rotative sleeves, one of said sleeves constituting a follower sleeve arranged for connection toand for rotation at a speed corresponding to the speed of theengine, and the other of said sleeves constituting a control sleeve and being arranged for rotation at a speed which is variable at will, but constant at any selected speed, means so to rotate said control sleeve at any selected speed within a range embracing the operative speeds of the follower sleeve, a fixed central core, affording supply and drainage connections, respectively, each of limited angular extent, within the inner sleeve, and a casing surrounding the outer sleeve and defining axially spaced annuli pressure connected to the shifter to efiect, respectively, opposite movement; thereof according to which annulus is pressurized, the two sleeves being complementally ported, in registry with each annulus, and each port registering, as it rotates, alternately with the pressure supply and the drainage connections, the ports for registry with one annulus being angularly spaced relative to those for registry with the other annulus, whereby to determine the connection of one or the other annulus to the pressure connection, and the other to the drain connection, in accordance with which of said two concentric sleeves tends to overrun or to lag behind the other.

2. A control valve as in claim 1, wherein the shifter constitutes the track ring of a variabledelivery pump which by its shifting effects decrease or increase in efiective fuel supply to the fuel system, and a plunger operatively connected to shift said track ring, and itself pressure-connected to the valves 'annuli for actuation automatically under control of said valve.

3. A control valve as in claim 1, including a variable-speed electric motor operatively connected to rotate the control sleeve at any one of a plurality of constant speeds, and means manually operable to alter the speed of said electric motor.

FREDERICK HENRY CAREY.

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

UNITED STATES PATENTS Number Name Date 955,852 Coyle Apr. 26, 1910 1,446,464 Horvath Feb. 27, 1923 1,644,167 Best Oct. 4, 1927 1,749,569 DeFlorez Mar. 4, 1930 1,886,975 Profitlich Nov. 8, 1932 1,936,566 Davenport Nov. 21, 1933 2,160,324 Berges May 30, 1939 2,198,035 Ferris Apr. 23, 1940 2,214,552 Ferris Sept. 10, 1940 2,243,655 Scott May 27, 1941 2,252,693 Becker Aug. 19, 1941 2,314,610 Day Mar. 23, 1943 2,399,685 McCoy May 7, 1946 FOREIGN PATENTS Number Country Date 5,877 Great Britain of 1884 264,998 Great Britain Feb. 3, 1927 489,922 Great Britain Aug. 5, 1938

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