US2640318A - Starting system for gas turbine engines, using multiple fuel pumps - Google Patents

Description

June 2, 1953 F. H. CAREY 2 640 31 STARTING SYSTEM FOR GAS TURBINE ENGINES, USING 8 MULTIPLE FUEL PUMPS Filed June 50, 1948 FUEL [TANK WILL m '2 I BURNER 26 12 I men PRESSURE T ENGINE DRIVEN STOPPED FUEL PUMP \29 IM-ANUAL j CONTROL 6 l3 I5 34' Eli".

ClRCUIT CONTROL VALVE STARTING Low PRESSURE I BOOSTER PUMP RUNNING 22 29 33 4Q 25 4', l Lmen 9 PRESS 39 COCK 7 3O JWWJ 2 TNROTTLE 36 20 2/ I H59 27, 38 37 ISOLATiNG VALVE Inventor Frezoie/clc 696% X Attorney;

Patented June 2, 1953 STARTING SYSTEM FOR GAS TURBINE EN- GINES, USING MULTIPLE FUEL PUMPS Frederick Henry Carey, Cheltenham, England,

assignor to Dowty Equipment Limited, Cheltenham, England Application June 30, 1948, Serial No. 36,011 In Great Britain July 9, 1947 6 Claims.

This invention relates to fuel supply systems for continuous combustion turbine engines. It is very desirable with these engines to eliminate the possibility of unburnt fuel from collecting in the combustion chambers during the starting operation. This frequently arises owing to inefficient atomisation of the fuel during the initial stages of starting, and is very undesirable because once fuel issuing from the burners is sufficiently atomised to form a combustible mixture with the air, any unburnt fuel in the combustion chambers will ignite and will most likely result in damage to the engine. The problem is not concerned solely with, but becomes more acute when the engine comprises an auxiliary turbine which is driven by energy expended by the firing of a cartridge and which drives the main turbine during starting. The advantage of using a cartridge and. auxiliary turbine is that heavy and cumbersome electric motors and associated accumulators which would be required if the main turbine were started up electrically are unnecessary. From the point of view of starting, however, the cartridge accentuates the starting problem in that the cartridge expends its energy in a very brief period of time which may be as small as two to four seconds during which the fuel supply to the combustion chambers of the main turbine should be brought into condition for normal running so that the main turbine can take over from the starter turbine before the impulse given by the cartridge has been fully used up. Again, it is usual and desirable on stopping, to drain the burners and the pipe lines in the vicinity of the burners, which all adds to the problem of rapid starting.

The present invention provides an improved fuel system which eliminates or considerably minimisesthe risk of unburnt fuel collecting in the combustion chambers whether the turbine be started electrically or by the firing of a cartridge, and which ensures the supply of fuel to the burners in a rapid and combustible condition to enable rapid starting without developing excessive general or local overheating.

The present invention consists in a fuel supply system for a continuous combustion turbine engine in which a fuel pump driven independently of the engine communicates with the engine burners through a valve-controlled passage, the valve means of which closes the passage whenever the engine is at rest and moves as a consequence of starting rotation of the engine to open the 'passage'to permit fuel from said pump to pass to the engine burners direct. By these means the engine may be brought from rest to a normal running condition in an extremely short period and in a safe and controlled manner. Just prior to the actual starting of the engine the drive to the pump is set in operation so that.

the pump may be delivering its maximum output before the engine starts to turn. As soon as the engine turns, the valve means controlling the passage from the pump to the burners will open the passage and fuel at full pump output will be fed to the burners. The control of the valve by the starting rotation of the engine will prevent the pump from delivering any fuel into the engine during the starting-up of the pump. Moreover, the operation of the pump before rotation of the engine will ensure that the lines leading to the valve means will be fully charged before the valve means opens the passage. It is preferred to arrange the valve means close to the burners.

The pump may be the means by which the fuel is supplied to the burners during normal running of the engine, but in systems employing one or more engine-driven supply pumps and an independently driven booster pump for priming the engine-driven pump or pumps, the booster pump may conveniently be utilised in accordance with the invention for supplying the fuel direct to the engine burners during the starting-up operation during which the booster pump will also act to prime the normal supply pump or pumps. In such a case the valve means controlling direct flow from the booster pump to the burners will be arranged to respond to normal running of the engine in order to close the passage when the engine runs normally in order to prevent fuel from the booster pump from passing to the burners direct during normal running.

The valve means, which may comprise one or more valve elements, may be controlled hydraulically; conveniently by the. pressure of fuel delivered by the supply system.

A fuel system embodying the improved starting arrangement in accordance with the invention will now be described by way of example with reference to the accompanying diagrammatic drawing of which- Figure 1 shows the system in the stopped condition Figure 2 illustrates the starting condition; and i which forms the subject of copending patentv application Serial No. 2,343, filed January 14,

3 1948, now Patent No. 2,608,2 i7, issued August 26, 1952.

In this system the turbine engine (not shown) incorporates burners of the type known as spill burners, one of which is indicated diagrammatically at H. These burners are distinguished by the fact that only a proportion of the fuel delivered to them passes out through their dis.- charge orifices whilst the remainder flows back along a return or spill line. lhe particular system also comprises a high p ssure pump which operates as a fixed delivery pump to circulate fuel around a circuit including the burners H, and a variable delivery fuel supply pump which operates normally to pass fuel from the tank M into the circulating flow set up by the pump 12 at a point somewhere between the inlet of the circulating pump 22 and the spill orifices of the burners; such a point may be at the connection 42, as will later appear in detail. The pumps [2 and it are driven by the engine and th pum t d iver t rou h t eL-i ndi cated at 15, which functions under nor al running conditions (Figure 3) to regulate the amount of fuel supplied at to the burners;

under starting conditions (Figure 2) this throttle 55 ou d e u sta lly ully o n. i oe- 1. in 511611 lQl R DQ S i i li l ,1 i l l f As is customary with systems for supplying fuel 0 u i e en ne there is r vided i h n the tank M a low pressure booster pump Iii d i n by an el ct ic m o n th or i Way the pum 6 s es s l ly for primin the supply pump or pumps, and with the particular system being described would serve to prime the n e of th pump is by way of the line 23, so long as valve i8 is open. The present invention, however, utilises the pump id in order to ensure adequate supply of fuel to the burners ii during the initial stages of starting the engine, whether the engine be started by a cartridge and an auxiliary turbine, or in any other way, e. g. by an electric motor.

In addition to low and high pressure valves 18 and I ,9 respectively, the system includes what may be termed an isolating valve 2s, a trip valve 21 and a Circuit-control valve 22. Various nonreturn valves are also included.

From a consideration of the drawing it will b .6. 11 that when the engine is at rest and the system is in the stopped condition (Figure 1) the low pressure cock l8 prevents flow from the booster pump it along the line 23 leading to the inlet of the supply pump i3 and also cuts off flow along the branch line 24 leading throu h the circuit control valve 22 on the one hand to the isolating valve 28 and on the other hand to a closed non-return valve 25 leading to the high pressure cock 19. In this condition the circulating pump i2 is still connected in its circuit but its delivery side 26 communicates with the tank M along a pipe line 2'1, a branch line 28, through a section of the high-pressure cock l9, and through a pipe 29. The movable element of the isolating valve 20 assumes the left hand position under the influence of a spring to, the trip valve 2| is closed by a spring 38, and the circuit control valve 22 assumes the right hand position by virtue of a spring 32. The high pressure cock 19 has been moved to the right by a hand lever 33.

When it is desired to start up the engine, the low-pressure cock I8 is first turned (see Figure 2) to permit flow from the booster pump 16 previously or simultaneously started by closing of the circuit of the electric motor H, to the inlet of the supply pump i3 and also along a pipe 35 as far as the isolating valve 20. Soon after the pump it has been set in motion the main turbine engine is started, let it be assumed by the firing of a cartridge which drives an auxiliary turbine which in turn drives the main turbine. At the same time the high pressure cock i9 is moved by hand to the left hand position shown in Figures 2 and 3. As soon as the engine turns, the pumps l2 and I3, which are driven by the engine, will also commence to rotate and the delivery pressure from the supply pump it flows through the pipe lines 35 and 33 upon the movable element of the isolating valve 26 which is sensitive to the pressure of pump it to shift this element against its spring 3%] to the righthand position shown in Figure 2. It has already been shown how the delivery from booster pump 16 reaches the isolating valve 20, so in this shifted position of the isolating valve it will be seen that the booster pump 16 can communicate with the burners by way of the path to the isolating valve already described, and then through the pipe 35, through a passage 3l in the isolating valve. and along the pipe line 21. The supply pump it (the throttle it being open) is also able to deliver through the branch passage 33 into the passage 37 and thus to the burners. During the initial stages of starting, the spring 31 of the trip valve 2i maintains the trip valve closed but as soon as the engine reaches or approaches normal running the pressure in the system will have risen such as to open the trip valve 2|. As soon as the trip valve opens, its spring will collapse on account of the greatly enlarged area of the element of the valve 21 which is exposed to the fuel pressure. The opening of the trip valve 2! permits fuel pressure to act by way of line 4 3 upon the element of the circuit control valve 22 which moves the valve to the left against its spring 32 as seen in Figure 3, with the result that the booster pump it is cut oil from the burners H, and thereafter delivers only to the supply pump 113.

It will be appreciated that the booster pump it; delivers a large quantity of fuel at low pressure and that this fuel is available to the burners H as soon as but not before the turbine starts to rotate. This quantity of fuel assisted by delivery from the supply pump 13 ensures effective atomisation of fuel issuing through the burner orifices and therefore ensures a readily combustible mixture without there forming in the combustion chambers of the engine any pools of unburnt fuel. By the time the cartridge has expended its energy, which may take up four seconds or less of time, the engine is able to achieve normal running in orderto take over from the auxiliary or starter turbine. mentioned above, as soon as normal running is achieved, the trip valve 2: is opened automatically, which in turn automatically brings about movement of the circuit control valve 22 into the normal running position shown in Figure 3. In this condition of the systemdirect communication between the booster pump it and the burners is cut oil by the element of the circuit control valve 22 closing the line 24. The change of position of the circuit control valve also permits the delivery from the supply pump 3 to flow past the throttle l5 and from the line 35 and branch line 39 through the high pressure cock 29 to a line and through the circuit control valve 22 to the line 4| leading to the intake pipe 42 of the circulating pump I2. The line 21 is connected to the outlet 26 of the high pressure pump I2; as soon as that pump builds up pressure to a value such that, acting on the right hand end of the shiftable element of isolating valve 20, and assisted by the spring 30 thereof, it will overcome the resisting pressures that urge such element to the right, that element will shift to the left. Since the booster pump pressure has been or is simultaneously cut off from the left hand end of isolating valve 20 by shift to the left of the circuit control valve 22-which latter movement is assisted by increasing pressure in line 21 communicated past trip valve 2I and line 44the only resistance to shifting of the isolating valve element to the left is the lesser outlet pressure of supply pump I3. The higher pressure in line 21 overcomes this resistance and shifts the isolating valve element to the left, to the same position it occupied in the stopped condition of the system. This leaves the supply pump I3 connected only to the spill side of the system at the inlet 42 of the circulating pump I2. The broken line arrows in Fig. 3 show how the normal running pressure delivered by pump I2 is conducted along conduit 21 to the righthand chamber of each of the isolating valve 20 and the circuit control valve 22 so as to cause the movable part of each valve to shift from the position shown in Fig. 2 to the position shown in Figure 3. The system thus functions normally with the circulating pump I2 circulating fuel through the burners II and with the supply pump I3 being primed by the booster pump I6 and injecting into the circulating flow near the inlet of the circulating pump. During normal running the speed of the engine will be governed by the opening and closing of the throttle I5. When the engine is to be stopped, the throttle I will be closed and the low and high pressure cocks I8 and I9 will also be returned to their stopped positions. The circuit control valve 22 and the trip vlave 2I will thereupon return under the influence of their respective springs to their stopped positions, and the isolating valve is already in that position. In the stopped position the supply pump I3 is able to deliver back to the tank through the non-return valve 25, prior to closing of thethrottle I5 and low pressure cock I8.

Although the invention has been described in connection with a system incorporating, in addition to the booster pump, two pumps used in a particular way, it is to be clearly understood that the invention can also be applied to systems using a single supply pump or using more than a single supply pump in any chosen arrangement.

I claim:

1. A fuel supply system for use with an aircraft continuous combustion turbine engine such as is started by an auxiliary turbine adapted itself to be driven by energy expended by the firing of a cartridge, said fuel supply system comprising at least one engine driven fuel supply pump and an independently driven tank booster pump operative during normal engine running to prime the supply pump or pumps, as the case may be, a passage for connecting the booster pump with the engine burners, valve means in said passage biased to close the passage whenever the engine is at rest and movable as a consequence of starting rotation of the engine to open the passage to permit 6 fuel from the booster pump to flow directly to the burners during starting of the engine, said valve means being responsive also to normal engine speed to close the passage and thus to prevent fuel from the booster pump from passing'directly to burners during normal running.

2. In combination with the burners of a continuous combustion turbine engine, a fuel supply system for said burners which includes a fuel pump driven by and during operation of the engine, another fuel pump driven independently of the engine, conduit means to connect each such pump with said engine burners, a valve in said conduit means biased to close off direct communication between the independently driven pump and the burners automatically whenever the engine is at rest, and means sensitive to pressure developed by said engine-driven pump, upon commencement of rotation of the engine, and operatively connected to said valve to open the same and thus to open said conduit means for direct passage of fuel from said independently-driven pump to the burners, during starting.

3. A fuel supply system as in claim 2, wherein the conduit means includes an inlet passage leading from the independently-driven pump to the inlet of the engine-driven pump, and a branch from said inlet passage leading from the independently-driven pump, by way of said valve, to the burners, and wherein the conduit means further includes a delivery passage leading from the engine driven pump to the burners, and a branch from said delivery passage leading to the means sensitive to the pressure developed by the engine driven pump which is operatively connected to the valve to bring about said opening of the same, during starting.

4. A fuel supply system as in claim 2, wherein the valve constitutes an isolating valve and is shiftable between two positions, an open or starting position and a closed position to which it is biased, and wherein the conduit means includes an inlet passage leading from the independentlydriven pump to the inlet of the engine-driven pump, and a branch from said inlet passage leading from the independently-driven pump, by way of the isolating valve, to the burners, and wherein the conduit means further includes a delivery passage leading from the engine driven pump to the burners, and a branch from said delivery passage leading to the means sensitive to the pressure developed by the engine driven pump to open the isolating valve during starting, and leading also to and past the isolating valve when the latter is opened, for delivery into said branch from the inlet passage and thence also to the burners, during starting.

5. A fuel supply system as in claim 2, wherein the engine-driven fuel pump constitutes a lowpressure fuel supply pump, said system including also a high-pressure engine-driven circulating pump and a closed circulating conduit in which said circulating pump and the burners are included, and wherein the conduit means for connecting each of the fuel supply pump and the independently-driven pump to the burners includes a passage leading from the independently-driven pump to the inlet of the fuel supply pump, and a branch from said passage leading from the independently-driven pump, by way of said valve, to the burners, and the conduit means further includes a delivery passage leading from the fuel supply pump to a connection to said closed circulating conduit for normal supply of fuel for discharge into that circulating conduit, and also a branch passage leading to the means sensitive to the pressure developed by the engine driven fuel supply pump which are operatively connected to the valve for opening the same.

6. In combination with the burners of a continuous combustion turbine engine, a fuel booster pump driven independently of the engine, to develop low pressure, engine-driven pump means, to develop high pressure, a first conduit means connecting the booster pump delivery to the intake of the engine-driven pump means, and from the latter to the burners, for the supply of fuel at high pressure to the burners during normal running, an isolating valve having means biasing the same towards closed position, but shiftable to open position by such pressure as is developed by the engine-driven pump during starting up; a second conduit means connecting the delivery side of said engine-driven pump means to the isolating valve, arranged to subject said valve to engine-driven pump pressure, to open the isolating valve upon commencement of delivery from said engine-driven pump means, during starting up; a third conduit means for connecting the booster pump to the isolating valve, and thence directly to the burners, for delivery of fuel at low pressure to the burners past the opened isolating valve; and a fourth conduit means connected to the delivery side of the engine-driven pump means, and connected to the isolating valve to subject said valve to the high pressure developed by said engine-driven pump means at runningspeed, and arranged to assist the isolating valve biasing means and to close said valve, and thereby to interrupt direct fuel supply from the booster pump to the burners automatically upon initiation or" running speed of the engine-driven pump means.

FREDERICK HENRY CAREY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,410,774 Chandler Nov. 5, 1946 2,417,215 Satterlee Mar. 11, 1947 2,427,835 Campbell Sept. 23, 19%; 2,432,177 1 Sdille Dec. 9, 1947

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