US3203178A - Fuel system for supplying gaseous fuel to a combustion chamber - Google Patents

Description

Aug. 31, 1965 H. sAvlLLE ETAL.

FUEL SYSTEM FOR SUPPLYING GASEOUS FUEL TO A COMBUSTION CHAMBER Filed May 25, 1963 United States Patent O 3,203,178 FUEL SYSTEM FOR SUPPLYING GASEOUS FUEL T() A COMBUSTION CHAMBER Harold Saville and Robin Michael Dakin, Coventry, England, assignors to Bristol Siddeley Engines Limited, Bristol, England Filed May 23, 1963, Ser. No. 282,708 Claims priority, application Great Britain, .lune 6, 1962,

3 Claims. (Cl. 60-39.28)

The invention relates to a fuel system for supplying gaseous fuel to a combustion chamber of a gas turbine engine or power plant and has as objects the provision of a reliable acceleration control, -a control at a fixed fuel flow to the engine or power plant or at a xed compres- Isor speed, or a control to give any required load/speed characteristic for an alternator or other power absorbing apparatus to be driven by the engine or power plant.

According to the invention, a fuel system for supplying gaseous fuel to a combustion chamber of a gas turbine engine or power plant comprises a flow-controlling valve in the fuel supply line leading to the combustion chamber, iluid-actuable means, arranged to operate the flow-controlling valve, a fluid control valve, arranged to effect operation of the fluid-actuable means, the fluid control valve being operable by pressure-responsive means, directly responsive to the delivery pressure of a compressor arranged to supply air to the combustion chamber and to the pressure of the fuel downstream of the flow-controlling valve.

Conveniently the luid-actuable means includes a piston, movable in a chamber, having an inlet to which a pressure lluid is admitted -under the c-ontrol of said fluid control valve and having an outlet; the piston being movable in the opening sense of the flow-controlling valve, when the fluid control valve operates to admit said fluid at a faster rate than it leaves the chamber, and in the closing sense of the flow-controlling valve, when the fluid control valve operates to admit said fluid at a slower rate than it leaves the chamber.

The aforesaid inlet lluid control valve may be connected in series with an outlet fluid control valve, operable by pressure-responsive means, responsive to the fluid pressure developed by a governor rotatable by a turbine of the engine or plant, said outlet fluid control valve being normally closed, except for a restricted leak path, when said inlet fluid control valve is open, and said inlet lluid control valve being normally open to a pre-adjustable setting when said outlet fluid control valve is open. The outlet fluid control valve may also be operable by two pressure-responsive means acting thereon in opposition to each other, one of the latter means being directly responsive to the pressure of fuel downstream of the flowcontrolling valve and the other` being responsive to the pressure in a fuel reservoir of xed capacity and supplied from the fuel supply line downstream of the flow-controlling valve through a xed restrictor.

The, or each, lluid control valve may be carried on a pivotally-mouuted arm, engageable by the pressure-responsive means. The or each arm may comprise a first member mounted on a xed pivot and carrying the lluid control valve, and a second member, engageable with one end Iof the first member and forming therewith a longitudinally-adjustable knuckle joint, the second member being longitudinally-adjustable with respect to a pivot therefor, the axis of the latter being spaced longitudinally from the axis of the pivot of the first member by a lixed distance, the second member also being engageable by at least one of said pressure-responsive means, whereby the effective force applied by the pressure-responsive means, `acting on the second member, is applied to the lirst member through the knuckle joint and whereby axial ad- ICC justment of the second member with respect to its pivot will alter the value of said effective force and therefore of the resultant moment of said effective force about the pivotal axis of said iirst member. A composite valvecontrolling arm of this kind forms the subject of our copending application Serial No. 282,787, tiled May 23, 1963, now Patent No. 3,176,540.

By way of example, one form of gaseous fuel system, according to the present invention for a gas turbine engine or power plant having an independent power turbine is now described with reference to the accompanying drawing, which is a diagrammatic part-sectional view of the components of the fuel system. Like reference numerals have been used in this drawing and in the drawing of the aforesaid co-pending application for parts appearing in both drawings.

Reference 1 indicates the fuel supply pipe leading to a fuel burner of the combustion chamber (not shown) of the engine or power plant. The pipe f1 contains a flowcontrolling valve, which, in this example, is a simple butterly valve 2. The buttery valve is shown in its open position but can be moved to a closed position by means of a shaft 3, driven by a pinion 4, engaged by a rack 5 formed on a piston 6, hereinafter described. For ease of illustration only, the shaft 3 and the butterfly valve 2 are shown in the plane of the paper, whereas in reality they will be co-axial with the pinion 4. A tapping for transmitting fuel gas delivery pressure downstream of the valve 2 is made through pipe 7.

The piston 6 has a flange 9 at the right-hand end thereof, as viewed in the drawing. A constant oil pressure, supplied through a pipe 8 from pipes 10 and 11, via a governor 36 (described hereinafter) leading from a pump 12, acts on the left-hand side of the flange 9 and an oil pressure in a chamber 13 in a block 14 acts on the righthand side of the piston. The piston 6 is normally in a balanced condition and moves to the right or left to maintain the oil pressure in the chamber 13 at a substantially `constant valve, this being lower than that supplied through the pipe 8, in accordance with the ratio of the areas ofthe flange 9 and the piston 6 on which the respective oil pressures are acting. Movement of the piston 6 to the left, as shown in the diagram, displaces oil through a return pipe 15 to the inlet side of the pump 12 to avoid hydraulic locking. The high pressure oil pipes 8 and 10 are connected by a pipe 16 with the chamber 13, through a halff ball valve 17, constituting the aforesaid inlet fluid control valve, carried on a member 18 of a pivotally-mounted acceleration control arm comprising the member 18 and another member 19 which are connected by a knuckle joint, as will be described hereinafter. The pivotallymounted arm is acted on by a pre-adjustable spring 25 and by plungers 21 and 22, carried on diaphragm 81, 82, respectively to the lluid pressures in the pipe 7 and a pipe 23, leading, via a fixed restrictor 83, from the delivery of a compressor of the engine. Thus when there is a change in either the pressure of the gas supply to the burner or the compressor delivery pressure, or both, the member 18 will open or close the half-ball valve 17. The pivotal movement of the member 18 in the opening sense is limited by an adjustable stop 26. There is a restricted leak path around the half-ball valve 17, so that, when the halfball valve is otherwise closed, there is a communication between the pipe 8 and the chamber 13.

The chamber 13 communicates through a passage 29 with a second half-ball valve 30, constituting the aforesaid outlet fluid control valve, carried on a second composite governing control arm comprising knuckle-jointed members 31, 32, similar to the members 18, 19. The second half-ball valve 30, when open, places the passage 29 in communication with a cavity 33. The latter communicates through the pipe 15 with the inlet side of the pump 12. Thus the pressure within the cavity 33 is lower than that within the chamber 13. There is a restricted leak path around the half-ball Valve 30, so that when the latter is otherwise closed, there will be a communication from the chamber 13 through the cavity 33 and the pipe 15 to the inlet of the pump 12. The member 31 is pivotally mounted, as will hereinafter be described, and is acted upon by a plunger 34, carried on a diaphragm '70, responsive to a pressure applied to the interior of a chamber 71 through a pipe 35 and derived from the governor 36.

The governor 36 has an internal cavity 86 therein, which communicates with a pipe 87, leading to the oil return pipe 15. Oil under pressure delivered from the pump l12, via the pipe 11 is led into a passage 88 in the governor housing, through a fixed restrictor 89 to another passage 90, from which oil is bled into the cavity 86 through a half-ball valve 84 carried on a pivoted arm 85. The passage 9i) also communicates with the pipe 35, so that the pressure of oil in the pipe is varied by the opening and closing of the half-ball valve 84. The arm 85 is engaged by a spring-biased plunger 91, which yis carried on a diaphragm 92 responsive to variation in the pressure difference between oil supplied to the passage 90 and oil in the cavity 86. The arm 85 is also engaged, in opposition to the biasing spring, by another plunger 93 movable by centrifugally-operable governor Weights 94, rotatable by a shaft 95, driven by the said independent power turbine. Thus as the speed of the power turbine varies, so the forces acting on the arm 85 will vary and hence the oil pressure in the pipe 35 will vary. This in turn will control the opening and closing of the halfball valve 30.

The composite governing control arm 31, 32 is also acted upon by the fuel pressure downstream of the valve 2, this pressure being applied through the pipe 7 and a passage 38 to a diaphragm 74, which carries a plunger 39, acting on a tubular guide 62 in which the member 32 is mounted. The fuel pressure-in the passage 38 also leads through a bank of xed restrictors 40, arranged in series one with another, into a gas reservoir 41 of xed capacity. The gas reservoir 41 connects with a chamber 42, which contains diaphragm 73, carrying a plunger 43, engaging the member 31. The opening movement of the arm 31 is limited by a stop 44. A bias in the closing sense can be applied to the arm 31 through a spring 47 by means of a lever 45, which turns a pinion 72, which engages a rack 46 for adjusting the compression of the spring 47. The arm 45 is connected to a corrector motor (not shown).

A ow control device 50, including a needle valve 104 controlled by a linear actuator 51, allows the compressor delivery from the line 23 to be bled to atmosphere past the needle valve 104 and through a port 105, thereby reducing the pressure in the pipe 23 and so varying the effect of the plunger 22 on the arm 19. A compressor overspeed governor 52 is also provided. This contains a pivotally-mounted arm 96 carrying a half-ball valve 53, which also acts to vent compressor delivery pressure from the line 23 into a cavity 97 within the housing of the governor 52 and thereby to reduce the loading of the plunger 22 on the arm 19. The cavity 97 is supplied with oil for lubrication of the governor from the delivery pipe 11 of the pump 12, via a fixed restrictor 98. Air vented through the half-ball valve 53 forms a mist which mixes with the oil in the cavity 97. The oil and air mixture leaves the cavity 97 by passing through the bearing of the governor shaft 103. The arm 96 is engaged by an adjustable spring 100 and a plunger 101, movable by centrifugally- `operable governor weights 182, rotated by the shaft 103, which is driven from the shaft of the compressor, supplying the pipe 23.

The movement of the piston 6 and hence of the valve 2 is effected by the flow of oil into and out of the chamber 13. When the flow into the chamber 13 through the pipe .be kept constant.

16 is equal to the flow from the chamber 13 through the passage 29, the piston 6 will remain stationary. When the flow into the chamber 13 is greater than the flow from the chamber, due to the half-ball valve 17 admitting more oil than can escape through the half-ball valve 30, the piston 6 will move to the left, as viewed in the drawing, thereby maintaining the oil pressure in the chamber 13 substantially constant, as aforesaid, and turning the valve 2 in the opening sense; but when the half-ball valve 30 opens to allow a greater outflow than inflow, the piston 6 will move to the right, as viewed in the drawing, thereby maintaining the oil pressure in the chamber 13 substantially constant and turning the valve 2 in the closing sense. The restricted leak paths around the half-ball valve 17 and 30 are such that with both valves otherwise closed, the outflow is greater than the inflow; but when the half-ball valve 17 is open to a pre-adjusted setting of its stop 26 and the halfball valve 31) is closed, except for the restricted leak path, the outflow is less than the inflow through the half-ball valve 17.

The two composite control arms 18, 19 and 31, 32 are so adjusted that, except during very short change-over periods, either (but not both simultaneously) the acceleration control arm 18, 19 or the governing control arm 31, 32 is functioning to control the valve 2, in the foregoing manner. When the governing control arm 31, 32 is in operation, the acceleration control arm 18, 19 holds the half-ball valve 17 fully-open to the said setting of its stop 26. Thus when the governing control arm 31, 32 moves from an equilibrium position in the closing sense of the half-ball valve 38, the piston 6 will move to the left, thereby turning the valve 2 in the opening sense, and when the control arm 31, 32 moves from an equilibrium position in the opening sense of the half-ball valve 30, the piston 6 will move to the right, thereby turning the valve 2 in the closing sense. When the acceleration control arm 18, 19 is in operation, the governing control arm 31, 32 holds the half-ball valve 30 closed, except for its leak path. Thus when the acceleration control arm 18, 19 moves from an equilibrium position in the closing sense of the halfball valve 17, the piston 6 will move to the right, i.e., turning the valve 2 in its closing sense, and when the control arm 18, 19 moves from an equilibrium position in the opening sense of the half-ball valve 17, the piston 6 will move to the left, i.e., turning the valve 2 in its opening sense.

Both half-ball valves 17 and 30, when closed, except for their leak paths, will cause the piston 6 to be moved to the right, i.e., in the closing sense of the valve 2; but the halfball valve 17 will only cause the valve 2 to open, if the half-ball valve 30 is closed, and the half-ball valve 30 will only cause the valve 2 to open, if the half-ball valve 17 is open to its pre-adjusted setting.

When either the acceleration control arm 18, 19 or the governing control arm 31, 32 is controlling the valve 2, the appropriate arm is in balance and it is upon the sensitivity of this balance that the system depends for its accuracy and sensitivity. When the acceleration control arm 18, 19 is controlling the valve 2, there are only two varying forces acting on the arm, namely that due to the gas burner pressure applied through the pipe 7 and that due to the compressor delivery pressure applied through the pipe 23. Hence for balance of the arm 18, 19, the gas pressure will normally be proportional to the cornpressor delivery pressure. Hence the pressure ratio across the burner during an acceleration will be held constant and the fuel mass flow Will be proportional to the compressor delivery pressure. Alternatively by modifying the compressor delivery pressure signal reaching the acceleration control, the acceleration control arm can be used for other purposes. For example, by making the pressure in the pipe 23 constant by using the ilow control to bleed off air from the pipe 23, the gas pressure can Similarly by reducing the pressure in the pipe 23 by the compressor overspeed governor 52,

as the compressor speed rises, the fuel pressure supplied to the engine may be controlled to give a particular compressor speed.

When the governing control arm 31, 32 is in operation, the balance on that arm is between four forces, namely the signal derived from the power turbine governor 36 through the pipe 35, the spring force applied through spring 47, the force due to the gas pressure applied through passage 38 and a force due to a delayed `gas pressure applied from chamber 42. The two latter forces are provided to stabilise the governing control arm and to enable isochronous governing to be achieved if desired. The gas pressure from the pipe 7 is applied on the member 32 through the passage 38 and the plunger 39, so that when the gas pressure alters due to the power turbine governor 36 sensing a change in speed, the half-ball valve 30 is restored substantially to the equilibrium position. This ensures that the sensitivity of the governor arm 31, 32

is adequate and will give stable running. There is however the disadvantage that there would be a change in governed speed when the load changes, known as a speed droop. For stable running of the engine, this may amount to as much as i.e., at full load, the speed Will be 20% lower than at low load. In order to reduce this speed deviation, if necessary down to zero, a force derived from a delayed feed back pressure is applied thro-ugh the diaphragm 73 and the plunger 43, the force slowly cancelling as much of the direct feed back pressure force, applied through the passage 38, the diaphragm 74 and the plunger 39, as required, by adjustment of the knuckle joint between the members 31, 32, as hereinafter described. Ultimately, with the gas pressures on the arm 31, 32 in perfect balance, the steady governed speed can be made to remain constant regardless of load changes. The delayed feed back pressure, which is applied through the chamber 42 and the plunger 43 must not alter too fast as otherwise instability will be reintroduced. The function of the gas reservoir 41 and the bank of restrictors 40 is to provide the desired delay.

Both the control arms in this example are of a composite nature comprising respectively the members 18 and 19 and 31 and 32. Referring firstly to the acceleration control arm 18, 19, the main member 18 is pivotally mounted on a pivot 55 and carries the half-ball valve 17 and is also acted upon by the plunger 21, i.e. by gas pressure applied through the pipe 7. The lower end portion 59 of the member 18, as viewed in the drawing, is hollow and contains a ball-shaped end 58 of the member 19, which is mounted for axial adjustment in an internally screw-threaded tubular guide 56, pivotally-mounted in the block 14 at 57, at a fixed distance from pivot 55. As the guide 56 and the member 19 are pivoted as a whole about the pivot 57, the ball-shaped end 58 will engage the tubular end portion 59 of the arm 18 and so act as a knuckle joint. The plunger 22 acts on the guide 56 and therefore on the member 19 and thus applies an effective force, through the knuckle joint, on the member 18. By axially adjusting the position of the member 19 in the guide 56, the distance between the ball-shaped end 58 and the pivot 57 is varied and so is the position of the ballshaped end 58 in the end portion 59 of the arm 18. Thus the resultant moment, about the pivot 55, of the force, applied through the knuckle joint, is altered. In this way adjustment of the member 19 in the guide 56, will vary the effect of the pressure derived through the pipe 23. The governing control arm 31, 32 is of similar construction. The member 31 is pivotally-mounted at 61 and the member 32 is mounted in a tubular guide 62 pivotallymounted in the block 14 at 63. The member 31 has a tubular end portion 64 and the member 32 has a ballshaped end 65, which co-operates with it and acts as a knuckle joint. The effective moment, about the pivot 61, of the gas force applied to the plunger 39 through passage 38 is adjustable by turning the member 32 in the guide 62. The amount of the adjustment determines the .resultant effect of the opposing forces applied by the plungers 39 and 43 and is termed a droop adjustment. The composite construction of the control arms 18, 19 and 31, 32 is more fully described in the aforesaid co-pending application.

What we claim as our invention and desire to secure by Letters Patent of the United States is:

1. A fuel system, for supplying gaseous fuel to a combustion chamber of a gas turbine engine or power plant, comprising a flow-controlling valve in the fuel supply line leading to the combustion chamber, fluid-actuable means for operating said How-controlling valve, a pivotallymounted arm, a fiuid control valve, carried on said arm and operable to move said fiuid-actuable means, pressure-responsive means, directly responsive to the delivery pressure of a compressor arranged to supply air to the combustion chamber and to the pressure of the fuel downstream of said flow-controlling valve, said pressureresponsive means acting on said arm and being operable to control the amount of opening of said fluid control valve, said uid-actuable means including a chamber, having an inlet to which a pressure fluid is admitted under the control of said fluid control valve and having an outlet; a piston movable in said chamber in response to the pressure of fluid therein, said piston being movable in the opening sense of said flow-controlling valve, when said fluid control valve opens to admit said fluid at a faster rate than it leaves the chamber, and in the closing sense, when said fiuid control valve moves towards its closed position to admit said fluid at a slower rate than it leaves the chamber, the fuel system also including a second pivotally-mounted arm, a second fluid control valve, said second fluid control valve being carried on said second arm and operable to control the flow of fluid through said outlet, said second uid control valve being connected in series with said inlet, that is said firstmentioned, uid control valve, a governor rotatable by a turbine of the engine or plant, pressure-responsive means, responsive to fluid pressure developed by said governor, said latter pressure-responsive means acting on said second arm and operable to control the amount of opening of said second fiuid control valve, the latter normally being closed, except for a restricted leak path, when said inlet uid control valve is open, and said inlet fluid control valve normally being open to a preadjustable setting when said second fluid control valve is open.

2. A fuel system, for supplying gaseous fuel to a combustion chamber of a gas turbine power plant, comprising a flow-controlling valve in a fuel supply line leading to the combustion chamber, pressure-operable means for operating said flow-controlling valve, a chamber through which a fluid is passed, said pressure-operable means being responsive to the pressure of said fluid within said chamber, an inlet valve through which said fluid is introduced into said chamber, an outlet valve through which said fluid leaves said chamber, said pressure-operable means being movable in the opening sense of said flowcontrolling valve, when said uid enters said chamber at a faster rate than it leaves, and in the closing sense of said flow-controlling valve, when said fluid leaves the chamber at a faster rate than it enters, rst and second pressure-responsive means by which said inlet valve is operable, said first pressure-responsive means being responsive to the delivery pressure of a compresor supplying air to said combustion chamber and said second pressure-responsive means being responsive to the pressure of fuel downstream of said flow controlling Valve, and a third pressure-responsive means by which said outlet valve is operable, said third pressure-responsive means being responsive to fluid pressure developed as a function of an operating condition of said power plant, said fuel system also Iincluding a lfuel reservoir of fixed capacity, :a Ifixed inlet restrict-or leading thereto land supplied yfrom said fuel supply line downstream of said flow-.con-

trolling valve, and -two fur-ther pressure-responsive means, operable to control the amount of opening of said outlet valve, said further pressure-responsive means acting in opposition to each other and one of said further pressureresponsive means being directly responsive to the pressure of fuel downstream of said how-controlling valve and the other of said further pressure-responsive means being responsive to the pressure in said fuel reservoir.

` 3. A fuel system, for supplying gaseous fuel to a combustion chamber of a gas turbine power plant, cornprising a owkcontrolling valve in a fuel supply line leading to the combustion chamber, a piston for operating said flow-controlling valve, a chamber through which a iiuid is passed, said piston being movable in said chamber in response to the pressure of said fluid therein, an inlet valve through which said fluid is introduced into said chamber, an outlet valve through which said fluid leaves said chamber, said piston being movable in the opening sense of said How-controlling valve, when said fluid enters said chamber at a faster rate than it leaves, and in the closing sense of said how-controlling valve, when said fluid leaves the chamber at a faster rate than it enters, first and second pressureresponsive means by which said inlet valve is operable, said iirst pressure-responsive means being responsive to the delivery pressure of a compressor supplying air to said combustion chamber and said second pressure-responsive means being responsive to the pressure of fuel downstream of said flow-controlling valve, a governor rotatable by a turbine of said power plant, and a third pressure-responsive means by which said outlet valve is operable, said third pressure-responsive means being responsive to iiuid pressure developed by said governor, said outlet valve normally being closed, except for a restricted leak path, when said inlet valve is Open, and said inlet valve normally being open to a pre-adjustable setting when said outlet Valve is open.

References Cited by the Examiner UNITED STATES PATENTS 2,588,522 3/52 Harris 60-3928 2,667,743 2/54 Lee 60-39.28 2,720,752 10/55 Chandler 60-39.28 2,954,667 10/60 Laurent 60-3928 FOREIGN PATENTS 845,269 8/60 Great Britain.

JULIUS E. WEST, Primary Examiner.

SAMUEL LEVINE, Examiner.

Claims (1)

1. A FUEL SYSTEM, FOR SUPPLYING GASEOUS FUEL TO A COMBUSTION CHAMBER OF A GAS TURBINE ENGING OR POWER PLATN, COMPRISING A FLOW-CONTROLLING VALVE IN THE FUEL SUPPLY LINE LEADING TO THE COMBUSTION CHAMBER, FLUID-ACTABLE MEANS FOR OPERATING SAID FLOW-CONTROLLING VALVE, A PIVOTALLYMOUNTED ARM, A FLUID CONTROL VALVE, CARRIED ON SAID ARM AND OPERABLE TO MOVE SAID FLUID-ACTUABLE MEANS, PRESSURE-RESPONSIVE MEANS, DIRECTLY RESPONSIVE TO THE DELIVERY PRESSURE OF A COMPRESSOR ARRANGED TO SUPPLY AIR TO THE COMBUSTION CHAMBER AND TO THE PRESSURE OF TH FUEL DOWNSTREAM OF SAID FLOW-CONTROLLING VALVE, SAID PRESSURE RESPONSIVE MEANS ACTION ON SAID ARM AND BEING OPERABLE TO CONTROL THE AMOUNT OF OPENING OF SAID FLUID CONTROL VALVE, SAID FLUID-ACTUABLE MEANS INCLUDING A CHAMBER HAVING AN INLET TO WHICH A PRESSURE FLUID IS ADMITTED UNDER THE CONTROL OF SAID FLUID CONTROL VALVE AND HAVING AN OUTLET; A PISTON MOVABLE IN SAID CHAMBER IN RESPONSE TO THE PRESSURE OF FLUID THEREIN, SAID PISTON BEING MOVABLE IN THE OPENING SENSE OF SAID FLOW-CONTROLLING VALVE, WHEN SAID FLUID CONTROL VALVE OPENS TO ADMIT SAID FLUID AT A FASTER RATE THAN IT LEAVES THE CHAMBER, AND IN THE CLOSING SENSE,

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