US3146591A - Fuel control in internal-combustion turbine engines - Google Patents

Description

H. G. TURNER Sept. 1,- 1964 FUEL CONTROL IN INTERNAECOMBUSTION TURBINE ENGINES Filed June 6, 1961 2 Sheets-Sheet 1 mm Q "a? W Q 9 wmm NW N. MN a v. L |l X\ ON 9 b L mm mm R R VN MN 3 I! m am am wm mm A ,w mm q Sept. 1, 1964 G. TURNER 3,146,591

FUEL CQNTROL IN INTERNAL-COMEUSTION TURBINE ENGINES Filed June 6, 1961 2 Sheets-Sheet 2 United States Patent 3,146,591 FUEL CGNTROL 1N INTERVAL-COMBUSTION TURBENE ENGINES Horace George Turner, Leclrharnpton, Cheitenham, England, assignor to The Plessey Company Limited, London, England, a British company Fiied June 6, 1%1, Ser. No. 115,594 Claims priority, application, Great Britain, .liune 1t), 1960, 20,425/69 5 Claims. (Cl. 6t3--?-9.28)

This invention relates to control systems and apparatus for internal combustion turbine engines and has for an object to provide improved systems and apparatus which while particularly suitable for use with vertical-lift jet engines are on account of their simplicity also well suited to use with ground-based gas turbines.

Another object is to provide improved fuel-metering apparatus for turbo-jet engines in which, as long as the engine speed is below a preset value, fuel delivery to the engine up to a preset maximum rate is varied, in accordance with the delivery pressure of the engine compressor, by means of a throttle valve and an automatic spill valve maintaining the pressure drop across the throttle valve constant, and in which the throttle valve includes means responsive to engine speed which reduce the area of the throttle aperture when the engine speed exceeds a predetermined or preset value.

One aspect of the invention consists in a fuel device for an internal-combustion turbine engine, comprising a throttle valve through which fuel is supplied, automatic spill by-pass means maintaining the pressure drop in the throttle valve constant, and automatic aperture control means for the throttle valve, including a piston element forming one wall of a control chamber, a spring means urging said piston element inwardly of said chamber, a source of pressure variable according to engine speed connected to said chamber via a restriction, and a vent valve for said chamber having a seat movable with said piston member and facing the interior of the chamber, a valve element co-operating with said seat, a valve loading spring urging said valve member onto its seat, and means limiting the movement of the valve element in the direction of the action of said loading spring. Other aspects and features of the invention will become apparent from the following description of an embodiment with reference to the accompanying drawing.

The accompanying drawing illustrates diagrammatically one form of the invention, and other features of the invention will be apparent from the following description with reference to the drawings of which FIGURE 1 is a sectional elevation of the pump and valve system, while FIGURE 2 is a diagram showing the arrangement of the invention in a turbo jet lift engine of an aircraft.

Referring now to the drawings, an engine-driven pump 10 provided with a pressure-relief valve 11 draws fuel from a source indicated at 12 and supplies it under pressure through a conventional overspeed trip valve 13 to a control unit indicated generally at 14. The control unit 14 consists of a body 15 containing a metering valve which consists essentially of a spool 16 sliding inside a cylindrical sleeve 17 provided with metering ports 18, through which fuel is supplied, via a shut-off valve 19, to a burner 20 arranged in the combustion chamber 45 see FIGURE 2, of a turbo jet engine 46 mounted in an aircraft indicated by its forward axis 50, the engine being shown positioned to act as a lift engine.

The sleeve 17 is rotated about its axis by means of gearing 21 from anengine-driven par-t, conveniently from the drive to the pump 10 as indicated at 47 in FIGURE 2, in order to reduce frictional resistance to axial movement of the valve spool 16 or sleeve 17. The fuel-pressure drop across the metering ports 18 is maintained constant by a device having a spring-loaded diaphragm 22 exposed on one side to fuel at the pressure at which it is supplied to the burner 20 and on the other side to fuel at the pressure at which it is supplied to the metering valve 16.

The supply pressure tends to move the diaphragm so as to open a spill valve 23 attached to it and thus to return fuel to the low-pressure side of the pump 10, and the combined effects of the loading spring 23a and the pressure of the fuel entering the burner 20 tends to oppose this action.

The upper portion of the body 15 contains two chambers 24 and 25 which are separated from each other by a diaphragm 26 connected to the spool 16, and the diaphragm and the spool are biased by a spring 27 in a direction to close the metering ports 18. The chamber 25 which faces the side of the diaphragm adjacent to the spool 16, is connected to atmosphere through an orifice 28, and the other chamber 24 is connected to the output of the engine compressor through a filter 29 and a restrictor 30.

Communication between the chamber 24 and the chamber 25 through a central orifice in the diaphragm 26 is normally cut off by a half-ball valve 31 which is urged in to the closing direction by a spring 32 extending between it and a plunger 33 in which it slides. Movement of the valve 31 in the closing direction within the plunger 33 is limited by a tail Men the valve shaft. The plunger 33 is moved by a lever 36 by means of a rack and pinion or of a cam and follower as shown at 35 and constitutes the engine control.

The lower part of the body 15 contains a chamber 37 into which the lower end of the sleeve 17 projects. A centrifugal governor 38 is connected to and driven by the sleeve 17 and is preloaded by a spring 39 tending to move the sleeve 17 toward chamber 24. The value of the preload applied by means of the spring 39 is adjustable through a screw 40, and the initial position of the governor Weights, and thus the governor gain, is adjustable through a further screw 41.

To start the engine, the control lever 36 is moved to a desired position, and the engine is turned by a convenient starter 48. Since the half-ball valve 31 is spring-loaded to its seat and seals the upper chamber 24 from the lower chamber 25, there is no escape of air from the upper chamber 24 to the lower chamber 25 and the upper chamber 24 is therefore at compressor delivery pressure. As the speed of the engine increases, the compressor delivery pressure increases until, overcoming the spring 27 it moves the spool 16 of the metering valve downwards, away from chamber 24, thus reducing the restriction imposed upon the fuel flow by the metering orifices 18 and increasing the fuel flow. Since the pressure drop across orifices 18 is kept constant by the spill valve 23, it will thus be seen that the metering orifices 18 meter to the burner a flow of fuel which varies in accordance with the compressor delivery pressure.

When the metering valve spool 16 has been depressed by the compressor delivery pressure to a position determined by the setting of lever as, engagement between the tail 34 and the plunger 33 prevents the half-ball valve 31 from following the diaphragm 26. The half-ball valve 31 is thus pulled off its seat, and the compressed air in the chamber 24 is partially vented to atmosphere through the chamber 25, causing the pressure in the chamber 24 to fall below the compressor-delivery pressure, thus terminating the travel of the metering valve and preventing further increase of the fuel flow to the engine burner 20. It will be seen that while the device varies the metered fuel flow in accordance with the compressor delivery pressure and thus with that component of compressor delivery pressure which is due to atmospheric pressure and which is therefore a function of altitude, it prevents the flow from ever exceeding a maximum flow dictated by the setting of the control lever 36. The engine is therefore enabled to run at steady-state conditions dictated by the setting of this control lever.

When the engine speed exceeds a predetermined value, the centrifugal force of the governor weights overcomes the effect of the spring 39 and moves the sleeve 17 downwards, thereby increasing the restriction of the metering ports and reducing the fuel flow to the engine.

That end of the sleeve 17 which faces the diaphragm 26 is immersed in fuel in communication with the low-pressure side of the pump. This arrangement provides lubrication of the gearing 21 and acts to absorb any leakage from the high-pressure side of the spool valve. The

chamber 37, into which the other end of the sleeve 17 extends, is also connected to the low-pressure side of the pump 10.

It will be seen that the device described provides automatic compensation for variations in altitude, since it is sensitive to compressor delivery pressure, but that for a given position of the control lever 36 there is one maximum (and steady-running) fuel flow. This feature makes the device particularly suitable for use with gas turbines used for vertical-lift applications since with these the permissible accelerating fuel flow varies with altitude but there is no significant variation in weight as the aircraft rises from the ground. Since the thrust developed is substantially proportional to the fuel flow, the lift thrust developed is substantially proportional to the position of the control lever 36 irrespective of altitude. The use of a cam-and-follower connection at 35 between the lever 36 and the plunger 33 gives a great amount of freedom of choice of the law of flow control by the lever position.

What I claim is:

1. An internal-combustion turbine equipped with an air-intake compressor having an outlet constituting a source of pressure variable according to engine speed and a fuel-control device comprising: a housing having a cylindrical bore, a fuel-inlet connection, and a fuel-delivery connection both said connections communicating with said bore at longitudinally spaced points; a throttle valve including two slide elements, one forming a cylindrical sleeve sealingly fitted in said bore for rotation about its axis and longitudinal movement in said bore, said sleeve having first and second port means extending through the wall of the sleeve at longitudinally spaced points, said port means being in respective continuous communication with said two connections, and the other element forming a valve spool sealingly fitted inside said sleeve for movement longitudinally thereof, said spool having two longitudinally spaced lands jointly isolating a length of the interior of the sleeve which communicates with both said port means, one of said lands being arranged in controlling co-operation with one of said port means to vary the effective cross-sectional area thereof according to the position of the spool along the sleeve; automatic spill bypass means maintaining the pressure drop in said one port means constant, and automatic aperture-control means for the throttle valve, said aperture-control means including a piston element operatively connected to one of said slide elements and forming one wall of a control chamber, a spring means urging said piston element inwardly of said chamber to reduce said effective area, a connection leading from said compressor outlet via a restriction to said chamber to urge said piston in a direction to increase said effective area; stop means adjustably limiting the movement of said one slide element against the action of said spring means; a vent valve seat for said chamber, said seat being movable with said piston element and facing the interior of the chamber, a vent valve-element cooperating with said seat, and a valve-loading spring urging said valve element on to its seat; and means responsive to the speed of the turbine and operative to move the other slide element in a direction to reduce the effective aperture of said port means when the turbine speed exceeds a predetermined value.

2. An internal-combustion turbine engine as claimed in claim 1, including means connectable to the engine and operative to rotate the sleeve at a speed proportional to engine speed, a centrifugal governor rotatable with the sleeve, and means for pre-loading the governor to select a desired maximum engine speed.

3. A device as claimed in claim 1, wherein the spool member is operatively connected with the piston member for common longitudinal movement, while the sleeve is movable in response to excess turbine speed.

4. A fuel control-device as claimed in claim 3, comprising means for rotating said sleeve in proportion with turbine speed, said excess-speed responsive means including a centrifugal governor rotatable with said sleeve and a preloaded spring counteracting axial displacement of the sleeve by the governor.

5. In a fuel control system for a gas-turbine power plant including a compressor driven by the turbine, a fixed-displacement fuel pump also driven by the turbine, and a combustion chamber, the combination comprising a valve housing having an inlet chamber communicating with the delivery side of the fuel pump and an outlet chamber communicating with burner means in the combustion chamber, a sleeve mounted in the valve housing for rotation about its axis and for axial displacement, said sleeve having at least one first port communicating with the inlet chamber, at least one second port communicating with the outlet chamber, a slide valve piston movable axially inside said sleeve to vary the available cross-section for the How from said first port to said second port but prevented from rotation about its axis relative to the valve housing, a chamber in the valve housing sub-divided by a movable partition at least operatively connected to the slide valve element, the chamber portion at one side of said partition communicating with said compressor so as to cause the pressure supplied by said compressor to urge said piston towards the position corresponding to maximum cross-section of the flow passage from said first port to said second port, first spring means opposing the action of said pressure upon said slide valve piston, further spring means urging said sleeve in the same direction in which the slide-valve piston is urged by said first spring means, selectively adjustable abutment means limiting the stroke of said partition and slide-valve piston under the action of said compressor-derived pressure, drive means interconnecting said sleeve with the turbine for proportional rotation therewith, a centrifugal governor rotatable with said sleeve and operative when the rotational speed of said sleeve exceeds a predetermined value, to move said sleeve in opposition to the action of said second spring means, a relief passage from said high pressure inlet chamber to a point at low pressure, a valve in said passage, and control means for said valve, responsive to the pressure difference between said inlet chamber and said outlet chamber, so as to maintain said pressure difference substantially constant, said partition being penetrated by a passage terminating in a valve seat at the high-pressure side of said partition, a restricted orifice being included in the connection between the compressor and the chamber at said one side of the partition, the stroke-limiting means comprising a valve element cooperating with said valve seat and movable with the partition when being held in contact therewith by the pressure acting at said side of the partition, and selectively adjustable means for limiting the amount of movement of said valve element in a direction away from said side of the chamber.

References Cited in the file of this patent UNITED STATES PATENTS Bastian Oct. 22, 1895 Blanchard Jan. 2, 1917 Niesemann Jan. 5, 1954 Kuzmitz June 21, 1960 Torell June 27, 1961 Judd Apr. 16, 1963

Claims (1)

1. AN INTERNAL-COMBUSTION TURBINE EQUIPPED WITH AN AIR-INTAKE COMPRESSOR HAVING AN OUTLET CONSTITUTING A SOURCE OF PRESSURE VARIABLE ACCORDING TO ENGINE SPEED AND A FUEL-CONTROL DEVICE COMPRISING: A HOUSING HAVING A CYLINDRICAL BORE, A FUEL-INLET CONNECTION, AND A FUEL-DELIVERY CONNECTION BOTH SAID CONNECTIONS COMMUNICATING WITH SAID BORE AT LONGITUDINALLY SPACED POINTS; A THROTTLE VALVE INCLUDING TWO SLIDE ELEMENTS, ONE FORMING A CYLINDRICAL SLEEVE SEALINGLY FITTED IN SAID BORE FOR ROTATION ABOUT ITS AXIS AND LONGITUDINAL MOVEMENT IN SAID BORE, SAID SLEEVE HAVING FIRST AND SECOND PORT MEANS EXTENDING THROUGH THE WALL OF THE SLEEVE AT LONGITUDINALLY SPACED POINTS, SAID PORT MEANS BEING IN RESPECTIVE CONTINUOUS COMMUNICATION WITH SAID TWO CONNECTIONS, AND THE OTHER ELEMENT FORMING A VALVE SPOOL SEALINGLY FITTED INSIDE SAID SLEEVE FOR MOVEMENT LONGITUDINALLY THEREOF, SAID SPOOL HAVING TWO LONGITUDINALLY SPACED LANDS JOINTLY ISOLATING A LENGTH OF THE INTERIOR OF THE SLEEVE WHICH COMMUNICATES WITH BOTH SAID PORT MEANS, ONE OF SAID LANDS BEING ARRANGED IN CONTROLLING CO-OPERATION WITH ONE OF SAID PORT MEANS TO VARY THE EFFECTIVE CROSS-SECTIONAL AREA THEREOF ACCORDING TO THE POSITION OF THE SPOOL ALONG THE SLEEVE; AUTOMATIC SPILL BYPASS MEANS MAINTAINING THE PRESSURE DROP IN SAID ONE PORT MEANS CONSTANT, AND AUTOMATIC APERTURE-CONTROL MEANS FOR THE THROTTLE VALVE, SAID APERTURE-CONTROL MEANS INCLUDING A PISTON ELEMENT OPERATIVELY CONNECTED TO ONE OF SAID SLIDE ELEMENTS AND FORMING ONE WALL OF A CONTROL CHAMBER, A SPRING MEANS URGING SAID PISTON ELEMENT INWARDLY OF SAID CHAMBER TO REDUCE SAID EFFECTIVE AREA, A CONNECTION LEADING FROM SAID COMPRESSOR OUTLET VIA A RESTRICTION TO SAID CHAMBER TO URGE SAID PISTON IN A DIRECTION TO INCREASE SAID EFFECTIVE AREA; STOP MEANS ADJUSTABLY LIMITING THE MOVEMENT OF SAID ONE SLIDE ELEMENT AGAINST THE ACTION OF SAID SPRING MEANS; A VENT VALVE SEAT FOR SAID CHAMBER, SAID SEAT BEING MOVABLE WITH SAID PISTON ELEMENT AND FACING THE INTERIOR OF THE CHAMBER, A VENT VALVE-ELEMENT COOPERATING WITH SAID SEAT, AND A VALVE-LOADING SPRING URGING SAID VALVE ELEMENT ON TO ITS SEAT; AND MEANS RESPONSIVE TO THE SPEED OF THE TURBINE AND OPERATIVE TO MOVE THE OTHER SLIDE ELEMENT IN A DIRECTION TO REDUCE THE EFFECTIVE APERTURE OF SAID PORT MEANS WHEN THE TURBINE SPEED EXCEEDS A PREDETERMINED VALUE.

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