Patent GB-941929-A (GB)
Title: Gas turbine engine
Inventor: HAWORTH LIONEL
IPC: F02C7/16
Filed: 1962-01-04
Abstract: 941,929. Fluid-pressure servomotor control systems. ROLLS-ROYCE Ltd. Jan. 4, 1962, No. 447/62. Heading G3P. [Also in Division F1] A gas turbine engine is provided with means for injecting a coolant/fuel mixture into the compressor intake. The engine comprises a reservoir which contains a mixture of coolant and fuel, a duct communicating with the reservoir and the hub of a compressor rotor of the engine, there being means for pumping the mixture through the duct so as to inject it into the air passing through the compressor. Means are provided for preventing flow through the duct except when the engine speed has a pre-determined value. A metering valve is provided for metering the flow of coolant/fuel mixture through the duct, also torque responsive means for adjusting the position of the metering valve so that the flow of coolant/fuel mixture is sufficient to maintain a pre-determined value of torque over a pre-determined range of ambient air temperature. The engine shown is a gas turbine propeller engine and the coolant/fuel mixture control unit is indicated at 26, the unit receiving mixture, say water/methanol mixture from a tank 20 by way of a pump 20<SP>1</SP> and line 21 and supplying mixture to the air compressor 12 through line 30. The unit is connected to a source of fluid under pressure through line 46, and is operatively connected to the engine throttle 51 by means of a link 50. The control unit is shown in detail in Fig. 2, the water/methanol mixture supply line being connected to an inlet 25 which comprises a metering restriction 27 controlled by a metering valve 28. The mixture flowing past the valve, when open, discharges through line 30 and thence into the engine compressor at the intake thereof. The metering valve 28 is mounted on a rod 29 to which is secured a piston 41 which is disposed within a cylinder 42, the piston being acted on at either side by fluid pressures and at its right-hand side by springs 43, 44. Oil under pressure passes through duct 46 under the control of valve 47, the position of the valve being controlled by the link 50 so that it is only open when the throttle lever is in the "takeoff" position. The oil under pressure flows to a chamber 53 which contains a shuttle valve 55,the valve portion 56 of which co-operates with the valve seat 54, and the valve portion 57 of which cooperates with the valve seat 61. The position of the valve 55 is determined by the position of the stem 70, the valve being connected rigidly to the stem by means of an arm 71. When the valve portion 56 is displaced from the seat 54, the pressure in the chamber 53 is high and this pressure which is communicated to the left-hand side of the piston 41 by way of duct 63 acts to move the piston 41 to the right against the loading of springs 43, 44 thus increasing the opening of the metering orifice 27 whereby water/methanol mixture passes through line 30 to the engine compressor. When the valve portion 56 is displaced towards the valve seat 54, the pressure in the chamber 53 is reduced and the metering valve 28 is moved to the left to restrict flow through the metering orifice. The stem 70 has secured at its ends diaphragms 66, 67, the space above the diaphragm 66 being open to atmosphere through port 72 and the chamber below the piston 67 being evacuated. The stem 70 and so the shuttle valve 55 thus takes up a position in dependence on atmospheric pressure. The spaces between the diaphragms 66, 67 and the piston portions of the stem 70 are filled with oil and act as vibration damping chambers. The stem 70 is also acted upon by a pair of push rods 80, 81, the push rod 81 being acted upon by a spring 83 and the push rod 80 being acted upon by oil pressure which is a measure of the torque being produced by the engine, this oil pressure being communicated through line 96. The turbine-compressor shaft is shown at 15 and this drives the propeller shaft 19 through epicyclic gearing 16<SP>1</SP>. The ring gear 18 is allowed a limited angular movement and is connected to a piston disposed within an oil-filled cylinder 100. The pressure developed in the oil is thus proportional to the engine torque; such a torque-meter system forms the subject of Specification 776, 023. The push rod 80 and so the stem 70 and shuttle valve 55 thus takes up a position in dependence on the torque developed by the engine. A low torque pressure switch 110 is provided whereby the switch 110 in the electric circuit 101 is opened when the engine torque and so the pressure in the line 96 is below a pre-determined value. The space 60 within the control unit 26 is connected to the suction side of the pump which delivers oil to the line 46,the space 60 being in communication with the space within the cylinder 42 to the right of the piston 41 by way of duct 64. Specification 703, 619 also is referred to.