Patent GB-1253880-A (GB)
Title: Fuel, speed and turbine variable inlet nozzle position control for a gas turbine engine
Inventor: MALJANIAN JOHN MARTIN
Filed: 1969-04-15
Abstract: 1,253,880. Gas turbine engine fuel control systems. CHANDLER EVANS Inc. April 15, 1969, No.19298/69. Heading F1G. The invention relates to a gas turbine engine of the kind comprising a separate power turbine there being adjustable inlet nozzles to the power turbine, the invention relating to a system for controlling fuel flow, engine speed and position of the turbine inlet nozzles. The invention is described with reference to an embodiment which is similar to that of co-pending Specification 1,253,879 but differs therefrom in that the chamber 159 below the diaphragm 157 is connected to the line 165 through restriction 166 and to tank pressure P T  through restriction 167 and not to ambient pressure. Also the line 139 is connected directly to boost pump pressure P B  when the spool valve 158 is in its upper, open position when pressure P PT  which is a measure of power turbine speed and acts in chamber 154 above diaphragm 157 is low. The line 139 is not connected through line 300 to the line 165 as in Specification 1, 253, 879. The line 165 is connected to chamber 200 of retard solenoid valve 195 as before, the valve member 196 being normally held in the open position by the energisation of solenoid 197 so that line 165 is normally connected to boost pump pressure P B . The valve 196 is closed by deenergization of solenoid 197 when the speed of the vehicle is to be retarded, the closing of line 165 to boost pump pressure P B  with the valve 161 in the open position and the valve 158 in the closed position (pressure P PT  being high) causes the high servo pressure P s  admitted through restriction 250 to chamber 164 to be transmitted through line 139 to the pressure selector 130 and this in turn is transmitted through line 216 to the inlet nozzle actuator 221 which causes the inlet nozzles to be moved to the braking i. e. negative pitch position. The servo pressure Ps is developed in a regulator 6 which comprises a spool valve disposed in a casing to which pump supply pressure P F  is admitted through inlet 5; the valve is loaded by spring 10 and servofluid at constant pressure P s  is supplied at outlet 12. The gas generator speed transducer 17 comprises a casing 18 and journal sleeve 20 within which is rotatably mounted a rotating member 21 which is driven from the gas generator shaft. A spool valve 29 is mounted within a cavity in the member 21 and is loaded radially outwardly by spring 31 and radially inwardly by spring 33. Fuel at pump outlet pressure P r  is supplied through line 16, chamber 23 and duct 25 to the chamber controlled by the spool valve, the fuel then passing to the chamber 37 and outlet 39 at pressure P N  proportional to gas generator speed. A fuel enrichment device 44 is provided through which fuel may pass to by-pass the fuel metering devices 85, 111, 174 and the by-pass valve 142, the device 44 comprising a metering valve 45 controlled by a spring and a diaphragm 51, fuel at pump pressure P F  being supplied through duct 52 and orifice 53 to the left hand side of the diaphragm and fuel at pressure downstream of the metering orifice being supplied through line 56 to chamber 55 at the right hand side of the diaphragm. The valve 44 is provided to supply a specific increase of fuel at a pre-selected gas generator speed. A pressure relief valve in the form of a spring-loaded ball 66 is disposed in the valve member 58 of the metering head pressure regulator 41, the ball valve opening and allowing fuel to pass back through line 59 in the event of excess fuel pump pressure P F  in line 3. The pressure selector valve 130 comprises three inlets 131, 132, 133 each controlled by a resilient reed valve 137 so that the greatest pressure only is transmitted to the chamber 136 and thence through line 216 to the chamber 219 of the inlet nozzle actuator 221. The method of operation of the control system is generally the same as that of Specification 1,253,879 except as referred to above.