Patent GB-1170350-A (GB)
Title: Gas Turbine Engine
IPC: F01D17/26
Filed: 1967-12-29
Abstract: 1,170,350. Gas turbine engines. FORD MOTOR CO. Ltd. Dec.29, 1967 [Dec.30, 1966], No.59041/67. Headings F1G and F1T. [Also in Division G3] A gas turbine engine comprises a power turbine having an adjustable inlet nozzle which can be adjusted by power-operated means to retard the rotation of the power turbine, the power-operated means being operated by pressure fluid supplied through a conduit which is opened by control means which are connected to operator-controlled means by power-actuated means which are activated by a predetermined movement of the operatorcontrolled means. The power turbine drives a motor vehicle and is of axial-flow type with inlet nozzle vanes which are pivotable in unison by a common operating lever 38 which is movable by a servomotor piston 34. The servomotor is controlled by a spool valve 62 which is acted upon by cam followers 78, 80 through centering springs 74, 76. Cam follower 78 is movable by a cam 92 to displace the valve 62 from its neutral position to admit pressure fluid from a supply passage 72 to one side or other of the piston 34, while cam follower 80 is movable by a cam 100 which is connected by linkage 104,106 to the lever 38 so as to return the valve 62 to the neutral position when the piston 34 has completed its movement. The cam 92 is carried by a shaft 94 which is connected to the accelerator pedal linkage. The cam follower 78 is operable not only by the cam 92 but also by fluid-pressure within a chamber 86 which can move the cam follower away from the cam; consequently when the accelerator pedal is released or when the chamber 86 is presssurized, the resultant movement of the cam follower 78 causes the piston 34 to turn the inlet nozzle vanes of the power turbine into a position in which they direct gas on to the reverse sides of the rotor blades to effect braking of the power turbine. Chamber 86 can be pressurized for this purpose by fluid admitted to it via a line 107 under the control of a valve 111 if the gas temperature of the turbine section of the engine, sensed by a probe 109, rises above a safe operating limit. When the vehicle transmission selector lever is put into the neutral position, it turns a valve 20 through 90 degrees anti-clockwise from the position shown to connect a line 156 to the chamber 86 via valve ports 123, 121 and a bore 119 in the shaft 94. If now the engine output shaft speed rises above the idling speed, a fluidpressure developed in a line 164 as a function of increase in speed of a pump or other member driven by the output shaft opens a valve 22 to admit a pressure fluid from a line 160 to the line 156, thereby pressurizing the chamber 86 to cause the piston 34 to rotate the nozzle vanes to a position of increased engine braking, thereby checking the speed increase. When the transmission selector lever is put into the drive position, the valve 20 resumes the position shown, cutting off the connection of the chamber 86 to the line 156 but establishing a connection via a manifold 144 and a passage 150 to the supply passage 72 whereby the chamber 86 is pressurized to maintain the nozzle vanes in the braking position. When the accelerator pedal is depressed, the resultant rotation of the shaft 94 disconnects the valve ports 121, 123 (and also further valve ports 120, 122) so that communication of pressure fluid to the chamber 86 (other than through the line 107 in the event of excessive gas temperature) is cut off, and the cam 92 causes the nozzle vanes to turn from a braking position to a driving position. If the accelerator pedal is released, pressure fluid can again pass via the valve ports 121, 123 to the chamber 86 to return the nozzle vanes to a braking position. Additionally, if the vehicle speed is then above a predetermined value, a valve 126 is opened by means of a speed-sensitive fluid-pressure communicated via a line 140, thereby allowing pressure fluid from passage 150 to pass by way of ports 120, 122 to the chamber 86, thereby supplementing the existing flow by way of ports 121, 123. The resultant increase of pressure in the chamber 86 turns the nozzle vanes to a position of maximum braking. Movement of the nozzle vanes to a braking position can also be effected by depressing a retarder pedal 170 (which is additional to the conventional brake pedal). Initial depression of the pedal 170 closes a switch to open a solenoid valve 196 to allow pressure fluid to pass via a line 210 to the chamber 86, thereby turning the nozzle vanes to the maximum braking position. So the pedal 170 is further depressed, it acts via a lever 178 to progressively increase the supply of fuel to the engine. The resultant progressive increase in the flow of gas on to the backs of the rotor blades causes a progressive increase in the braking effect.