GB778319A - Emergency safety mechanism for fuel control devices - Google Patents

Abstract

778,319. Gas turbine plant. BENDIX AVIATION CORPORATION. Jan. 25, 1955 [March 3, 1954], No. 2241/55. Class 110 (3). [Also in Group XXIX] A gas turbine fuel system comprising a fuel conduit for supplying fuel to the burners, a valve for controlling the flow of fuel actuated by the pilot and means responsive to at least one engine operating condition for controlling the position of the valve, has auxiliary control predetermined position irrespective of variations of the condition for a particular position of the pilot control means. Fuel is supplied to the control housing 10 by a pump (not shown) through a conduit 12 which terminates in a metering orifice 14 controlled by a metering valve 20. The valve 20 reciprocates and rotates in the valve cylinder 16 and is movable by an all-speed governor 28, an hydraulically operated piston 30 positioned as a function of engine speed, a second hydraulically operated piston 32 positioned as a function of compressor discharge pressure and a temperature responsive thermostat 100, 34 responsive to compressor intake temperature. To accelerate the engine, the pilot's lever 26 is rotated in the direction indicated. This rotates the cam 46 through the rack 40 and shaft 36. The cam 46 acting through pivoted lever 48, shaft 52, pivoted levers 54, 58 and plate 64 compresses the governor spring 66. The spring 66 acting through the plate 68 attached to the valve shaft 22 moves the valve 20 axially until the flange 96 engages a cam follower lever 92 positioned by the cam 90. The engine then accelerates and the increase of speed acting through piston 30 rotates the cam 90 which allows the valve 20 to open still further. As the engine reaches the speed selected by the pilot the flyweights 80 act through the spring 66 to close the valve 20. The temperatureresponsive means 100, 34 determines the axial position of the cam 46 by means of a bell-crank 104 and shaft 88. The cam 46 is freely rotatable on the shaft but is constrained to move axially with it by pins 106, 108. The valve 20 is rotated by the piston 32 responsive to the compressor discharge pressure through a rack and pinion 112, 114, shaft 116, bevel gearing 118, 120. The gear 120 is formed on a sleeve 122 having a slot 124 in which engages an arm 126 attached to the valve stem 22. The face 128 of the valve 20 is sloped so that the angular position of the valve defines the area of the metering orifice 14. For emergency operation at maximum power, the pilot's lever 26 is provided with auxiliary control means to fix the axial and angular position of the metering valve 20. The auxiliary control mechanism comprises a shaft 150 having a temperature bias lock member 154 fixed at one end, a bevel gear 152 at the other end and between them a pressure and speed rack lock member 156. When the lever 26 is placed in the take-off or maximum power position, the lock members 154, 156 are in the position shown and limit the movements of racks 84, 112 and the shaft 88 so that the minimum fuel flow through the valve 20 is sufficient to ensure take-off. In all other positions of the lever 26, the racks 84, 112 and shaft 88 are free to operate. Other forms of locking mechanism are described. In one of these the locking mechanism engages notches in the racks 84, 112 and shaft 88. In another the lever 26 closes an electrical switch which energizes solenoids limiting the movements of the racks and the shaft. Specification 753,305 is referred to.