Patent GB-744013-A (GB)
Title: Improvements in fuel control for a gas turbine power plant
IPC: F02C9/16
Filed: 1953-06-22
Abstract: 744,013. Gas turbine plant. UNITED AIRCRAFT CORPORATION. June 22, 1953 [June 21, 1952], No. 17306/53. Class 110(3) [Also in Group XXIX] A fuel control for a gas turbine engine comprises a fuel metering valve having a ported valve member movable in axial and angular motions to vary the effective area of the ports, means responsive to speed variations of the compressor of the engine for moving the valve member in one of said motions, means responsive to pressure variations at or adjacent the compressor discharge for moving the valve member in the other of said motions, and means responsive to variations in compressor inlet air temperature for moving the valve member in either of said motions. In the embodiment described fuel is delivered by pumps 20, 22 in series through a conduit 42 to the metering valve 46 and thence through a conduit 48, shut-off valve 50, conduit 52, dump valve 54, conduit 56, pressurizing valve 60 and conduits 392, 394 to primary and secondary fuel manifolds 14, 16 feeding burners 12 in the combustor 10 situated between the turbine 2 and compressor 4. The metering valve includes a fixed sleeve 64 with a port 66 with which coacts a port 68 of the angularly and axially movable valve sleeve 70. Angular adjustment of the sleeve is by rack and pinion-72. 74 actuated by a servomotor 76 controlled by a bellows 82 subject to compressor discharge pressure. An additional bellows 86, which is evacuated, provides for absolute pressure detection. Axial movement of the sleeve is effected by a follower servomotor 96 which is movable in response to adjustment of a three-dimensional cam 102 in the rotary sense by rack and pinion 164, 162 and axially by variations of fluid pressure on a plunger 106, a plunger 104 at the opposite end of the cam being subject to a loading pressure. The rack 164 is operated through a follower servo 166 responsive to the air intake temperature of the compressor which is sensed by an element 172 operating a cam 170. The pressure acting on the plunger 106 varies inversely with the speed of the turbine, being regulated by a centrifugal valve 128 carried in a turbine-driven rotor 116. Fuel under pressure is delivered by a conduit 134 to a chamber 120 housing the rotor and urges the valve 128 radially inwardly. This action is balanced by control by the valve of the pressure acting on its inner end and this pressure is led by a conduit 138 to the plunger 106. A valve 186 maintains a constant pressure drop across the coacting ports 66, 68 to determine the maximum fuel flow permissible under transient conditions, e.g. during acceleration. From the interior of the valve sleeve 70 fuel flows in parallel paths to the conduit 48, one path being through ports 202, 204 which are so arranged that only angular movement of the sleeve 70 varies the flow area whereby a minimum fuel flow, related to compressor discharge pressure, is established during deceleration to prevent extinguishing of the burners. Another path is through unrestricted ports 210 in a sleeve 212. a passage 216, idling sneed governing valve 218, and passage 220. The valve 218 is actuated jointly by a flow-responsive diaphragm associated with a venturi 250 and acting through a spring 236 which is adjusted bv a control arm 246 acting through a cam 242, follower servo 240, and lever 238. The valve 218 controls the fuel flow according to the idling speed selected by the arm 246, and closes in response to higher speeds. A third path frnm the interior of the sleeve 70 is through coacting ports 264, 266 in the sleeve 70 212 respectively, the sleeve 212 being adjusted axially to reduce the flow area in response to increase of speed by a follower servo 270 which is governed by a three dimensional cam 276 rotatable by a control lever 290 and having a plunger 278 which is subject to the pressure produced by the valve 128. The governing action of the sleeve 212 is compensated for variations of compressor inlet temperature and discharge pressure by the movements of the sleeve 70. A valve 296 maintains a substantially constant pressure drop across the ports 264, 266 and across the idling speed valve 218. An overspeed valve 308 subject to the pressure set up by the valve 128 spills fuel from a space 214 surrounding the sleeve 212 should the turbine overspeed. The shut-off valve, which is operated by a lever 348, coacts with a seat 352 and has a portion which controls a passage 358 leading to an actuating plunger 362 of the dump valve such that when the shut off valve is open the passage 358 is pressurized to cause the dump valve to interconnect the conduits 52, 56, but when the shut-off valve is closed the passage 358 is vented to enable the dump valve to be spring urged to a position in which the conduits 52, 56, 58 are connected to a drain 374. Fuel flows through a chamber 388 of the pressurizing valve direct to the primary manifold 14 and, as pressure builds up, opens the valve to pass to a chamber 390 and thence to the secondary manifold 16. The pressure at which this valve opens is made dependent upon combustor pressure by a tapping 396 leading to the back of the closure mem. ber 378 of the valve.