Patent GB-1521828-A (GB)
Title: Fuel control apparatus for a combustion engine
IPC: F02C9/46
Filed: 1976-09-09
Abstract: 1521828 Gas turbine engine fuel control systems BENDIX CORP 9 Sept 1976 [25 Sept 1975]  37463/76 Heading FIG  The invention relates to a fuel control system for a gas turbine engine, fuel being supplied by pump 30 at pressure P 1  to inlet 40 in casing 38, the fuel passing through passage 48, through metering orifice 50, passage 52 at pressure P 2 , past pressurizing valve 152 to passage 56 at pressure P 3 , through cut-off valve 58 to outlet 44 thence through line 46 to the engine combustion section 16. The metering orifice 50 is controlled by a metering valve 62 which is movable by a piston 66 disposed in chamber 68, the piston being loaded on its upper side by servopressure P s , and at its lower side by servo-pressure P 3  the pressure Ps being derived from fuel at pressure P 2  in passage 52 downstream of the metering valve 62 through passage 70 which comprises a restriction 72; the pressure P s  is also controlled by means of a solenoid-controlled valve 90 co-operating with restriction 84, the valve when open communicating passage 70 through chamber 86 and passage 88 with passage 56 at pressure P 3 . The pressure P' 3  below piston 66 is derived from pressure P 3  in passage 56 through passage 74 containing restriction 76. The position of the metering valve 62 is sensed by a slug of magnetic material 188 carried by the valve which co-operates with a coil 198, the signal being transmitted through lines 200, 202 to the electronic sensing unit 36. The fuel pressurizing valve 152 cooperates with opening 54, the valve being acted on to its lower side by pressure P 2  and at its upper side by pressure P 3  in passage 56, also by loading of spring 156. The cut-off valve 58, is moved axially by control lever 136 and comprises a spool having lands 134, 132 which co-operate with fuel passages 56 and 60; when the land 132 closes passage 60, fuel from passage 56 passes through slot 150 in land 134 to chamber 146 and thence through passages 148 and 108 back to the suction side of the pump 30. The position of the lever 136 is sensed by a potentiometer 204 and communicated through lines 212, 214 to the electronic unit 36. Compressor discharge pressure is communicated through line 168 to chamber 164 in which is disposed evacuated capsule 162, movement of which is sensed by magnetic material 174 and coil 180 and transmitted to the electronic unit 36 through lines 184, 186. The pressure drop P 1 -P 2  across the metering orifice 50 is maintained constant by valve member 106 which is controlled by diaphragm 112 which is subject at its upper side to pressure P 1  transmitted through passages 120, 118, and at its lower side to pressure P 2  transmitted through passage 122 containing restriction 124; if the pressure difference is too great, the valve 106 opens to allow fuel to pass from passage 48 through passage 108 back to the suction side of the pump. A pressure relief valve 128 is provided to open if pressure P 1  is too great. An emergency system is provided in case of electric failure in which case the solenoid 92 would cause valve 90 to close and solenoid 220 would cause valve 218 to open. Fuel would now pass from passage 48 through line 216 to open valve 218, through chamber 232 under control of valve 230 to passage 234 to passage 56; the valve 230 is controlled by three-dimensional cam 248 acting on tappet 242, the cam being controlled rotationally by control lever 260 and axially by evacuated capsule 254 which is disposed in chamber 246 subject to atmospheric pressure PA.