Patent GB-1250693-A (GB)
IPC: F02C7/264
Filed: 1969-11-24
Abstract: 1,250,693. Jet propulsion plant - reheat fuel control. BENDIX CORP. Nov. 24, 1969 [Dec. 3, 1968], No. 57390/ 69. Heading F1J. The invention relates to a flow responsive apparatus for sensing flow of pressurized fuel to the reheat fuel manifold of a gas turbine engine, the apparatus comprising a fluid-flow responsive member which is adapted to actuate an ignition system control member. A gas turbine engine is shown in Fig. 1 and comprises a reheat fuel manifold 40, a reheat ignition means 64, and a variable area propulsion nozzle 26 comprising flaps 44 movable by actuators 46 under control of a unit 48. Reheat fuel is supplied from tank 52 and pump 53 through line 50, the line containing an on/off valve 62, a filter 60 which provides a pressure drop from P 1  to P i  and a metering valve 58, the valves 62, 58 being controlled by control lever 56. The reheat fuel flow sensing device 70 is connected to receive fuel at varying pressures in the line 50, and is connected to control the ignition device 64, also the variable area nozzle control unit 48 through line 247. The device 70 comprises an inlet 74 connected to fuel line 50 upstream of filter 60 at pressure P 1  through line 76, and an inlet 78 connected to fuel line 50 downstream of filter 60 at pressure P i  through line 80. Fuel entering inlet 74 passes through filter 86 and duct 90 containing restriction 91 to chamber 92 at pressure P x , the fuel then passing through duct 94 under control of valve 96, 116 to chamber 98 at pressure P' x  to the left of piston 100. Fuel at pressure P i  entering inlet 78 passes to chamber 106 the chambers 92, 106 being separated by a diaphragm 108 which carries valve 116. The piston 100 is urged to the left against stop 122 by a spring-loaded tappet member 124, 126, 130 the stem portion 124 being slidable in a sleeve 128, and when the piston is moved to the right into contact with stop 138 by pressure P'x the stem 124 engages lever 144 which is pivotally mounted at 150. The chamber 118 to the right of the piston 100 is connected to pressure P 2  through duct 120 from inlet 82 and line 84, P 2  being the fuel pressure in line 50 downstream of metering valve 58. The lever 144 carries at its lower end a valve member 156 which is normally urged to close valve opening 162 by spring 160. Fuel at pressure P r  from source 181 is communicated through line 179 to inlet 168, through filter 172 to ducts 170, 176 and restriction 178 to the chamber 166 to the right of stepped piston 164, the piston being shown in Fig. 2 in its leftward position against stop 198 to which is is urged by spring 194. The stepped portion 174 of the piston is acted on by fuel at pressure P r  in duct 170. The piston 164 cooperates with ducts 226 and 180. The pressure P r  in chamber 166 is connected through duct 180 and annulus 182 in valve member 184 to duct 187 and valve 156, 162. A sleeve member 186 is secured within the housing 72 by bolts 190, the sleeve member having a transverse internal flange 188, also a valve seat 202 which cooperates with a valve-member 204 loaded by spring 206; the valve-member 204 carries a stem 248. A pawl member 254 is pivotally mounted within the piston 164, the pawl member having arms 252, 260, 262 which engage with the stem 248 of valve 204, the sleeve 186 and the inside of the piston head 164 respectively. The piston 164 carries a stem 264 comprising a cam surface 266, the cam acting through follower 268 and stem 272 with a lever 278 pivotally mounted at 286, the lever being loaded by spring 280. As the piston 164 moves to the right in response to flow of fuel to the reheat manifold the cam 266 acts to close the contacts of switches 282 whereby the reheat ignition device 64 is energized. The valve-member 184 is urged to the left by spring 218 and comprises an annulus 182 which in the position shown interconnects the ducts 180, 187; the valve-member 184 comprises also a bore 230, a transverse bore 232 and annulus 234, also a bore 236, also a valvemember 222 which co-operates with branch 224 of duct 170, the end 238 of duct 230 co-operating with a valve-member 240. The duct 244 cooperates with annulus 234 and transverse bore 232 of valve member 184 and leads through line 247 to the nozzle control unit 48, Fig. 1. The chamber 200 to the right of valve 204 communicates through duct 214 and adjustable orifice 212 and duct 210 with chamber 148, the chamber 148 communicating through duct 152 and line 155 with fuel at low pressure P o  at inlet side of pump 53. The piston 100 acts as a flow measuring device and moves from its leftward position against stop 122 to its rightward position against stop 138 as the reheat fuel manifold 40 becomes filled. The rightward movement of the piston moves the lever 144 clockwise such movement causing the reheat ignition device 64 to be energized. Before reheat is selected the stepped piston 164 is in the position shown in Fig. 2 against the stop 198, the pressure P r  in duct 170, 176 being communicated through orifice 178 to the chamber 166 at the right of piston 164, the outlet from chamber 166 through duct 180, annulus 182 and duct 187 being closed by valve 156. As the piston 100 moves to the right in dependence on the filling of the reheat manifold, the lever 144 acts to open valve 156 so that pressure in chamber 166 to the right of piston 164 is released to low pressure P o  in chamber 148 and piston 164 moves to the right against spring pressure 206 due to fuel pressure P r  acting on annulus 174. As the piston moves to the right it closes off duct 180 and opens valve 204 against spring force 206 by reason of the arm 252 of pawl member 254 contacting stem 248 of valve 204. Thus the chamber 166 now communicates with chamber 148 at low pressure P o  through open valve 202, passage 208 in valve-member 204, chamber 200, duct 210, adjustable orifice 212, 214 and duct 210. Rightward movement of the piston 164 acts through cam device 264, 266 and lever 278 to energize the reheat ignition device. As the piston 164 moves to the right it opens duct 226 to pressure P r  in duct 170, the pressure passing to chamber 216 to the left of piston 184, whereupon the piston 184 is moved to the right against loading of spring 218. The valve 222, 224 is thus opened and fuel at pressure Pr from duct 170 now passes through ducts 236, 232 in piston 184 to duct 244 and line 247 to the device 48 which controls opening of the nozzle flaps 44. As the piston 164 moves to the right, the arm 260 of the pawl member 254 contacts the end of fixed sleeve 186 whereby the pawl is moved clockwise and the arm 252 disengages from the rod 248; the valvemember 204 is thus closed by the force of spring 206, and the pressure in chamber 166 starts to increase whereupon the spring 194 acts to move the piston 164 back to the first position. In Fig. 9 (not shown) in place of the cam arrangement shown in Fig.2 a servo-piston is utilized for closing the switches 282 to energize the reheat ignition device.