Patent GB-703165-A (GB)
Title: Improvements in or relating to control systems for aircraft propulsion power plants including a reciprocating internal combustion engine and an exhaust driven turbine
Inventor: CATFORD ADRIAN LESLIE
IPC: F02D29/00
Filed: 1950-10-31
Abstract: 703,165. Motor power plant. NAPIER & SON, Ltd., D. Oct. 19, 1951 [Oct. 31, 1950], No. 26555/50. Class 110 (3). [Also in Groups XXIV, XXVII and XXIX] A control system for aircraft propulsion power plants of .the kind comprising a reciprocating internal combustion engine 1, Fig. 1, driving a constant speed airscrew 3 and an exhaust driven turbine 2 the rotor of which is not directly con- .nected to the crankshaft of engine 1, but is arranged to drive a compressor 7 for supplying combustion air to the engine 1 and also to deliver power to an airscrew 4, includes boost control mechanism responsive .to the combustion air pressure in a line 27 for controlling the speed of turbine 2 by varying the loading of the constant speed governor 14 of airscrew 4 to maintain the air supply to engine 1 at a constant pressure for any given setting of the boost control mechanism, and a main control member 28 arranged to control simultaneously the boost setting, the fuel supply to the engine 1, the setting of governor 13 of airscrew 3, and the setting of a stop device arranged to limit the movement of the load varying mechanism of the governor 14 to 'thereby prevent the speed of the turbine rising .above a maximum dependent on the setting of member 28. The arm 29, Fig. 2, of member 28 controls via a cam 32 the loading spring 33 of governor 13. Arm 30 controls a piston valve 120 and arm 31 controls :a lever 41 which moves simultaneously cams 50, 72, Fig. 3, and a lever 43. Cam 72 controls the piston valve 71 of a piston 69 carrying the stop device 70 and movement of the piston valve is followed by movement of the piston. Cam 50 controls via levers 51, 46, 47, the injection pumps la of .engine 1. Lever 43 controls via link 53, a floating lever 54 which sets a loading spring 55 opposing the pressure in line 27 which acts on diaphragm 56 to control a valve 65. The valve rod 52 is attached to an evacuated capsule 60, and the valve controls the application of pressure fluid from source 64 to either end of piston 61 which controls, via link 18, the spring 62 of governor 14 and hence the :speed of the turbine 2 to maintain a constant boost pressure. If the aircraft climbs to cause piston 61 to abut stop 70, the speed of the turbine is limited and the pressure above the piston increases to move a piston 80 which, via 'link 81, floating lever 44 and link 45, acts on lever 46 to reset the spring 55 and also the pump 1a to deliver less fuel in accordance with the reduced boost pressure. Movement of piston 80 is prevented momentarily by a braking pad 90 applied due to sudden changes in speed of airscrew 4 caused, e.g. by atmospheric conditions, to prevent hunting. The lines from valve 103 of governor 14, to the pitchchanging mechanism are tapped and the pressures therein act on pistons 95, 96 actuating valves 92, 93 controlling the inlet of pressure fluid from source 65 to the pad 90. The pressure fluid causing opening of either valve bleeds slowly to the rear of the associated piston to cause closure of the valve after a short interval. The exhaust pipes 10, Fig. 4, contain reheat burners 9 and the application of fuel or compressed air from engine driven blower 5 thereto is controlled by a valve 138 movable by a piston 137 controlled through lines 134, 162 from the valve 120. During starting and low speed running, valve 120 applies pressure 'fluid from source 126 to hold shuttle valve 123 as shown, whereby piston 137 positions valve 13'8 to supply air to the burners. As engine speed is increased by movement of member 28, valve 120 reverses valve 123 to move piston 137 to supply fuel to the burners 9. A piston 152, Fig. 5, is controlled simultaneously with piston 137 and actuates valves 153 in branches 154 from pipes 10 to an auxiliary turbine 11 and valves 155, 156 in lines from blower 5 to a piston device 12 and the turbine 11 respectively. Thus the supplying of fuel to burners 9 coincides with the bringing into use of the auxiliary turbine. The device 12 is subjected to air from blower 5 to balance axial thrust of turbine 2 when turbine 11 is not running. The blower 5 is driven by the engine through a variable speed gear 6, which may be of the kind described in Specification 620,737, [Group XXIV], including two constant mesh' gear trains which are alternatively engaged by clutches, under the control of a piston 124, and a hydraulic coupling with an overspeed gear, the supply to the coupling being controlled by a piston 125. When the engine is started, the valve 120 is positioned by member 28 to connect source 126 to a passage 128 causing the hydraulic coupling to be supplied. As member 28 is advanced toward cruising position, the low speed gear is engaged. Piston 152 controls, in addition to valves 153, 155 and 156, a piston valve 185 which, up to cruising, connects line 186 to source 188 and line 187 to exhaust 189, thus holding shuttle valve 122 in the position shown in Fig. 2. When member 28 is advanced to cause actuation of piston 152, said lines are reversed, and the valve 122 will move to reverse the connections to piston 124, thereby engaging they high speed gear. The burners 9 are supplied by a swash plate ; pump 139, driven by the engine and having an inlet line 182 and outlet line 140. The swash plate 167 is positioned by a piston 169 urged to decrease delivery by a spring 178 and increase delivery by pump outlet pressure. Opposite sides of the piston communicate through a variable restriction 177 and the leak-off from the spring side is controlled by mechanism which may be of the kind-described in Specification 648,871, [Group XXIX], including hinged valves 175 actuated by Bourdon tubes 172 sensitive to temperature at the feelers 171 in pipes 10.