GB642585A - Improvements in or relating to an internal combustion turbine power plant - Google Patents

Abstract

642,585. Centrifugal compressors; roots blowers; gas turbine and jet propulsion plant; stuffing-box substitutes. LOCKHEED AIRCRAFT CORPORATION. Feb. 10, 1947, No. 3824. Convention date, June 2, 1945. [Classes 110(i), 110(ii), 110(iii) and 122(v)] [Also in Groups XI, XII, XXII, XXXIV and XXXV] A gas turbine plant, shown in Fig. 1, as arranged for aircraft propulsion within an air channel S and fitted with an airscrew B and a propulsion jet 79, comprises four detachable parts. The part 22 contains the reduction gearing and the airscrew shaft, a part 21, the air-compressor, a part 31, an exhaust heat-exchanger and a part within the forward end of the part 31, the turbine and combustion chamber. An assembly 146 secured below the part 22 comprises, on one shaft, a dynamotor 213, Fig. 10, a highpressure stage Roots' blower 147 for the fuel-injection air, and two centrifugal pumps 156, 165 for the lubricating oil and fuel. The shaft is driven by the turbine through a self-engaging clutch. An oil sump 176, with cooling fins, is secured below the part 21. The plant is shown in horizontal section in Figs. 5 and 6. The air inlets 35 are lined with a sound-deadening material M. They lead to compressor blades 57, on the rotor R, which are mainly in radial planes but have inlet and outlet portions bent in the direction of rotation. The blades 57 deliver to a bladed passage 61 in a contra-rotating ring 60 which delivers to a bladed diffuser 64. The blades 58, Fig. 16, in the ring 60 are of aerofoil section and the blades 59 in the diffuser are of sheet material. The compressed air passes through an outer annular channel 82 and enters the tubes 84, Fig. 6, of the exhaust heat-exchanger. The tubes discharge past swirl vanes 100, 101, into an annular combustion chamber 12. The heated gases on leaving the combustion chamber act upon reaction blades 102 on the contra-rotating ring 60, then upon Francis-type blades 105 on the rotor R, and last upon impulse blading 106, 107. The turbine discharge passes through an annular arrangement of separate channels 118, along the outsides of the tubes 84 between the cylindrical shells 81, 120 and out through the propulsion nozzle 79. The annular combustion chamber 12 surrounds the turbine and includes heat-resisting walls 88, 90. Air from the main stream passes between the wall 88 and the casing wall 63. Air extracted by pipes 122, Fig. 6, passes around the starting-gas container 195, between the channels 118 into a space 121, between a baffle 124 and a casing wall 125 and between that wall and the heatresisting wall 90. These air streams join with the combustion products at the combustion chamber throat. The fuel-injection ring is enclosed by a U-shaped shield 300 supported by swirl-producing blades 100, 101. The ring comprises a chamber 94, Fig. 7, receiving compressed air from the high-pressure Roots' blower and a chamber 93 receiving fuel from the fuel pump. The outlets 97, 98 produce a spray of mixed air and fuel. The rotor trunnion 42 is mounted in a bearing sleeve 43 and a shaft-extension 44, in a bearing sleeve 47. These sleeves are formed with portions 49, Fig. 4, of reduced thickness and separated from the body of the sleeve on three sides to form bearing tongues extending from their roots in a direction against the rotation. End thrust is taken by bearing tongues 51 at one end of the sleeve. The rotor is formed with many passages 129, for a flow of cooling oil, connecting the axial inlet and outlet passages 128, 130. The contrarotating ring 60 is mounted on a bearing which comprises a number of segmental bearing blocks 71, Fig. 11, anchored to the casing part 24 by round headed pins 74, and riding in a bearing groove in the ring 60. Oil from the bearing groove passes to an annular cooling passage 110 and is discharged into a trough 113 by a passage 112. A heat-resisting gas seal is provided between the ring 60 and the rotor R which comprises a ring 67 of Invar steel, Fig. 8, in halves, which is pressed by centrifugal force into contact with the ring 60, and a carbon inset 69 which bears upon the rotor R under the gas pressure in clearance 70. The speed-reducing gear includes two aligned oppositely rotating cross-shafts 133 carrying large bevels 138 and pinions 143. The shafts are supported in bearings 134 on the stator part 39 and in outer bearings 135. Teeth cut in the shaft-extension 44 engage the bevels 138 and the pinions 143 engage a crown-bevel 142 on the tubular power shaft 139. The driving member of the self-engaging clutch for driving the motor-generator carries a pinion engaged by the bevels 138. The cooling oil from the outlet 130 in the rotor R passes through a coiled tube cast in the wall of the oil sump 176 before entering the sump. The fuel and the air for the fuel injection, both before and after the high-pressure stage pump, pass through conduits in the structure of the sump 176 and take up heat from the oil. The speed of the plant is determined by the setting of a control lever 240, Fig. 10, and the corresponding spring-loading of a piston 242, which is opposed by the delivery pressure of the fuel pump 165. Movement of the piston 242 varies the valve opening at 241 in the fuel-supply line 193. In starting, specially generated combustion products are directed by a nozzle 199 on to the blades 102 of the contra-rotating ring 60 and the ring operates as an air-compressor until sufficient pressure is obtaining for starting the main combustion chamber. The starting arrangement is shown in Fig. 10. Movement of the control lever 240 from the "off " to the " idle " position opens the fuel valve 241 a little and closes the switch 270, 213 of the lead from the battery 206 to the dynamotor 213 which puts into operation the air-pump 147, the lubrication oil pump 156 and the fuel pump 165. A piston valve 190, in the position shown, passes air, through pipe 200, and fuel, through pipe 263 and valve bore 203, to a pipe 197 where they mix and pass into the tank 195. The circuit of a glow ignition device 204 is also closed and. after a predetermined time, the device ignites the gas mixture. The pressure generated operates on a shoulder 264 of the valve and moves it downwards against a spring 262, so opening a passage from the tank 195 to the nozzle 199. A bellows device 208 is subjected to the air-pressure on the delivery side of the contra-rotating ring and, when there is sufficient pressure, moves a switch arm from contact 210 to contact 211. This breaks the circuit of the ignition device 204 and short-circuits the series coil 214 of the dynamotor which is then ready to run as a generator to charge the battery with a voltage control comprising a carbon pile 220 and a pressure piece 221 under the influence of a solenoid 218 which carries the charging current. The downward movement of the valve 190 opens the main injection air and fuel lines 96, 95 by way of annular grooves 191, 194. In case of battery failure, the motor-generator and pumps can be driven by hand-gear 230 through a self-closing clutch. The Roots' blower casing is built up of three plates of a hydraulically pressed graphite and silver combination. The rotor R is of cast chromium steel and the blades are cast cobalt-alloy or sintered tantalum and are chromium plated. They are positioned in the mould for the rotor and secured by the casting. The oil passages in the rotor are defined in the mould by cores of refractory material or steel tubes cooled by the passage of air during the casting. The blades and cores are placed in a wax injection mould. The wax unit is provided with a coating of refractory plaster and the wax melted out. The plaster mould is heated to 2100‹F in a neutral atmosphere and molten heat treatable chromium steel is injected.