GB676839A - Improvements in displacement engines of the rotary screw wheel type - Google Patents

Abstract

676,839. Meshing-screw compressors and engines. AKTIEBOLAGET LJUNGSTROMS ANGTURBIN. June 23, 1950 [July 11, 1949], No. 15718/50. Class 110(ii) The invention deals with a compressor or engine of the type shown in Specification 627,162 comprising one rotor having helical lands of convex cross-section lying substantially outside the pitch circle and a co-acting rotor with lands of generally concave cross-section lying substantially within the pitch circle. The helical or cam angle of the male rotor, i.e. the smaller angle between the longitudinal axis of the rotor and the direction of the tops of the threads, exceeds 50 degrees, and the male rotor has three or more threads, while the wrap angle, i.e. the tota angular displacement of the thread along the rotor length lies between 200 degrees and 325 degrees in order to pro vide an enlargement of the inlet and outlet openings o: the casing relatively to the stroke volume. The male rotor has a length to diameter ration lying between 0.5 anc 1.1. Fig. 1 shows one arrange ment of compressor with male and female rotors 16, 18 inlet and utlet ports 44, 46 shaft seals 32, 34, 36, 38, anc rotor synchronizing wheels 40 42 which ensure clearances between the co-operating lands and grooves. The inlet and outlet ports and the edges of the male and female threads may all have their edges rounded off. The female and male threads are rounded off as shown in Figs. 6 and i respectively. The nose portions 64, 66 are directed in the direction of rotation of the thread. Fig. 13 shows a twostage compressor having lowpressure and high-pressure stages 166, 168 respectively and an intercooler 156. Air enters the L.P. compressor through an inlet 152 and is delivered to the intercooler through an inlet 154. The H.P. compressor has inlet and outlet ports 158, 162. Outer bearings 170, 172 are provided but no central bearings. A seating device 174 is placed centrally. The H.P. compressor has a short rotor with length to diameter ratio of 0.5 to 0.7 with a moderate wrap angle and the L.P. rotor has a ratio of 1.5 to 2 and a wrap angle preferably greater than 250 degrees. The axial forces are approximately balanced. In a modified plant, Fig. 14 (not shown), the intercooler is dispensed with. Fig. 15 shows a gas power plant in which a compressor 200 and engine 202 have a rotor 204-206 supported on bearings 208, 210. Shaft seals 214, 216 are provided. Compressed air passes through apertures 220 in the shaft 222 and apertures 224 in the casing into the cooling systems 226 and 228. The warmed air then flows through a duct 230 to the combustion chamber 232 and enters the engine through an inlet 236. Exhaust gases are discharged through an outlet 238. The high-pressure ends of the compressor and the engine are adjacent, the axial and radial forces on the rotors being approximately balanced . U.S.A. Specification 2,457,314 also is referred to.