GB816811A - Improvements in supersonic axial-flow compressors - Google Patents

Abstract

816,811. Axial-flow compressors. SOC. NATIONALE D' ETUDE ET DE CON- .STRUCTION DE MOTEURS D' AVIATION. June 4, 1957 [June 11, 1956], No. 17761/57. Class 110 (1). A supersonic axial-flow compressor comprises a rotary blade ring in which the axial component of the absolute discharge velocity is supersonic, conversion of kinetic energy into pressure energy taking place in a stationary annular diffuser extending downstream of the ring, the conversion being due to the formation of a shock-wave downstream of which the flow becomes subsonic. The absolute discharge velocity may be purely axial to give a normal shock-wave or may be inclined to give an oblique shock-wave. In the latter case, blades may be provided at the outlet of the diffuser, to remove the whirl. In the compressor shown, the air passes through stationary guide blading 2 and contra-rotating impeller blading 6, 7, and the shock-wave 17 occurs in a bladeless annular diffuser passage 16 at, it may be, the narrowest part 18 of the passage. The convergent part of the passage upstream of the throat 18 forms a supersonic diffuser. The relative velocity at the blades 6 is subsonic at the roots with a Mach number between, say, 0.7 and 1.2, and supersonic at the tips with a Mach number between, say, 1.2 and 1.6, while the relative velocity at the blades 7 is wholly supersonic. Radial struts 5 are provided. The two impellers may be rotated in opposite directions by two oppositely-rotating turbine stages. Alternatively, as shown, the driving-shaft 9 drives the second impeller directly through a splined connection 10 and drives the first. impeller indirectly through a splined connection 11 and reversing gear 13. The boundary layer may be controlled by suction through porous walls of the diffuser 16 or through slots in the walls.