GB1523875A - Supersonic compressors - Google Patents

Abstract

1523875 Supersonic compressors R S DE CHAIR 2 Sept 1975 [3 Sept 1974] 38380/74 Heading F 1C A supersonic compressor comprises an annular array of passages 12, Figs. 1 and 2, each passage being defined between two circumferentiallyspaced side walls 13, 14 and two radially spaced walls 15, 16 so as to afford a throat 35, Fig. 4, and divergent downstream portion 34, the wall 16 extending further upstream than the wall 15 and defining an intake portion of the passage in the form of a supersonic compression ramp which is separated from the adjacent supersonic compression ramp by the side walls 13, 14. As shown in Figs. 1 and 3, the wall 15 has separate upstream portions each extending between side walls 13, 14, contacting the wall 13 along a line 24 and contacting the wall 14 along the boundary edge 25 of the latter. The wall 16 is slightly concave upstream of the lips 18 of the wall 15, thereby forming the supersonic compression ramps which produce an oblique shock wave 31 at each of the front edges 19 of the wall 16. Each shock wave 31 terminates on or just outside the lip 18 and is followed by a fan of shock waves 32. The supersonic compression terminates at a normal shock wave 33 in the divergent passage 34 which follows the throat 35. Thereafter the flow is subsonic. The leading edges 26 of the walls 13, 14 are substantially parallel to the shock wave 31. When the compressor is not operating at its design point and the inlet flow is consequently not parallel to the walls, 13, 14, it is turned into the direction of the walls by an oblique shock wave at one side of each wall and an expansion fan on the other side of each wall. Air not accepted by the compressor spills over the outside of the outer wall 15. To control this spillage, a casing 45, Fig. 8, may be provided to afford a gap 42 outside the lips 18 through which the spillage flows. This casing may extend either upstream, Fig. 6 (not shown), or downstream Fig. 7 (not shown) of the lips 18, or as shown in Fig. 8, both upstream and downstream of the lips Control of the spillage flow is effected in accordance with the pressure difference across the gap 42 by means of a valve in the duct 44 downstream of the gap or, in the case of Fig. 6, by moving the casing towards the lips 18. Boundary layer control slots may be provided in the inner wall 15. The supersonic compressor may comprise either a rotor or a stator, provided that in the latter case it is preceded by means, e.g. compressor stages, for providing the supersonic inflow. The inner and outer walls 16, 15 may be interchanged.