GB695948A - Improvements in or relating to centrifugal gas compressors - Google Patents

Abstract

695,948. Centrifugal compressors. DE HAVILLAND ENGINE CO., Ltd., HALFORD, F. B., MOULT, E. S., and COCKBURN, D. M. Dec. 6, 1950 [Dec. 12, 1949], No. 31838/49. Class 110(i) [Also in Group XXXIII] In a centrifugal compressor having a single inlet eye, the impeller delivers to an axially-extending bladed annular diffuser passage by way of a bladeless annular transfer passage which is bent through, preferably, approximately a right angle, so that its exit faces away from the inlet eye. The air leaving the impeller B<SP>2</SP>, Fig. 1, of a centrifugal compressor flows by way of an annular transfer passage C to an axially extending diffuser comprising cylindrical walls D, D' and rows of short diffuser blades D<SP>3</SP>- D<SP>6</SP> of aerofoil section and progressively increasing pitch. Instead of a number of rows, there may be a single row of diffuser blades, of greater length. Either or both of the walls D, D<SP>1</SP> may depart from the cylindrical form to give the diffuser an increasing cross-sectional area in the direction of flow. The impeller may be of helico-centrifugal form, so as to reduce the angle through which the air has to turn in the transfer passage. Fig. 9 shows a construction in which the impeller has an axially directed portion P<SP>3</SP> extending into the transfer passage C. To reduce turbulence at the inner wall C2, Fig. 10, of the transfer passage C, boundary layer control may be effected by air which flows into or out of a chamber Q through passages Q<SP>1</SP>. The passages Q<SP>1</SP> may be directed downstream or upstream according to whether the flow through them is outward or inward. Fig. 11 shows a modification in which variable-pitch diffuser blades D3, D<SP>4</SP> are rotatably mounted on spindle R, S and connected by gear wheels R<SP>1</SP>, S<SP>1</SP> to a double-sided annular rack T. The rack T carries a short operating rack T<SP>2</SP> which is connected by a gear wheel U to an operating member U<SP>1</SP>. The compressor may form part of a gas turbine plant. If the air has a tangential component of flow on leaving the diffuser, the direction of the axes of the combustion chambers may be given a corresponding tangential component. The diffuser blades may be designed for supersonic flow and the propagation of pressure by shock wave formation. According to the Provisional Specification, the passages Q<SP>1</SP> may be of annular form. The supply of air to the chamber Q may be by a separate impeller or by a bleed from the downstream end of the diffuser. If air is to be withdrawn, a pump or an ejector comprising a venturi tube located. in the air stream may be used. Reference has been directed by the Comptroller to Specification 669,357.