GB776606A - Improvements in or relating to centrifugal compressors - Google Patents

Abstract

776,606. Centrifugal compressors. ROLLSROYCE, Ltd. May 6, 1955 [April 14, 1954], No. 11082/54. Class 110 (1). A centrifugal compressor comprises an impeller of the kind in which the hub/tip ratio of diameters of the impeller vanes is 0.50 or less at the impeller eye, the Mach number of the incident stream at the vane tips in the impeller eye is at least 0.85 under maximum rotational speed static conditions at sea level, and the maximum peripheral speed at the impeller outlet tip exceeds 1500 feet per second under the same conditions, and an axial-flow stage immediately at the entry to the impeller vanes, the axial-flow stage comprising a row of rotor blades followed by a row of stator blades. The compressor shown, which forms part of a jetpropulsion gas turbine engine, comprises a double-sided centrifugal impeller 10, preceded on each side by toroidal inlet shoots 13, fixed inlet guide vanes 14, and axial-flow rotor blading 15 and stator blading 16. The leading edges of the centrifugal impeller vanes 11, which are shaped to give the necessary entry angles, may be formed as separate rotating guide vanes. The rotor blades 15, which have a hub/tip ratio of about 0.4 at their inlet edges, may be pivoted, as shown, on a ring 20 splined to the rotor shaft 21. Annular swellings 12a may be provided, each affording a rib 18 and shoulders 17 to locate the roots of the blades 16.