GB879320A - Multi-stage radial flow compressors - Google Patents

Abstract

879,320. Centrifugal compressors. SULZER FRERES S.A. April 2, 1958 [April 4, 1957], No. 10657/58. Class 110 (1). A multi-stage radial-flow compressor comprises a housing divided in an axial plane and diffuser inserts which surround each impeller and which are each followed by a deflecting bend and then by a separate insert which constitutes a return duct extending from the bend to the impeller inlet of the next stage, and between each diffuser insert and the preceding upstream return duct insert there projects a divided intermediate partition made as a structural unit with the housing halves, these partitions supporting the inserts and taking the pressure forces exerted in the axial direction by the working medium. Partitions 24, each preferably with an inside diameter smaller than the maximum diameter of the adjacent impeller, comprise semi-annular discs formed integrally with each half of the horizontally split casing 1, or welded to each half. Each interstage return passage is formed mainly by an insert 25 integral with guide blades 26 and ribs 28. Diffusion is provided by inserts 6 formed with blades 7 and each centred in a recess in the adjacent insert 25 and, it may be, helping to support the latter against the adjacent upstream partition 24. Each insert 25 is located radially and axially in a shouldered seat 29 in the adjacent downstream partition 24 and also lies against a part of the side surface of the partition near its outer diameter. Bores 33 and 34 equalize the pressures in chambers 40 and 41 with those prevailing in the corresponding parts of each return passage. Leakage around inserts 6 renders the pressure in each chamber 39 approximately equal to that at the exit from the corresponding diffuser. A pressure approximately equal to that at each impeller outlet is communicated by leakage to each chamber 37 and 38. The resultant forces on the stator parts provide an axial thrust towards the inlet end of the compressor, the partitions 24 being subjected to bending stresses and the inserts 6 and 25 being substantially free from bending stresses. The inserts 6 and 25 can therefore be made with relatively thin walls from grey (for example, nodular) cast iron or a cast light alloy, such as aluminium silicon alloy, whereas the casing 1, for reasons of strength, is of cast steel.