GB685814A - Improvements in and relating to radial centrifugal compressors and pumps - Google Patents

Abstract

685,814. Centrifugal pumps and compressors. ESCHER WYSS AKT.-GES. Feb. 26, 1951 [March 3, 1950], No. 4622/51. Class 110(i) In a diffuser for a centrifugal pump or compressor comprising passages adjacent the impeller and widening in the direction of flow, the inlet of each passage is approximately circular in crosssection, with an area which is less than twice that of a square of which the side is equal to the internal outlet width of the impeller passages, the circumferential spacing of the inlets being not more than three times the said width and the outlet cross-section of each diffuser passage being at least three times the inlet cross-section. In a multi-stage compressor of which the last two stages are shown in Fig. 1, the diffuser passages are contained in members 3, 4 each split into two parts, preferably on a plane through the compressor axis. The member 4, and partitions 5, 6, 7 are held in place in a housing 8 by stepped portions 4<SP>1</SP>, 5<SP>1</SP>, 7<SP>1</SP>. The diffuser passages 10 are straight, and of at least approximately circular cross-section. The diffuser passages 11 are curved, as shown in Fig. 2, the cross-section changing from approximately circular at the inlet to approximately elliptical at the outlet. The major axis of the ellipse is perpendicular to the plane of curvature and bears a ratio to the minor axis b which exceeds by at least unity the ratio of the total deflection angle a to a right angle. The angle # of entry into the diffuser passages is preferably less than the angle y at which the fluid leaves the impeller 2. The outlet cross-section of the passages 10, 11 may be square and rectangular respectively, in each case with the corners rounded off by circular arcs of which the radii may be equal to the radius of the circular inlet cross-section. The width of the passage 12 may be progressively reduced. Preferably, it is constricted at 13 to a cross-sectional area not greater than that of the outlets of the diffuser passages 10. The discharge volute 9 is preferably so shaped in cross-section that the product of the velocity of flow and the distance from the impeller axis is constant. The diffuser passages may be shaped so as to deflect the flow into the radial or axial direction. In the case of straight diffuser passages, the diffuser members may be split into individual parts on planes passing through the axes of the passages.