GB930474A - Improvements in centrifugal pumps and the like - Google Patents

Abstract

930,474. Centrifugal pumps &c. RESEARCH & DEVELOPMENT PTY. Ltd. Jan. 18, 1961 [Jan. 19, 1960], No. 2051/61. Class 110 (1). In a centrifugal pump, blower, fan, compressor or the like of the volate type, means are provided for segregating and directing or for producing, segregating, and directing fluid of differing energy levels so that in the casing fluid of higher energy level envelops or substantially envelops fluid of lower energy level. The outer end of each impeller blade 4, Fig. 2, is formed with a groove 11 to reduce the energy imparted to the fluid in a zone 13 below that imparted to the fluid in two side zones 12, to compensate for the energy losses caused by friction between the casing walls and the fluid in the zones 12, whereby the fluid enters the discharge volute 20 with substantially uniform energy. The groove 11 is offset from the centre line of the impeller blade towards the impeller back plate 5 to counteract the effect of the single axial intake 8 which would otherwise cause the fluid energy to be greater adjacent the back plate 5 than adjacent the front plate 6. The groove 11 may extend to the back plate 5 which may then extend radially beyond the groove to impart additional energy by frictional drag. The discharge volute may in this case be offset from the central plane of the impeller. To assist in directing the higher energy fluid in the zones 12 towards the casing walls, the impeller side plates 5, 6 may be flared outwardly at 16; the casing side walls may be correspondingly bevelled at 43 and 54. To exclude higher energy fluid from the discharge, the entry 19, Fig. 4, to the volute 20 is located in a circumferential ridge 22, Figs. 2 and 4, with sloping sides 23 and located nearer the pump axis than the nearby outer wall 21 of the casing, the ends of the ridge merging into the outer wall at 24 and 25. The ridge 22, which contains the cutwater 26, may be offset from the central plane of the casing. The crosssectional area of the casing increases, as is usual, in the direction of rotation from the cutwater 26 to the beginning 28 of the volute 20 to accommodate the fluid discharged by the impeller, and thereafter decreases so as to maintain a constant average velocity in the region of the entry 19 to the volute. The impeller front plate 6 may be omitted. Where the fluid is abrasive, as with slurry or dredge pumps, the casing is provided with a peripheral lining, which may be formed in two parts 29, 31, and separate side linings 33, 45. The linings and the impeller are of hard metal as in the lower half of each figure or of natural or synthetic rubber bonded to metal reinforcements as in the upper half. Where hard metal linings are used, resilient sealing rings such as 57 are provided between the linings and the outer shell of the casing.