Pressure Fluctuations due to Air Entrainment in a Screw-Type Centrifugal Pump.

Abstract

It is reported recently that the pump head deterioration near the best efficiency point, from single-phase flow to the choke due to air entrainment became less in a screw-type centrifugal pump than in a general centrifugal pump. Moreover, at a narrow tip clearance, the pump head became partially higher in two-phase flow than that in single-phase flow. However, the internal pressure fluctuations on this pump due to air entrainment have not been studied yet. For that reason, we have examined the influences of void fraction, flow coefficient and impeller tip clearance on pressure fluctuations in the casing. At narrow tip clearance, the pump head increment in two-phase flow mainly depends on the pressure increasing in the volute casing. And the void fraction became larger, the influence of tip clearance on pressure distribution became less. Moreover, we have observed the internal flow patterns by using a stroboscope and a halogen sheet light. Then, we have investigated the influences of flow coefficient on air-water two-phase pump performance.