Abstract：Two inducers respectively with constant and variablepitch are designed to improve the suction performance of a low specific speed centrifugal pump with a flow rate ratio of 30(maximum flow rate over minimum one) based on a design principle that the head generated by an inducer should match the suction head of the main impeller of a pump. The cavitating flows in the centrifugal pumps with two inducers are simulated by using the SST turbulence model and the mixture cavitation model under a few working conditions, and the head breakdown characteristics and bubble distribution features are analyzed to disclose the mechanisms for the head breakdown caused from cavitation at various flow rates. The performance curves of the pumps with the two inducers are measured on a highspeed pump test rig. The predicted hydraulic and suction performance curves are compared with the measurements, and good agreement is achieved. It is confirmed that the design principle adopted here can be as an essential guidance on design of inducer with excellent suction performance. The head breakdown curves with decreasing inlet pressure are different from one flow rate to another. The slope of the head breakdown curve at a high flow rate is sharper than that at a low flow rate and the head declines slowly with reducing net positive suction head available. The shape of the curve at a middle flow rate is in rectangular shape. Compared with the constantpitch inducer, the variablepitch inducer is subject to an even smaller incidence angle and even high head, allowing a highspeed centrifugal pump to have a more wide range of flow rate for stable operation.
