Design And Numerical Simulation On The Multistage Centrifugal Pump With Semi-open Complex Impeller.

The special multistage centrifugal pump with low specific-speed, such as the charging pump used in the chemical volume control system of AP1000 nuclear device, not only has the characteristic of small flow and high lift, but also should assure the hydraulic performance achieving the multi-operating requirements while the flow rate charges from zero to maximum. Meanwhile, the problems like compactness for structure, instability of the head in the small flow rate or overload of the power in the large flow rate should also be emphasized in the design process. In order to give the design method, the charging pump was used to investigate the performance of semi-open complex impeller with multirow balance hole and double flow passage guide vane in volute shape. A hydraulic model was designed to reach the requires by 3-demension flow simulation and performance prediction method, based on computational fluid dynamics (CFD).The design principle and methods of semi-open impeller, complex impeller and guide vane were studied. The definitions of critical parameters were given. The essential points of structure design in the straight blade of complex impeller and double volute flow passage were analyzed.The diameter of a centrifugal pump with single-stage semi-open impeller and its numerical simulation method was given. The model considering forward and backward clearance, balance hole and sealing rings was calculated by different modeling types, mesh partition methods and turbulence modes, in order to analyze the influence of calculation accuracy for performance prediction curve. Also this can verify and perfect prediction method based on simulation.According to four special operating conditions, power requires and structure compactness of AP1000 charging pump, a low specific-speed multistage centrifugal pump with semi-open complex impeller was designed, containing multirow balance hole and double channel-type guide vane in the volute shape. Based on the method of CFD simulation certified in this paper, the hydraulic performance was estimated, and the essential diameters determining the efficiency in every operating point were analyzed. As the results, the suggestion in the structure and design was provided, improving the flow passage components, and making the charging pump to satisfy with the requirements of stability and safety.The methods of designing the multistage pump and the performance prediction by three-dimension numerical simulation are provided. And the hydraulic performance achieves the requirements of multi-operating conditions. It would be very significant to the research for multistage centrifugal pumps with low specific speed and to the application of nuclear pumps.