Study on the Impeller Hydraulic Performance for the Contra-Rotating Axial Flow Pump

This paper discusses the design method and performance of the front and rear impellers of the contra-rotating axial flow pump. A definition of specific speed has been given. The design head of rear impeller is suggested to increase appropriately. By analyzing the inlet and outlet velocity triangles of the twin impellers in detail under design and off-design point, the paper gives a matching condition and formulas for working out the two triangles. Based on the velocity triangles and ‘lift method’, the geometric parameters of the twin impellers have been designed, the results have been analyzed qualitatively, and the hydraulic performance has been predicted. A practical design shows that at the same design head of the twin impellers, the relative velocity at the middle of inlet and outlet of rear impeller are larger than that of the front impeller, while the stagger angle is smaller and the head curve is much steeper.