Abstract: The axial flow pump of high specific speed is widely used for flood control, waterlog drainage, and other special occasions, but its hydraulic efficiency is generally low. To achieve energy-saving effects and a higher efficiency, this paper adopts orthogonal tests to optimize the impeller and diffuser of a 1400 axial flow pump, and examines the internal flow behaviors of the pump and its optimized version. First, a geometric parameter analysis is made for the impeller and diffuser, and control factors are imposed on the parameterized control dimensions. Then, we design a set of orthogonal tests using hydraulic efficiency as the objective index, and conduct a range analysis of the test results so as to determine the key factors in the pump’s hydraulic performance. Thus, orthogonal test optimization of the impeller and guide vanes is achieved for different levels of the key factors via adjusting the geometric parameters of the blade airfoil. We found that flow separation and backflow vortices in the impeller and diffuser sections optimized by cross-test are suppressed effectively, and the pressure concentration area on impeller surface is expanded, resulting in a greater driving force and a significant reduction in the hydraulic losses in the sections of impeller, diffuser and outlet pipe. And an improvement on the pump’s hydraulic efficiency by 13.2% has been achieved in and the pump head is increased to the design level of 6.3 m.

Key words: axial flow pump, impeller, diffuser, hydraulic efficiency, orthogonal test