Three-dimensional design method for mixed-flow pump blades with controllable blade wrap angle

摘要

In this article, a direct and inverse iteration design method for mixed-flow pumps was introduced, and a three-dimensional design platform for mixed-flow pumps was established. Through iteration calculation of two kinds of stream surfaces to solve both the continuity equation and motion equation of the fluid at the same time, and therefore obtaining the quasi-three-dimensional flow field inside the mixed-flow pump, the accuracy of the flow field calculation was improved. By repeating iteration of the direct calculation and inverse design, influence of blade shape on flow field calculation was fully considered, thus assuring that the final design of blade camber line complies with actual flow pattern. After comparing and analyzing the meridional velocity distribution, as well as the relative circulation distribution and expelling coefficient in the blade zone, it was proved that compared with others designed by conventional methods, the impeller designed with three-dimensional design platform has a better hydraulic performance, especially the blade energy conversion capacity that witnessed a significant improvement. With this three-dimensional design platform, a parametrization was applied to velocity moment distribution and blade leading and trailing edges positions. The influence of velocity moment distribution parameters P and α_0, and the blade leading and trailing edges positions parameters θ_h and θ_t on blade wrap angle and the internal flow of the impeller were analyzed. By curve fitting, the functional relationship between blade wrap angle ψ and parameters θ_t, P and α_0 was obtained. The blade wrap angle control strategy during the process of mixed-flow pump impeller design was then put forward, thus realizing three-dimensional design of mixed-flow pump blades with controllable blade wrap angle. The performance test for the mixed-flow pump model suggested that the three-dimensional design method with controllable blade wrap angle, by controlling blade wrap angle size and adopting direct and inverse iteration design method, ensures a better hydraulic and cavitation performance for the mixed-flow pump impeller designed with three-dimensional design platform.