Design Method of Meridional Contours Based on Velocity Distribution of Multi-stage Composite Impeller

In order to deal with the integrated design problem of meridional contours of the multi-stage composite impeller, a method based on axial velocity distribution is proposed. The cubic spline curve is used to fit the shroud and hub to get the central axis of the meridional contours, and combined with the result of numerical simulation analyzing the meridional velocity distribution after obtaining the variation of the cross flow section area. Then adapting the dimensionless method to establish the constraints model that used in the design differential equations according to medial axis theory to draw the appropriate meridional contours. Research results show that: the cross flow section area of this type of impeller is not linear or parabolic distribution which is different from existing theory; crowding-out effect is the main reason of the error in meridional velocity calculation; and the design method proposed is easy to control the shape of the axial flow channel, and has practical engineering value.