Refinement of the Mean Streamline Method of Blade Section Design

Abstract

The Mean Streamline Method of cascade blade section design developed by Wislicenus correlates the differences in the shape of the blade camber-line and the one-dimensional mean flow streamline. Recent effort has been directed toward the extension of this design method, to cover a wider range of loading distributions, including trailing edge loaded blades, and blades with higher than usual solidities (C/S). A computer analysis of many available blade shapes for subsonic compressors and pumps with differing loading distributions that have been tested experimentally was made. Relations between the deviation of the camber-line from the mean flow streamline as a function of the lift coefficient, solidity, a loading distribution parameter and blade stagger angle were found. Using these correlations, a computerized design method was developed which rapidly produces blade shapes with specified design characteristics. A radial equilibrium theory is utilized to compute the actual blade surface pressure distribution. When a blade is to be designed which is similar to existing designs, the method has proven very reliable.