Inverse Design of Centrifugal Impellers by Simultaneous Modification of Blade Shape and Meridional Contour

Abstract

A numerical procedure for the design of a centrifugal compressor impeller with prescribed isentropic Mach number distribution along the blade suction and pressure side is described. Both the blade shape and the endwalls are defined at the same time. This method is a combination of a 3D and a quasi-3D flow analysis programs with a quasi-3D geometry modification algorithm. The 3D analysis program is used for a given impeller geometry to calculate the velocity distribution along the blade. The difference between the desired velocity at pressure and suction side and the one calculated by the 3D analysis program for the actual geometry, is used to calculate the required modification of the mean velocities and swirl in the flow. These values are added to the values given by the quasi-3D analysis program to define the new quasi-3D target used for the modification of the geometry. The endwalls are designed with the transpiration method so that a prescribed distribution of mean velocity at hub and shroud is reached. The blade shape is modified until a prescribed swirl distribution is obtained. An iterative use of these programs results in a geometry for which the calculated 3D velocity is equal or as close as possible to the desired one. The practical application of this procedure to the design of centrifugal compressor impellers is illustrated by an example.