Three-Dimensional Inviscid Effects in Axial Flow Turbomachinery and Limitation of Cascade Theory

The general objective of the investigation reported in this paper is to obtain a reliable understanding of the three dimensional inviscid effects in axial flow turbomachinery. The calculation is based on the method of distributed singularities.The blades are represented by a series of line vortices and line sources which have their axes along the radial direction and are arranged along the blade camber surface. The basic perturbed velocity fields due to radial vortex lines of constant strength and radial source lines of variable strength are computed from a modified theory based on Tyson’s and Rossow’s formulation. A computer program to obtain the three dimensional flow field in a turbomachinery with arbitrary number of blades, number of singular points per blade, and various hub/tip ratios was developed. Examples illustrating the three dimensional effects due to hub/tip ratio, stagger angle, number of the blades were carried out. The effects of the radial variation of the strength of the radial source line were examined. The three dimensional effects are found to be appreciable for low hub/tip configuration with fewer number of blades.