Experimental study of endwall flow in a compressor cascade

Abstract

Improvement in calculating methods for end?wall boundary layers of blade rows can only come about by a greater understanding of the physics of the flow from which realistic models can be built of the terms that go into the averaged three?dimensional boundary layer integral equations. The necessity for more experimental information on the details of flow in the end?wall regions is evident. Detailed measurements of the boundary layer development on the blade passage end?walls and within the tip clearance were made in a large?scale low aspect?ratio compressor cascade with variable tip clearance. They were supplemented by extensive measurements of the static pressures on the end?wall and the blades as well as with skin?friction measurements using hot?film and Preston tube methods. Flow visualisation tests were carried out in the blade passages and within the tip clearance using both a wind tunnel and a water flow facility. The measurements and flow visualisation experiments were used to build up a physical picture of the end?wall and tip?clearance flows and to verify some of the concepts of end?wall calculating methods. Quantitative estimates of such parameters as skin?friction coefficients, blade defect forces, tip?clearance coefficients, and correction factors relating average and true momentum flux have been made.