Measurement of the development of the boundary layer in the annulus walls of a fourstage compressor

There are few available measurements of boundary layers in multistage compressors when the repeating stage condition is reached. Tests were performed in a small four stage compressor; the flow was essentially incompressible and the Reynolds number based on blade chord was about 50,000. Two series of tests were performed: in one series the full design number of blades were installed; in the other series half the blades were removed to reduce the solidity and double the staggered spacing. Initially it was wished to examine the hypothesis proposed by L. H. Smith that staggered spacing is a particularly important scaling parameter for boundary layer thickness; the tests tend not to bear out this view. The integral thicknesses agree quite well with those published by Smith.