Comparison of three dimensional quasi-linear large swirl theory with measured outflow from a high-work compressor rotor

Abstract

A three-dimensional perturbation theory for incompressible strongly swirling flow in an annulus is applied to predict the outflow from a high-work compressor rotor (1)(2). A comparison of the analytical result with the experimental result is presented. The theory treats inviscid, incompressible flow through a highly loaded blade row in a long annular duct with uniform inlet. Trailing vorticity is shed from each blade which is represented by a lifting line of bound vorticity. The flow field between successive sheets of vorticity is assumed to be irrotational. The theoretical results are compared to data obtained in the M.I.T. Blowdown Compressor Test Facility (3). The mean circulation distribution is estimated from the mean pitchwise Mach number obtained from the experiment. The agreement of the predicted mean axial and radial velocity with the experimental results represents one confirmation of the theory. The pitchwise-varying velocity are evaluated by the theory at an axial distance of .02 tip radius which corresponds to the probe position if the lifting line is placed slightly ahead, but almost along the trailing edge of the blade. The theory predicts well the pitchwise variation of the velocity due to the effect of shed vorticity which results from the spanwise variation of circulation. The effect is pronounced near the blade tips. Corrections of the theory due to compressibility are omitted here, but will be available shortly.