A New Throughflow Approach for Transonic Axial Compressor Stage Analysis

Throughflow theory is based on an axisymmetric treatment of the circumferentially averaged flow. The present study proposes a new averaging procedure working normal to the central streamline. Used in a throughflow calculation process, this technique offers a more accurate and realistic modeling inside the blading; in addition it is well suited for the nearly normal shock calculation as well as the choking prediction. Based on pressure equilibrium, a numerical integrating procedure was developed. It provides the physically correct solution stemming from calculation without driving the flow towards an imposed one. In order to evaluate the shock position and the associated losses, a rapid and exact method derived from the quasi-3D characteristics method is incorporated. The reliability of this approach is proven by comparison with measurements conducted on an axial transonic compressor stage, as well as to a 3D viscous numerical simulation of the rotor flow. The results show a good representation of the flow outside the casing boundary layer and reveals the sensitive behavior of the predicted performance to the quality of the quasi-3D shock modeling.Copyright © 1995 by ASME