CFD-based analysis of multistage throughflow surfaces with incidence

摘要

A numerical finite-volume solution of Euler equations is performed in the meridional plane of complete axial flow turbomachinery. The throughflow equations contain blade force terms that model the effects of the real blades on the flow and are resolved by further equations. Under the axisymmetric flow assumption, incidence involves a discontinuity through the leading edge, which introduces strong unphysical losses. Incidence is modeled by solving an inverse problem in the front part of the bladed region. The inverse method provides the geometry of the throughflow surface that replaces the discontinuous profile of swirl velocity with a specified, conveniently smooth profile across the leading edge region. The specified velocity profile and computed ideal geometry are used to update the blade force. The Euler solution is compared to a streamline curvature solution in analyzing a three-stage turbine. In the design condition with up to 2° of spanwise-averaged incidence, the method does not significantly affect the prediction of overall performance. In a strong off-design condition with up to 13° of average incidence, performance is predicted with the same accuracy as in the design case.