A primary variable throughflow code and its application to last stage reverse flow in LP steam turbine

摘要

This paper presents a new methodology of throughflow calculation which is based on primary variable Euler equations with viscous force assumption. The passage averaged time dependent compressible Euler equations are derived from the corresponding three-dimensional Euler equations in rotating frame by applying a density-weighted averaging procedure along the pitch of the blade passage. The effects of leaned and bowed blade can be discriminated through the blade force of the new throughjflow method. In addition, the necessary supplemental models, such as viscous force model, loss model, and flow angle model, are discussed in the paper. Time marching finite difference method is employed for solving the equations. Van Leer's flux vector splitting and Warming & Beam's second order upwind difference scheme are applied for the spatial derivative terms. Calculations of the flow in a steam turbine last stage are compared with matrix throughflow claculation and with experimental results. The reverse regions can be reasonably simulated and a between-blades-reverse swirl is captured at far off-design condition by the present method. The resutls show there is good agreement between the experimental data and simulation results.