Experimental and Numerical Investigation of Interactions Between Axial Turbine and Non-Axisymmetric Exhaust Hood

Abstract

This paper describes experimental and numerical studies on the coupled flow field in a single turbine stage and exhaust hood model. The turbine stage with 22 stator blades and 30 rotor blades is especially designed for the hood model, which is a typical design for Westinghouse model 300/600 MW steam turbine. Unsteady pressure at the rotor blade, hood outer casing, unsteady total pressure at the stage outlet and velocity distributions at the turbine outlet and hood exit, in addition to static pressure distributions at the diffuser tip and hub end-walls and at hood outer casing, are measured and compared with numerical predictions. The flow details in the exhaust system with the whole annulus stator and rotor blade rows are simulated by employing CFD software CFX-5. It is found that the swirl angle profile and total pressure profile caused by the upstream turbine at the diffuser inlet have an unfavorable effect on the exhaust hood performance. The non-axisymmetric back-pressure generated by the downstream exhaust hood leads to the local flow varying for each stator and rotor blades and low frequency fluctuation in the aerodynamic force on the blade.