Experimental and numerical investigation of interaction between turbine stage and exhaust hood

The current article describes the experimental and numerical studies on the flow field in a coupled turbine stage and exhaust hood model. The low subsonic stage with 22 stator blades and 30 rotor blades is especially designed for the hood model, which is a typical design for a 300/600 MW steam turbine. Velocity distributions at the inlet, outlet, and hood exit stages, in addition to static pressure distributions at the diffuser tip and hub end-walls and at the hood outer casing, are measured and compared with the numerical prediction. The flow details in the exhaust system with the whole annulus stator and rotor blade rows are simulated by employing the computational fluid dynamics software. Good agreements between numerical and experimental results are demonstrated. It is found that the swirl angle profile and total pressure profile due to the upstream turbine stage at the diffuser inlet have an unfavourable effect on the exhaust hood performance.