AERODYNAMIC OPTIMIZATION OF THE DIFFUSER TOWARDS IMPROVING THE PERFORMANCE OF TURBINE AND EXHAUST HOOD

Exhaust hood of large steam turbines is designed to recover the leaving kinetic energy of the last stage turbine while guiding the flow from the turbine to the condenser, which is of great importance to the overall performance of the steam turbine. The influences imposed by the strong flow interactions between the last stage turbine and the non-axisymmetric exhaust hood have not been taken into account properly in the current exhaust hood design approaches. The purpose of this paper is to optimize the diffuser in order to guarantee the aerodynamic performance of the turbine and the exhaust hood under the operational conditions. Considering the flow interactions between the turbine and the exhaust hood, the profiles of the diffuser end-wall were improved. The coupled turbine and exhaust hood calculations and the experiments were carried out to. validate the effects of the optimization. It's found that the redesigned diffuser can enhance the pressure recovery ability of the exhaust hood and increase the power output of the last stage turbine.