Numerical investigation and shape design improvement of a turbine inlet combined valve

Nowadays, the development of turbines tends to enlarge the capacity and increase the corresponding parameters. Turbine inlet valve is an important part of turbine governing system. Consequently, the high pressure turbine requires good performance of the inlet valve. In this paper, the aerodynamic performance of a real ultra-supercritical power unit turbine inlet combined valve is analyzed in detail via numerical method. At the same time, the shape design of valve plug is improved by means of specific effective methods, including geometrical analysis and quick selection of the angles. A porous medium model is adopted to deal with the strainer structure and it has a good effect on the numerical simulation. The SST turbulence model is finally selected for calculation to obtain reliable results. The results show that the flow in the combined valve presents obvious flow separation nearby the valve plug and downstream of the throat. According to the analysis of pressure and static entropy, it can be concluded that the main pressure loss is concentrated in the strainer and control valve chamber, and an obvious vortex appears in control valve chamber with energy dissipation. Suitable optimization theory plays an effective role in the research. In this process, much attention has been paid to the decrease of pressure loss. Parabola and quick opening shapes are adopted to improve the shape of valve plug and a series of shapes with different angles are tested. The two best optimization models are selected and their results are analyzed. The results show good performance and the pressure loss coefficient reduces from 2.0% to 1.7%.