Numerical Investigations on the Cooling Performance of the Internal Bypass Cooling System of the Ultra-Supercritical Steam Turbines Using CFD and Conjugate Heat Transfer Method

摘要

The cooling effect of the internal bypass cooling system in high pressure cylinder of an ultra-supercritical steam turbine using the conjugation of the flow calculation and heat transfer method was numerically studied in this paper. Three-dimensional Reynolds-Averaged Navier-Stokes(RANS) solutions and k-s turbulent model with scalable wall function were used to analyze the cooling performance based on the CFD software ANSYS-CFX. The details of the flow pattern of the fluid domains and temperature distributions of the solid domains in the system were illustrated. The temperature field of the high pressure cylinder was compared between the steam cooling case and the non-cooling case without consideration of the steam cooling of the internal bypass cooling system. The main conclusion that can be drawn out of this research work is that the high pressure inner casing and the large part of axial thrust balance piston can be effectively cooled by the internal bypass cooling system. In addition, the resulting temperature distributions of the inner casing are uniformed compared to the non-cooling case. The temperature of the outer casing of the high pressure cylinder increases a little compared to the non-cooling case.