Optimization Research On Aerodynamic Performance Of Exhaust Hood In Steam Turbine

Exhaust hood of steam turbine is an important part of the steam turbine and condenser.The aerodynamic performance of the exhaust hood will affect the economy and safety of the condenser.Based on computational fluid dynamics(CFD)software,the Navier-Stokes equation and k-600 MW turbulence equation of three dimensional exhaust hood and last stage coupling flow field were solved.The aerodynamic performance of a 600 MW steam turbine exhaust cylinder was optimized.The main research contents are as follows:The influence of the initial diffusion angle,the diameter and the axial length of the guide on the aerodynamic performance of the exhaust hood was studied.The results indicate that the aerodynamic performance of the exhaust hood has been improved with the increase of the initial diffusion angle.There is a flow separation in diffuser when the initial angle increases to 30°.The most appropriate value is 25°.It is not conducive to the aerodynamic performance of the exhaust hood that the diameter and the axial length of the guide are too large or too small.The most appropriate value of the diameter and the axial length of the guide are 5000 mm and 900 mm,respectively.The most appropriate value of the three variables was selected as the modification scheme of the guide.Comparing with the aerodynamic performance of the exhaust hood before reformation,the static pressure recovery coefficient of the outlet of the exhaust hood increases by 7.2%,as well as the total pressure loss coefficient of the outlet of the exhaust hood reduces by 8.4%.The aerodynamic performance is improved obviously.Based on quadratic orthogonal regression design,the flow guide device at the top of the exhaust hood is installed.The regression orthogonal equation between the installation parameters of the guide plate and the coefficient of static pressure recovery is obtained.The equation is remarkably unlost with nonlinear relation,and there is no influence between the three factors.The optimal solution of the regression equation is solved.The best way to install the guide plate is that the distance between two plates is 429 mm,the height of the guide plate is 700 mm,and the width of the guide plate is 969 mm.The channel vortex is broken and the aerodynamic performance of the exhaust hood has been improved obviously after the diversion plate is installed The static pressure recovery coefficient of exhaust hood outlet was increased by 3.0%,the total pressure loss coefficient was reduced by 5.8%,and the standard deviation of the outlet is reduced by 3.043.The static pressure recovery coefficient of exhaust hood outlet under different loads after the optimization was always higher than that before the optimization.After optimization,the total pressure drop of different loads is less than that before optimization,that is,the loss of total pressure after optimization is reduced.This shows that the optimal design of the installation flow guide device is feasible under different loads.