Study of Coupling Numerical Flow Field Simulation of Low–pressure Last Stage Exhaust Passage in Steam Turbine

摘要

The model of coupled exhaust hood with condenser throat and the model of coupled exhaust hood, condenser throat with last stage are simulated based on the Realizable k-ε turbulence model. Calculated results show that due to the ignoring of the inlet swirl in the model coupled exhaust hood with condenser throat, the flow field is symmetrical and the pressure loss is small. Due to the influence of last stage, the flow field of the inlet of the exhaust hood is uneven in the model of coupled exhaust hood, condenser throat with last stage, and the vortexes changed more complex, resulting in the increase of the pressure loss of each part and a great influence in the diffuser pipe. The proportion of pressure loss of diffuser pipe in total pressure loss increases from 0.086 to 0.358, and there is a 70% decline of proportion of pressure loss in volute and condenser throat. In addition, the proportion of the pressure loss in volute is the largest one in these two coupled models. So more attention should be paid to the influence of the last stage and weaken the vortexes in the volute when design or optimize the exhaust passage of steam turbine.