Combined 3D numerical analysis of the low pressure exhaust hood coupling with the last two cascades in steam turbine

Numerical methods are widely used to study the flow field in large power steam turbines. However, most of the previous numerical simulations studied the exhaust hood separately without taking account of the effect of the inhomogeneous flow from the last stage. In order to obtain more accurate and detailed information of the three dimensional flow in exhaust hood, a combined numerical model, which couples the exhaust hood with the last two stages, was introduced in this paper, meanwhile, the mixing plane approach was used. The Reynolds averaged N-S equations with RNG k-ε turbulence model was adopted to analyze the flow field in the exhaust hood considering the coupling effect between the exhaust hood and the last two stages. It is shown clearly that the presented combined model can give more accurate numerical results than the previous single model. The study provides a more reasonable numerical model for investigating the flow filed in the exhaust hood and it may give some significant data for the optimal design of exhaust hood in steam turbine.