Flow Analysis Of Long Blades Of Last Stage And Last Two Stages In Air Cooling Steam Turbine

Aerodynamic performance of the blade influences the efficiency of the flow part of the steam turbine directly. Therefore, the design of the blade occupies a crucial position in the design process of a steam turbine. Research object of this paper is the steady and unsteady flow analysis of the last stage and the second last stage of the air-cooled turbine being developed for the Shanghai Electric Power Equipment Co., Ltd. steam turbine plant.This article briefly describes the status quo of research of unsteady flow of the long last stage blades (LSBs) in steam turbine and carries out numerical simulation on the last two stages and the last stage of air-cooled steam turbine. The research contents of this article are composed of the steady calculation and result analysis of the last two stages and last stage, the unsteady calculation and result analysis of the last stage in the air-cooled steam turbine. The unsteady calculation adopts the Non Linear Harmonic (NLH) function, to be aimed at blades preliminary designed, to analyze the aerodynamic performance and possible loss of the LSBs, and analyze the influence of the unsteady flow on LSBs based on the results. Based on the steady and unsteady results, existed problems and solutions are provided.The results show that:the overall design of the blade profile is excellent, there is little loss in the static cascades and the steam vapor expands well in the rotor cascades. However several problems exist as following:the import area in the final stage stationary blade passage vortex; the design of the last stage bucket is not reasonable locally; last stage blades are under unsteady gas excitation force. Asked the following solutions to address the problems, the following solutions are proposed:shorten the distance between the stator blade and the bucket ensuring the installation; modify the local blade contour; adjust the back pressure, flow and the distance between the stator blade and the bucket etc. Compare the results of steady and unsteady calculation, the results are as following:the isentropic efficiency, torque and the power obtained from the unsteady calculation are all lower than that of the steady calculation, however the flow is increased.