汽轮机排汽缸的气动研究进展

Recent Advances in the Study of Aerodynamic Performance of Steam Turbine Exhaust Hoods

汽轮机排汽缸是连接凝汽式汽轮机末级出口至冷凝器的通道,改善其气动性能可提高汽轮机的效率。本文从数值分析及试验两方面对排汽缸的研究进行了分析,并对提高气动性能的新型措施进行了归纳。分析表明:末级与排汽缸湿蒸气汽液两相流的联合数值分析是排汽缸流场数值分析的发展方向;模型试验是排汽缸研究的主要方法,由于进口气流对排汽缸性能的影响敏感,进口流场应反映末级出口气流的真实状况,并要特别注意叶栅顶部出口气流的模拟。提高排汽缸气动性能的新型措施为:采用具有负超高的扩压器和非对称扩压器;中分面布置轴向栅格型涡阻尼器;采用除湿措施,减少湿度损失;冷凝器喉部结构及加强系统的改进。

The exhaust hood of a steam turbine is a passage for connecting the outlet of the last stage of a condensing type steam turbine with its condenser.To improve its aerodynamic performance can lead to a higher efficiency of the steam turbine. An analysis is conducted of the study of exhaust hoods from the following two aspects: numerical analysis and experiments.In addition,innovative measures to enhance the aerodynamic performance of exhaust hoods are also summarized.It has been found through the analysis that a joint numerical analysis of wet steam gas-liquid two-phase flow in the last stage and exhaust hoods represents the current development trend of numerical analysis of flow fields in exhaust hoods,and model experiments are the main methods for the study of exhaust hoods.As the performance of exhaust hoods is greatly influenced by inlet steam flows,the inlet flow field should reflect the actual conditions of the last stage outlet flows. Moreover,special attention should be paid to the simulation of outlet steam flows on top of the cascade.The innovative measures to improve the aerodynamic performance of exhaust hoods can be given as follows: adoption of a diffuser with a negative excessive height;adoption of an unsymmetrical diffuser;split-face arrangement of an axial-grid type vortex damper;adoption of moisture removal measures to minimize wetness-caused losses;improvement in condenser throat structure and reinforcement system.