叶轮带平衡孔的汽轮机级内蒸汽流动仿真分析

Simulation Analysis of Steam Flow in Turbine Stage with Balance Hole in Impeller

针对某200MW冲动式汽轮机组低压缸叶轮开设平衡孔的第二级内部流动状况进行有限元分析,分析结果表明:该级出现了负的反动度,叶轮后流体压力大于叶轮前流体压力,导致该级叶轮出现负的轴向推力,能平衡掉部分工作汽流产生的正的轴向推力,但直平衡孔的结构减少了平衡轴向推力的轴向投影面积,削弱了平衡正轴向推力的效果;在级的流线云图中显示该级级后蒸汽经平衡孔倒流回级间,并同隔板漏汽一起汇入主汽流,影响了级效率,该级叶轮直平衡孔的结构有必要重新进行设计,研究成果为高效冲动式汽轮机的设计提供了理论参考。

Finite element analysis is carried out on the flow condition of the second stage of a 200MW impulse turbine with balance holes in the impeller of low pressure cylinder.The results show that negative reaction occurs in this stage,and the fluid pressure behind the impeller is greater than that in front of the impeller,which leads to negative axial thrust of the impeller,which can balance the positive axial thrust generated by part of the working steam flow,but the structure of the straight balance hole reduces the axial projection area of the balanced axial thrust and weakens the effect of balancing the positive axial thrust;In the streamline nephogram of the stage,it is shown that the steam flows back to the stage through the balance hole,and converges into the main steam flow together with the diaphragm leakage,which affects the efficiency of the stage.It is necessary to redesign the structure of the straight balance hole of the stage impeller.The research results of this paper provide a theoretical reference for the design of high efficiency impulse turbine.