工业汽轮机调节级部分进汽瞬态数值研究

针对采用喷嘴调节的汽轮机调节级效率和安全性问题,基于时均的N-S方程,采用六面体结构化网格和有限容积法,对某机组调节级内部流动进行了数值计算。给出了不同工况下调节级内部压力和速度分布图,分析了4阀开和3阀开工况下调节级内部流动。给出了动叶旋转一周扭矩的变化,并将非定常扭矩进行了傅里叶变换,得到了频谱图。研究结果表明,部分进汽使调节级内部流动不均匀,4阀开,动叶所承受最大瞬时扭矩是进汽弧段平均扭矩的2.2倍,3阀开,动叶所承受最大瞬时扭矩是进汽弧段平均扭矩的1.8倍,这可以为调节级动叶安全性校核提供参考;频谱图显示,动叶受到与转速相关的低频激振力;3阀开工况下调节级的效率比4阀开工况下降低7%。

Numerical simulation of unsteady flow in the control stage of an industry steam turbine under partial admission condition

In order to solve the problems of the efficiency and safety of the control stage in a steam turbine.Based on RANS with the application of structural hexahedron mesh and finite volume method,the flow field of the control stage in a steam turbine was calculated.Pressure contour and velocity contour were performed to analysis the flow field of the control stage under different conditions.Torque of the blade rotating one circle were performed.Amplitude-frequency map of the torque was obtained according to the FFT analysis.The results indicate that the flow field is nonuniform under partial admission condition.The maximum torque of the blade is 2.2 times larger than that in the flow area under four valves open condition,while under three valves open condition the maximum torque of the blade in the blocked area is 1.8 times larger.It can help to check the safety of the blade.Spectrum analysis indicates that the typical low frequency of the exciting force is caused by the rotating speed of the blade.The efficiency of the control stage under three valves open condition is 7％ lower than that under four valves open.