工况不确定性对汽轮机末两级气动性能的影响研究

汽轮机运行条件存在随机波动性，对汽轮机的稳定运行造成一定影响。以往的研究多将汽轮机的工作环境条件作为确定因素，未考虑其随机变化的影响。本文将汽轮机背压、径向气流角和进口流量作为服从一定概率分布的随机变量，采用多项式混沌方法结合计算流体力学（CFD）模拟仿真，研究了以上参数的随机波动对某汽轮机末两级叶片气动性能的影响。结果表明：计算进口边界条件的设置方法对汽轮机末两级总体性能的计算结果影响不大，当给定进口流量边界条件时，末两级效率的计算结果最高；在接近堵塞工况时，进出口条件的随机变化对通流流量的影响不大，但效率存在明显的波动，进口气流角对总体性能的影响相对较小；当背压和进口流量存在随机波动时，末级动叶中激波位置小范围波动，激波位置对径向气流角的波动不敏感。

Study on the influence of working condition uncertainty on aerodynamic characteristics of last two stage blades of steam turbine

The operating conditions of steam turbine have a certain degree of random fluctuation, which has potential impact on the stable operation of steam turbine. The working environment conditions of steam turbine were taken as the determined conditions in conventional investigations, and the influence of such random variations was not considered. In this paper, the back pressure, radial flow angle and inlet flow of steam turbine were taken as random variables subject to certain probability distribution, and the influence of the random fluctuations of the above parameters on the aerodynamic performance of the last two stage blades of a steam turbine was studied by CFD simulation combined with the polynomial chaos method. The simulation results show that the method for calculating the inlet boundary condition has little effect on the computational result of the overall performance of the last two stages of steam turbine. When the inlet flow boundary conditions are given, the last two stages have the highest efficiency;when approaching the blocking condition, the random change of inlet and outlet conditions has little effect on the flow rate, but the efficiency fluctuates obviously. The influence of inlet airflow angle on the overall performance is relatively small; when the back pressure and inlet flow fluctuate randomly, the shock wave position in the last stage rotor blade fluctuates in a small range. The shock position is insensitive to the fluctuation of the radial flow angle.