大型汽轮机长叶片全工况动应力数值计算及试验研究

Numerical calculation and experimental study on dynamic stress of the long blade of large steam turbine under full working conditions

针对当代大型汽轮机全工况灵活性运行关注的突出问题,以哈尔滨汽轮机厂有限责任公司1000 MW等级空冷汽轮机低压末级叶片为研究对象,提出了一种长叶片动应力仿真分析方法。结合长叶片动态试验,论证了计算方法的有效性。理论分析表明,汽轮机低负荷运行工况下流动分离引起叶片表面涡激效应是叶片动应力增加的重要因素。从工程应用的角度出发,将气动流场叶片表面压力脉动值作为结构场激振力的激振因子,进而计算分析叶片在不同工况下的动应力是可行且有效的。经过多方案比较,仿真计算与试验结果取得了很好的一致性。叶片仿真和动态试验的结果表明,末级叶片最大动应力出现在20%负荷附近,叶身动应力峰值约为许用值5%,具有足够的耐振强度和安全裕度,能很好满足大型汽轮机全工况灵活性安全可靠运行要求。

Aiming at the outstanding problems of flexible operation in full working conditions of contemporary large steam turbines,a new dynamic stress simulation analysis method for the long blades was proposed by taking the low-pressure last stage blade of a 1000 MW air-cooled steam turbine in Harbin Turbine Company Ltd.as the research object.The validity of the calculation method was demonstrated by the long blade dynamic test.The theoretical analysis shows that the vortex-induced effect on the blade surface caused by flow separation is a key factor to increase the dynamic stress of the blade under low load operating conditions.For the engineering application,it is feasible and effective to calculate and analyze the dynamic stress of the blade under different working conditions by taking the pressure fluctuation value on the blade surface of the aerodynamic flow field as the excitation factor for the structural field excitation force.By comparing several schemes,the simulation results are in good agreement with the test results.Both of the simulation and dynamic test results show that the maximum dynamic stress of the last stage blade appears at about 20%load,and the peak value of the dynamic stress of the blade is about 5%of the allowable value,which has sufficient vibration resistance strength and safety margin,and can well meet the requirements of flexible,safe and reliable operation of the large steam turbine under full working conditions.