水滴特征对汽轮机叶片司太立合金水蚀的影响

Effect of water droplet characteristics on water erosion of stellite alloy for steam turbine blades

汽轮机叶片在运行过程中受蒸汽凝结水作用会发生水蚀损伤,镶嵌司太立合金是通用的抗水蚀防护方法。通过数值计算研究了水滴的速度、尺寸对司太立合金水蚀的影响规律。结果表明:水滴速度和尺寸均会对司太立合金应力产生显著影响,随着水滴碰撞速度的增加,司太立合金最大等效应力升高,当速度超过293 m/s后,最大等效应力大于屈服强度,并产生较高的次生应力;随着水滴尺寸的增加,最大等效应力显著提升且超过司太立的屈服强度,但当水滴半径超过750μm后,碰撞最大等效应力基本不变,且大尺寸水滴在高速碰撞过程中分裂成更小的水滴,并与司太立合金继续发生碰撞,产生高于司太立合金疲劳极限的次生应力;碰撞速度和水滴直径越高,其产生高于疲劳极限的次生应力峰数增加,加速司太立合金的疲劳损伤。

Steam turbine blades are damaged by water erosion due to the action of steam condensate during operation.Embedding Stellite alloy is a general method to resist water erosion.In this paper,the influence of water droplet speed and size on water erosion of Stellite alloy is studied by numerical calculation.The results show that,the velocity and size of water droplets have a significant effect on the stress of Stellite alloy.With the increase of water droplet collision velocity,the maximum equivalent stress in Stellite alloy increases.When the velocity exceeds 293 m/s,the maximum equivalent stress is greater than the yield strength,and higher secondary stress is produced.With the increase of water droplet size,the maximum equivalent stress increases significantly and exceeds the yield strength of Stellite,but when the water droplet radius exceeds 750μm,the maximum equivalent stress is basically unchanged.Large water droplets split into smaller water droplets in the process of high-speed collision,and continue to collide with Stellite alloy,resulting in secondary stress that is higher than the fatigue limit of Stellite alloy.The higher the impact velocity and water droplet diameter,the greater the number of secondary stress peaks above the fatigue limit,which will accelerate the fatigue damage of Stellite alloy.