弯叶片对二次水滴运动特性及水蚀的影响

Effects of Bowed Blade Design on Water Erosion and Movement of Secondary Water Droplets

为探索减轻工业汽轮机末级叶片水蚀的主动控制措施,从气液两相流动的运动特性出发,研究了水滴在级环境下的运动特性与二次水滴侵蚀问题.通过比较静叶不同弯曲设计对二次水滴的影响,得到了弯叶片影响静叶表面水滴运动特性的机理,提出以弯叶片控制二次水滴撞击范围与强度的方法.结果表明:静叶反弯能够减小二次水滴在叶展中部的速度,这一作用对二次水滴在静叶表面的运动也适用;静叶反弯能够增大二次水滴在叶片两端的速度,有利于二次水滴顺利通过动叶栅通道,减少二次水滴对动叶的撞击;静叶反弯通过改变二次水滴速度分布,大幅降低了动叶顶部吸力侧的水蚀程度,静叶反弯25°可使动叶高侵蚀率区域面积减小90%以上.

To reduce the erosion damage over last stage blades of industrial steam turbines caused by water droplets,an active control method was developed based on the liquid-steam two-phase flow to study the movement characteristics of secondary water droplets and the water droplet erosion.By comparing the effects of stator blades in different bendings on the movement characteristics of secondary water droplets,the influencing mechanism was obtained,thus proposing the method to use bowed blades to control the impact range and intensity of secondary water droplets.Results show that a negatively bowed stator blade can reduce the speed of secondary water droplets in the mid span of the blade,which is also effective on the movement of water droplets on the stator surface;the negatively bowed stator blade improves the speed of secondary water droplets on endwalls of the stator,which is beneficial to the secondary droplets passing through the rotor blade passage,and to the reduction of secondary droplets impulse on the rotor blade;the negatively bowed stator blade can greatly reduce the degree of water erosion at the top of rotor blade on the suction side by changing the velocity distribution of secondary water droplets;a bowed stator blade with -25° angle can reduce the high erosion area at the top of rotor blade by more than 90%.