叶顶密封周向流动及流体激振抑制方法研究

Research on suppression method for circumferential flow and fluid-induced vibration of blade tip seal

控制叶顶间隙流体进口预旋及周向流动是减小密封流体激振力的主要方法。基于计算流体力学方法,通过在汽轮机某级叶顶间隙入口的动(围带)、静(汽缸)部件上增加新型微型叶栅,研究新型结构对叶顶间隙流体周向流动及流体激振抑制效果。结果表明:在新型微型叶栅的作用下,流体在叶顶密封入口由正预旋变为负预旋,密封有效阻尼系数由负变正,有效抑制了流体激振,提高了转子稳定性;将微型叶栅安装在围带上时对流体激振的抑制效果整体优于安装在汽缸上,且每两动叶片间数量为10个(围带叶栅)与6个(汽缸叶栅)时,转子系统稳定性最好。

The main method to reduce fluid-induced vibration is to control the inlet preswirl and circumferential flow of tip clearance. This paper established three-dimensional computational fluid dynamics(CFD) models of a steam turbine control stage, to study the effect of a new structure on circumferential flow and fluid-induced vibration, by adding the micro cascades on the shroud and cylinder inlet of tip clearance. Calculated results show that under the action of micro cascades, the fluid preswirl at sealing inlet changes from positive to negative, and the effective damping coefficient changes from negative to positive. It was proved that the fluid-induced vibration is effectively suppressed and the rotor stability is improved. It has better suppression effect of fluid-induced vibration when the micro cascades mounted on the shroud rather than on the cylinder. The rotor system has the best stability when there are 10 micro cascades on the shroud and 6 micro cascades on the cylinder between two rotor blades.