耦合热、动载荷的超超临界汽轮机迷宫密封动力特性

密封汽流激振严重影响超超临界汽轮机的安全运行,采用DEFINE_CG_MOTION和DEFINE_PROFILE控制宏建立转子的涡动方程,通过Workbench流固耦合方法计算热、动载荷下密封齿形变,根据快速傅里叶变化得到机组运行时的密封动力特性,并对转子稳定性进行分析。结果表明:蒸汽可导致密封齿膨胀变形,温度对密封齿长度变化影响可达1%~1.5%,压力和离心作用对其影响较小。热、动载荷使迷宫密封直接刚度减小,直接阻尼先增加后减小,交叉刚度先减小后增加,动力系数的最大变化为原来的2倍。35~55 Hz内转子稳定裕度急剧下降,转子对密封汽流激振更敏感。热、动载荷引起的压力波动集中在低频范围,密封周向压力波动可增高18.5 kPa。密封高压区的压力波幅剧增是汽流激振显著的主要原因。 

Dynamic characteristics coupled thermal and dynamic loads for labyrinth seal in ultra-supercritical steam turbine

The operating safety of ultra-supercritical steam turbine is seriously affected by steam flow excited vibration in labyrinth seal. The DEFINE_CG_MOTION and DEFINE_PROFILE control macro were used to establish rotor whirl equation. The deformation of seal teeth under thermal and dynamic loads was calculated by Workbench fluid-solid coupling method. So the operating dynamic characteristics in seal were obtained by fast Fourier transform, and the rotor stability was analyzed. The results show that the steam flow can cause the deformation of seal teeth. The temperature made seal teeth length increase by 1%-1.5%, and the pressure and centrifugal effect had little influence on it. Under the action of thermal and dynamic loads, direct stiffness decreased, direct damping increased first and then decreased, cross-coupling stiffness decreased first and then increased, the maximum variation of dynamic coefficient was twice as before. Rotor stability margin decreased sharply in 35-55 Hz, so the rotor was more sensitive to the steam flow excited vibration. Due to the thermal and dynamic loads, the pressure fluctuations concentrated in low frequency range. The circumferential pressure fluctuations in seal could be increased by 18.5 kPa. The dramatic increase of pressure fluctuations in high pressure zone is the main reason for intense steam flow excited vibration.