汽轮机转子半锥形涡动的密封汽流激振及动力特性

为探究转子半锥形涡动时密封汽流激振及动力特性,采用FLUENT用户自定义函数和相对旋转模型实现1000MW机组转子的锥形涡动,展现了半锥形涡动时汽流激振特征,并通过快速傅里叶变换得到密封动力特性,分析了半锥形涡动下转子的动力稳定性。结果表明:转子半锥形涡动时,动力系数波动显著。kzz与kyy的绝对值是平行涡动的4倍。直接阻尼czz和cyy发生相反的变化。交叉刚度kzy与kyz均减小,激振力Fz在切向上的作用增强。交叉阻尼在25Hz后相对变化小于35%。锥形涡动对稳定性影响随涡动频率的增加显著增强,不利于转子稳定。密封内湍流效应增强、齿顶射流改变和涡系在空间上的演化会加剧密封内部压力的波动和不均,扩大汽流激振影响,导致转子稳定性降低。

Steam Flow Excited Vibration and Dynamic Characteristics of Semi-conical Whirl Turbine Rotor

The user-defined function of FLUENT and the relative rotation model were used to simulate the semi-conical whirl motion of 1000 MW rotor. The characteristics of steam flow excited vibration in the seal were explored. Meanwhile, the dynamic characteristics were obtained through the fast Fourier transform, and the dynamic seal-rotor stability in the semi-conical whirl motion was analyzed. The results show that the dynamic coefficients fluctuate significantly when the rotor whirls in semi-conical orbit. The absolute values of kzz and kyy are four times that of parallel whirl motion. The direct damping czz and cyy have the opposite variation. The cross-coupling stiffness kzy and kyz are decreased, and the working effect of exciting force Fz is increased in the tangential direction. The relative change of cross-coupling damping is less than 35% after 25 Hz. With the increase of whirl frequency, the effect of semi-conical whirl on the seal-rotor stability increases significantly, which is not conducive to the rotor stability. The increase of the turbulence effect, the change of teeth-top jet flow and the evolution of vortexes in space will aggravate the pressure fluctuation and unevenness in the seal, which enhance the influence of steam flow excited vibration and lead to the decreasing of rotor stability.