光滑环形气体密封动态特性研究

Dynamic characteristics of smooth annular gas seal

光滑环形气体密封动态特性对透平机械转子系统稳定性有直接影响。建立三维数值分析模型,应用基于微元理论的密封动力特性系数识别方法计算光滑环形气体密封在2种出口状态(非阻塞/阻塞)、5种偏心率(ε=10%,30%,50%,70%,80%)以及3种长径比(L/D=0.5,1.0,1.5)工况下密封动态流动特性。结果表明:在不同出口状态下(L/D=1.0),密封直接刚度系数均随偏心率及涡动频率的增加而减小,交叉刚度系数绝对值与直接阻尼系数随偏心增加而增大。密封在高偏心情况下,必须考虑偏心率对密封特性系数的影响,不能简化为传统四个动力特性系数。不同涡动频率下,有效阻尼系数随偏心率、长径比增大表现相反的变化趋势,低频涡动、高偏心、长径比越大的转子系统更容易失稳。

Dynamic characteristics of smooth annular gas seal have a direct impact on the stability of turbomachinery rotor system.Here,a 3-D numerical analysis model was established,the identification method of seal dynamic characteristic coefficients based on micro element theory was used to calculate sealing dynamic flow characteristics of smooth annular gas seal under working conditions of 2 outlet states(non-blocking/blocking),5 eccentric ratios(ε=10%,30%,50%,70%,80%)and 3 aspect ratios(L/D=0.5,1.0,1.5).The results showed that under different outlet conditions(L/D=1.0),the seal direct stiffness coefficients decrease with increase in eccentricity and whirl frequency,and absolute values of cross stiffness coefficients and direct damping coefficients increase with increase in eccentricity;in the case of high eccentricity,effects of eccentricity on sealing characteristic coefficients must be considered,the latter can’t be simplified to the traditional 4 dynamic characteristic coefficients;under different whirl frequencies,effective damping coefficients have the opposite trend with increase in eccentricity and aspect ratio;the rotor system with low-frequency whirl,high eccentricity and larger aspect ratio is easier to lose stability.