转子-轴承-干气密封系统振动响应及结构优化

Vibration Response and Structure Optimization of Rotor Bearing Dry Gas Seal System

目的为了提高干气密封系统在运行工况下的稳定性,对密封螺旋槽槽型参数进行优化。方法根据转子-轴承-干气密封系统轴向振动动力学模型,建立双自由度振动方程。在特定的工况下,通过Maple软件多次拟合求解气膜非线性方程,得到气膜轴向刚度和阻尼。运用MATLAB软件中的龙格-库塔法对三阶的非线性振动方程数值求解,绘制不同螺旋角度下的时间历程图和相图,分析对比不同螺旋角度下静环的振动位移。结果从螺旋角度与静环振动位移的关系得出,当α=74.53°时,静环振动位移最小,其最大振幅为7μm,最大振速为7μm/s;当α=73.78°时,静环振动位移最大,其最大振幅为16.5μm,最大振速为17μm/s。改变螺旋角度可以调节和减小静环的振幅。结论在考虑叶轮转子的气动力和轴承油膜力的干气密封系统下,螺旋角度的增加能够提高系统运行的稳定性,增加螺旋角度(0.5°~0.6°)使得动静环的追随性最佳,对干气密封结构的设计提出了指导。

Objective To improve stability of dry gas sealing system under operating conditions and optimize the parameters of the sealed spiral groove.Methods A two degree of freedom vibration equation was established according to the axial vibration dynamics model of rotor bearing dry gas sealing system.Under specific conditions,the axial stiffness and damping of the film were obtained by multiple solutions of nonlinear equation with Maple software.The Runge-Kutta method in MATLAB software was used to numerically solve the third-order nonlinear vibration equation and draw time histogram and phase diagram under different helix angles.The vibration displacement of static ring under different helix angles was analyzed and compared.Results From the relationship between the spiral angle and the static ring vibration displacement,it can be seen that whenα=74.53°,the static ring vibration displacement was the smallest,its maximum amplitude was 7μm,the maximum vibration speed was 7μm/s;whenα=73.78°,the static ring vibration displacement was the largest,the maximum amplitude was 16.5μm and the maximum vibration speed was 17μm/s.Changing the helix angle could adjust and reduce the amplitude of the stationary ring.Conclusion Under the dry gas sealing system considering the aerodynamic force of the impeller rotor and the oil film bearing force,increase of the spiral angle can increase the stability of system operation.Increasing the spiral angle(0.5°-0.6°)achieves the best follow-up of the dynamic and static rings.It provides guidance for design of the hermetically sealed structure.