液膜密封振动及冲击动力学特性

Dynamic analysis for vibration and impact of liquid film sealing

液膜密封运行过程因工况瞬时变化、系统振动及润滑不足等因素易引发端面接触冲击,严重影响密封寿命。建立考虑端面接触的液膜密封动力学模型,采用直接数值求解方法对运动方程、质量守恒空化边界雷诺方程、微凸体接触方程在全时间域内耦合求解,研究了液膜空化、轴向扰动及运行工况瞬变对密封稳定性与冲击特性的影响。结果表明:液膜空化有效提高了系统抗干扰能力,膜厚越小,受扰动后震荡频率越大且恢复至稳定状态的时间越长;发生端面冲击时膜厚振动频率显著大于全液膜状态下所受扰动情况。随转速及密封腔压力变化值的不断扩大,接触载荷值及冲击频率均不断增大,冲力响应越显著,在端面接触发生瞬间有明显的速度方向突变。

Due to working conditions’ instantaneous change for liquid film sealing’s operating process, system vibration and insufficient lubrication are easy to cause rub-impact of seal face, and seriously affect seal service life. Dynamic model of a liquid film sealing system considering seal face contact was established. Then the system’s equations of motion, Reynolds equation considering mass conservation under cavitation boundary condition and asperity contact equation were solved simultaneously in full time domain using the direct numerical integration method to investigate effects of liquid film cavitation, axial disturbance and transient variation of operating conditions on the system’s sealing stability and impact characteristics. Results showed that liquid film cavitation can effectively improve the system’s anti-disturbance ability;the smaller the film thickness, the larger the liquid film’s oscillation frequency, and the longer the time needed for steady state to recover;the liquid film’s vibration frequency during seal face impact is significantly larger than that during its being disturbed under the full liquid film state;contact load value and impact frequency increase and impact responses are more significant with increase in rotating speed and pressure variation of sealing cavity, there is obvious sudden change of velocity direction at the moment of seal face contact.