高速低温两相机械密封膜压特性研究

Study on Film Pressure Characteristics of High Speed and Low Temperature Two-phase Mechanical Seals

为研究高速、低温涡轮泵机械密封在两相状态下的膜压特性,基于均相流理论,建立包含热效应、离心惯性效应以及实际气体效应的机械密封流体膜轴对称相变模型,以液氧为密封介质分析离心惯性项对流体膜压力和相变的影响机制,研究工况参数对膜压系数的影响规律。结果表明:考虑离心惯性项时,外压式机械密封膜压有所降低,相变程度有所增大;等温条件下,随介质温度升高,膜压系数存在不稳定峰值,非等温条件时,介质温度的轻微变化将影响密封运行稳定;当介质温度大于90 K时,介质压力的增大虽使膜压系数减小,但也使密封稳定性增强;膜厚为2.0μm时存在膜压系数最大值,密封承载力较大但密封稳定性较差。

In order to study the film pressure characteristics of mechanical seals of high-speed and low-temperature turbopump under two-phase condition,based on the theory of homogeneous flow,the axisymmetric phase change model of mechanical seals fluid film including thermal effect,centrifugal inertia effect and actual gas effect was established.The influence mechanism of centrifugal inertia term on the pressure and phase change of fluid film was analyzed with liquid oxygen as sealing medium.The results show that the external pressure mechanical seal film pressure decreases and the phase change level increases when considering the centrifugal inertia term.Under isothermal conditions,the film pressure coefficient has an unstable peak with the increase of medium temperature.In non-isothermal conditions,the slight change of medium temperature will affect the stability of seal operation.When the medium temperature is more than 90 K,the increase of medium pressure decreases the film pressure coefficient,but enhances the sealing stability.When the film thickness is 2.0μm,there is a maximum film pressure coefficient,and the sealing bearing capacity is larger but the sealing stability is poor.