热耗散变形下螺旋槽干气密封微尺度气膜流动特性研究

RESEARCH ON FLOW CHARACTERISTICS OF MICRO-GAS FILM IN THE SPIRAL GROOVE DRY-GAS SEAL UNDER THE THERMO-ELASTIC DEFORMATION CONSIDERING THE THERMAL DISSIPATION

  • 摘要: 螺旋槽干气密封在高压、高速旋转时内部会产生一定量的热,导致密封环发生热弹变形,从而对密封性能产生影响。首先在速度滑移边界条件下,求出螺旋槽内的气膜压力和气膜速度,然后推导出气膜的无热耗散能量方程及有热耗散能量方程,进而利用气膜的压力、速度和能量方程,通过 Maple 和 Matlab 软件求解槽内气膜的温度分布。然后由热弹变形理论,求解出密封环的变形量,获得螺旋槽内气膜厚度的解析式。最后利用广义雷诺方程求出理论泄漏量,并与泄漏量的实验值进行比较。研究结果表明:随着气体从外径流入内径,槽内温度的分布规律是先升高后降低,槽根部周围温度较高;热弹变形量与温度变化的规律一致,而气膜厚度的变化趋势与之相反;干气密封中的泄漏量随变形量增大而增大,考虑热耗散有变形的泄漏量更接近于实验值。

     

    Abstract: A spiral groove dry-gas seal generates a finite amount of heat in high speed running, which will lead to the thermo-elastic deformation of a sealing ring. The thermo-elastic deformation has an impact on the sealing performance. The gas film pressure and velocity of a spiral groove can be obtained based on the boundary conditions of a slip-flow, and the energy equation considering the thermal dissipation of the gas film is derived. The temperature distribution of the gas film can be solved out by using the film pressure, the velocity and energy equation under the help of software Maple and Matlab. Based on thermo-elastic deformation theory, the deformation formula of a sealing ring and a gas film-thickness formula can be obtained. And the theoretical leakage rate can be obtained by using the general Reynolds equation, which will be compared with the experimental leakage rate. The results show that the temperature of the groove is increasing firstly and then decreasing when the gas flows from the external into the interior, the temperature is higher next to the groove root. The changed trends of the thermo-elastic deformation and temperature are consistent, and the trend of gas film thickness is opposite compared with the thermo-elastic deformation. With the increase of deformation, the leakage rate is large, and the leakage rate of the thermo-elastic deformation considering the thermal dissipation is closer to its experimental value.

     

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