水蒸气润滑螺旋槽干气密封性能分析

Analysis on Dry Gas Seal Performance of Steam-lubricated Spiral Groove Dry Gas Seal

水蒸气润滑干气密封是一类特殊的干气密封,端面的润滑气体为水蒸气。为了研究水蒸气润滑干气密封的性能,采用无限窄槽理论,并采用RK方程来表达水蒸气的实际气体的行为。对螺旋槽的气膜压力控制方程进行了修正,分析水蒸气润滑干气密封的开启力、气膜刚度、泄漏率、气膜摩擦力矩和热平衡气膜厚度。结果表明:低压时,泄漏率随膜厚增加先减小再增加,中高压时,泄漏率随膜厚增加而增加,实际气体行为对泄漏率的影响较大;摩擦力矩随膜厚增加而减小,实际气体行为对摩擦力矩无影响;当温度为300℃,压力为0.5MPa时,在常见的工作膜厚范围内,剪切发热速率始终大于膨胀吸热速率,不能获得热量平衡膜厚,压力为2和5MPa时,实际气体的热量平衡膜厚均小于理想气体,两者相差分别为0.886%和2.932%。

Steam-lubricated dry gas seal is a special kind of dry gas seal,and the lubricating gas is steam.To study the performance of steam-lubricated dry gas seals,the infinite-groove theory was used,and the RK equation was used to express the actual gas behavior of water vapor.The gas film pressure control equation of the spiral groove was modified to analyze the opening force,gas film stiffness,leakage rate,film friction torque and thermal equilibrium film thickness of the vapor-lubricated dry gas seal.The results show that the leakage rate is first decreased and then increased with the increasing of film thickness at low pressure,and is increased with the increasing of film thickness at medium and high pressure.The actual gas behavior has much influence on the leakage rate.The friction moment is decreased with the increasing of film thickness,and the actual gas behavior has no influence on the friction moment.When the temperature is 300℃,and the pressure is 0.5 MPa,within the scope of the common working film thickness,the shear heating rate is always greater than the expansion heat absorption rate,and the heat balance film thickness cannot been obtained.When the pressure is 2 MPa and 5 MPa,the heat equilibrium film thickness of the actual gas is less than that of the ideal gas,and the difference between them is 0.886%and 2.932%,respectively.