Abstract: To study the vaporization characteristics and sealing performance of liquid films for dynamic pressure mechanical seals, a computational model of liquid film vaporization in the sealing gaps was established involving the relationship between saturation temperature of water and pressure, viscotemperature effect and Newtonian fluid internal friction effect. Taking the spiral groove mechanical seal as an example, the influences of working conditions on the liquid film vaporization characteristics and sealing performance were analyzed. The results show that when the temperature of the medium increases, there is a critical temperature value where the average vapor phase volume fraction suddenly increases and the critical temperature value increases as the rotating speed increases. The increase of medium pressure and rotating speed has an inhibiting effect on vaporization. Increasing the rotating speeds tends to reduce the higher degree of vaporization quickly and a sudden change occurs at a certain rotating speed. The abrupt rotating speed may increase with the increasing of medium temperature. The sealing performance is obviously affected by the change of working conditions, especially the rate of change in sealing performance increases rapidly at critical vaporization temperature and abrupt rotating speeds. The liquid film vaporization first occurs in the leeward weir areas of spiral groove and rapidly covers the weir areas and advances to the dam areas with the increasing of medium temperature. With the increasing of rotating speeds, the circumferential distribution of the vapor phase of the lubrication film is more uniform and the high vaporization areas move to the outside diameter side.

Key words: dynamic pressure mechanical seal, vaporization characteristic, sealing performance, operating parameter

摘要： 为了研究动压型机械密封液膜汽化特性和密封性能，建立了涉及水的饱和温度与压力的关系、黏温效应以及牛顿流体内摩擦效应的密封间隙液膜汽化计算模型，以螺旋槽机械密封为例分析了工况变化对液膜汽化特性及密封性能的影响规律。研究结果表明：介质温度升高时，存在平均气相体积分数突增的临界温度值，且随转速的增大临界温度值增大；介质压力和转速的增大对汽化有抑制作用，转速增大易使较高的汽化程度迅速降低且在某转速值处出现突变点，介质温度升高使得突变转速值增大；密封性能受工况变化的影响明显，特别是在汽化临界温度值、突变转速值处性能的变化速率迅速增大；液膜汽化首先发生在螺旋槽背风侧堰区，且随介质温度升高快速覆盖槽堰区并向坝区推进；随着转速的增大，润滑膜气相的周向分布更加均匀且高汽化区域会向外径侧移动。

关键词: 动压型机械密封, 汽化特性, 密封性能, 工况参数