Abstract: In order to study the variation of average film thickness of end faces in contacting mechanical seal in running-in period,the change of surface topography was studied by fractal parameters characterization.Based on the fractal model of mechanical seals,an average film thickness prediction model of end faces in contacting mechanical seal was established by solving the volumes of surface voids of end faces.Running-in tests of two mechanical seals of B104a-70 type were carried out with water as test medium.Test temperature was 20℃,test pressure was 0.5 MPa,rotating speed was 2900 r·min^-1,and spring pressures were 0.15 MPa and 0.3 MPa respectively.The results indicated that the end face of the soft ring tended to be smoothed rapidly and average film thickness decreased rapidly in running-in period.The average film thicknesses of two tested mechanical seals were both about 0.295 μm in the normal wearing stage.Surface topography had significant influence on average film thickness,while spring pressure had little influence on average film thickness.Studying the changes of surface topography and average film thickness has important significance both in the prediction of operating characteristics and in the design of end faces of contacting mechanical seals.

Key words: mechanical seal, end face, running-in, average film thickness, fractal theory

摘要： 为研究和掌握接触式机械密封端面磨合过程平均膜厚的变化规律,采用分形参数表征磨合过程中密封端面形貌的变化,基于机械密封端面接触分形模型,通过求解端面上微空穴的体积,建立接触式机械密封端面平均膜厚预测模型。对两套B104a-70型机械密封进行磨合试验,试验密封流体为20℃清水,压力为0.5 MPa,转速为2900 r·min^-1,弹簧比压分别为0.15 MPa和0.3 MPa。研究结果表明,随着磨合过程的进行,软质环端面迅速趋于光滑,端面平均膜厚迅速减小;当进入正常磨损阶段后,两套机械密封试件的平均膜厚均稳定在0.295 μm左右。这也表明,密封端面的形貌对平均膜厚的影响较大,而弹簧比压对平均膜厚的影响较小。掌握磨合过程中端面形貌及平均膜厚的变化规律,对接触式机械密封实际运行时端面间工作特性的预测和密封端面设计具有重要意义。

关键词: 机械密封, 端面, 磨合, 平均膜厚, 分形理论