基于逾渗理论的机械密封界面静态泄漏预测方法

Predicting Method for Static Leakage of Contacting Mechanical Seals Interface Based on Percolation Theory

针对现有机械密封泄漏机理研究存在的不足,利用Hertz理论研究机械密封界面接触力学问题,揭示了孔隙率随端面形貌、端面载荷等参数的变化规律;基于逾渗理论,探讨了不同网格层数下密封界面的逾渗阈值与孔隙率的关系,建立了密封界面泄漏通道模型,以及泄漏率与端面形貌参数关系表达式;研制了机械密封静态泄漏测试装置,测试了6组不同端面形貌试件在一定介质压力下的泄漏率.结果表明:密封界面的初始孔隙率?0随着分形维数D的增大而增大;端面比压pc增大,孔隙率?减小,并随着D的增大和尺度系数G的减小,?快速减小,直至填实.在端面比压作用下,密封界面的孔隙率均大于0.593,密封界面泄漏通道可以简化为单层网格逾渗模型.密封环的表面越粗糙,其密封界面的孔隙率越大,而由孔隙连通形成的泄漏微通道孔喉尺寸就越大,致使密封界面的泄漏率越大;泄漏率理论预测值与试验结果具有良好的吻合度,验证了本文泄漏预测方法的合理性.

Owing to the shortage of mechanical seals leakage mechanism, mechanical problems of mechanical seals interface were investigated based on the Hertz theory. The variation law of porosity of the contact interface with the variation of surface topography as well as the end load were also discussed. Based on percolation theory, the relationship between percolation threshold and porosity of seals interface under different grid layers were explored, and leakage channel model of seals interface was also established, as well as the relationship between leakage rate and surface topography parameters were also established. A static leakage experimental device of mechanical seals was developed,and the leakage rates of mechanical seals was investigated on six groups of sample under different surface topography and medium pressure. The results show that the initial porosity ？0 of the contact interface increased with the increasing of fractal dimension D. The porosity ？ decreased with the increasing of the end load pc, and rapidly decreased with the increasing of D and the decreasing of fractal roughness G until compacted without gap. Under the action of face pressure, the porosity of seals interface was greater than 0.593, and leakage channel model of seals interface can be simplified as a single-layer grid percolation model. The more the surface of the seal rings was roughened, the greater the porosity of the seals interface, and the pore throat size of the leakage channel formed by the interconnected pore becamelarger,resulting in a greater leakage rate at the seals interface.The experimental results were in good agreement with the theoretical predictions,which indicated the rationality of the leakage prediction method.