雷列台阶-环槽端面密封机理与性能研究

基于质量守恒的JFO空化边界条件建立了雷列台阶-环槽机械密封端面润滑理论模型,采用有限单元法求解Reynolds控制方程,获得了端面膜压、密度比与液膜流线分布,分析了其密封机理与性能规律.结果表明:密封环端面内径侧的圆环浅槽和端面中部的圆环深槽组合结构可造成合理的空化现象,达到空化减漏的目的.其中,端面中部的圆环深槽是端面高压侧雷列台阶和端面低压侧圆环浅槽的隔离带,使得端面低压侧压力分布受端面高压侧压力分布的影响极小.密封流体进入低压侧圆环浅槽时,端面间隙突然发散,压力低于该工况温度下的饱和蒸汽压,整个圆环浅槽区液膜空化,达到零泄漏并出现大量的回流现象.外径侧雷列台阶提供良好的动压承载能力,实现了端面的非接触.雷列台阶和环槽织构的组合应用使得该机械密封具有优良的综合性能.

Mechanism and Performance of End Face Seal of Rayleigh Steps and Annular Grooves

Lubrication theory model of mechanical seal end face of Rayleigh steps and annular grooves was established based on the JFO cavitation boundary conditions. The Reynolds control equation was solved by the finite element method. Pressure, density ratio and streamline distribution of the fluid film were obtained, and sealing mechanism and sealing performance were analyzed. The results show that the combination of the shallow annular groove of the inner diameter side and the deep annular groove in the middle of the sealing surface can cause a reasonable cavitation phenomenon, which can achieve the purpose of reducing leakage. The deep annular groove in the middle of sealing surface, the isolated zone of the high pressure area of the outer diameter side and the low one of the inner diameter side, led to the result that pressure distribution of the low pressure area was almost not influenced by that of the high pressure area. When the sealing fluid entered the shallow annular groove, the sealing gap suddenly diverged and became larger, which led to lower pressure than the saturated vapor pressure at the operating temperature. The liquid film in the whole shallow annular groove cavitated and caused zero leakage or a large amount of backflow phenomenon. A good bearing capacity was provided by the Rayleigh steps at the outer diameter side and the non-contact state of the end faces was achieved. The combination of Rayleigh steps and annular grooves rendered the mechanical seal excellent comprehensive performance.