Generalization of lubricating and sealing performance using dimensionless parameters on low-friction and zero-leakage mechanical seals

Surface texturing techniques on the sliding surfaces for mechanical seals have been studied to achieve the contradictory functions of sealing and lubrication. In this study, the dimensionless load-carrying capacity and stiffness coefficient are defined to express the performance of hydrodynamic lubrication for textured surface structures in order to eliminate the effects of shaft size, rotation speed, and type of fluid as design parameters. A database of the relationship between dimensionless load-carrying capacity and aspect ratio of Rayleigh-steps arranged at the outer side of the sliding surface are calculated in advance. The hydrodynamic pressure distributions are calculated by solving the Reynolds equation in the steady-state condition. Consequently, the dimensional load-carrying capacity and film stiffness coefficient could be obtained instantly without solving the Reynolds equation. Furthermore, the dimensionless cavitation pressure is defined, and the sealing performance of the reversed Rayleigh-step is evaluated. JFO boundary condition is applied to the cavitation boundary in order to consider the mass conservation at the cavitation regions. The results indicate that the sealing performance could be changed depending on the value of the dimensionless cavitation pressure.