Transient thermo-elasto-hydrodynamic study of herringbone-grooved mechanical face seal during start-up stage

A comprehensive numerical solution is developed for the transient thermo-elasto-hydrodynamic (TEHD) characteristics of mechanical face seals. Transient lubrication features of the fluid film, transient thermal deformation features of the seal rings, dynamic behavior, and rough faces contacting are coupled. The finite volume method is utilized for the fluid film solution, and the Duhamel's principle contributes to calculation of the time-varying solid properties. An overall flowchart for the numerical solution is established, with an approach of Parallel Dual Time Steps (PDTS approach) proposed and utilized for the explicit time solver. Both of the efficiency and accuracy of the PDTS approach are evaluated by comparing with the reference. An outer-herringbone-grooved face seal in a start-up stage is studied. The simultaneously existing physical effects of the face expansion and the seal ring movement are successfully simulated with the proposed method. Neglecting viscosity-temperature effect and convergent gap forming could underestimate the load-carrying capacity of the fluid film; smaller contacting force but larger maximum contacting pressure are found comparing with the THD and HD results; performance keeps varying at steady speed due to thermal lag effect. The proposed numerical solution could be impactful for mechanism analyzing of the undesirable running of mechanical face seals related to the transient TEHD effects.