Abstract:The stable operation of bidirectional hydrodynamic mechanical seal needs clean blocking fluid and assistance system. To solve this problem, a bidirectional self-pumping hydrodynamic-static mechanical seal was presented in this paper. Fluent was used to carry out numerical simulation on pumping-out and pumping-in hydrodynamic mechanical seals, so as to achieve the opening force, lea-kage and stiffness of mechanical seals and to analyze the relationship between flow field characteristics and sealing performance. The results show that the pumping-in hydrodynamic mechanical seal has larger opening force, while the pumping-out hydrodynamic mechanical seal has smaller leakage. Both of them do not need assistance system to provide blocking fluid. The flow direction of the fluid in the groove of the pumping-out type is around-90°, the fluid flows from the root to the outside of the groove. For the pumping-in type, the flow direction of the fluid in the groove is around 70°, while that in the area linking the seal dam and groove root is around-80° and both direct at the drainage hole. Pumping-in and pumping-out hydrodynamic mechanical seals have great capabilities to antiparticle. The stiffness of the pumping-in hydrodynamic mechanical seal is bigger than that of the pumping-out type. The research provides the theoretical foundation for the design, manufacture and operation of the bidirectional self-pumping hydrodynamic-static mechanical seal.