Hydrodynamic-hydrostatic hybrid cooling mechanism and pressure buildup and phase transition control laws in a novel mechanical seal under ultra-high-speed conditions

Under the cryogenic and ultra-high-speed conditions, mechanical seals are prone to failure due to the liquid film phase change caused by significant frictional heat. Thus, a hybrid hydrostatic-hydrodynamic concept of cooling (HDSC), pressure buildup, and phase control is proposed. Also, a novel mechanical seal with a series-connected cooling flow channel integrated with the hydrostatic orifices, hydrodynamic grooves, and sealed chamber is developed. A three-dimensional coupled flow-heat transfer and continuous boiling model is established to investigate the coupled multiphase flow mechanism, hybrid hydrostatic-hydrodynamic cooling mechanism, and pressure buildup and phase control laws in the novel mechanical seal. The results show that the structure generates a self-adaptive forced convection cycle, driven by hydrodynamic pumping and hydrostatic pressure, which either injects coolant or expels hot fluid. This effectively suppresses the temperature rise at the inner diameter side. Dual Taylor vortices in the sealed chamber further enhance heat transfer. The hybrid hydrostatic-hydrodynamic cooling effect significantly reduces the sealing temperature and viscosity loss, and improves the liquid film pressure buildup, viscosity retention, phase control, and load-carrying capacity of liquid film. Compared with the no-cooling and hydrostatic cooling seal structures, the HDSC seal increases the peak pressure by 18.5% and 20.8%, reduces the temperature rise by 20.7% and 17.9%, and decreases the vaporization area ratio to only 3.25% at 30,000 rpm. This demonstrates a significant enhancement in the seal's thermal management capability and operational stability.HighlightsA novel non-contact mechanical seal structure is proposed, featuring hydrostatic and hydrodynamic cooling channels.A 3D coupled flow, heat transfer and continuous boiling numerical model is developed for the series-connected flow channel in novel mechanical seals.Hydrostatic-hydrodynamic hybrid cooling mechanism and pressure buildup and phase control laws are systematically investigated and revealed.The dual-mode circulating flow in hydrostatic orifices can enhance heat transfer and suppress temperature rise, then improve anti-vaporization capability.A highly feasible structure and approach are proposed for cooling, pressure buildup and vaporization suppression in non-contact mechanical seals.