Leakage control and cooling mechanisms in LO2 lubricated mechanical seals with backflow channels under high-speed conditions

To address the problem that low-viscosity media are prone to causing excessive leakage of mechanical seals under high-speed conditions, this paper proposes a leakage suppression scheme based on the channel backflow control. A continuous boiling numerical model for mechanical seals is established, considering the fluid film, channel fluid, sealing chamber fluid, and sealing rings. The leakage control and cooling mechanisms of mechanical seals under high-speed conditions are systematically investigated. The results show that when the rotor rotates at high speed, fluid enters the sealing clearance from the sealing chamber. Due to the hydrodynamic effect, a local high-pressure region forms at the downstream pumping groove root, where the pressure exceeds the sealing chamber pressure. A portion of the fluid is pumped into the channel, flows back to the sealing chamber, and subsequently re-enters the sealing clearance. Thus, a complete circulation is formed between the sealing clearance and the sealing chamber. Continuous fluid exchange realizes leakage suppression and active dissipation of frictional heat on the sealing end faces. At 20000 r/min, the backflow channels reduce the leakage rate by 54.16% compared with the double-row spiral groove seal due to the backflow pumping effect. Meanwhile, the backflow pumping effect enables effective heat migration, reducing the end face temperature rise by 9.53% and the vapor area ratio by 5.14% correspondingly. The backflow pumping effect weakens with increasing inlet temperature, film thickness, and downstream pumping groove depth, but strengthens with increasing rotational speed and channel inlet angle. When high-pressure fluid flows back into the sealing chamber, radial impingement generates two vortices. An increase in medium pressure enlarges the vortex area, thereby significantly enhancing heat transfer on the outer sidewalls of sealing rings. The results show that the proposed scheme effectively controls seal leakage and sealing face temperature rise.