An Experimental Test on a Cryogenic High-Speed Hydrodynamic Non-Contact Mechanical Seal

The non-contact mechanical seal of a high-speed turbopump in a liquid rocket engine operates under very harsh conditions (such as rapid start-up, cryogenic, highspeed, high- pressure and low-viscosity sealing fluid). The performance of the seal is very different to the performance under normal running conditions. In this paper, for the sake of safety, an experiment is carried out with liquid nitrogen as the sealing fluid. The experimental results with liquid nitrogen are expected to provide an equivalent seal performance as would be experienced with liquid oxygen and liquid hydrogen rocket engine. The main performance parameters, including face temperatures, leakage, face friction force, and friction coefficients, are measured in the speed-up, stable, and speed-down stages. The results show that in the speed-up stage, with rapidly increasing speed, the local face temperature rises dramatically to even higher than the vaporization temperature of liquid nitrogen, and a two-phase flow phenomenon occurs. In the start-up and stable stages, the friction coefficients are 0.25 and 0.13, respectively. After the test, it was found that the wear thickness of the rotor was 0.2 mm, and serious point corrosion appeared on the surface of the stator.