Effect of phase change on sealing performance parameters and surface topography of a spiral groove mechanical seal

A spiral groove mechanical seal (SGMS) would experience failure due to phase change of fluid film between two end faces. The purpose of this experimental study is to investigate the effect of phase change on the sealing performance parameters (e.g., leakage rate, face temperature rise and wear rate) and surface topography of an SGMS by using water as medium. The interfacial fluid film undergoes the evolution from all-liquid phase to liquid-vapor mixed phase and then to all-vapor phase by changing pressure and temperature. The changes of leakage rate and face temperature during the phase evolution process, as well as the surface topography and the wear rate of an SGMS under different phase states after the experiment, are analyzed. The results show that compared with an SGMS in all-liquid phase state, the leakage rate of a two-phase SGMS in stable operation is obviously reduced, but the leakage rate fluctuates obviously as the face temperature is close to saturation temperature and the two-phase SGMS is in unstable state. During the phase change period, the lubrication state of an SGMS changes from hydrodynamic lubrication to mixed lubrication and there is obvious wear that appeared on the sealing face. The wear rate of an SGMS with phase change is about 2/5 of that of a plain end face seal underwent the same phase evolution process. An SGMS would be in a stable two-phase state by controlling media temperature and media pressure which is vital to reduce leakage, keep small wear rate and prolong seal life.