Experimental and numerical investigation of liquid film phase change in textured mechanical seals with inner herringbone and spiral grooves

Liquid film phase change is a critical factor in the performance degradation of mechanical seals. However, experimental data regarding the evolution of phase change and groove-type differences for typical hydrodynamic grooves such as inner herringbone and inner spiral grooves are still insufficient. In this study, phase change experiments were conducted on mechanical seals with these two groove types using high-temperature hot water as the working medium. The effects of rotational speed and medium temperature on phase change evolution were systematically investigated, the temperature distribution on the back surface of the stationary ring was synchronously measured, and the influence of film thickness on sealing performance was analyzed using a numerical model. The numerical predictions show good agreement with the experimental data. Within the studied ranges of 383–403 K medium temperature and 300–1800 r·min −1 rotational speed, the results demonstrate that, compared with the inner spiral groove seal, the inner herringbone groove seal exhibits a 6.44%–33.61% higher phase change rate, an 18.4%–35.4% lower leakage rate, and an average back-surface temperature up to 4.88 K lower. Phase change in the inner spiral groove seal concentrates at the low-pressure inner-diameter side and propagates outward along the spiral grooves, whereas in the inner herringbone groove seal it is additionally distributed on the leeward side of the grooves. The phase change rate decreases with increasing rotational speed but increases significantly with medium temperature. Film thickness analysis reveals a stable operating interval and a phase-change-sensitive interval. The dimensionless friction torque gradually attenuates and plateaus as film thickness increases, while the leakage rate exhibits a continuous upward trend.