Abstract: To improve the leakage controlling capability and enrich the design method of zero/negative leakage in mechanical seals with Rayleigh steps, it was comparatively studied by developing the finite element numerical model that the cavitation induction mechanism of annular groove at sealing face and the influencing law and level of induced cavitation zone on sealing performance. The results indicate that there is only the hydrostatic effect and the hydrostatic pressure is lower at the annular groove zone under the larger groove depth. it greatly changes the film pressure distribution at sealing face, namely, restricts and separates the high-pressure zone of liquid film at forward Rayleigh steps, thus the cavitation effect is induced significantly in the reverse Rayleigh steps. The restriction and separation level tends to be stable when its dimensionless depth exceeds 20. The length of cavitation zone is increased by up to 82% due to the induction effect of annular groove, which effectively improves the cavitation suction level and increases the operating range with negative leakage. The main groove depth of reverse Rayleigh step significantly affects the induction effect of annular groove and its optimum range is 8~15, in which the relative changes of cavitation length ratio and reverse suction rate are less than 2%. It makes the mechanical seals remain a good leakage-controlling capability in a certain amount of wear for end faces.

Key words: mechanical seal, annular groove, cavitation induction, negative leakage, finite element analysis