关键词: 机械密封, 液体润滑, 波度, 锥度, 空化, 有限控制体积法

Abstract:

In order to further probe into the influence factors of cavitation start and evolution, the mathematical model of liquid film lubricated mechanical seals considering the micro circumferential waviness and radial taper was established based on the mass-conservative cavitation model. Liquid film governing equation was discretized by the finite control volume method and was solved by the Gauss-Seidel relaxation iterative algorithm. The effects of different waviness amplitudes, waviness numbers and tapers on the cavitation characteristics were analyzed. The results indicated that the start and evolution of the cavitation were affacted by the combined action of the hydrodynamic lubrication effect produced by the circumferential waviness and the hydrostatic lubrication effect which was greatly influenced by radial taper. To a large extent, changing of the cavitation area along the circumferential direction was influenced by the waviness, while that along the radial direction depended on the taper. The rupture position of liquid was located where film thickness diverged in the depression region at the start stage of cavitation, while the subsequent rupture direction remained unchanged at the evolution stage of cavitation. The cavitation rate was dramatically accelerated at the situations of dimensionless waviness amplitude not beyond 0.5 and waviness number greater than or equal 8, or dimensionless negative taper value greater than 0.5, which promoted the occurrence of cavitation. But under the same waviness amplitude and waviness number less than 8 or the taper tending to be positive, the cavitation rate was retarded, which effectively inhibited the occurrence of cavitation.

Key words: mechanical seals, liquid lubricated, waviness, taper, cavitation, finite control volume method