Effects of waviness and taper on cavitation characteristics of liquid lubricated mechanical seals

doi:10.11949/j.issn.0438-1157.20151733

Abstract

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

摘要：

为进一步探究机械密封液膜中空穴初生、演变等影响因素,基于质量守恒空化模型,建立考虑微观波度和锥度的液体润滑机械密封数学模型,采用有限控制体积法对控制方程进行离散,综合分析不同波幅、波数及锥度对空化特性的影响。结果表明:波度产生流体动压润滑效应,锥度产生流体静压润滑效应,两者共同影响空穴的初生和演变,而又影响空穴沿周向和径向的变化;空穴初生时,液膜破裂位置位于膜厚沿周向发散的低压区,且在空穴演变时其沿某一半径方向保持不变;量纲1波幅不超过0.5且波数不低于8或量纲1负锥度大于0.5的工况均可加快空化率,促进空化发生;而相同波幅且波数小于8或锥度趋向于正锥度的工况均可减缓空化率,有效抑制空化发生。

关键词: 机械密封, 液体润滑, 波度, 锥度, 空化, 有限控制体积法

CLC Number:

TH117.2

LI Zhentao, HAO Muming, YANG Wenjing, HAN Jie, REN Baojie. Effects of waviness and taper on cavitation characteristics of liquid lubricated mechanical seals[J]. CIESC Journal, 2016, 67(5): 2005-2014.

李振涛, 郝木明, 杨文静, 韩婕, 任宝杰. 波度和锥度对液体润滑机械密封空化特性影响[J]. 化工学报, 2016, 67(5): 2005-2014.

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