Cavitation mechanism of spiral groove liquid film seals

doi:10.11949/j.issn.0438-1157.20160742

Abstract

Abstract:

Cavitation occurrence in liquid film has a direct impact on hydrodynamic lubrication performance of mechanical seals. A physical model of liquid film seal in spiral grooves was built with consideration of surface roughness and the JFO cavitation boundary condition on mass conservation. The anomalous physical domain composed of spiral curves was transformed into an inerratic computational domain by coordinate transformation. Finite control volume method was adopted to discretize the liquid film governing equation and the Gauss-Seidel relaxation iterative algorithm was used to solve the algebraic iterative equation. The cavitation occurrence in liquid film was analyzed by multiple factors of liquid film thickness, surface roughness, upstream/downstream pumping function, grooving position of spiral groove and cavitation pressure. Results show that cavitation occurrence was easily strengthened at thin films but weakened at thick films. Effects of surface roughness on cavitation or pressure distribution was depressed or even disappeared with increase of liquid film thickness. In case of upstream pumping seal, the circumferential width of cavitation was larger than that of downstream pumping seal, the width for middle grooving seal was larger than that of inner grooving seal, as well as the width enlargement with increase of inner dam reached to maximum when the radial width of inner dam was equal to that of outer dam. However, in case of downstream pumping seal, the width of middle grooving seal was smaller and decreased with increase of the inner dam. Effects of grooving position on cavitation were closely related to the function of spiral groove. Cavitation shranked at lower cavitation pressure but promoted at higher cavitation pressure. High cavitation pressure was beneficial to improving load-carrying capacity of the liquid film.

Key words: liquid film seals, cavitation mechanism, upstream pumping, downstream pumping, cavitation pressure

摘要：

液膜中空化的发生直接影响着密封流体动压润滑性能，基于质量守恒的JFO边界条件，建立考虑表面粗糙度的螺旋槽液膜密封物理模型，经坐标变换将不规则物理域转换成规则计算域，采用有限控制体积法离散控制方程并求解，分析了膜厚、表面粗糙度、螺旋槽功用（上游泵送和下游泵送）、螺旋槽开槽位置及空化压力对液膜中空化发生的影响。结果表明：较小膜厚工况易促生空穴，而较大膜厚易削弱空穴，且随着膜厚增大，表面粗糙度的影响降低甚至被忽略；当密封为上游泵送型时，空穴区周向宽度明显大于下游泵送型，而螺旋槽位置对空化的影响与螺旋槽功用密切相关；选取较小空化压力使空穴缩减，而较大者反之，且后者对提升液膜承载有利。

关键词: 液膜密封, 空化机理, 上游泵送, 下游泵送, 空化压力

CLC Number:

TH117.2

LI Zhentao, HAO Muming, YANG Wenjing, CAO Hengchao, REN Baojie. Cavitation mechanism of spiral groove liquid film seals[J]. CIESC Journal, 2016, 67(11): 4750-4761.

李振涛, 郝木明, 杨文静, 曹恒超, 任宝杰. 螺旋槽液膜密封端面空化发生机理[J]. 化工学报, 2016, 67(11): 4750-4761.

References 28

[1]	郝木明, 李振涛, 任宝杰, 等. 机械密封技术及应用[M]. 2版. 北京:中国石化出版社, 2014:76-78. HAO M M, LI Z T, REN B J, et al. Mechanical Seal Technology and Application[M]. 2nd ed. Beijing:China Petrochemical Press, 2014:76-78.
[2]	郝木明, 胡丹梅, 郭洁. 新型上游泵送机械密封的性能研究[J]. 化工机械, 2001, 28(1):12-15. HAO M M. HU D M, GUO J. Performance study of the new upstream pumping mechanical seal[J]. Chemical Machinery, 2001, 28(1):12-15.
[3]	王玉明. 下游泵送双列螺旋槽端面密封:2307157Y[P]. 1999-02-10. WANG Y M. Downstream pumping double spiral groove face seal:2307157Y[P]. 1999-02-10.
[4]	王涛, 黄伟峰, 王玉明. 机械密封液膜汽化问题研究现状及进展[J]. 化工学报, 2012, 63(11):3375-3382. DOI:10.3969/j.issn.0438-1157.2012.11.001. WANG T, HUANG W F, WANG Y M. Research and progress of mechanical seals operating with vaporization transition[J]. CIESC Journal, 2012, 63(11):3375-3382. DOI:10.3969/j.issn.0438-1157. 2012.11.001.
[5]	陈汇龙, 吴强波, 左木子, 等. 机械密封端面液膜空化的研究进展[J]. 排灌机械工程学报, 2015, 33(2):138-144. DOI:10.3969/j.issn. 1674-8530.14.0085. CHEN H L, WU Q B, ZUO M Z, et al. Overview on liquid film cavitation in mechanical seal faces[J]. Journal of Drainage and Irrigation Machinery Engineering, 2015, 33(2):138-144. DOI:10.3969/j.issn.1674-8530.14.0085.
[6]	唐飞翔, 孟祥铠, 李纪云, 等. 基于质量守恒的Laser-Face液体润滑机械密封数值分析[J]. 化工学报, 2013, 64(10):3694-3700. DOI:10.3969/j.issn.0438-1157.2013.10.029. TANG F X, MENG X K, LI J Y, et al. Numerical analysis of Laser-Face liquid mechanical seal based on mass conservation[J]. CIESC Journal, 2013, 64(10):3694-3700. DOI:10.3969/j.issn. 0438-1157.2013.10.029.
[7]	SWIFT H W. The stability of lubricating films in journal bearings[J]. Minutes of the Proceedings of the ICE, 1932, 233:267-288. DOI:10.1680/imotp.1932.13239.
[8]	STIEBER W. Das Schwimmlager:Hydrodynamische Theorie des Gleitlagers[M]. Berlin:VDI Verlag, 1933.
[9]	JAKOBSSON B, FLOBERG L. The finite journal bearing, considering vaporization[J]. Wear, 1958, 2(2):85-88.
[10]	OLSSON K O. Cavitation in dynamically loaded bearings[J]. Wear, 1967, 55(2):295-304.
[11]	ELROD H G. A cavitation algorithm[J]. Journal of Lubrication Technology, 1981, 103(3):350-354. DOI:10.1115/1.3251669.
[12]	KUMAR A, BOOKER J F. A finite element cavitation algorithm[J]. Journal of Tribology, 1991, 113(2):276-284. DOI:10.1115/1. 2920617.
[13]	VIJAYARAGHAVAN D, KEITH T G. Development and evaluation of a cavitation algorithm[J]. Tribology Transactions, 1989, 32(2):225-233. DOI:10.1018/10402008908981882.
[14]	FESANGHARY M, KHONSARI M M. A modification of the switch function in the Elrod cavitation algorithm[J]. Journal of Tribology, 2011, 133(2):024501. DOI:10.1115/1.4003484.
[15]	QIU Y, KHONSARI M M. On the prediction of cavitation in dimples using a mass-conservative algorithm[J]. Journal of Tribology, 2009, 131(4):41702-41711.
[16]	李京浩. 机械密封空化效应的数值计算方法与试验研究[D]. 北京:清华大学, 2011. LI J H. Numerical computational method and experimental study for cavitation in mechanical seals[D]. Beijing:Tsinghua University, 2013.
[17]	郝木明, 庄媛, 章大海, 等. 考虑空化效应的螺旋槽液膜密封特性数值研究[J]. 中国石油大学学报(自然科学版), 2015, 39(3):132-137. DOI:10.3969/j.issn.1673-5005.2015.03.018. HAO M M, ZHUANG Y, ZHANG D H, et al. Numerical study on sealing performance of spiral groove liquid film seal considering effects of cavitation[J]. Journal of China University of Petroleum, 2015, 39(3):132-137. DOI:10.3969/j.issn.1673-5005.2015.03.018.
[18]	李振涛, 郝木明, 杨文静, 等. 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. DOI:10.11949/j.issn.0438-1157.20151733. LI Z T, HAO M M, YANG W J, et al. Effects of waviness and taper on cavitation characteristic of liquid lubricated mechanical seals[J]. CIESC Journal, 2016, 67(5):2005-2014. DOI:10.11949/j.issn. 0438-1157.20151733.
[19]	YU T H, SADEGHI F. Groove effects on thrust washer lubrication[J]. Journal of Tribology, 2001, 123(2):295-304. DOI:10.1115/1. 1308014.
[20]	赵一民, 胡纪滨, 吴维, 等.螺旋槽旋转密封环润滑状态转变预测[J]. 机械工程学报, 2013, 49(9):75-80. DOI:10.3901/JME. 2013.09.075. ZHAO Y M, HU J B, WU W, et al. Prediction of lubrication condition transition for spiral groove rotary seal rings[J]. Journal of Mechanical Engineering, 2013, 49(9):75-80. DOI:10.3901/JME.2013.09.075.
[21]	PINKUS O, LUND J W. Centrifugal effects in thrust bearings and seals under laminar conditions[J]. Transactions of the ASME, 1981, 103(1):126-136. DOI:10.1115/1.3251600.
[22]	PAYVAR P, SALANT R F. A computational method for cavitation in a wavy mechanical seal[J]. Journal of Tribology, 1992, 114(1):199-204. DOI:10.1115/1.2920861.
[23]	JAMES D D, POTTER A F. Numerical analysis of the gas-lubricated spiral-groove thrust bearing-compressor[J]. Journal of Lubrication Technology, 1967, 89(4):439-443. DOI:10.1115/1.3617023.
[24]	LEBECK A O. Principles and Design of Mechanical Face Seals[M]. New York:John Wiley & Sons Inc., 1991:53-58.
[25]	XIONG S W, WANG J Q. Steady-state hydrodynamic lubrication modeled with the Payvar-Salant mass conservation model[J]. Journal of Tribology, 2012, 134:031703. DOI:10.1115/1.4006615.
[26]	刘丁华, 胡纪滨. 空化模型对径向直线槽端面密封性能分析的影响[J]. 北京理工大学学报, 2012, 32(11):1101-1104. DOI:10.15918/j.tbit1001-0645.2012.11.019. LIU D H, HU J B. Effect of cavitation model on the performance of radial grooved face seals[J]. Transactions of Beijing Institute of Technology, 2012, 32(11):1101-1104. DOI:10.15918/j.tbit1001-0645.2012.11.019.
[27]	顾永泉. 机械端面密封[M]. 东营:石油大学出版社, 1994:3. GU Y Q. Mechanical Face Seal[M]. Dongying:China University of Petroleum Press, 1994:3.
[28]	PATIR N, CHENG H S. Application of average flow model to lubrication between rough sliding surfaces[J]. Journal of Lubrication Technology, 1979, 101(2):220-229. DOI:10.1115/1.3453329.