Analysis of turbulence effect on cavitation cooling flow in mechanical seals with Rayleigh steps

doi:10.11949/0438-1157.20250654

Abstract

Abstract:

In the high-speed operation of mechanical seals, the cross-scale lubricating film flow transitions into a turbulent state. Turbulence effects significantly influence the viscous heat generation and cavitation flow patterns within the liquid film. To reveal this influence mechanism, a thermo-hydrodynamic lubrication numerical model was developed for Rayleigh step-type mechanical seals under both turbulent and laminar flow regimes. A comparative analysis was conducted on the cooling mechanisms and flow behavior of the liquid film under different flow states. The results demonstrate that turbulent flow promotes cavitation formation in the reverse step grooves while weakening vortex motion in the liquid film region. Under laminar flow conditions, where turbulent kinetic energy is absent, a flow stagnation zone forms at the groove root, leading to a temperature trough. Both liquid film and seal face temperatures being notably lower than those under turbulence. As rotational speed increases, the temperature difference between the two regimes becomes more pronounced, reaching up to 25 K. Conversely, turbulent flow creates a larger cavitation area, resulting in better cooling of the liquid film and end faces. This also enhances the cavitation suction effect, reducing leakage by approximately 46%. However, the increased negative hydrodynamic pressure effect reduces the opening force by approximately 6%. These findings indicate that turbulence alters the flow and heat transfer processes of the lubricating medium within the sealing gap, thereby influencing seal face temperature, pressure distribution, cavitation area, and overall sealing performance.

Key words: high speed, mechanical seals, cavitation flow, turbulence effect, sealing performance

摘要：

机械密封高速运行时跨尺度液膜润滑流动处于湍流状态，湍流效应可显著影响液膜黏性产热与空化流动规律。为揭示该影响机制，针对瑞利台阶型机械密封建立了湍流与层流流态下的热流体动力润滑数值模型，对比分析了不同流态下的液膜流动冷却机理与规律。研究结果表明，湍流流动促进了反向台阶槽内空化的产生，削弱了液膜区涡旋流动。由于层流下湍流动能为零，在槽底根处形成流动死区，出现温度谷值区，且其液膜和端面温度明显低于湍流流态，随转速增加，二者温差更加显著。相反，湍流流动下获得更大的空化面积，对液膜和端面产生了更佳的冷却效果，同时增强了空化抽吸效应，减少了约46%的泄漏率，但负流体动压效应的增加致使开启力下降约6%。湍流效应可显著改变密封间隙内润滑介质的流动与传热过程，进而改变密封温度、压力、空化面积以及密封性能。

关键词: 高速, 机械密封, 空化流动, 湍流效应, 密封性能

CLC Number:

TH 117

Xuezhong MA, Congcong LI, Wanlong WANG, Hao CHEN. Analysis of turbulence effect on cavitation cooling flow in mechanical seals with Rayleigh steps[J]. CIESC Journal, 2025, 76(12): 6339-6350.

马学忠, 李聪聪, 王万龙, 陈浩. 瑞利台阶型机械密封空化冷却流动湍流效应分析[J]. 化工学报, 2025, 76(12): 6339-6350.

Figures/Tables 18

Fig.1 Geometric structure of double row Rayleigh step mechanical seal

Table 1 Geometric and operational parameters

参数名称	数值
密封环内径r_i/mm	47
密封环外径r_o/mm	57
RS主槽圆周角γ/(°)	21
RS和RRS引流槽圆周角ϕ/(°)	1.5
密封间隙h₀/μm	6
引流槽深度h₁/μm	100
RS主槽深度h₂/μm	10
RRS主槽深度h₃/μm	30
RS内径r₃/mm	54
RRS内径r₁/mm	48
进口压力p_i/MPa	0.5~2.5
空化压力p_c/kPa	30
环境压力p₀/MPa	0.1
密封介质	水

Fig.2 Grid and thermal boundary conditions

Table 2 THD physical property parameters

参数	数值
动环材料	不锈钢
静环材料	碳石墨
动环热导率k_r/(W/(m·K))	15
静环热导率k_s/(W/(m·K))	20
动环比热容c_r/(J/(kg·K))	500
静环比热容c_s/(J/(kg·K))	670
黏温系数α_T /K^-1	0.0175
冲洗液速度U_f/(m/s)	7
介质温度T₀/K	303.15
环境温度T_L/K	303.15

Fig.3 Grid independent verification

Fig.4 Model correctness verification

Fig.5 Cavitation flow mechanism

Fig.6 Comparison of temperature, pressure, cavitation, and viscosity distributions in liquid films under laminar and turbulent flow conditions

Fig.7 Comparison of temperature, pressure, and liquid volume fraction values at cross-section 1-1 on the end face

Fig.8 Temperature, pressure and liquid volume fraction distribution at different speeds

Fig.9 Comparison of liquid volume fraction and streamlines under different speeds

Fig.10 The influence of rotational speed on sealing performance

Fig.11 Liquid film temperature, pressure and liquid volume fraction under different medium pressures

Fig.12 Comparison of liquid volume fraction and streamlines under medium pressures

Fig.13 The influence of medium pressure on sealing performance

Fig.14 Distribution of liquid film temperature, pressure and liquid volume fraction under different RRS main groove depths

Fig.15 Comparison of liquid volume fraction and streamlines under different RRS main groove depths

Fig.16 The influence of RRS main groove depth on sealing performance

References 36

[1]	Lin Q Y, Wei Z Y, Wang N, et al. Effect of large-area texture/slip surface on journal bearing considering cavitation[J]. Industrial Lubrication and Tribology, 2015, 67(3): 216-226.
[2]	Lee J, Jelly T O, Zaki T A. Effect of Reynolds number on turbulent drag reduction by superhydrophobic surface textures[J]. Flow, Turbulence and Combustion, 2015, 95(2): 277-300.
[3]	田浩轩. 高温水空化流动特性及其热力学效应研究[D]. 西安: 西安理工大学, 2023.
	Tian H X. Investigation on characteristics of cavitating flow and thermodynamic effects in high temperature water[D]. Xi'an: Xi'an University of Technology, 2023.
[4]	Ma X Z, Li C C. Lubrication flow law and cooling mechanism considering cavitation in mechanical seals with Rayleigh step pattern[J]. Applied Thermal Engineering, 2025, 258: 124755.
[5]	马学忠, 李聪聪. 双列反向台阶型机械密封空化流动与冷却机理[J]. 中国机械工程, 2025, 36(10): 2266-2273.
	Ma X Z, Li C C. Cavitation flow and cooling mechanism in mechanical seals with double row reverse step[J]. China Mechanical Engineering, 2025, 36(10): 2266-2273.
[6]	彭龙龙, 汪久根, 彭娟娟, 等. 表面织构对油水混合液润滑轴承湍流润滑性能的影响[J]. 润滑与密封, 2015, 40(11): 30-34.
	Peng L L, Wang J G, Peng J J, et al. Influences of surface texture on turbulent lubrication of journal bearing with oil and water mixture[J]. Lubrication Engineering, 2015, 40(11): 30-34.
[7]	Wang B, Zhang H Q, Cao H J. Flow dynamics of a spiral-groove dry-gas seal[J]. Chinese Journal of Mechanical Engineering, 2013, 26(1): 78-84.
[8]	沈伟, 彭旭东, 江锦波, 等. 高速超临界二氧化碳干气密封实际效应影响分析[J]. 化工学报, 2019, 70(7): 2645-2659.
	Shen W, Peng X D, Jiang J B, et al. Analysis on real effect of supercritical carbon dioxide dry gas seal at high speed[J]. CIESC Journal, 2019, 70(7): 2645-2659.
[9]	Feng H H, Jiang S Y, Ji A M. Investigations of the static and dynamic characteristics of water-lubricated hydrodynamic journal bearing considering turbulent, thermohydrodynamic and misaligned effects[J]. Tribology International, 2019, 130: 245-260.
[10]	马学忠, 崔元召, 肖晓鑫, 等. 高速机械密封端面引流槽-环槽复合通道冷却特性与密封性能研究[J]. 润滑与密封, 2025, 50(2): 1-10.
	Ma X Z, Cui Y Z, Xiao X X, et al. Cooling characteristics and sealing performance of the inlet groove- annular groove composite channel in high-speed mechanical seals[J]. Lubrication Engineering, 2025, 50(2): 1-10.
[11]	Wang L, Pei S Y, Xiong X Z, et al. Investigation of the combined influence of turbulence and thermal effects on the performance of water-lubricated hybrid bearings with circumferential grooves and stepped recesses[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2014, 228(1): 53-68.
[12]	Luan Z G, Khonsari M M. Computational fluid dynamics analysis of turbulent flow within a mechanical seal chamber[J]. Journal of Tribology, 2007, 129(1): 120-128.
[13]	Luan Z G, Khonsari M M. Analysis of conjugate heat transfer and turbulent flow in mechanical seals[J]. Tribology International, 2009, 42(5): 762-769.
[14]	张伟政, 赵吉军, 马学忠, 等. 湍流效应对高速机械密封端面型槽冷却性能影响分析[J]. 化工学报, 2023, 74(3): 1228-1238.
	Zhang W Z, Zhao J J, Ma X Z, et al. Analysis of turbulence effect on face groove cooling performance of high-speed mechanical seals[J]. CIESC Journal, 2023, 74(3): 1228-1238.
[15]	马学忠, 肖晓鑫. 高速机械密封搅拌流动与热效应特性研究[J/OL]. 摩擦学学报, .
	Ma X Z, Xiao X X. Characteristics of the stirring flow and thermal effect in high-speed mechanical seals[J/OL]. Tribology, .
[16]	张肖寒. 液膜润滑机械密封湍流效应研究[D]. 杭州: 浙江工业大学, 2020.
	Zhang X H. Study on turbulent effect of liquid film lubricated mechanical seals[D]. Hangzhou: Zhejiang University of Technology, 2020.
[17]	Nau B S. Observations and analysis of mechanical seal film characteristics[J]. Journal of Lubrication Technology, 1980, 102(3): 341-347.
[18]	Zhang J Y, Meng Y G. Direct observation of cavitation phenomenon and hydrodynamic lubrication analysis of textured surfaces[J]. Tribology Letters, 2012, 46(2): 147-158.
[19]	Qiu Y, Khonsari M M. Experimental investigation of tribological performance of laser textured stainless steel rings[J]. Tribology International, 2011, 44(5): 635-644.
[20]	Pascovici M D, Predescu A, Cicone T, et al. Experimental evidence of cavitational effects in a Rayleigh step slider[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2011, 225(6): 527-537.
[21]	马学忠, 孟祥铠, 王玉明, 等. 雷列台阶-环槽端面密封机理与性能研究[J]. 摩擦学学报, 2016, 36(5): 585-591.
	Ma X Z, Meng X K, Wang Y M, et al. Mechanism and performance of end face seal of Rayleigh steps and annular grooves[J]. Tribology, 2016, 36(5): 585-591.
[22]	Olver A V, Fowell M T, Spikes H A, et al. ‘Inlet suction’, a load support mechanism in non-convergent, pocketed, hydrodynamic bearings[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2006, 220(2): 105-108.
[23]	Salant R F, Homiller S J. Stiffness and leakage in spiral groove upstream pumping mechanical seals[J]. Tribology Transactions, 1993, 36(1): 55-60.
[24]	Wang Y L, Wu J H, Xu L S. Influence of turbulent cavitating flow on performance characteristics of spiral groove liquid film seal[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2022, 236(1): 70-79.
[25]	Feng H H, Peng L P. Numerical analysis of water-lubricated thrust bearing with groove texture considering turbulence and cavitation[J]. Industrial Lubrication and Tribology, 2018, 70(6): 1127-1136.
[26]	Wang W, He Y Y, Li Y, et al. Investigation on inner flow field characteristics of groove textures in fully lubricated thrust bearings[J]. Industrial Lubrication and Tribology, 2018, 70(4): 754-763.
[27]	Cross A T, Sadeghi F, Rateick Jr R G, et al. Temperature distribution in pocketed thrust washers[J]. Tribology Transactions, 2015, 58(1): 31-43.
[28]	李宇. 热效应对涡轮泵空化流动影响机理研究[D]. 哈尔滨: 哈尔滨工业大学, 2020.
	Li Y. Study on the influence mechanism of dynamic effects on cavitation flow of turbo pump[D]. Harbin: Harbin Institute of Technology, 2020.
[29]	吴望一. 流体力学[M]. 2版. 北京: 北京大学出版社, 2021.
	Wu W Y. Fluid Mechanics[M]. 2nd ed. Beijing: Peking University Press, 2021.
[30]	Li Y, Song P Y, Xu H J. Performance analyses of the spiral groove dry gas seal with inner annular groove[J]. Applied Mechanics and Materials, 2013, 420: 51-55.
[31]	Sun J J, Ma C B, Yu Q P, et al. Numerical analysis on a new pump-out hydrodynamic mechanical seal[J]. Tribology International, 2017, 106: 62-70.
[32]	Wang J L, Lei L S, Li J K, et al. Effect of two-phase flow lubrication on sealing performance of spiral groove mechanical seal under high speed and low temperature conditions[J]. Advances in Mechanical Engineering, 2024, 16(4): 16878132241248154.
[33]	Chen H L, Wu Q B, Xu C, et al. Research on cavitation regions of upstream pumping mechanical seal based on dynamic mesh technique[J]. Advances in Mechanical Engineering, 2014, 6: 821058.
[34]	Zhang G Y, Li X K, Zhao W G, et al. Theoretical and experimental on two-phase flow mechanism of low-temperature high-speed hydrodynamic mechanical seal[J]. Acta Aeronautica et Astronautica Sinica, 2023, 44(23): 628229.
[35]	Brunetière N. A modified turbulence model for low Reynolds numbers: application to hydrostatic seals[J]. Journal of Tribology, 2005, 127(1): 130-140.
[36]	Zhang G Y, Zhao W G, Yan X T, et al. A theoretical and experimental study on characteristics of water-lubricated double spiral-grooved seals[J]. Tribology Transactions, 2011, 54(3): 362-369.