Cavitation Flow and Cooling Mechanism in Mechanical Seals with Double Row Reverse Step

doi:10.3969/j.issn.1004-132X.2025.10.013

Abstract

Abstract:

The thermal-hydrodynamic lubrication （THD） numerical model of mechanical seals with double row reverse Rayleigh steps was established by the CFD method， and the THD characteristics and cavitation flow laws were investigated. The results indicate that large-scale cavitation occurs in the double row reverse Rayleigh step， forming a low-temperature region， which has a significant cooling effect on the liquid film end face and sealing ring. It may be seen from the changes in speed， pressure， and groove depth that larger cavitation areas are correlated with high-speed， low-pressure and shallow grooves. The level of cavitation cooling depends on the cavitation area， and on the cavitation intensity. Temperature valleys and peaks are formed at the rupture and reformation boundaries of the liquid film in the groove， and vortex flow is formed under the combined action of pressure flow and shear flow. The edge position of the vortex corresponds well with the position of cavitation regeneration and the end of the high-temperature zone. The formation of large-area cavitation effect in the reverse step groove also leads to good suction effect in the seal， greatly reducing the seal leakage rate.

Key words: mechanical seal, double row reverse step, cavitation, viscous heat, vortex, cooling mechanism

摘要：

基于计算流体动力学建立了考虑空化效应的双列反向瑞利台阶型机械密封热流体动力润滑（THD）数值模型，并研究了THD特性和空化流动规律。研究结果表明，在双列反向瑞利台阶中发生大面积空化现象，形成低温区域，进而对液膜端面和密封环体产生了显著的冷却作用；从转速、压力以及槽深的变化规律来看，高速、低压和浅槽时空化面积更大，但空化冷却的水平不仅取决于空化面积，还与空化强度相关；同时，由于润滑介质的液化与汽化，在槽内液膜的破裂和重整边界处形成温度谷值和峰值，并在压差流、剪切流共同作用下形成涡旋流动，且涡旋的边缘位置与空化重生以及高温区结束的位置一致；反向台阶槽槽内大面积空化效应的形成促使密封产生良好的抽吸效应，大大降低了密封泄漏率。

关键词: 机械密封, 双列反向台阶, 空化效应, 热效应, 涡旋流动, 冷却机理

CLC Number:

TH117

Xuehong MA, Congcong LI. Cavitation Flow and Cooling Mechanism in Mechanical Seals with Double Row Reverse Step[J]. China Mechanical Engineering, 2025, 36(10): 2266-2273.

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.

Figures/Tables 15

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

Tab.1 Geometric and operational parameters

参数名称	数值	参数名称	数值
密封环内径 r_i	47 mm	IRRS主槽深度h₄	40 μm
密封环外径r_o	57 mm	ORRS内径r₁	48 mm
RS主槽圆周角γ	21°	IRRS内径r₂	51 mm
RS和RRS引流槽圆周角ϕ	1.5°	RS内径r₃	54 mm
密封间隙h_o	6 μm	进口压力p_i	1 MPa
引流槽深度h₁	100 μm	空化压力p_c	30 kPa
RS主槽深度h₂	10 μm	环境压力p_o	0.1 MPa
ORRS主槽深度h₃	50 μm	密封介质	水

Fig.2 Computational Domain Model

Tab.2 THD physical property parameters

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

Fig.3 Grid independent verification

Fig.4 Model correctness verification

Fig.5 Cavitation cooling and flow mechanism

Fig.6 Comparison of temperature distribution of sealing liquid film with and without cavitation

Fig.7 Overall temperature distribution of sealing ring under cavitation effect

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

Fig.9 The influence of rotational speed on sealing performance

Fig.10 Liquid film temperature， pressure， and liquid volume fraction under different medium pressures

Fig.11 The influence of medium pressure on sealing performance

Fig.12 Distribution of liquid film temperature， pressure， and liquid volume fraction under different ORRS main groove depths

Fig.13 The influence of ORRS main groove depth on sealing performance

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