Dynamic contact analysis of dry gas seal during start-stop process considering material properties and surface topography of seal rings

doi:10.11949/0438-1157.20201639

Abstract

Abstract:

The end-face contact during the start-stop process of the dry gas seal is inevitable.In order to reveal the mechanical characteristics when the end faces are in contact, the dry gas seal can operate stably. Using statistical contact theory and equivalent damping ideas, considering the material properties of the seal ring, an analytical model suitable for analyzing the normal dynamic contact stiffness and dynamic contact damping of the dry friction interface of the dry gas seal is derived. The real surface morphology of the seal ring was measured through experiments, and the initial parameters of the contact model were determined. The results show that the dynamic contact stiffness increases with the increase of contact pressure and disturbance amplitude. The effect of disturbance frequency on dynamic contact stiffness is much smaller than contact pressure or amplitude effect. Dynamic contact damping increases with the increase of contact pressure and decreases with disturbance frequency or amplitude. The current calculation results are closer to the GW model by comparing it with various contact models. The sealing rings' pairing is silicon carbide as the rotating ring and graphite as the stationary ring. When the end face is not worn, the contact surface's dynamic characteristics are mainly dynamic contact stiffness, and the dynamic contact damping is weak. The change of normal contact is mainly considered in the contact stage before the 50% critical detachment speed.

Key words: dry gas seal, start-stop process, interface, dynamic contact, microscale

摘要：

干气密封启停阶段的端面接触是不可避免的，为了揭示端面发生接触时的力学特性以保证干气密封稳定运行，运用统计学接触理论和等效阻尼思想，考虑密封环材料属性，推导出适用于分析干气密封干摩擦界面法向动态接触刚度和动态接触阻尼的解析模型，并通过实验测得密封环真实表面形貌，确定了接触模型的初始参数。探究干气密封端面发生接触时动态接触刚度和接触阻尼等参数的变化规律。结果表明，动态接触刚度随接触比压、扰动振幅的增大而增大。扰动频率对动态接触刚度的作用效果远小于接触比压或振幅对接触刚度的作用效果。动态接触阻尼随接触比压的增大而增大，随扰动频率和振幅的增大而减小。通过与多种经典接触模型对比，当前的计算结果与GW模型更为接近。针对干气密封碳化硅作为动环、石墨作为静环的配对方式，在端面未发生磨损时，结合面的微扰动态特性以动态接触刚度为主，动态接触阻尼较弱。法向接触特性的变化主要考虑50%临界脱开转速之前的接触阶段。

关键词: 干气密封, 启停过程, 界面, 动态接触, 微尺度

CLC Number:

TH 133.36

Xuejian SUN, Pengyun SONG, Wenyuan MAO, Qiangguo DENG, Hengjie XU, Wei CHEN. Dynamic contact analysis of dry gas seal during start-stop process considering material properties and surface topography of seal rings[J]. CIESC Journal, 2021, 72(8): 4279-4291.

孙雪剑, 宋鹏云, 毛文元, 邓强国, 许恒杰, 陈维. 考虑密封环材料属性和表面形貌干气密封启停阶段的动态接触特性分析[J]. 化工学报, 2021, 72(8): 4279-4291.

Figures/Tables 13

Fig.1 The structure of the dry gas seal and the microscopic surface of sealing rings

Fig.2 End face contact of the dry gas seal and deformation of asperity[32,35]

Fig.3 End face structure of the dry gas seal and contact position of seal rings

Fig.4 The experimental device and the test curve of surface profile

Table 1 Experimental data of root mean square deviation and root mean square slope

实验数据序号	静环		动环
实验数据序号	R_qs/μm	R_dqs	R_qr/μm	R_dqr
1	0.0500	0.0587	0.0700	0.0544
2	0.0600	0.0623	0.0600	0.0553
3	0.0600	0.0623	0.0700	0.0579
4	0.0600	0.0625	0.0700	0.0546
5	0.0600	0.0625	0.0700	0.0558
6	0.0600	0.0583	0.0700	0.0567
7	0.0800	0.0627	0.0600	0.0561
8	0.0500	0.0580	0.0700	0.0581
9	0.0600	0.0623	0.0600	0.0553
10	0.0500	0.0581	0.0700	0.0560
平均值T_e	0.0590	0.0608	0.0670	0.0560
文献结果T_r	0.0640	0.0628	0.0700	0.0522
T_r与T_e相对误差	8.47%	3.29%	4.48%	-6.78%

Table 2 Structure parameters and material parameters of the model

参数	数值	参数	数值
软材料的硬度 H/GPa	0.7	密封环外径 r_o/mm	77.78
等效弹性模量 E^①/GPa	23.65	密封环槽根半径 r_g/mm	69
最大接触压力因子 K^②	0.577	螺旋角 α/(°)	15
塑性指数ψ	18.6	槽坝比 γ	1
微扰频率 ω/Hz	40	槽数 N_g	12
微扰振幅 X₀/μm	0.002~0.02	动环	碳化硅
密封环内径 r_i/mm	58.42	静环	石墨

Fig.5 Model verification of contact force

Fig.6 The effect of contact pressure on separation based on surface heights (h)and real contact area (Am)

Fig.7 The effect of contact pressure on dynamic contact stiffness and static contact stiffness

Fig.8 The effect of contact pressure on dynamic contact damping

Fig.9 The film thickness of separation speed effect on dynamic contact

Fig.10 The effect of surface-topography parameters on dynamic contact stiffness and dynamic contact damping

Fig.11 The effect of dynamic parameters on dynamic contact stiffness and dynamic contact damping

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