Influence of support boundary conditions of a seal ring on deformation of mechanical seal end face

doi:10.11949/0438-1157.20190584

Abstract

Abstract:

The mechanical seal ring is supported on the shaft or in the seal cavity by an auxiliary O-ring. Different structural designs will change the seal ring support boundary. Aiming at the three structural models of mechanical seals, this paper simulates the deformation of the end facies of friction pair of mechanical seals by using ANSYS finite element analysis software, and discusses the deformation law of the surfaces of mechanical seals under different stress boundary conditions of rubber O-ring. When SiC is used in both rotating ring and static ring, it is found that divergent clearance is formed on the end faces of the friction pairs of the three kinds of support structures in static state (structural analysis), and the deformation of the end faces is greatly affected by the contact stress of the support boundary. And the thermal structure coupling analysis shows that the three end facies of the rotating ring and the static ring are convergent. When graphite is used in the rotating ring and SiC is used in the static ring, it is found that the end gap may be convergent or divergent, which is related to the support boundary. Therefore, the different supporting boundary conditions of the O-ring will affect the end deformation of the rotating ring during operation. So different support boundary conditions of O-ring of rotating ring will affect the deformation of seal ring s end face. At the same time, the elastic modulus of the material of the dynamic and static rings has a great influence on the deformation of the end face, thus affecting the sealing performance. The research has guiding significance for mechanical seal design.

Key words: mechanical seal, O-ring, support boundary condition, end face deformation, numerical simulation, model, material

摘要：

机械密封的密封环是通过辅助O形圈支撑在轴上或者密封腔内，不同的结构设计会改变密封环支撑边界。针对三种机械密封结构模型，利用ANSYS有限元分析软件，模拟机械密封摩擦副端面的变形，讨论了橡胶O形密封圈不同受力边界条件下机械密封端面变形的规律。研究发现当动环、静环均采用SiC时，在静态（结构分析）时，该三种不同支撑结构的摩擦副端面均形成发散间隙，端面变形受支撑边界接触应力的影响较大；热结构耦合分析发现其动环、静环端面间隙呈收敛间隙运转时，热边界条件影响更大。当动环采用石墨，静环采用SiC时，发现其端面间隙可能为收敛型也可能为发散型，这与支撑边界有关。故密封环支撑边界条件的不同会影响动环端面变形，同时动、静环材料的弹性模量对端面的变形有较大影响，从而会影响密封性能。该研究对机械密封设计有指导意义。

关键词: 机械密封, O形圈, 支撑边界条件, 端面变形, 数值模拟, 模型, 材料

CLC Number:

TB 42

Jinhong WANG, Zhi CHEN, Fan LIU, Jianming LI. Influence of support boundary conditions of a seal ring on deformation of mechanical seal end face[J]. CIESC Journal, 2020, 71(4): 1744-1753.

王金红, 陈志, 刘凡, 李建明. 密封环支撑边界条件对机械密封端面变形的影响[J]. 化工学报, 2020, 71(4): 1744-1753.

Figures/Tables 12

Fig.1 Simplified diagram of three mechanical seal structures

Fig.2 Gap forms of end face of friction pair

Table 1 Material parameters of friction pairs and O-rings[19]

材料	E/ GPa	$ε$	ρ/(g/cm³)	k/(W/(m·K))	α/K^-1	C/(J/(kg·K))
SiC	380	0.15	3.12	100	5×10^-6	875
碳石墨	25	0.15	1.8	96.3	6.5×10^-6	710
丁腈橡胶	7.8×10^-3	0.49	1.2	—	—	—
聚四氟乙烯	0.28	0.40	2.3	0.256	10.3×10^-5	—

Table 1 Material parameters of friction pairs and O-rings[19]

材料	E/ GPa	$ε$	ρ/(g/cm³)	k/(W/(m·K))	α/K^-1	C/(J/(kg·K))
SiC	380	0.15	3.12	100	5×10^-6	875
碳石墨	25	0.15	1.8	96.3	6.5×10^-6	710
丁腈橡胶	7.8×10^-3	0.49	1.2	—	—	—
聚四氟乙烯	0.28	0.40	2.3	0.256	10.3×10^-5	—

Fig.3 Grid partition of structure 1

Fig.4 Stress boundary diagram of structure 1

Fig.5 Thermal boundary conditions of structure 1

Table 2 Grid irrelevance test

网格尺寸/mm	网格数	节点数	动环内径处温度/℃	动环端面中径处与对应静环端面的温差/℃
0.6	595	659	41.60	0.85
0.4	1462	1510	41.98	0.84
0.3	2426	2569	42.19	0.83
0.2	5472	5522	42.38	0.82
0.1	21215	21117	42.39	0.82

Fig.6 Temperature nephogram of friction pairs

Fig.7 Deformation of mechanical seal face in structural analyses

Fig.8 Contact force distribution between rubber O-ring and rotating ring with different structures(both rotating ring and static ring SiC)

Fig. 9 Deformation of mechanical seal face in coupling analyses（both rotating ring and static ring SiC）

Fig.10 Deformation of paired friction pair structure of rotating ring carbon graphite and static ring SiC

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