Leakage rate analysis and dimple shape design of mechanical seal with oriented dimples based on multi-wedge phenomenon

doi:10.11949/0438-1157.20190905

Abstract

Abstract:

The geometrical shape of dimples has significant influence on the leakage rate of mechanical seal with dimples. Based on the wedge effect theory, the relationship between the geometrical shape of dimples and the leakage rate is studied. Firstly, the analytical method of equilateral triangular dimples multi-wedge phenomenon is extended to the elliptical, diamond, rectangular and isosceles triangular dimples. The wedge feature of elliptical, diamond, rectangular dimples is two centrosymmetric wedges, and the wedge feature of isosceles triangular dimples is two non-centrosymmetric wedges. Secondly, the effect of multi-wedge phenomenon on the outlet suction flow rate, reversed flow rate and leakage rate is analyzed. The low pressure zone induced by the divergent wedges is the main influencing factor of the outlet suction flow rate. The high pressure zone induced by the convergent wedges is the main influencing factor of the reversed flow rate. The leakage rate is affected by the combination of the former two factors. Finally, based on the understanding of the multi-wedge phenomenon, two wedge-shaped structures with the strongest suction ability and the strongest return ability were selected and combined to design a new type of dimple. Compared with the original four oriented dimples, its leakage rate is the smallest.

Key words: mechanical seal, oriented dimple, multi-wedge phenomenon, leakage rate, design, two-phase flow, numerical simulation

摘要：

微孔的几何形状对微孔端面机械密封泄漏率有较大的影响，所以基于楔效应理论研究了微孔几何形状与泄漏率的关系。首先，应用等边三角形多楔现象的研究方法，对椭圆形、菱形、矩形、等腰三角形四种方向性微孔的多楔现象进行了分析，椭圆形、菱形和矩形微孔表现为中心对称两楔性质的微孔，等腰三角形微孔表现为非中心对称两楔性质的微孔。然后，分析了多楔现象对回吸率、回送率和泄漏率的影响，发散性楔形成的低压区是回吸率的主要影响因素，收敛性楔形成的高压区是回送率的主要影响因素，泄漏率受前两者的综合影响。最后，基于对多楔现象的理解，选取回吸能力最强和回送能力最强的两个楔形结构进行组合，设计出一种新的微孔，相比于原来的四种方向性微孔，其泄漏率最小。

关键词: 机械密封, 方向性微孔, 多楔现象, 泄漏率, 设计, 两相流, 数值模拟

CLC Number:

TH 117.2

Huwei CHEN, Hua JI, Donglin FENG, Qian LI, Zhi CHEN. Leakage rate analysis and dimple shape design of mechanical seal with oriented dimples based on multi-wedge phenomenon[J]. CIESC Journal, 2020, 71(4): 1723-1733.

陈胡炜, 吉华, 冯东林, 李倩, 陈志. 基于多楔现象的微孔端面机械密封泄漏率分析及孔形设计[J]. 化工学报, 2020, 71(4): 1723-1733.

Figures/Tables 11

Fig.1 Micro-dimples distribution and calculation domain

Table 1 Calculation parameters

参数	数值	参数	数值
微孔深度h_p/μm	5	液膜厚度h₀/μm	2
微孔长半轴a/mm	0.4269	微孔面积比S_p /%	20
内径压力p_i/Pa	1×10⁵	空化压力p_c/Pa	2334^[10]
外径压力p_o/Pa	3×10⁵	转速n/(r/min)	600~3000
润滑剂黏度μ/(Pa·s)	0.001	润滑剂密度ρ/(kg/m³)	998.2

Fig.2 Wedges structure of θ-z plane

Fig.3 Diagram of β of different dimples

Fig.4 Pressure distribution of dimple unit close to ri (E, n=2400 r/min)

Fig.5 Pressure distribution of dimple unit close to ri (D, n=2400 r/min)

Fig.6 Pressure distribution of dimple unit close to ri (R, n=2400 r/min)

Fig.7 Pressure distribution of dimple unit close to ri (T, n=2400 r/min)

Fig.8 Effect of α on Qs, Qrf and Q (n=2400 r/min)

Fig.9 Design process and geometric model of N dimple

Fig.10 Leakage rate of E(α=45°)，D(α=45°)，R(α=45°)，T(α=45°) and N

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