Performance analysis on diffuser self-pumping hydrodynamic and hydrostatic mechanical seal

doi:10.11949/0438-1157.20191586

Abstract

Abstract:

The opening force of the seal end face is an important index to ensure the non-contact operation of the non-contact mechanical seal. To overcome the shortcoming that the opening force of the seal face decreases with the increase of the rotating speed, a kind of diffuser self-pumping hydrodynamic and hydrostatic mechanical seal was designed based on the working principle of the diffuser of the centrifugal pump or compressor. The three-dimensional flow fields of the seal face was analyzed by Fluent, the sealing performance of the self-pumping mechanical seal was compared with ordinary self-pumping mechanical seal, and the influence of structural and operational parameters on the performance of self-pumping mechanical seal was discussed. Results show that the opening force of the face of self-pumping mechanical seal with the diffuser is more than 50% higher than that of the ordinary self-pumping mechanical seal with the same spiral groove parameters, and the opening force increases with the speed. With the increase of the width of diffuser ring, the opening force and the leakage rate increase significantly. Reducing the depth of diffuser ring can effectively improve the opening force. Even the structure size of the expansion ring is changed, the effect of the width ratio of groove to diffuser ring, groove number and helix angle on the diffuser self-pumping mechanical seal sealing performance is not affected. Consequently, through the matching of structural parameters, the better sealing performance can be obtained under certain operating conditions.

Key words: mechanical seal, interface, opening force, diffuser, CFD, numerical simulation, leakage rate

摘要：

密封端面开启力是保证非接触式机械密封非接触运行的重要指标。为克服普通自泵送流体动静压型机械密封端面开启力随转速增大而减小这一不足，基于离心式泵或压缩机的扩压器工作原理提出了一种扩压式自泵送流体动静压型机械密封。数值模拟比较了普通自泵送和扩压式自泵送流体动静压型机械密封的密封性能，探讨了密封面结构参数和工况参数对扩压式自泵送流体动静压型机械密封性能的影响规律。结果表明：扩压式自泵送流体动静压型机械密封相比同等螺旋槽参数的普通自泵送流体动静压型机械密封的密封界面开启力提升了50%以上，并随转速增大而增大；随着扩压环槽增宽，开启力和泄漏率都显著增大；减小扩压环槽深度，能有效提高开启力；扩压环槽结构尺寸的变化基本不影响槽扩宽比、槽数和螺旋角对密封性能的影响规律。在一定的工况参数下，通过结构参数匹配，扩压式自泵送流体动静压型机械密封可以获得较优的密封性能。

关键词: 机械密封, 界面, 开启力, 扩压, 计算流体力学, 数值模拟, 泄漏率

CLC Number:

TH 136

Cheng GE, Jianjun SUN, Xuchen SU, Chenbo MA, Qiuping YU. Performance analysis on diffuser self-pumping hydrodynamic and hydrostatic mechanical seal[J]. CIESC Journal, 2020, 71(5): 2202-2214.

葛诚, 孙见君, 苏徐辰, 马晨波, 於秋萍. 扩压式自泵送流体动静压型机械密封性能分析[J]. 化工学报, 2020, 71(5): 2202-2214.

Figures/Tables 20

Fig.1 Structure of rotating and stationary seal ring

Fig.2 Sampling calculational region

Fig.3 Grid independence verification and meshing generation

Table 1 Boundary condition setting

边界	边界类型
引流孔道E	pressure-inlet（P\|E=p _o）
内径AB	pressure-outlet （P\|AB=p _i）
外径CD	pressure-outlet （P\|CD=p _o）
环槽FG、HI	periodic boundary（P\|FG=P\|HI）
液膜AD、BC	periodic boundary（P\|AD=P\|BC）
引流孔低面与环槽上表面	interface
环槽下表明与液膜上表面	interface
液膜下表面与螺旋槽上表面	interface
螺旋槽出口JK与扩压环内径侧面LM	interface
螺旋槽底面	moving wall
螺旋槽两侧面和内径侧面	moving wall
其余壁面	stationary wall

Table 2 Numerical simulation parameters

参数	数值
密封环外径，r _k/mm	46.5~50
螺旋槽外径，r _o/mm	44.5
螺旋槽根径，r _g/mm	35.5
密封环内径，r _i/mm	26.5
扩压环深，h _k/μm	40~60
螺旋槽深，h _g/μm	50
膜厚，h _c/μm	1.2
槽台宽比，γ	0.5~0.9
槽数，N _g	16~30
螺旋角，α/(°)	22~50
引流环槽宽，L/mm	2
引流环槽深，H/mm	0.5
引流孔径，D/mm	2
密封介质压差，Δp/MPa	0.1~0.9
转速，n/(r?min^-1)	600~6000

Fig.4 Comparison between Fluent calculated value and literature value

Fig.5 Performance curve of mechanical seal

Fig.6 Pressure nephogram of liquid membrane between seal faces (h k= h g=50 μm, N g=18, γ=0.5, α=22°, Δp=0.5 MPa, n=4000 r·min-1)

Fig.7 Effect of diffuser ring width on sealing performance (h k=50 μm，r o=44.5 mm，N g=18，γ=0.5，α=22°，Δp=0.5 MPa)

Fig.8 Pressure nephogram of different diffuser ring width (h k=50 μm，r o=44.5 mm，N g=18，γ=0.5，α=22°，Δp=0.5 MPa，n=4000 r·min-1)

Fig.9 Effect of groove length on opening force of seal face (r k=49.5 mm，h k=50 μm，N g=18，γ=0.5，α=22°，Δp=0.5 MPa)

Fig.10 Effect of diffuser ring depth on sealing performance (r k=49.5 mm，r o=44.5 mm，N g=18，γ=0.5，α=22°，Δp=0.5 MPa)

Fig.11 Effect of diffuser ring depth on pumping flow （r k=49.5 mm，r o=44.5 mm，N g=18，γ=0.5，α=22°，Δp=0.5 MPa）

Fig.12 Effect of diffuser ring depth on dynamic and static pressure change of liquid membrane (r k=49.5 mm，r o=44.5 mm，N g=18，γ=0.5，α=22°，Δp=0.5 MPa，n=4000 r·min-1)

Fig.13 Pressure nephogram of different diffuser ring depth (r k=49.5 mm，r o=44.5 mm，N g=18，γ=0.5，α=22°，Δp=0.5 MPa，n=4000 r·min-1)

Fig.14 Effect of width ratio of groove to diffuser ring on sealing performance (r k=49.5 mm，h k=50 μm，r o=44.5 mm，N g=18，α=22°，Δp=0.5 MPa)

Fig.15 Effect of groove number on sealing performance (r o=44.5 mm，γ=0.75，α=22°，Δp=0.5 MPa，n=4000 r·min-1)

Fig.16 Effect of helix angle on sealing performance (r o=44.5 mm，N g=22，γ=0.75，Δp=0.5 MPa，n=4000 r·min-1)

Fig.17 Effect of differential pressure on sealing performance (r o=44.5 mm，N g=22，γ=0.75，α=30°，n=4000 r·min-1)

Fig.18 Effect of speed on sealing performance (r o=44.5 mm，N g=22，γ=0.75，α=30°，Δp=0.5 MPa)

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