Hydrostatic and hydrodynamic characteristic analysis of three-wedge gas bearing

doi:10.3785/j.issn.1008-973X.2024.09.021

Journal of ZheJiang University (Engineering Science)

2024, Vol. 58

Issue (9): 1970-1980 DOI: 10.3785/j.issn.1008-973X.2024.09.021

Hydrostatic and hydrodynamic characteristic analysis of three-wedge gas bearing

Chenxin ZHANG(

),Weirong HONG*(

),Shuiying ZHENG

Institute of Process Equipment, Zhejiang University, Hangzhou 310027, China

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Abstract

A three-wedge gas bearing, with both hydrostatic and hydrodynamic pressure characteristics, was specially designed for the bearing-rotor system of the air compressor in hydrogen fuel cell vehicle. The mechanism of hydrostatic and hydrodynamic coupling effect, the flow field characteristics, and the dynamic and static parameters of the bearing were investigated. These results were also compared with those of traditional cylindrical gas bearings. To analyze the flow field characteristics of the bearing, a dynamic mesh program was developed using UDF in Fluent software, and a related CFD transient simulation method was proposed to solve the nonlinear gas film forces and the dynamic parameters of the bearing at any eccentric journal position. The analysis showed that the hydrodynamic and hydrostatic pressure effect intensity of the three-wedge bearing varied with the external working condition, but kept on coupling with each other, ensuring that the bearing always provided effective and stable support for the rotor. At low rotational speed, the hydrostatic pressure effect was the main factor affecting bearing performance, and the three-wedge gas bearing exhibited similar working performance to cylindrical bearing. The three-wedge gas bearing can thus provide stable support for on-board compressor rotor during start-stop and acceleration. With the increase of the rotational speed, the hydrodynamic pressure effect of the three-wedge gas bearing was significantly enhanced. The three-wedge gas bearing can thus provide support for high-speed compressors with lower gas supply pressure than the cylindrical bearing. Therefore, compared with the traditional cylindrical gas bearing that required external gas sources, the three-wedge gas bearing can provide a stable support for the rotor only using the internal gas circuit of the hydrogen fuel cell vehicle. It adapted well with the working environment inside the hydrogen fuel cell vehicle where the gas supply pressure was limited, and the rotor underwent frequent start-stop and speed changes.

Key words： gas bearing hydrostatic and hydrodynamic pressure coupling effect dynamic pressure effect bearing characteristics hydrogen fuel cell vehicle

Received: 12 July 2023 Published: 30 August 2024

CLC:

TH 117.2

Corresponding Authors: Weirong HONG E-mail: chenxin_zhang@126.com;hongwr@zju.edu.cn

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Cite this article:

Chenxin ZHANG,Weirong HONG,Shuiying ZHENG. Hydrostatic and hydrodynamic characteristic analysis of three-wedge gas bearing. Journal of ZheJiang University (Engineering Science), 2024, 58(9): 1970-1980.

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https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2024.09.021 OR https://www.zjujournals.com/eng/Y2024/V58/I9/1970

三楔气体轴承的动静压特性分析

针对氢燃料电池汽车车载空压机的轴承-转子系统，提出兼具静压和动压特性的三楔式气体轴承. 开展轴承动静压耦合作用机制和流场特性、动静态参数研究，并与传统的圆柱气体轴承进行对比. 为了计算轴承的流场特性，在Fluent软件的用户自定义函数（UDF）中编写动网格程序，并提出相应的计算流体力学（CFD）瞬态模拟方法来求解轴颈任意偏心位置时的轴承非线性气膜力与动态参数. 研究表明，在运行工况变化时，三楔气体轴承动静压效应的强度会不断变化，但始终能通过耦合效应为转子提供有效、稳定的支承. 在低转速范围内，静压效应是影响三楔气体轴承性能的主要因素，表现出与圆柱气体轴承相似的支承效果，保证车载压缩机在启停或升速过程中的稳定运转. 当转速增大时，三楔气体轴承的动压效应显著增强，能在更低的供气压力下为高速旋转的车载压缩机提供支承. 相较于需要外接气源的圆柱气体轴承，三楔气体轴承能在仅利用氢燃料电池汽车供气系统内部气路的情况下为转子提供稳定的支承，适应车载空压机中气体压力有限且须频繁启停、变速的工作环境.

关键词： 气体轴承, 动静压耦合, 动压效应, 轴承特性, 氢燃料电池汽车

Fig.1 Structural diagram of three-wedge gas bearing and its flow field

Tab.1 Three-wedge gas bearing parameters

Fig.2 Entity structure of three-wedge gas bearing

Tab.2 Mesh independence verification

Fig.3 Modeling and meshing of three-wedge gas bearing fluid field

Fig.4 Calculation principle of dynamic mesh method

Fig.5 Coordinate direction of bearing flow field mesh model

Fig.6 Circumferential pressure distribution of gas bearing fluid film under different rotational speeds

Fig.7 Circumferential density distribution of gas bearing fluid film under different rotational speeds

Fig.8 Circumferential pressure distribution around gas bearing orifices under different rotational speeds

Fig.9 Gas film pressure nephogram under different rotational speeds

Fig.10 Circumferential pressure distribution of gas bearing fluid film under eccentricity of 0.3

Fig.11 Bearing capacity of gas bearing under different rotational speeds and eccentricities

Fig.12 Stiffness coefficients of gas bearing under different rotational speeds and eccentricities

Fig.13 Damping coefficients of gas bearing under different rotational speeds and eccentricities

Fig.14 Structure and fluid field comparison of gas bearings

Fig.15 Comparison of load capacity between three-wedge and cylindrical gas bearings under different rotational speeds and eccentricities

Fig.16 Comparison of static equilibrium positions between three-wedge and cylindrical gas bearings on FCV compressor rotors under different rotational speeds

Fig.17 Comparison of hydrodynamic characteristics between three-wedge and cylindrical gas bearings on compressor rotors in fuel cell vehicle under different rotational speeds


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