三楔气体轴承的动静压特性分析

Hydrostatic and hydrodynamic characteristic analysis of three-wedge gas bearing

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.

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.