高浮起量空气静压止推轴承气膜流动特性分析

Analysis on film flow characteristics of high lifting air static thrust bearings

为明确空气静压轴承在高浮起量下的静/动态特性,采用瞬态模型分析支撑气膜湍流形成演变规律和能量耗散过程;结合双向流固热耦合的方法对流场特征区域的流态演变、温度分布、马赫数变化、涡量特征等进行描述;将理论分析与实验测试结果相结合,明确高浮起量下空气轴承气膜内部流场特征,以及系统的承载能力、刚度特性和微振动特性。研究表明:高浮起量下空气轴承气膜流场存在气动加热现象且伴随着负压产生;气膜内部的较大压降和流体的压缩性增强会导致空气轴承的静态特性变差;考虑流固热耦合效应能有效保证高浮起量下空气静压止推轴承静态特性的计算准确性,在1 MPa供气压力、50μm气膜的高浮起量时对承载力的计算误差仅为2.2%,对刚度的计算误差仅为2.7%。

In order to clarify the static/dynamic characteristics of aerostatic bearing under high lifting,the transient model was used to analyze the formation and evolution of supporting gas film turbulence and the energy dissipation process.Then,the flow state evolution,temperature distribution,Mach number variation and vorticity characteristics in the characteristic region of the flow field were described by the method of bidirectional fluid-solid thermal coupling.Furthermore,the theoretical analysis and experimental test results were combined to clarify the characteristics of the internal flow field of the air bearing film,the bearing capacity,stiffness characteristics and micro-vibration characteristics of the system under high lifting.The results showed that there was a phenomenon of aerodynamic heating in the film flow field of air bearing with negative pressure under high lifting.The large pressure drop inside the gas film and the enhanced compressibility of the fluid led to the bad static characteristics of the air bearing.Considering the fluid-solid thermal coupling effect,the calculation accuracy of static characteristics of aerostatic thrust bearings can be effectively guaranteed under high lifting.Especially,the calculation errors of bearing capacity and stiffness were only 2.2%and 2.7%,respectively,when air was supplied with 50μm film at 1 MPa.