静压气体轴承气膜力及其与转子耦合动力学特性研究

Research on gas film force of aerostatic gas bearing and its coupled dynamics with rotor

针对静压气体轴承,进行三维实体建模,采用供气孔区域非结构化网格和非供气孔区域结构化网格相结合的网格划分方法;采用基于有限体积法的计算流体动力学(CFD)商业软件对三维稳态可压缩气体Navier-Stokes(N-S)方程进行求解;根据计算结果,通过数据拟合获得了考虑转子偏心和转速的静压气体轴承气膜支承力模型.基于有限元法建立了气体轴承-转子系统动力学模型,采用Newmark逐步积分法求解了系统的临界转速和不平衡响应.在此基础上进行实验测试,验证了数值仿真结果.研究结果表明:低速、小偏心下,气膜主支承力随偏心呈近似线性变化;高速、大偏心下,气膜主支承力急剧增大,气体轴承的动压效应显著增强;气膜x,y向耦合支承力随转速和偏心呈非线性变化;转子系统一、二阶临界转速对当前结构刚度变化比较敏感,而三阶临界转速对此不敏感.因此,气体轴承气膜支承力的非线性特性及其与转子耦合动力学特性较为复杂,在对气体轴承进行结构设计时,应充分考虑其与转子的耦合,合理设计工作转速范围.

For aerostatic bearings with tangential gas supply, a three dimensional solid model was developed. Combining structured mesh with unstructured mesh, three-dimesional compressible Navier-Stokes （N-S） equations were solved with computational fluid dynamics （CFD） commercial software based on finite volume method. According to the simulation results, gas film supporting force model related to rotor eccentricity and speed was de-rived with data fitting. Dynamics model of aerostatic bearing-rotor system was built with finite element method and critical speed and unbalance response were solved using Newmark integration method. Experimental tests were performed to verify the numerical simulation results. Research results show that film main supporting force changes linearly in the state of low-speed, small eccentricity, whereas increases rapidly under high-speed and large eccentricity, and effect of dynamic pressure of aerostatic bearing significantly enhances. Coupling supporting force between x and y directions changes nonlinearly with speed and eccentricity; First and second critical speed are sensitive to the current structural stiffness while the third one is not. Therefore, nonlinear characteristics of gas hearing and coupled dynamics of rotor-bearing system are complex; in the case of bearing structure design, coupling between gas bearing and rotor, work speed range should be taken in to full account.