【作者】 于贺春；

【导师】 王祖温； 马文琦；

【作者基本信息】 大连海事大学 ， 轮机工程， 2011， 博士

【摘要】 静压气体轴承具有运转速度高、精度高、能耗低等优点,在高速精密机床、精密测量仪器、高速转子等设备上具有良好的适用性。当前,随着转子速度的不断提高,一方面高转速带来的动压效应对轴承的动静态特性影响更加突出,雷诺方程无法满足流场精确计算的需求；另一方面高转速导致的诸多非线性因素使转子动力学的线性理论无法满足高速气体轴承-转子系统的研究需求。本文以提高高速静压气体轴承-转子系统的稳定性为目的,针对静压气体轴承的流场计算、静压气体轴承的动静态特性分析、气体轴承-转子系统特性的耦合研究、系统特性的实验测试等方面开展了系统深入的研究,主要研究内容包括：分析不同流场数值计算方法对静压气体轴承的适用性。以静压气体止推轴承为研究对象,采用基于雷诺方程的有限差分法及基于N-S方程的有限体积法中的层流模型、湍流模型及二者混合等四种方法对静压气体轴承的流场进行计算。雷诺方程和湍流模型无法满足流场精确计算的需求；选择基于N-S方程的层流模型作为高速静压气体轴承研究中的计算方法。采用三维流场计算方法研究轴承结构及工况对静压径向气体轴承动静态特性的影响。采用分区划分、局部加密的三维建模方法；通过旋转坐标系与静态网格相结合的方法实现静压气体轴承动态特性的三维计算。计算结果表明：高速状态下,动压效应提高了轴承的主承载能力及刚度,偏心率越大,动压效应越明显；随着转速的增高,主刚度增大,主阻尼减小,交叉刚度和交叉阻尼的变化则因偏心率的不同而不同；随着供气压力的提高,主刚度增大,交叉刚度则在大偏心范围内随供气压力提高而增大,阻尼的变化则因转速和偏心率的不同而不同；高转速、大偏心状态下,受动压效应的影响,环面节流静压气体轴承的主刚度和交叉阻尼大于小孔节流,而交叉刚度和主阻尼则小于小孔节流；随着供气孔个数的增加,主阻尼增大,安装方式对轴承特性的影响可以忽略；切向供气提高了轴承的主阻尼,减小了交叉刚度,有利于提高系统的稳定性,但耗气量较大。提出一种基于CFD计算结果的静压气体轴承-转子系统特性的耦合研究方法。通过对不同工况下气膜力的CFD计算结果的拟合,得到气膜力随转速和偏心率变化的非线性关系式；将所得的拟合关系式与转子动力学方程进行耦合求解,实现流场精确计算结果与转子动力学方程的耦合,充分考虑动压效应及转子位移对系统特性的影响。气膜力的非线性使系统中不平衡量的改变和响应幅值的增加不是线性变化关系。设计并搭建高速轴承-转子系统的测试系统,设计新型切向非均匀孔径供气和新型垂直分区非均匀压力供气的静压气体轴承,并对不同轴承结构和工作状态下的系统特性进行测试对比分析。提出一种基于静压气体轴承原理的高速轴承-转子系统非接触式加载方法。所提出的基于CFD计算结果的系统特性的耦合研究方法具有较高的计算精度；与垂直供气相比,切向供气轴承能够减小转子的跳动幅值,定性地证明动态特性理论分析的正确性；新型切向非均匀孔径供气轴承可以有效地提高系统的稳定性；新型垂直分区非均匀压力供气轴承能够减小一阶临界转速附近的跳动幅值,但其后出现了局部增大现象；实验工况下,加载会增加额外的系统振动,且会增大各阶临界转速的跳动幅值；随着供气压力提高,垂直均匀供气轴承-转子系统的一阶临界转速附近的跳动幅值减小,但其后出现了局部增大现象；对于切向供气轴承,供气压力的提高可以提高系统的稳定性。更多还原

【Abstract】 Aerostatic bearings have been successfully used in high-precision machine tools, high-precision measuring instruments, high-speed rotors and so on because of their advantages such as high-speed, high-precision, and small power dissipation. Now with the increases of rotating speed, several problems arise. On the one hand, the influence of the dynamic effect caused by high rotating speed on the characteristics of them becomes more prominent, the calculation based on Reynolds equation could no longer satisfy the calculation accuracy requirement. On the other hand, the nonlinear factors caused by high rotating speed makes the linear theory of rotor dynamics unable to satisfy the research requirement of high-speed gas bearing-rotor system.In this paper, the improvement of system stability for high-speed aerostatic bearing-rotor system is taken as the research purpose, the systematic and in-depth research on the calculation of aerostatic bearing flow, the analysis of aerostatic bearing characteristics, the coupled research of the gas bearing-rotor system’s characteristics, the experiment of the system. The main research work includes:The applicability of different calculation methods on aerostatic bearings is analyzed. The thrust aerostatic bearings are chose as a subject, the finite difference method based on Reynolds equation and the finite volume method (FVM) based on N-S equations are both used. For FVM, the laminar model, the turbulent model and the mixture of them are used. The four types of calculation results are compared with experiment results and analyzed. The Reynolds equation and the turbulent model of FVM are not able to satisfy the calculation accuracy requirement. Based on the comparisons of calculation accuracy and efficiency, the laminar model of FVM is chose for the subsequent study. The boundary layer separation, change of the flow state from turbulent to laminar and increase of viscosity are used to explain the pressure recovery after the pressure depression in the flow field.The static and dynamic characteristics of radial aerostatic bearings of different structure under different working conditions are studied with the three-dimension calculation method. The three-dimension models of radial aerostatic bearings are built, the model is divided into different districts, the calculation grids are refined in some districts. The static girds combined with the rotating coordinate are used for dynamic calculation. The dynamic effect improves the main load capacity and the main stiffness under high-speed working conditions, and the greater the eccentricity, the more obvious dynamic effect pressure. With the increase of rotating speed, the main stiffness increases, the main damping decrease, and the changes of the cross stiffness and the cross damping depend on the eccentricity. With the increase of gas supply pressure, the main stiffness increases, the cross stiffness increases within the bigger eccentricity range, and the changes of the damping depends on the eccentricity and the rotating speed. Under high-speed and big eccentricity working conditions, the influence of dynamic effect on the orifice-compensated aerostatic beaings is greater than that on the orifice-restricted aerostatic beaings, the main stiffness and the cross damping of the orifice-compensated are bigger than them of the orifice-restricted, but the cross stiffness and the main damping of the orifice-compensated are smaller. With the increase of the number of gas supply holes, the main damping increases and the influence of installation types of bearings can be ignored. The tangential gas supply holes can improve the main damping and decrease the cross stiffness with a large gas consumption, which is helpful to the system stability.The interaction method of aerostatic bearing-rotor system based on the calculation results from CFD is proposed. The nonlinear function of load capacity with rotating speed and eccentricity is obtained through fitting the calculation results under different working conditions. The nonlinear function is used to couple with the rotor dynamic equation, which realizes the coupling between the accurate flow calculation and the rotor dynamic equation. The influence of the dynamic effect and the rotor displacement on the system is fully considered in this method. The results show the relation between the imbalance amount and the response multitude is nonlinear caused by the nonlinear gas film force.The high-speed bearing-rotor experiment system is built, the new types of aerostatic bearings with tangential nonuniform supply holes and radial nonuniform district supply pressure are designed, the bearing-rotor system with different structure aerostatic bearings are test under different working conditions. One non-contact load exerting method based on the principle of aerostatic beaing is proposed, which can exert dynamic or static load on high-speed rotors. The compassion between experiment and theoretical results shows the proposed fluid-solid interaction method has a high calculation accuracy. Compared with the radial gas supply holes, the tangential gas supply holes can reduce the amplitude of the rotor runout, which certifies the correctness of the theoretical analysis of dynamic characteristics. The new type of aerostatic bearings with tangential nonuniform supply holes can improve the system stability. The new type of aerostatic bearings with radial nonuniform district supply pressure can reduce the amplitude of the rotor runout near the first order critical speed, but after the speed the amplitude increases. Under experiment conditions, the exerted load will increase the vibration of the system, and increase the amplitude of the critical speed. For the aerostatic bearings with radial gas supply holes, the amplitude of the rotor runout near the first order critical speed can be reduced with the increase of supply pressure, but after the speed the amplitude increases. For the aerostatic bearings with radial gas supply holes, the increase of supply pressure can improve the system stability.更多还原