【作者】 韩东江；

【导师】 杨金福；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 动力机械及工程， 2014， 博士

【摘要】 气体轴承支承的高速涡轮轴系具有结构紧凑、轴承功耗低、转速高、功率密度大等优点,广泛应用于空气制冷机、高速永磁电机、微型燃气轮机等高速微型动力设备中。高转速下轴承非线性气膜力引起的气膜振荡是影响轴承-转子系统稳定性的关键问题之一。本文重点开展气体轴承-转子系统稳定分析与实验研究,主要工作内容如下：1.对气体轴承-转子系统稳定性进行定性分析。提出了包含旋转惯性项、轴颈涡动项、轴颈挤压项以及轴承供给压力项在内的有限长气膜力分析模型,以轴颈偏心率为函数给出工程稳定性判别准则及其推论,当ε≤εmax,且dε/dt≤0时,轴承-转子系统在工程上是可以稳定运行的；转子的偏心率在某转速点满足ε≤εmax,且偏心率对转速的导数小于0(即dε/dω≤0),作为转子继续升速的判据。并根据工程稳定性判别准则,从设计阶段和在线调整阶段,给出了提高轴承-转子系统稳定性的措施和方法。2.提出了基于图谱分析的转子非线性振动行为分析方法。以气膜振荡起始点为界,选用不同的图谱来分析气膜振荡前后的动力学特征,给出了气膜振荡发生前不平衡量引起同频涡动的分析图谱和气膜振荡发生后气膜非线性引起低频涡动与振荡的分析图谱,并在实验中验证了非线性振动行为分析方法的有效性和合理性。3.搭建高速气体轴承-转子系统实验台。完成动力单元、实验台本体、振动测试单元以及远程监控单元的设计与搭建工作,其轴系设计转速在60000rpm；实验台能够呈现气膜涡动与振荡等非线性振动现象,实现了轴承气参数可控、可测量,转子的振动数据可在线监测、离线存储与分析,并实现实验现场的远程监控。4.开展气膜约束状态下转子模态实验分析。制定模态实验方案,从激励的选取,测点布置方案的选取,激励与响应信号特征分析以及频响函数估计与评价几个方面论述模态实验过程,实验结果表明：设计转速内,转子平动、锥动、一阶弯曲固有频率随供气压力的增加而增加,且设计转速避开转子一阶弯曲和二阶弯曲临界转速值在合理裕度以上。模态实验结果为轴系升降速实验控制方案的制定,以及后续低频振动特性分析,提供基础性数据支撑。5.开展转速、轴承供气压力、金属橡胶对轴承-转子系统稳定性影响的实验研究。采用非线性振动行为分析方法,重点分析分岔点、分岔点前和分岔点后转子动力学行为特征,结果表明：随着转速的增加,气体轴承-转子系统发生气膜振荡,发生气膜振荡的工频转速在两倍于平动临界转速以上；合理的轴承供气压力能够推迟分岔点,即气膜振荡的起始点,进而提高轴系稳定运行的裕度；金属橡胶垫能够起到进一步推迟气膜振荡起始点的作用,同时降低轴系平动、锥动、一阶弯曲临界转速值及相应的振动幅值,提高轴系稳定性。6.将稳定调整措施在气体轴承支承的高速微型动力设备中进行工程应用验证。实验结果验证了基于图谱分析的非线性振动行为分析方法以及工程稳定判别准则的合理性和实用性。更多还原

【Abstract】 High-speed turbomachinery shafts supported by gas bearing are widely used in high speed micro-turbomachinery, such as air refrigerating machines, high speed permanent magnet motors, micro gas turbines and so on, as it has the advantages of compact structures, low power consumption of gas bearings, high speed, high power density, et al. Gas whip induced by the nonlinear gas film force in high speed state is one of the key issues which affects on the stability of rotor-bearing system. In the following, the thesis presented here concentrates on theoretical analysis and experimental investigation on the stability of rotor-bearing system and the main work of the thesis is as follows:1. A qualitative analysis on stability of gas bearing-rotor system is carried out. The analytical model of gas-film force for finite length journal bearing including the items of rotary inertia, whirling, squeezing and bearing supply pressure is proposed. Engineering stability criterion and its inference are given by function of the eccentricity ratio and it means, when the eccentricity ratio ε≤εmax and dε/dt≤0, rotor-bearing system can be in stable operation state in the engineering and when the eccentricity ratio of rotor meets ε≤εmax and dε/dε≤0at a certain speed, the rotor speed can continue to rise up. According to engineering stability criterion, it presents the methods and measures for improving the stability of rotor-bearing system form the design of bench to the on-line adjustment of stability of rotor-bearing system.2. Based on the spectrum analysis, nonlinear vibration analysis method on the stability of rotor-bearing system is proposed. It means the different spectrum plots are used to analyze the dynamic characteristic of rotor system before or after the speed of bifurcation and gives the analysis methods of spectrum plots of synchronous whirl induced by the residual unbalance before the speed of bifurcation point and whirling and whip induced by nonlinear of gas film force after the speed of bifurcation point. This method is agreement with the experimental data.3. The bench of high-speed aerostatic bearing-rotor was built which included the design and building of unit of power element, test rig, the vibration signal testing and remote monitoring. The bench aims to achieve speeds to60000rpm, control and measure the parameters of bearing gas, monitor the vibration of rotor online and test rig remotely, store and analyze the data of vibration.4. Experimental modal analysis (EMA) was presented in gas film constraint state. It details analysis process including experimental scheme, selection of incentive and arrangement of measuring points, analysis on signal feature of incentive and response, estimation and evaluation of function for frequency response. The results show that the natural frequency of the cylindrical, conical and first bending modes increases along with supply pressure in design speed range and the design speed staggers the speed of first bending while the speed of second bending mode is above the design margin of safe speed. The results of EMA provide evidences for the regulation of run-up or coast-down experimental scheme and the analysis on characteristics of low frequency vibration.5. Experimental investigations of the effect of speed rate, bearing supply pressure and metal rubber on stability of rotor-bearing system were carried out. By analysis method of spectrum plots, the research concentrates on the dynamic characteristics of rotor system in/before/after the speed value of bifurcation state and the results show that when more than twice the cylindrical critical speed is reached, gas whip (i.e. a large vibration) will appear and the speed of bifurcation increases(i.e. gas whip onset speed)with the supply pressure increasing reasonably, thus improving the margin of stable operation of rotor system. The metal rubber pad can achieve to further postpone gas whip occurrence and reduces the cylindrical, conical and first bending critical speed as well as the vibration amplitude, thus improve the stability of rotor system.6. The application of stable adjustment measures of high-speed micro-turbomachinery in engineering field was verified. The analysis of spectrum plots on stability of rotor-bearing system is agreement with experimental results, thus it means the validity and practicability of engineering stability criterion.更多还原