【作者】 李美；

【导师】 李仲兴；

【作者基本信息】 江苏大学 ， 载运工具运用工程， 2012， 博士

【摘要】 空气弹簧悬架系统具有变刚度、低振动频率、抗路面冲击的特性,能有效改善车辆的行驶平顺性、乘坐舒适性以及操纵稳定性,还可降低车辆对路面的破坏等性能。在国外,空气弹簧已广泛应用于车辆悬架系统,而在国内,缺乏系统的空气悬架系统设计理论,空气悬架系统的研发能力较低,绝大多数整车及零部件生产企业缺乏空气悬架系统的设计开发能力,影响了参与国际市场竞争。开展空气悬架系统关键部件——空气弹簧系统的关键技术研究,既能满足提高车辆悬架系统性能的要求,又能为我国相关企业参与国际市场竞争提供有力支持,同时推进我国汽车悬架行业的科技进步。以管路连接主副气室的带附加气室空气弹簧系统为研究对象,应用CFD技术对系统内部气体流动进行数值模拟,探索带附加气室空气弹簧系统的动态特性机理。运用有限元分析理论,建立空气弹簧主气室的有限元模型,分析空气弹簧主气室的非线性特性。利用ABAQUS/Standard模块分析初始气压、帘线角、帘线间距和帘线层数对空气弹簧承载性能的影响；用Explicit模块分析空气弹簧主气室的动态特性与弹簧内部初始气压和激振频率的关系。运用均熵修正理论,建立连接管路的动态分布模型,分析管路对气体流动产生的“时滞”效应。综合空气动力学、流体力学和热力学理论,考虑系统部件之间气体流动过程中热量的交换,假设带附加气室空气弹簧系统各部件内的气体压力均匀(整体等效气压),基于变质量系统理论,推导带附加气室空气弹簧系统的振动微分方程,为系统特性分析奠定理论基础。在等效气压模型基础上,研究带附加气室空气弹簧系统的自由振动和受迫振动响应特性。结果表明：系统响应特性受附加气室容积、连接管路内径等因素的影响明显。随附加气室容积的增大,系统的固有频率逐渐降低,当附加气室容积从OL增加至与主气室等容积时,系统的固有频率由1.8Hz降低至1.45Hz；随管路内径的增大,自由振动的周期先增大后减小,连接管路内径为12mm时,系统的自振频率最小,约为1.34Hz；增设附加气室后,系统的自由振动是有阻尼振动,随附加气室容积的增大,系统的阻尼比增大；随着连接管路内径的增大,带附加气室空气弹簧系统的振动衰减变慢,阻尼比减小,说明连接管路的阻尼作用降低。探索CFD与动网格技术在带附加气室空气弹簧系统特性分析中的应用,应用有限体积法对系统内部的三维湍流进行数值模拟,得到带附加气室空气弹簧系统的内部压力场、速度场、温度场等,分析系统内部气体的流动现象和规律,研究带附加气室空气弹簧系统的动态特性机理。根据系统内部流动的数值模拟结果,应用面积加权平均法求解带附加气室空气弹簧系统工作高度位置的等效气压,并与理论计算得到的整个气室等效气压进行对比。结果显示,两者之间存在一定差异。在不考虑连接管路内径影响时,通过数值模拟获得系统工作高度位置的等效气压,在此基础上求解动刚度,并对其进行三维曲面拟合、试验验证及误差比较等,建立工作高度位置等效气压下带附加气室空气弹簧系统的动刚度模型。设计了带有连接管路的带附加气室空气弹簧特性试验系统,提出了带附加气室空气弹簧系统静态特性和动态特性的试验方案,并在INSTRON 8800数控液压伺服激振试验台上对不同连接管路内径、不同附加气室容积的空气弹簧系统进行静态和动态特性试验,得到位移、载荷、气压等随时间的变化关系,求解空气弹簧系统动刚度,并与工作高度位置等效气压下模拟得到的动刚度进行对比,验证了利用局部等效气压求解系统动刚度的准确性。通过试验和动刚度模型分析空气弹簧系统动刚度的影响因素和影响规律,为弹簧系统内部参数的匹配和选择奠定基础。提出两种附加气室容积可调的结构方案,讨论附加气室容积可调的实现方法。更多还原

【Abstract】 Air spring suspension system, mainly characterized in its variable stiffness, lower resonance frequency and road-friendliness, has been applied to vehicle. The riding performance and handling stability of vehicle with air spring suspension system have been improved. Furthermore, the damage to road from vehicle with air suspension system is greatly reduced. In developed countries, air spring suspension system has been widely used. However, domestic research level in this filed lags behind developed countries. Being lack of appropriate design theory, vehicle manufacturing enterprises are short of own intellectual properties about air spring system which affects their international market competitiveness. Priority should be given to key technologies in development of the key component—the air spring. It can not only improve the performance of suspension, provide great support to related companies to participate in international market, but also make the science and technology progress in our national suspension system industry.The research focuses on a complex system, which consists of the main air spring chamber, the auxiliary chamber and the connecting pipe allowing air flow between the two chambers; In order to study on dynamic characteristics mechanism of air spring system with auxiliary chamber, interior air flow is numerically simulated with CFD technology.With the finite element analysis method, a non-linear model of the air spring is established to analyze its special non-linear characteristics. In the Standard block of ABAQUS, the influence of initial pressure, cord angle, cord layers and cord layer spacing on the loading capacity of the spring is analyzed respectively. The results can help to develop and choose the main rubber chamber. In the Explicit block, the dynamic characteristics of the main chamber changing with the initial pressure and exciting frequency is analyzed.With the mean entropy correction theory, the dynamic distribution model of the connecting pipe is derived in order to display the air flow hysteresis, which is caused by the air restriction because flowing in the connecting pipe. On basis of theories of the aerodynamics, fluid mechanics and thermodynamics, the heat conduction in the air flow considered, the vibration differential equation of the spring system under the overall equivalent air pressure is derived with the mass changeable theory, which lays the theoretical foundation for further analysis of the system characteristics.When the equivalent air pressure model is established, the response of free vibration and forced vibration of the air spring system with auxiliary chamber is analyzed. The result shows that the system natural characteristics are related to the volume of the auxiliary chamber and the diameter of the connecting pipe. With the volume of the auxiliary chamber increasing, the system resonance frequency goes down accordingly. To be specific, the auxiliary chamber volume increases from OL to the same volume as the main chamber, the frequency decreases from 1.8Hz to 1.45Hz accordingly. As the diameter of the pipe rises, the free vibration period firstly increases to some extent, then starts to decline, the resonance frequency reaches its lowest value (approximately 1.34Hz) when the pipe diameter is 12mm; As the auxiliary chamber integrated into the system, the free vibration of the system becomes to damping vibration system. When the volume of the auxiliary chamber increases, the system damping ratio will rise. And when the pipe diameter increases, the damping will decrease.The application of the CFD and dynamic mesh technology is explored in performance analysis of the air spring system with auxiliary chamber, and the finite volume method is used to simulate the three-dimension turbulent flow in the system. Consequently, the pressure field, temperature field and velocity field are got. The phenomena and laws of the flow inside the system are analyzed, and the mechanism of dynamic characteristics for the spring system with auxiliary chamber is investigated.With the simulation results of interior flow of the spring system, the area weighted mean method is employed to analyze the equivalent air pressure at the working height position. And it is compared with the overall equivalent air pressure. The result shows some differences between the two methods. Then, without considering the connecting pipe effect, the dynamic stiffness model of the air spring system with auxiliary chamber is established via three-dimension curve fitting, experimental verification and error comparison.An experimental platform for the air spring system consisting of the main air spring chamber, the auxiliary chamber and the connecting pipe is developed based on INSTRON 8800 NC hydraulic servo exciting system. The experimental scheme of the static and dynamic characteristics for the spring system is proposed respectively. On the platform a serial of experiments are carried out under different auxiliary chamber volume and different pipe diameters. The curves of displacement, load, and interior pressure vs time are obtained respectively, the dynamic stiffness is calculated and is compared with that simulated stiffness from equivalent air pressure at working height position. The method calculating dynamic stiffness with the equivalent air pressure at working height position is verified. Experimental method and model simulation are respectively used to analyze the influencing factors towards the spring dynamic stiffness, and all these work will lay the theoretical foundation for matching and choosing for the spring interior properties.Two structural schemes are proposed to adjust the volume of the auxiliary chamber, and methods to adjust the volume are discussed.更多还原