| 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.
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