刚柔耦合多体动力学在四缸车用柴油机中的运用

【作者】 李东海；

【导师】 沈颖刚；

【作者基本信息】 昆明理工大学 ， 动力机械及工程， 2007， 硕士

【摘要】 多体动力学广泛应用于航天、车辆、机器人等机械系统中，多刚体动力学已经得到了成功地应用。随着机械系统朝着轻质、高速、大型和复杂的方向发展，系统的运行速度加快，运行精度的要求越来越高，将部件作刚体假设的多刚体系统动力学已无法解释系统复杂的动力学形态，因此对柔性体部件的研究成为了广大学者的研究重点。曲轴柔性对动力学响应的影响在柴油机动力学分析中并不多见，本文尝试将刚—柔耦合多体动力学方法应用于柴油机的曲轴动力学响应及扭转振动、活塞敲击及二次运动中。本文以4100QB柴油机为研究对象，从多体动力学理论上全面系统地分析了柴油机活塞—轴系的多体动力学响应，并在Adams软件中建立实体模型。为了提高计算的精度，对曲轴进行了有限元分析，利用模态叠加原理，使模型中的曲轴刚性体转化为柔性体，并将曲轴的柔性体加入动力学响应中，计算出了主轴承及连杆轴承的受力情况，证明了利用柔性曲轴计算的结果精度更高，更能反映真实情况。由于曲轴的运行环境及结构特性非常复杂，所以在研究曲轴扭转振动的过程中必须考虑到曲轴柔性对扭转振动的影响。面对理论研究相当成熟的扭转振动，作者先建立了Rayleigh模型，进行了扭转振动计算。并在多体动力学软件Adams中进行了曲轴扭转振动分析。将两者计算出的数据与实验数据对比分析，得出Rayleigh法在主、强谐次中计算的结果与实际吻合较好，而用Adams计算的其它谐次结果与实际吻合较好，所以在计算曲轴扭转振动分析中要结合两种方法的优点来提高计算结果的精度。采用试验方法获取了敲击点处的点迁移率特性，并结合多体动力学方法分析获得了活塞和缸套敲击点处的等效质量、等效刚度和等效阻尼，建立了活塞敲击过程的动力学模型，综合考虑缸内燃气压力、连杆作用力、活塞和缸套的摩擦力，利用Matlab语言对活塞敲击力及活塞二次运动进行计算和分析，获得与柴油机实际运转工况较为接近的活塞敲击力。同时利用adams软件分析了活塞偏置量及质量对活塞敲击力的影响。更多还原

【Abstract】 The Multibody System Dynamics widely apply in astronautics, the vehicles, the robot and so on in the mechanical system, the multi-rigid dynamics already obtained have applied successfully. Is facing the light quality along with the mechanical system, high speed, large-scale and the complex direction develops, the system running rate speeds up, the movement precision request is more and more high, makes the rigid body supposition the part the multi-rigid body systems dynamics to be unable to explain the system complex dynamics shape, therefore to flexible body part research into general scholar’s research key. The crank flexibility sees not much to dynamics response influence in the diesel engine dynamics analysis, this article will attempt just - the supple coupling Multibody System Dynamic method to apply in the diesel engine crank dynamics response and the torsional vibration, the piston rap and two movements.This article take the 4100QB diesel engine as the object of study, theoretically systematically has comprehensively analyzed the diesel engine piston - shafting Multibody System Dynamics response from the polysome dynamics, and establishes the full-scale mockup in the Adams software. In order to enhance the computation the precision, has carried on the finite element analysis to the crank, using modality principle of superposition, causes in the model the crank rigid body to transform as the flexible body, and joins the crank flexible body in dynamics response, calculated the main bearing and the connecting rod bearing stress situation, had proven calculates the result precision using the flexible crank to be higher, can reflect the real situation.Because the crank movement environment and the structure characteristic is extremely complex, therefore must consider the crank flexibility in the research crank torsional vibration process to the torsional vibration influence. Facing fundamental research quite mature torsional vibration, the author has established the Rayleigh model first, Has carried on the torsional vibration computation. And has carried on the crank torsional vibration analysis in Multibody System Dynamics software Adams. Data and empirical datum contrast analysis calculates which both,Obtains theRayleigh law the result which in host, in the strong harmony time calculates and actual tallies well, but other harmony inferior result which calculates with Adams and actual tallies well, therefore must unify two methods in the computation crank torsional vibration analysis the merits to enhance the computed result the precision.Used the testing method to gain the drop-point place spot transport ratio characteristic, and unified the Multibody System Dynamic method analysis to obtain the piston and the cylinder jacket drop-point place equivalent mass, the equivalent stiffness and the equivalent damping, has established the piston rap process dynamics model, overall evaluation cylinder internal combustion gas pressure, connecting rod action, piston and cylinder jacket friction force, carries on the computation and the analysis using the Matlab language to the piston rap strength and the piston two movements, obtains with the diesel engine actual operation operating mode closer piston rap strength. Meanwhile has analyzed the piston bias quantity and the quality using the adams software to the piston rap strength influence.更多还原