【作者】 李德水；

【导师】 闫兵；

【作者基本信息】 西南交通大学 ， 车辆工程， 2010， 硕士

【摘要】 曲轴是柴油机中的重要组成部分,其振动是引发内燃机振动的重要因素,它的性能直接影响着柴油机的可靠性和寿命。近年来,随着各种新技术的应用,对内燃机的可靠性和动力性要求越来越高,已有的曲轴轴系振动分析方法越来越难以完全满足内燃机设计的要求。因此,对曲轴轴系振动问题的更精确、更全面的研究显得非常重要。本文以某一小型柴油机曲轴系为研究对象,模态分析理论为基础,分别对曲轴系在自由状态和约束状态下的多种情况进行试验模态分析。结合试验模态分析的结果,探讨曲轴系各种动态特性仿真建模方法的优缺点。并在发动机运转状态下,对联轴器的扭转刚度、负载的转动惯量和活塞连杆与曲柄销等接触处的润滑情况等因素对曲轴系扭转振动的影响进行了研究。本论文的主要工作如下：首先,对某一小型柴油机的曲轴轴系在自由状态和约束状态下的多种情形进行模态敲击试验,并对其进行模态参数识别。将自由状态和约束状态下各种情形的模态试验结果进行对比分析。通过对比分析得出飞轮对曲轴的模态影响较大；主轴承及其润滑油膜的约束支撑刚度对曲轴的弯曲和纵向振动影响较大,对曲轴的扭转振动影响较小。因此可通过对自由状态下带飞轮、皮带轮及活塞连杆曲轴的模态试验来获得运转状态下曲轴的扭转振动模态特性。其次,以柴油机曲轴系实物为原型,在三维建模软件Pro／Engineer中建立曲轴系的三维实体模型；同时,将曲轴系实体模型导入有限元软件ANSYS中建立其自由状态和约束状态下的多种动态特性仿真计算有限元模型,并对其进行计算模态分析。通过与模态试验结果的对比分析,探讨自由状态和约束状态下各种动态特性仿真建模方法的准确性、优缺点及适用情况。最后,在发动机运转状态下,对联轴器扭转刚度、负载转动惯量及活塞连杆与曲柄销接触处的润滑情况等因素对曲轴系扭转振动的影响进行了研究,得出了轴系扭转振动频率随联轴器扭转刚度、负载转动惯量及润滑变化的规律。更多还原

【Abstract】 As an important part of diesel engine, the vibration of crankshaft is an important factor causing engine vibration, the performance of which directly affects the engine reliability and life. In recent years, with the application of new technologies on engine, the requirements for engine’s reliability and power performance have become higher and higher. The existing analysis method of engine vibration is difficult to satisfy the requirements of engine design. Therefore, it is very important to study the vibration of crankshafts more accurately and comprehensively.It focuses on the crankshafts of a small diesel engine, and then tests the model of crankshafts in free state and constrained state based on modal analysis theory.Combining with the results of experimental modal analysis, disscusses the advantages and disadvantages of dynamic characteristics simulation modelling methods for crankshafts. Then in engine’s operating condition, studies the influence of coupling’s torsional stiffness, load’s moment of inertia and lubrication conditions on crankshafts torsional vibration.The main contents are as follows:Firstly, it focuses on the crankshafts of a small diesel engine and tests the crankshafts model in free state and constrained state, and the modal parameters of crankshaft in different states are obtained. Then compares and analyzes the modal test results of free state and constrained state. From the contrastive analysis we know that the flywheel has great effect on crankshafts modal characteristics, moreover, the crankshaft’s bending and longitudinal vibration is affected by the restraining and supporting stiffness of main bearing, which has little effect on the crankshafts torsional vibration.Therefore,we can get the torsional vibration mode characteristics.of opreating crankshafts from modal tests on the crankshafts with flywheel, pulley, piston and connecting rod in the free state.Secondly, take diesel engine crankshafts as physical prototypes, create a series of three-dimensional solid model of crankshafts using the three-dimensional modeling software of Pro/Engineer. At the same time, take the solid model of crankshafts into the finite element software of ANSYS to build the dynamic characteristics simulation models in free state and constrained state and calculate the crankshafts modals. From the contrastive analysis with modal test results, disscusses the dynamic characteristics simulation modelling methods of crankshafts which is more excellent and applicable.Finally, in engine’s operating condition, study the influence of coupling’s torsional stiffness, load’s moment of inertia and lubrication conditions on crankshafts torsional vibration. From the studies, we can obtained the variation of torsional vibration frequencies changed with coupling’s torsional stiffness, load’s moment of inertia and lubrication conditions.更多还原