【作者】 刘博；

【导师】 毕凤荣； 高俊华；

【作者基本信息】 天津大学 ， 动力工程， 2018， 硕士

【摘要】 柴油机作为动力源在各个领域得到了广泛的应用。近年来,由于能源与环境要求的不断提高,高功率密度柴油机成为发展方向,同时也带来了柴油机运动副摩擦磨损加剧等问题。柴油机连杆小头轴承相比其他润滑轴承,由于冲击载荷高和飞溅润滑供油压力低的特点,轴承润滑情况恶劣,并且轴承距离燃烧室近,轴承工作温度高使得其润滑条件变得更加复杂,因此开展基于热弹性流体动力学(TEHD)模型的连杆小头轴承润滑研究具有良好的研究意义和工程应用意义。本文以某六缸柴油机为研究对象,首先利用Hypermesh软件对活塞、连杆、活塞销和曲柄销进行网格划分,建立有限元模型,利用模态验证方法验证了活塞和连杆有限元模型的准确性,考虑计算效率问题,通过Craig-Bampton子结构法进行模态缩减,保留有限元模型计算所需主节点和主自由度,在AVL-EXCITE软件平台中搭建了活塞—连杆—曲柄销柔性多体动力学模型。然后基于热弹性流体动力学理论通过定义连杆小头轴承供油边界条件和热边界条件建立连杆小头轴承TEHD润滑模型,通过仿真计算得到连杆小头轴承润滑性能评价参数,并与连杆小头弹性流体动力学(EHD)润滑模型计算结果进行对比探究热负荷对轴承润滑性能的影响。并基于连杆小头轴承TEHD润滑模型,探究供油温度、轴承间隙和表面粗糙度对连杆小头轴承润滑性能的影响规律。研究结果表明,热负荷对连杆小头轴承润滑性能有很大影响,计及热负荷的影响,轴承最大油膜压力增加,最小油膜厚度降低,摩擦功耗增加,粗糙峰接触百分比增加,轴承润滑情况恶化,因此基于热弹性流体动力学润滑模型计算得到的连杆小头轴承性能结果更为严苛,在对连杆小头轴承摩擦副失效机理分析研究应基于TEHD模型展开,并且随着供油温度升高、轴承间隙和表面粗糙度的增加,轴承最大油膜压力升高,最小油膜厚度降低,润滑性能变得恶劣,因此在加工设计过程中要尽量降低供油温度,轴承装配间隙和轴瓦表面粗糙度,对改善轴承润滑,降低摩擦磨损,提高寿命都用重要作用。更多还原

【Abstract】 As the power source,diesel engine has been widely used in various fields.In recent years,as the requirement of energy and environment improving,the development direction has turned to the high power density diesel engine.However lots of problems arose during the development such as joint wear and etc.Compared with the other bearings,the connecting rod small end bearing lubrication is poor.Due to the high impact load which it has to bear and the low splash lubrication oil supply pressure,what’s more,as it’s close to the combustion chamber,the high bearing operation temperature makes the bearing lubricate condition more complex.The research on the connecting rod small end bearing lubrication which is based on the thermal elastic hydrodynamics(TEHD)model has good research significance and practical significance.In this paper,a six-cylinder diesel engine was used as the research object.The finite element model was established by using Hypermesh software to model the piston,connecting rod,piston pin and crank pin,and the accuracy of the finite element model of the piston and connecting rod was verified by modal test verification method.Considering the computational efficiency problem,the model condensation was made by Craig-Bampton sub-structure method to retain the master nodes and the main DOFs which were required to calculate,and the flexible multi-body dynamics model of the piston-connecting rod-crank pin was built on the AVL-EXCITE software platform.The small end bearing TEHD lubrication model was established by defining the oil supply boundary condition and the thermal boundary condition of the connecting rod small end bearing.The evaluation parameters of the small end bearing lubrication performance were obtained by simulation calculation.The results in this case were compared with the results which were calculated under the small end bearing elastohydrodynamics(EHD)lubrication model to study the influence of the heat load on bearing lubrication performance.The influence of oil supply temperature,bearing clearance and surface roughness on lubrication performance of connecting rod small end bearing is studied based on the TEHD lubrication model of small end bearing.The results show that the thermal load has a great influence on the lubrication performance of the small end bearing,the maximum film pressure increases,the minimum oil film thickness reduces,the friction power loss and the rough peak contact percentage increase,the bearing lubrication situation deteriorates considering the impact of heat load.The bearing performance which was calculated by the thermal elastic hydrodynamics lubrication model is more rigorous.The analysis of friction pair failure mechanism should be based on the TEHD model.And with the increase of oil supply temperature,bearing clearance and surface roughness,the maximum oil film pressure increases,the minimum oil film thickness reduces,and the bearing lubrication performance get bad.What’s more,in the process of machining design,the bearing assembling clearance and the surface roughness should be reduced as much as possible,besides it plays an important role in improving bearing lubrication reducing friction and wear,and improving parts life.更多还原