Diesel Engine Connecting Rod Small End Bearing Lubrication Performance Research Based On The Thermal Elastic Hydrodynamics Model

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.