Design Of Light And Medium Diesel Engine Block

The cylinder block is an important component of engine,which plays the role of skeleton in the working process.The realization of engine function is based on the permission that the cylinder block is reliable enough.Nowadays,the engine performance has been improved continuously and the vehicle demanding has been upgraded continuously.In order to meet engine functions' requirements,the design of cylinder block should be improved.Based on the typical failure modes of light and medium diesel engines,this paper discusses the design concepts of main bearing wall,cylinder bore,water jacket,lightweight and engine mounting from the perspective of reliability.And then,the paper proposes the improvement programs,which are verified by simulation or test.Sub-model simulation method was implemented to confirm the failure reason of the main bearing wall.In order to meet the requirements,improvement programs which could enhance the local structural rigidity had been adopted,such as increasing screw length of main bearing bolts and increasing the thickness of main bearing.The optimization scheme had been verified by simulation analysis and fatigue test.Cylinder bore deformation shapes and failure risks were analyzed,and the key parameters of bore deformation were confirmed.In order to meet the requirements,improvement programs which could reduce deformation had been adopted,such as balancing wall thickness,optimizing cylinder head bolts arrangement,and strengthening the rigidity of cylinder roof.The optimization of bore deformation had been verified by simulation analysis and measurement.The influence of water jacket structure on the cooling capacity of cylinder block was evaluated by some parameters,such as flow rate,convective heat transfer coefficient and cooling uniformity of each cylinder.And some improvement programs were implemented,such as increasing the water distribution chamber and adjusting the throttle hole of the cylinder cushion,etc.The cooling capacity of the water jacket was compared and analyzed by simulation and test.Different lightweight methods were evaluated by some parameters,such as modal frequency,vibration velocity,and the critical role of skirt wall thickness and the bottom structure on NVH was confirmed.The cylinder block design should ensure the balance between lightweight and NVH through keeping key parameters,so as to obtain the best matching scheme between lightweight and NVH.The crack failure of cylinder block was analyzed,which showed the truth that the changing of vehicle mounting system had a great impact on the reliability of cylinder block.In order to meet the boundary requirements of the vehicle,improvement programs had been adopted,such as optimizing screw hole position and strengthening local structural stiffness.