Research On The Influence Of Connecting Rod And The Bearing To Diesel Engine Body Vibration Based On AVL-EXCITE

Diesel engines are widely used as main power supplying equipment in construction machinery,vehicles,ships,etc.Meanwhile,due to the strong vibration and noise generated in itself,diesel engines also contribute a lot in environmental noise pollution.To reduce this influence,good noise and vibration performance becomes an important goal in engine designing.In modern engine designing process,virtual prototype makes it possible to study the relationship between design parameters and optimization value before producing.In terms of vibration performance,connecting rod is a determinant factor because of its position and complex stress condition.Thus exploring the relationship between the working conditions of connecting rod and engine vibration performance can provide valuable direction in low vibration engine development.This paper takes a 6-cylinder diesel engine as research object;the influence on engine vibration with different connecting rod working conditions is studied.First,finite-element models of engine body,crank and connecting rod are constructed using code HyperMesh.Models are verified by modal analysis.Substructure method is used in this case for modal reduction.Based on the mass matrix and stiffness matrix of main nodes obtained in finite-element models,a coupled multi-dynamics model of connecting rod,crank and engine body is built with code AVL-EXCITE.Second,rigid connecting rod model and flexible model are introduced into the multi-dynamics model respectively in this phase.By obtaining the vibration acceleration of different selected positions,the influence of different models on engine vibration is explored.The simulation result shows that when considering flexible model,acceleration value of selected positions drops.Meanwhile,flexible processing makes the main bearing stress in piston movement direction decrease,and peak value of minimum oil film thickness decrease the same time.Using flexible connecting rod model,the influence of bearing clearance on engine vibration and lubrication of bearing itself is analyzed while end-bearing clearance is set to 0.05 mm,0.07 mm and 0.09 mm separately.Simulation result shows there is limited influence(0.03mm—0.09mm)on vibration when bearing clearance changing.However,clearance has impact on shaft centerline orbit,minimum oil film thickness and friction loss: with the clearance increase,the minimum oil film thickness and friction loss decrease.The results demonstrate that the flexibility of connecting rod has an effect on engine vibration performance and main bearing stress.Thus simulation with flexible connecting rod model is more accordant with real situation.Besides,allowed variation in end-bearing clearance has limited effect on vibration,but matters a lot on bearing lubrication.Conclusion of this research will contribute to the low vibration diesel engine development.