| Diesel engines are widely used in various industries due to their compact structure,high thermal efficiency,and low operating and maintenance costs.With the development of technology,modern diesel engine design not only aims for high power density,but also low pollution,low emissions,low noise,and high reliability.The diesel engine consists of various fixed and moving parts,of which the main role of the crankshaft connecting rod mechanism is to convert the thermal energy generated by the combustion of fuel into mechanical energy,and its operational stability is essential to the overall performance of the engine.Therefore,it is indispensable to study the dynamic characteristics of the crankshaft connecting rod mechanism and the vibration and noise it causes under conditions that simulate its actual operation as closely as possible.In this paper,a multi-rigid body dynamics model of the crankshaft connecting rod mechanism was established for a 620V8 diesel engine,and its correctness was verified by comparing it with the calculation results of the traditional particle force method.Based on this model,the crankshaft and connecting rod were softened using the finite element method,and the effects of crankshaft connecting rod deformation on the piston side thrust,total crank pin force and main shaft bearing force were investigated.At the same time,the dynamic stress distribution and overall deformation of the crankshaft and connecting rod were analyzed.Based on the rigid-flexible coupling dynamics model of crankshaft and connecting rod softening,the effect of crankshaft rotation inhomogeneity on the dynamic characteristics of the crankshaft connecting rod mechanism was investigated by using cylinder pressure drive instead of constant speed drive.Based on the sliding bearing fluid film elasticity theory,the diesel engine main bearing oil film elasticity parameters were obtained.Then,the effect of main bearing oil film elasticity on the dynamic characteristics of the crankshaft connecting rod mechanism was investigated by using a spring support to simulate oil film elasticity instead of the original rigid support.Finally,the piston side thrust and main shaft bearing force were obtained from the above dynamics models respectively,which are loaded onto the finite element model of the whole machine for transient response analysis,and then the boundary element method was applied to calculate the radiated noise of the whole machine caused by the crankshaft connecting rod mechanism,and then the effects of crankshaft connecting rod deformation,crankshaft rotation inhomogeneity and main bearing oil film elasticity on the vibration noise of the whole machine were explored one by one. |
PDF Full Text Request