Research On Structural Vibration And Noise Radiation Of Passenger Car Diesel Engine

With the improvement of people’s living standards,there are more and more motor vehicles,and the noise problem is increasingly serious.Continuing strong noise can temporarily reduce people’s hearing,and in severe cases lead to irreversible hearing loss.Internal combustion engine noise is the main noise source of automobiles and motorcycles.A study shows that among the acceleration noise of large and medium-sized automobile vehicles in China,the internal combustion engine noise accounts for about 65%,and the acceleration noise of cars and cars,the internal combustion engine noise accounts for about 55% to 65%.In various engine noises,radiated noise on the engine surface is the main noise.The radiated noise on the surface of the engine consists of combustion noise and mechanical noise.It is the noise generated by combustion and mechanical vibration inside the engine.Combustion noise refers to the noise produced by the combustion of cylinders through the pistons,connecting rods,crankshafts,cylinders,etc.Mechanical noise refers to vibration noise generated by mechanical impact between moving parts such as pistons,gears,and valve trains.Compared with gasoline engine,diesel engine has the characteristics of large torque and low power,and has better power and economy,which is more suitable for daily travel.The vibration and noise of diesel engine is larger than that of gasoline engine.In this paper,a multi-body dynamic model of crank-link mechanism consisting of piston,cylinder,connecting rod and crankshaft are established based on Yunnei Dynamics the diesel engine.At the same time,a simplified finite element model such as the airframe,oil pan,and body cover was established.According to the actual operating conditions of the engine,the multi-body dynamics software was used to analyze the stress history curve of the crankshaft bearing in one working cycle.The load is introduced into the acoustic analysis software to simulate the engine surface vibration and noise.Finally,it is compared with the bench test data to provide reference for the improved design of the engine.The main research content of this article is as follows:Based on the engine parameters provided by Yunnei Power,a three-dimensional model of crankshaft,piston,connecting rod and other crank connecting rod mechanism was established.Assembly of crankshaft,piston,connecting rod body,piston pin,etc.into a crank connecting rod mechanism.At the same time,I performed a modal analysis of the body.The relationship between the kinematics and dynamics of the crank-linkage mechanism was analyzed,and the relationship between the force and the movement of the components in the crankshaft movement was obtained.Based on the multi-body dynamics analysis theory and method,the multi-body dynamics simulation analysis was performed on the crank linkage mechanism.A multi-body dynamics simulation model of crank-link mechanism is established according to the power diagram and rated power of the actual work of the engine.In the post-processing,the displacement,speed and acceleration curve relationships of the piston and the time-load curve of the bearing capacity of the crankshaft main shaft are analyzed.The data on the bearing capacity of the crankshaft’s main shaft is derived in the form of a table,which is used as the input excitation of the engine structure surface vibration and radiation noise.According to the actual parameters of the engine,a simplified body,body cover and oil pan model have been established in consideration of the calculation scale and efficiency.The acoustic finite element model of the engine is established,and the force data of the crankshaft bearing obtained from the multi-body dynamics simulation analysis is imported through the interface.The direct vibration response solver was used to calculate the vibration of the engine structure surface,and the vibration acceleration of the structure surface was obtained.An acoustic-vibration coupling solver is used to calculate the sound pressure level and sound power level at the sound pressure level and field point of the acoustic finite element.A bench test was performed on the engine to actually measure the surface vibration of the engine structure.We compare the measured data with the finite element simulation results to verify the simulation results.Combined with computer simulation analysis and engine bench test,it provides a reference for the engine’s subsequent improved design.