Research On The Vibro-acoustic Performance And Influencing Factors Of Highly-intensified Diesel Engine

The NVH performance of highly-intensified and high-power diesel engines,a kind of power source for military vehicles,is of vital importance.In the early stage of design of internal-combustion engine,vibration analysis and acoustic radiation prediction should be conducted,the vibro-acoustic performance during operation should be comprehensively understood and the influence of structural design parameters on the vibro-acoustic response of the whole engine should be explored,which are all significant to guide the design of the engines with low vibration and noise.In this paper,a highly-intensified V-type diesel engine is taken as the research model,and the structural vibro-acoustic performance is deeply studied by the comprehensive application of FEM,Multi-body Dynamics,WBT(Wave Based Technique)acoustics and other methods.The main works includes:(1)The finite-element model of the whole diesel engine is established to conduct the simulation of the coupling boundary of the assembly.Theoretical and experimental modal analysis of the whole engine and components is carried out to verify the rationality of the finite-element model.Modal reduction of the whole engine,connecting rod and crankshaft parts is carried out to obtain a structural condensation model.(2)The vibro-acoustic analysis of diesel engine is started based on EXCITE platform.In the Piston&Rings module,the piston body dynamic model is established by considering the radial-stiffness,lubrication and thermal factors of piston,and the vibration load of piston-liner is calculated;In the Power Unit module,the piston slap force is calculated using piston dynamics model.Considering the flexibility of the whole engine,the connecting rod and the crankshaft,the multi-flexible dynamic model of the whole engine is established,and the vibration results of the structure surface are obtained by simulation;In the Acoustics module,the WBT method is used to establish the acoustic model of the whole engine and predict the structural radiation noise.(3)Based on the structural vibro-acoustic simulation model of the whole engine,the influence of different modeling methods on the vibration noise of the connecting rod is studied,which shows that the flexibility of the connecting rod as a core transmission component has a damping effect on the excitation energy.Therefore,flexible body modeling is used in the flexible multi-body dynamics modeling of the whole engine;The influence of running speed and load on vibro-acoustic of the whole engine is studied,so as to fully understand the vibration and sound performance of diesel engine at work;The important design parameters of the core components in the excitation energy transfer process—the sensitivity of the piston pin-offset,the piston-liner clearance and the main-bearing clearance to the vibro-acoustic response of the whole engine are studied,and the optimal design scheme is obtained.The optimized structural radiation noise is significantly reduced in the 1500?3000 frequency domain,and the whole engine reduces0.69 d B(A)in the calculation of the sound power level in the frequency domain.