Simulation Of Vibration And Noise Of The Engine Valve Train

In recent years, the conventional engine as the main power source of vehicle was developing rapidly in the direction of light weight, high speed and low noise. Valve train is not only one of the core mechanism supporting engine normal operation, but also a main vibration noise sources of the high speed engine, more and more people or engineers pay attention to its vibration and noise. So it's necessary to develop the simulation of vibration and noise of valve train in the design phase, because it will provide theoretical guidance for the structure's low-noise design, and shorten design and development cycles, cutting costs.This article consider an overhead camshaft valve train engine as study object, AVL EXCITE TD software was used for valve train kinematics and dynamic analysis, and utilizing the finite and boundary element method, research engine radiation noise caused by valve train's exciting force.Valve train exciting force mainly include valve seating force, camshaft bearing force, striking force between rocker arm and valve stem and valve spring force and so on. According to the noise generated path, valve train vibration and noise are divided into two categories, one is directly impact or friction noise caused by components interaction, one is engine vibrations radiation noise excited by the exciting force of valve train. AVL EXCITE TD software was used to build a multi-mass kinematic model of valve train mechanism, for evaluating and analyzing kinematics law of the original intake and exhaust cam profile at 1500 RPM, and build a multi-mass dynamic model basic on the kinematic model, for studying valve train's dynamic characteristics when engine speed is at 4000 RPM, 5000 RPM, 6000 PM respectively. Properly simplify and establish finite element model of the engine for constrained modal analysis, studying the first 20 order natural frequencies and mode shapes of the engine. After the previously calculated excitation forces was converted into the frequency domain by FFT, applied them on finite element model of the engine in different load combination forms, creating the engine frequency response analysis model. Then it was solved for extracting vibration velocity of the engine surface under each load combination conditions. Finally, considering the engine surface vibration velocity as boundary conditions, creating boundary element model. The engine noise radiation prediction was studied base on boundary element method, calculating the acoustic power, and radiation efficiency of the engine radiation noise, analyze to find out the main radiation frequency band, separate radiated noise for each exciting force within the main frequency band, identify the main radiation source by analyzing sound intensity distribution color map, providing theoretical guidance for low-noise design of the structure.