Study On Motorcycle Engine Knocking Noise Radiation Simulation

Currently, with the increase of vehicle performance requirements of customers, aswell as the increasingly stringent emission regulations, the vehicle vibration and noiseproblems are becoming increasingly prominent. Motorcycle engine knock radiationnoise has become an aspect of motorcycle product quality that consumer complain. Thisissue has been concerned by each motorcycle manufacturers. With the development ofcomputer technology, it has become possible to ascertain the level and position of pistonknock noise radiation in the engine design phase. This method point out the directionfor the structural vibration and noise reduction, and make it possible to design an enginewith reasonable noise level.At present, piston knock noise simulation methods are mainly finite elementmethod (FEM) and boundary element method (BEM) based on computer numericalcalculation. Based on a certain type of motorcycle engine as the research object, Thisarticle use the finite element method, boundary element method on the simulation to theengine piston knock noise prediction.Noise radiations generated by the vibration, but vibration come from theincentives in cylinder. Based on the accurate exciting force, we can obtain the moreaccurate knocking radiation noise.First of all, this article centre on the exciting force oncylinder, the exciting force simulation on cylinder is discussed in detail in this article.The incentive status and exciting force on piston knock is obtained. Afterwards, engine3D model and finite element model is established. By the modal analysis, this articlegets the engine sensitive modal frequency and the modal vibration mode. In addition,knocking exciting force that obtained from simulation converts to frequency domain.And load it into the engine. So, the frequency response calculation of engine iscompleted, the engine vibration velocity spectrum is obtained. Finally, engine surfaceboundary element grid is established. Frequency response calculation result is taken asboundary condition to calculate engine knocking noise. The article gets the engine noiselevel, radiation efficiency, noise source area.By means of CAD/CAE technology, the knocking noise simulation can predictnoise radiation in the engine design stage, without frequent trial-manufacture, test.According to noise control target of the product, we design reasonable enginestructure, indicate the direction of noise reduction.