A Research On Prediction And Reduction Of Radiated Noise From Engine Cylinder Head Cover

With the development of the automobile industry, people require better NVHperformance of Vehicle，which gives the designers a higher challenge. At the same time,the CAE technology, including the finite element method and boundary element method,has been widely used in the design process of engine and its parts. The CAE technologycan predict vibration and noise from product design and development stage，guide thedesign and development of engine and its parts, short the development cycle, improvethe efficiency and quality of product development， greatly save the cost of design,which not only adapt to the rapidly changing market demands, but also enhance themarket competitiveness.In this paper, by application of CAE analysis technology at the engine design anddevelopment stage, radiated noise from the structure of cylinder head cover, andvibration and radiated noise weak links were investigate; meanwhile, on the conditionthat engine parameters and the overall structure of engine has been determined,Cylinder head cover can’t carry out major structural changes, and even if it carry outmajor structural changes, vibration and noise reduction is also limited, the materialreplacement of the cylinder head cover is researched. Comparing radiated noise fromthe structure of cylinder head cover with different material was carried out to illustratethe material parameters and material damping’s effect on the radiated noise. The maincontents and conclusions are as follows:1） Based on employing first order element and second order element withdifferent grid size on cylinder head cover body, by Contrasting results of FEM modaland modal test, the selection of discrete element was accomplished, which ensure thecorrectness of the finite element mesh model.2） Based on mastering the modeling method of the finite element mesh model,second-order element was employing on the discretion of cylinder head cover body atits design stage. The dynamic characteristics and a reliable finite element mesh model ofthe head cover body were obtained, which laid the foundation for its vibration andradiated noise prediction.3） Aim to obtain the boundary conditions of the vibration frequency response ofthe cylinder head cover, the transient FEM model of Engine powertrain mountingsystem at4000rpm was established. 4） Based on establishing a reliable finite element mesh model, Forced response ofcylinder head cover were accomplished by imposing the displacement boundaryconditions on itself, which laid the foundation for the prediction of radiated noise.Based on the BEM model of cylinder head cover, radiate noise of cylinder head coverwas predicted by using FEM forced response result.5）By comparing FEM forced response results of cylinder head covers withdifferent material, the results indicate that: Octave resonance phenomenon was occurredbetween0Hz to1000Hz, the descending order of vibration of the cylinder head cover:the PA6_E6000-type cylinder head cover、the PA6_E9200-type cylinder head cover、the AZ91D-type cylinder head cover、the ZL101-type cylinder head cover；Thedescending order of vibration of the cylinder head cover between1000Hz to3000Hz:the ZL101-type cylinder head cover、the AZ91D-type cylinder head cover、thePA6_E6000-type cylinder head cover、the PA6_E9200-type cylinder head cover, mainlybecause of the damping action.6） By comparing the results of radiate noise of cylinder head covers with differentmaterial, the results indicate that: The descending order of the acoustic performance ofthe cylinder head cover:PA6-type cylinder head cover、the AZ91D-type cylinder headcover、the ZL101-type cylinder head cover；material damping play a key factor inacoustic performance；PA6damping reduces vibration and noise obviously between1000Hz to3000Hz; the options for low-noise materials of the cylinder head cover:preferred PA6, followed by magnesium alloy, and finally aluminum.