The Study On The Effects Of Diesel Engine Structure And Material On Psychoacoustics Parameters Of Radiated Noise

Diesel engine can produce a lot of noise while running,which makes it an annoying noise source.Since nowadays people’s demand on auditory comfort has been increasing,sound quality of diesel engine’s noise has been studied.However,most researches were completed by experiments and few of them focused on the influence of structures and materials.Therefore,this paper used loudness,sharpness,roughness and PSIL as evaluation indexes to analyze the influence on sound quality caused by the structural improvements and materials changes.Based on an inline six-cylinder diesel engine,finite elements models of the engine were built using Altair Hypermesh.Then the results of finite elements modal analysis were compared with those results gained by modal tests to make sure the finite elements models were capable for further researches.Based on AVL EXCITE Power Unit,modal reduction of the finite elements models were carried out and the multi-body dynamics simulation model was constructed after different connection units were set properly.After that,the whole engine’s multi-body dynamics simulation was carried out using the pressure inside the cylinder as original motivation while at the same time taking piston lateral force and main bearing force into consideration.The vibration velocity on the diesel engine’s surface was obtained.Using vibration velocity on the diesel engine’s surface as boundary condition,the radiated noise was simulated by LMS Virtual.Lab Acoustics through direct boundary elements method after boundary elements model and the model of radiated noise field were constructed.By analyzing the simulated sound pressure level and sound power level,it could be concluded that the oil pan,cylinder head cover and timing gear cover were the main noise sources on this diesel engine.After structural improvements or material changes were respectively implemented on oil pan,cylinder head cover and timing gear cover,loudness,sharpness,roughness and PSIL of the simulated noise were computed both before and after these changes.Then analyzed the influence on sound quality by comparing the psychoacoustics parameters mentioned above.The results turned out that structural improvements or material replacements on single part of the diesel engine hardly had any influence on PSIL and could only improve part of the psychoacoustics parameters.Therefore,in order to improve sound quality,more than one optimization measures are required.Besides,it also proves that it is possible to study the sound quality of diesel engine’s radiated noise through CAE methods and simulations.