The Research On Structure Noise Prediction And Its Optimization Control For Diesel Engine

The vibration and noise of diesel engine has been the key parameter for thediesel engine's performance. The research on structural noise prediction fordiesel engine is an important aspect in the diesel engine's development process.In this paper, a series of researches focused on the prediction of the structurenoise and the acoustics optimization for the diesel engine have been conductedsystemically, which targeted on the diesel engine typed 4120SG.Subjected to the precision of diesel engine structural noise prediction, aseries of researches, which include the simulation of major mechanical forces, theprocessing of contact surface using the finite element method and theconstructing the whole diesel engine's finite element model, have been conductedintensively. (1) The multiple-body dynamics method is employed to compute themechanical forces generated by the crankshaft and valve-train, which overcomesthe shortcoming of the genetic precision; To getting better simulate results, theinfluence of elasticity of the crankshaft and block on the mechanical forces hasbeen intensively discussed, and the effect of oil film on main bearing force hasbeen inspected; The mechanical force induced by the valve-train was measuredthrough employing the strain gauge method on the 4120SG diesel engine. Aftercomparison between the simulating force and the measured force, the simulatingmethod is proved to be right. (2) To solve the problem of how to process thecontact surface of combined structure using the finite element method, thetheoretical research on the dynamic parameters' identification was conducted,firstly. And the dynamic equation and its answer was deduced; Furthermore,targeted on the combined structure of two steel plate, the experiment research andthe parameters identification of contact surface was done; Several processingmethods for the combined surface's dynamic parameters in finite element modelwas proposed and its precision was compared between the test data and numericaldata. (3) The research on how to constructing the whole engine's finite elementmodel with high precision was inspected. Based on the modal testing results of the major parts and combined structure, The correlation analysis of finite elementmodel and the dynamic model updating based on the structure eigenvaluesensitivity analysis have conducted respectively, which guarantees thecorrectness of the whole diesel engine's dynamic model; Finally, the majorcomponents, such as block, oil-pan, cylinder cover, as well as the cover plate forcrankshaft case and tappet case have been built in the finite element model for thewhole diesel engine.To look through the vibration and the radiated noise of diesel engine, therelated vibration and the acoustic test were conducted. The vibration of dieselengine's surface was measured by laser-vibmeter; the noise source identificationfor diesel engine was inspected through the sound intensity data.The vibration and the radiated noise of diesel engine were computed byemploying the finite element method and the boundary element method. Thecontribution of valve-train to the whole diesel engine's vibration was examined.The comparison between the simulating data and the testing data has shown thatthe simulating data has high agreement with testing data at a certain frequency inthe 1000Hz rang. Furthermore, the computed acoustic parameters were analyzed.The comparison of the contour map between the computed data and the testingdata verified that the computed data is correct.The related research on the structural noise optimization was inspectedfinally. Based on the achievements on diesel engine structural noise predictionand the results of sound intensity identification, the acoustic sensitivity analysiswas conducted, which provides the guide for development of low noise dieselengine; The new reduce noise scheme, which realizes through changing theconstrain position of tappet cover plate, has been proposed, and the reduce noiseeffect of this scheme also was evaluated through the boundary element method.