Research On Numerical Simulation Of Structural Noise/Intake Noise And Optimization Design

In order to enhance the level of study on the noise and vibration, especially to deepen the application of numerical simulation technique to the engine and vehicle noise and vibration control, and promote the application of numerical simulation technique to a broader and deeper degree in this research domain, this dissertation mainly focused on the following items in depth and meticulous: the study on engine noise and vibration test method, numerical simulation method, advanced structural optimization, which also involved the applicable engineering problems with actual significance for the enterprises.Systemic study on the method of engine noise source identification was performed in this dissertation, which included the evolution of the vibration velocity method, the supplement of two theory of noise radiation ratio respectively for two types of component, the introduction of the application of sound intensity to the prediction of engine sound power level and identification of noise source.An integrated numerical simulation method was proposed, which comprised of the multibody-dynamic method, finite element method and acoustic simulation method. The comparison of the test result and predicted results validated the precision of this method, and testified the high prediction efficiency. And the application of the integrated method to the low noise engine block design was studied.Taking the engine oil pan as example, the key points in the numerical simulation of noise and vibration for cover-type components was studied, for example the treatment of boundary condition attached with grommet and gasket, the simulation measures of structure and fluid coupling. A new method, namely "Boundary condition linear simplification method" was proposed for the NVH performance simulation of the component, which has complex boundary condition, and two structure-fluid coupling methods were compared. All of these studies supplied actual and reliable numerical simulation approach for the NVH performance of cover-type components.The root of how the intake system noise is caused and the requirement of intake system design were illustrated. The boundary condition used in the 3D simulation of intake system snorkel noise actually is the linear source characteristic, in this dissertation, the determination measures of the linear source characteristic, which included least square method, 1D finite volume method and round piston radiator hypothesis method, were studied, also making a comparative analysis and validation for these three methods. Which make up the extracting methods for boundary condition of intake system snorkel noise 3D simulation at different design phases. Moreover, the method to improve the accuracy of acoustic performance simulation of intake system was studied assisted by the test validation. In addition, the studies included the simulation method of snorkel noise, structural radiation noise, CFD performance and structure modal, which supplied an integrated numerical solution approach for the acoustic and aerodynamics performance of intake system.At last, from the viewpoint of numerical design, the application of structural optimization to the engine block light-weight design and oil pan low noise design was attempted, the topology optimization and shape optimization were involved in the single cylinder engine block light weight design; and the topography optimization was involved in the low noise oil pan design, which explored a path for the application of structure optimization technique to the engine complex components.The studies in this dissertation are pioneering, which has a significant promotion for the enhancement and development of engine low noise and vibration design. It evolves and improves the theory and method of modern design for I.C. engine, and achieves several productions with great engineering application value.