Simulation Study On Engine Noise Radiation

Currently, with increasing attention to the living environment and vehicle vibration noise comfort, as well as a variety of noise and vibration standards and regulations Introduction and upgrade, the vibration and noise control has become an important research direction of modern internal combustion engine design. To evaluate the internal combustion engine vibration and noise radiation levels and optimize the structure of the engine based on the numerical simulation model at the design stage,is very important for Internal combustion engine products to meet the increasingly stringent requirements for noise and enhance the market competitiveness. This paper is based on a 6-cylinder diesel engine for the study, with the comprehensive use of the finite element method, multi-body dynamics and boundary element method for structural vibration and engine noise prediction, to provide reference for structural improvements. The main work is as follows:① Read the related Themes information and theoretical knowledge, analyze historical and current status of the engine structure vibration and noise radiation prediction,determine the content of the research and technology programs;② In considering the simulation time and speed, with the appropriately simplified three-dimensional model, create the finite element model of the engine and do modal analysis. Modal analysis obtain with modal frequencies and mode shape related to engine noise and vibration, which can be used to verify the reasonableness and reference for improvement.③ Build multi-body dynamics simulation model of the engine in ECXITE Power Unit software, combined with the finite element model for flexible multibody dynamics analysis to obtain the main driving forces of the engine. Due to the finite element model of the engine has a large number of degrees of freedom, using matrix static reduction, the degree of freedom model can be reduced from millions to thousands, while ensuring precision at the same time saving time and resources.④ The exciting force in time domain is transformed into frequency domain by FFT, as the response calculation of boundary conditions. Calculation of vibration speed of the engine surface using MSC Nastran software, will be boundary conditions for acoustic simulation. Analysis of the surface velocity distribution, can obtain the structure surface noise radiation intensity in different frequency.⑤ Create the acoustic boundary element model, import engine surface vibration velocity to Virtual. Lab Acoustic simulation software, calculate surface radiation noise of the engine, get the sound pressure, sound intensity and sound power and radiation efficiency at sound field points, combined with the frequency response analysis results, provide a reference for the improvement of structure.