Structural Noise Prediction And Analysis Of 4L20 Marine Diesel Engine

The prediction and control of marine diesel engine noise which is one of the most important noise sources on board has become an important research orientation in the field of marine engineering.4L20 marine diesel engine is taken as the object of study, the prediction of structural noise is calculated in the research. And additionally, corresponding advices about noise optimization are given.The paper focuses on the solution of completing prediction calculation of structural vibration and sound radiation of the diesel engine. The study sets up a solid model of crank mechanism, the calculation of exciting forces such as side thrust of pistons and main bearings load is finished with the help of Multi-body Dynamics based on the indicator diagram. And the load of one operating cycle is analyzed. Moreover, the finite element method (FEM) grid is divided on the basis of the solid model of the engine and then ANSYS Parametric Design Language (APDL) is also employed to impose the calculated load whose purpose is to get the structural vibration response and analysis of the surface vibration when ignition is switched on is taken after the calculation. In addition, analysis of serious vibration parts is carried on in frequency domain to provide a basis for low-noise optimization design of diesel. With the boundary condition of the result of vibration response, calculation and analysis of sound radiation of the engine are made with three different projects of the field points and the theory of direct boundary element method (BEM). With a view to radiation situation in near, far field and classic field points with the variety of sound pressure level at different moments, suggestions about structural noise control in severe sound radiation zones (for example oil pan,skirt of engine)are made.Multi-body Dynamic method, FEM, and BEM are taken in the study to measure and calculate of structural noise prediction of 4L20 diesel which could supply reference to the noise prediction and low-noise mechanical design of marine diesel engines.