内燃机结构噪声预测方法的研究/Research on the structural noise prediction of internal-combustio
The structural noise prediction has been an important aspect in the field of internal-combustion engine research. Knowing the radiant level of engine noise at the stage of design and doing optimization of whole engine structural noise control based on simulative model have great significance to insure internal-combustion engine satisfing more and more strict requirements of engine noise and to promote the product competitive capability. Based on 12V230 diesel engine, the research of internal-combustion engine structural noise prediction is done systematically by using FEM and BEM, and the research on structural noise prediction of 12V230 diesel engine is achieved. Furthermore, the vibration and noise of 12V230 diesel engine are measured to validate the correctness of model and the theoretic method. In detail, the main work is as follows:
(1)The actuality of the research of internal-combustion engine structural noise prediction is reviewed firstly after referring to some literature, and then the method and technical path of this research is gived.
(2) The 3-D entity models and the finite element models of main construct of 12V230 diesel engine are established, and the modal analysis is done. Comparing the difference results of modal analysis which considered different element size without the modal experiment, the finite element models of the sump、block、cylinder heads and valve cover are constructed. The combined surface is dealed with the RBE2 and the coupling-node, and then the finite element model of whole engine is built to receive the natural frequencies and mode shapes, which establish the base to structure response analysis and noise optimization.
(3)The main loads of 12V230 diesel engine are calculated, such as cylinder pressure, main bearing force, valve train force, piston impact force and side push force. Then the values, phase angles and positions of these loads have been determined. The response of engine structure is calculated by software of MSC.Nastran. And the effect of valve train to the response of engine structure has been analyzed, which shows the valve train has a relative effect to the response of engine structure.
(4) The boundary element model of 12V230 diesel engine is built, and then the response of engine exterior is imported into the boundary element model. Afterward, we can predict 12V230 diesel engine structural noise and calculate the main acoustic result, such as sound pressure, sound intensity, radiation power and radiation efficiency by software of LMS.Sysnoise. The result shows that the sump and valve cover structural noise is the main part of whole engine radiant noise, so the structural sensitivity and noise optimization are done by the re-calculation method, and the result of optimization is evaluated, which provides the guide for development of low noise internal-combustion engine.
(5) The vibration and noise of 12V230 diesel engine were measured, then the experimental results and the theoretic results are compared to prove that the reliability of internal-combustion engine structural noise prediction by FEM and BEM.