Research On Vibro-acoustic Characteristics And Optimization Of Diesel Engine

The research on vibro-acoustic characteristics of diesel engine has been an important research branch in the field of modern diesel engine technology. Knowing and grasping the vibration and noise performance of diesel engine at the stage of design and doing the vibration response analysis and noise prediction of whole engine based on simulation model have great significance to ensure diesel engine satisfying more and more strict requirements of vibration and noise and to promote competitive capability. Using FEM/BEM to simulate the vibro-acoustic characteristics of 6L16/24 type diesel engine. Through the sensitivity analysis of its main components, the structure modification for reduction of vibration and noise of diesel engine is achieved. In details, the main work is as follows:(1) Through referring to the related literature, the domestic and foreign research status of vibration and noise of diesel engine is presented, and also the theory and method of mechanical vibration and noise prediction is reviewed. Finally FEM/BEM is determined to predict the noise of diesel engine.(2) The 3-D entity models and finite element models of block, cylinder head and oil pan are established, and modal analysis is done respectively. Considering the thin walled parts such as covers etc, the finite element of diesel engine combination structure is established through RBE2 element and MPC algorithm simulating the assembly relation between components, and modal analysis is done also. Comparing to its operational modal analysis, the result verifies that the finite element of diesel engine combination structure is reasonable, which provides a basis for the simulating of vibration and noise of diesel engine.(3) The main loads of diesel engine considered are:air pressure on the bottom of cylinder head, air pressure on the cylinder liner, main bearing force and piston side push force. The influence of system damping is considered by setting the Rayleigh damping coefficient. And vibration response is achieved using ANSYS to calculate the transient response analysis of diesel engine combination structure.(4) The boundary element modal of diesel engine is established. Through the spectral analysis program written by APDL, convert the nodal speed data changes over time to frequency on the surface of structure. And structure radiation noise of diesel engine is calculated by the software of SYSNOISE.(5) The sensitivity analysis of covers of diesel engine is presented by the method of model reconstruction. The transient response analysis and noise prediction are done at the base of reconstructed model. The result shows that surface vibration amplitude of modified structure and sound intensity level of space points have declined, which reached the purpose of reduction of vibration and noise.