The Modal Analysis And Structural Improvement Of YC485Q Diesel Engine Block

The cylinder block is the main backbone of diesel engine. The vibration of cylinder block has a great impact on the complete machine’s vibration, noise radiation and strength. Researching the dynamic characteristic of cylinder block plays an important guiding role for the vibration, noise control and strength design of diesel engine.In this paper, YC485Q diesel engine block is the research object and the research content is the component part of Yuchai cooperation project. Using experimental modal analysis and finite element modal analysis method combination to research the dynamic characteristic of YC485Q diesel engine block. Also research the combination of modal analysis for cylinder block and cylinder head. The improving measures are put forward against the cylinder block’s weak positions and has carried on the finite element analysis, obtained a good improvement effect. The specific contents of the research are as follows:1. The cylinder block was supported freely, and experimental modal analysis for cylinder block was carried out by the method of SIMO. Collecting and processing the data through IMAS4.2modal analysis system. Using the frequency domain identification method to identify the modal parameter. And get the first six order natural frequencies, damping and modal shaps. Under the excitation of combustion pressure, cylinder block dose not appear resonance phenomenon when diesel engine work. By natural frequency, modal distribution of the cylinder block is relatively dense.2. Using ANSYS software to achieve the parametric modeling of cylinder block by command input mode. After validating cylinder block model is correct through the static analysis, solving the calculated modal of cylinder block with the same test boundary conditions. Comparing the result of finite element modal analysis results and the experimental modal analysis and the results are identical with each other, which shows that the finite element model of cylinder block is correct. Through modal shaps analysis shows that cylinder block skirt has obvious vibration and small stiffness. So cylinder block skirt is the main research object of vibration control.3. After validating the model of cylinder block and cylinder head are correct through the test, completing the cylinder block, cylinder head and other parts of the assembly in ANSYS software by the splicing technology of command flow. ANSYS modal analysis ignores the nonlinear factors. This article adopted equivalent contact area method to simulate the nonlinear problem of bolt connection. After the modal analysis solution, obtain the first six order modal frequency and modal shap of combination mode. The result shows that The original cylinder block of modal shap play a leading role in the combination mode. After assembly with cylinder head, the vibration of the cylinder block skirt does not improve. 4. Against the obvious vibration problems of cylinder block skirt, comparing several improvement schemes, finally chooses the method that increase trapezoidal frame at the bottom of cylinder block to improve the cylinder block. Increase the trapezoidal frame on the cylinder block and the combination model of cylinder block and cylinder head, then carry out the finite element analysis. The result shows increasing the trapezoidal frame improves large the modal frequencies of the two structure. And the vibration of cylinder block skirt are well controlled.This article research significance lies in:the preliminary study is carried out about the parametric modeling of cylinder block. The relevant data of modal analysis and the structure improvement scheme of cylinder block can be used for reference in the engineering.