Strength Analysis Of Al Cylinder Head Considerd Multi-Field Coupling

In design of diesel engines the performance of engine is often easy to achieve the requirements, but its duaribility and reliability are relatively hard to reach the expected objectives. The cylinder head is the most complicated in the components of a diesel and its service life affects seriously the performance of diesel. The structure of cylinder head is subjected to the pre-stress of bolts, the thermal load and the pressure of the gas. Therefore the thermal and strength analyses of the cylinder head under the working conditions are very significant for optimization of the diesel engine.A finite element model of cylinder head, including cylinder head, cylinder line, crank case, bolts, cooling water jacket and valve seat rings is bult with Pro/E. The solid meshes of thermo-mechanical coupling analysis are got by ANSYS and the fluid domain grids of CFD analysis are gained by Gambit. Then the heat transfer analysis of cooling water jacket is carried out using software FLUENT. According to the result, the convective boundary conditions on the surface of the water jacket are obtained. On such basis, the thermal analysis of cylinder head is conducted with reference to data of the experience. After defining contact surfaces between different components, the finite element model is obtained on the basis of solid meshes. Two different types of contact models for the interference-fit of valve seat and cylinder head are discussed. The strength analysis of cylinder head is carried out under the thermal-mechanical coupling loads. The result shows that the high stress zones exist around the valve guides holes that should make a special consideration in diesel design. Finaly, the low cycle fatigue life of the cylinder head is predicted.