New thermo-mechanical analysis of cylinder heads using a multi-field approach

The results of a thermo-mechanical analysis of a natural gas, internal combustion engine cylinder head are presented in this paper. The results are pertinent to the evaluation of overheating damage in critical areas. The three-dimensional geometries of the cylinder head and the water jacket were modeled by means of a computer-aided engineering tool. Commercial finite element and computational fluid dynamics codes were used to compute details of mechanical stress in the head and flow details in the cylinder and cooling jacket, respectively. A six-cylinder, four-stroke diesel engine and a spark-ignition natural gas engine were modeled over a range of speeds at full load. Computed results, such as maximum allowable cylinder pressure, output power, BMEP and BSFC, were validated by experimented data in the diesel engine model. The results were in good agreement with experimental data. The results show high stresses at the valve bridge. Cylinder head temperatures and comparison of output power with high stress measurements, often exceeding the elastic limit, were found at the valve bridge.