Numerical study on convective heat transfer of a spark ignition engine fueled with bioethanol

Spark ignition (SI) engine performances depend strongly on the in-cylinder heat transfer from the combustion gas to the wall in the combustion chamber, especially the convective heat transfer. Thus, the model governing the in-cylinder gas side convective heat transfer of an engine is very important in prediction of the engine performances and it can be developed through the evaluation of the coefficient of heat transfer. This study aimed to contribute to the knowledge in this field for the case of bioethanol fueled engine. Simulation approach was applied in this study, where MATLAB was used as the simulation tool. Two optimized choice of correlations were applied for the evaluation of heat transfer coefficient, which are the Hohenberg's correlation and Eichelberg's correlation. In both correlations, same parameters are required, including the in-cylinder volume, mass burned fraction, in-cylinder pressure, and in-cylinder temperature. All those parameters vary with the crank angle and were determined from the simulation of combustion process with engine geometries from the real engine. According to the graph of the heat transfer coefficient against the crank angle obtained from both correlations, it can be concluded that the convective heat transfer from the gas to the combustion chamber wall in bioethanol fueled engine behaves in a similar manner with gasoline, natural gas and diesel fueled engine. The convective heat transfer changes proportionally with the in-cylinder pressure and in-cylinder temperature. From the comparison graphs, bioethanol fueled engine has a higher in-cylinder convective heat transfer from the start of the combustion process until its peak, but is lower during the end of the combustion process if compared to gasoline fueled engine. © 2014 Elsevier Ltd.