Abstract: The combustion system in a high specific power diesel was studied. Firstly, 3D numerical simulation of the combustion process in the chamber was carried out by AVL-Fire. The WAVE model, the Dukowicz model and the Eddy Break Up model were utilized to predict the fuel atomization, evaporation and combustion processes, respectively, and the k-ε two-equation turbulence model was employed to predict the turbulent flow. The predicted average pressure and effective power agree well with the measured ones, verifying the employed numerical models. Secondly the detailed analysis of the numerical three-dimensional flow field, thermal field and oil distribution during the combustion process were carried out, and the disadvantages of the original combustion system were found out.. The structure of combustion system was modified on the basis of the above-mentioned analysis. Then The modified combustion system was also numerically simulated by using the same numerical models as the original chamber. Finally the numerical results of the original and the modified combustion system show that the performance of the combustion system is significantly affected by the shape of the combustion chamber, and that the combustion organization of the modified combustion system is significantly improved compared with that of the original one, resulting in great increase in the effective power and heat release rate of the combustion system.

Key words: power machinery and engineering, diesel, combustion system, numerical simulation, modification