| In the present study, a theoretical model for the spray evaporation in a direct injection diesel engine is developed taking into consideration the unsteady evaporation period. For this purpose, the liquid droplets temperatures, masses and velocities are studied.; Solving the conservation of energy and mass equations together with the equation of state, a set of ordinary differential equations is achieved. These equations are solved using a special numerical technique. This technique, based on a fourth order Runge-Kutta integration method, will be described.; Calculated results are compared with experimental data and were found to be in good agreement. Analysis of the obtained results shows that the combustion chamber constituents temperature is a dominant factor in the spray evaporation process and in shaping the temperature history of the evaporating droplets. The combustion chamber pressure and the spray volume play a secondary role in the evaporation process. Also, it was found that the wet-bulb temperature varied with engine operating conditions, and it could reach the critical temperature by one or more of these factors; preheating the inlet air, increasing the engine speed, and slightly retarding the injection timing from engine specifications. |
