Prediction of Physical Delay Period RiDirect Injection Diesel Engine Combustion

A semi-empirical mathematical model for predicting the physical part of ignition delay period in the combustion of diesel engines with swirl is developed. This model is based on a single droplet evaporation model. The governing equations, namely, equations of droplet motion, heat and mass transfer were solved simultaneously using a Runge-Kutta step by step method. The computation was executed until somewhere in the vapor layer around the liquid droplet a near stochiometric mixture of the fuel vapor and air having at least the self-ignition temperature of the fuel formed. The predicted physical delay time for a particular Dl. diesel engine is in good agreement with engine standard data and data in the literature. Also validity of the model is examined with variation of the combustion chamber and fuel injection system data. From the parametric studies it seems that the physical delay period is particularly effected by fuel initial temperature, injection pressure, swirl level, and ambient temperature. Also from examination of the results an algebric relation for quick calculation of physical delay time is derived