Development of a Mathematical Model for Prediction of Pollutants Emission in D. I. Diesel Engines

Major pollutants emission from Direct-Injection (D.I) diesel engines are predicted by means of a mathematical model. In order to construct such a model, an integral Multi-Zone Combustion Model (MZCM) is formulated, which basically consists of jet mixing and combustion submodels. In MZCM, variation of injection pressure is considered. Also time period of ignition delay is predicted by considering the physical and chemical processes. The MZCM provides input data such as zonal temperature, pressure, and mixture strength to the emission model. In the emission model, the major pollutants in diesel engines, such as Nitrogen Oxides (NOx) and soot particles are evaluated. For calculation of NOx concentration, extended Zeldovich mechanism has been used. For prediction of soot particles concentration, the amount of net soot is calculated by considering the difference between the rates of soot formation and soot oxidation inside zones. Results show that, soot particles form in the fuel rich zones and its oxidation occurs in the oxygen-rich zones of the fuel jet. NOx concentration in the middle zones of the jet (near stoichiometric) is high, while in the tip and tail of the jet is low. For verification, the model is validated with the conditions of typical medium and high speed D. I. diesel engines. The comparison shows a good agreement between the experimental and predicted results.