Diesel combustion appears to be the most prominent way to improve fuel efficiency for global CO2 emissions reduction. To achieve this, the combustion inside the cylinder should be studied and the pollutant emissions, especially NOx and soot, need to be considered simultaneously. Over the past, substantial advances have been made in the modeling of combustion in direct injection diesel Engines and the progress is attributed to the development of a new model, which take into account explicitly all the described phenomena. In the current work, the operating characteristics of direct injection diesel engine is studied using Extended Coherent Flame Model for 3 zones (ECFM-3Z) model in a CFD tool named es-ICE, an expert system for internal combustion engines. The present study is validated with the experimental work performed by Colin et. al. The combustion and emission characteristics are studied by varying the swirl ratio. It is found that in cylinder pressure and temperature increases with swirl ratio. NOx emissions increases and soot levels decreases at higher swirl ratio. © 2013 All rights reserved.