Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2009.2078.2087DjavareshkianM.H.GhasemiA.112009911The objective of this study, is to simulate spray flow with different break-up models and investigate the processes of spray breakup and mixture formation. Effect of these models on the DI diesel engine combustion and performance is also investigated. The 3 Dimensional Naiver-Stokes equation is solved with SIMPLEC algorithm. An eddy break-up combustion model and a diesel auto-ignition model were implemented to simulate the ignition and combustion process in a diesel engine. All the simulations were carried out by the use of FIRE CFD tool. Results were validated via., available experimental data for OM_355 DI diesel engine for mean cylinder pressure. The results show that there have been good agreements between experiments and the CFD calculations. The research demonstrated that practically all the break-up models are capable of simulating the spray processes, as long as model constants are properly chosen and they affect the combustion simulation results.]]>Andreassi, L., S. Ubertini and L. Allocca,2007Baritaud, T.,1997Baumgarten, C.,2006Brink, A., C. Mueller, P. Kilpinen and M. Hupa,2000Burger, M., G. Klose, G. Rottenkolber, R. Schmehl and D. Giebert et al.,2002Dukowicz, J.K.,1979Dukowicz, J.K.,1980FIRE.,2006Kunsberg-Sarre, V.C. and R. Tatschl,1998Liu, A.B. and R.D. Reitz,1993Liu, F.S., L. Zhou, B.G. Sun, Z.J. Li and H.J. Schock,2008Naber, J.D. and R.D. Reitz,1988Pilch, M. and C.A. Erdman,1987Pirouzpanah, V.,2003Post, S.L. and J. Abraham,2002Reitz, R.D. and F.V. Bracco,1982Su, T.F., M.A. Patterson, R.D. Reitz and P.V. Farrell,1996Tatschl, R. and H. Riediger,1998Tatschl, R., H. Riediger and M. Bogensperger,1998Tatschl, R., H. Riediger, V.K. Sarre and N. Putz,2000Tatschl, R., C.K. Sarre and E. Berg,2002Ueki, H., M. Ishida and D. Sakaguchi,2005Barata, J.,2008