The modeling of engine processes continues to develop as our basic understanding of the physics and chemistry of the phenomena of interest steadily expands and as the capability of computers to solve complex equations continues to increase [1] A new generation of computer based methods has been emerged for calculating the detailed pattern of gas flow, heat transfer and combustion in reciprocating  engines by solving numerically the governing partial differential equations representing the conservation laws.

The gas motion inside the engine cylinder plays a very important role in determining the thermal efficiency of an internal combustion engine. A better understanding of in cylinder gas motion will be helpful in optimizing engine deign parameters [2].

In this paper, an attempt has been made to study the combustion processes in a compression ignition engine and simulation was done using computational fluid dynamic (CFD) code FLUENT. An Axi symmetric turbulent combustion flow with heat transfer is to be modeled for a flat piston 4-stroke diesel engine. The unsteady compressible conservation equations for mass (Continuity), axial and radial momentum, energy, species concentration equations can express the flow field and combustion in axisymmetric engine cylinder.  Modeling with variation of initial swirl ratios along with combustion was analyzed in formulating and developing a model for combustion process.