Effect of Fuel Spray Characteristics on Combustion and Emission Formation in a Large Medium Speed Diesel Engine 982583

In this study the effect of spray characteristics such as spray penetration, spray cone angle and Sauter Mean Radius have been shown to influence fuel vapor distribution, vapor mixing in air and combustion chamber gas turbulence. The effect can be seen in the combustion results, i.e. cylinder pressure, heat release, cumulative heat release, fuel vapor concentration, soot and NOx-formation.

In KIVA2-CFD code the Magnussen EDC ( Eddy Dissipation Concept ) model were used for the fuel vapor and soot particles combustion, the Tesner & Magnussen model for the soot formation and the extended Zeldovich model for the NO-formation. Mainly the modified TAB-model or alternatively χ-squared droplet distribution method (DDM) were used for the spray. The TAB-model constants and the initial SMR in the DDM-model were varied logically in order to obtain different kinds of spray characteristics and accordingly different spray behavior in combustion and non-combustion cases. In the non-combustion cases spray penetration, spray cone angle and droplet size were compared with the corresponding empirical correlation values. After that some cases were computed with the combustion in order to see the effect on the combustion results and the emission rates. The cylinder pressures and heat release rates were compared with the corresponding experimental data.

The combustion results show that by using such TAB-model constants set, which provides a large enough spray penetration, droplet sizes and spray angle, thus a high enough gas turbulence, air motion in combustion chamber and fuel vapor mixing corresponded well with the combustion results