Multi-Component Modeling of Diesel Fuel for Injection and Combustion Simulation 2013-24-0007

Accurate simulation tools are needed for rapid and cost effective engine development in order to meet ever tighter pollutant regulations for future internal combustion engines. The formation of pollutants such as soot and NOx in Diesel engines is strongly influenced by local concentration of the reactants and local temperature in the combustion chamber. Therefore it is of great importance to model accurately the physics of the injection process, combustion and emission formation.

It is common practice to approximate Diesel fuel as a single compound fuel for the simulation of the injection and combustion process. This is in many cases sufficient to predict the evolution of the in-cylinder pressure and heat release in the combustion chamber. The prediction of soot and NOx formation depends however on locally component resolved quantities related to the fuel liquid and gas phase as well as local temperature.

The AVL FIRE CFD code has physical sub models for multi-component spray evaporation and multi-component combustion implemented. This work presents the validation of these models under realistic IC engine conditions. For this purpose five binary mixtures of Decane and Hexadecane were considered. The simulation results for the binary mixtures are compared against experimental data recorded in a special optical test engine. It is shown that an optimization of the parameters of the multi-component spray model could improve the predictions for liquid-length and spray penetration over a wide range of injection pressures as well as combustion chamber pressures and temperatures. The basic ignition and combustion behavior of these mixtures was simulated and compared to the experimental results from the optical test engine. Comparisons for ignition delay and flame lift-off-length are presented.