Modeling Ignition and Combustion in Direct Injection Compression Ignition Engines Employing Very Early Injection Timing.

Abstract

An ignition and combustion model has been developed to predict the heat release rate in direct injection compression ignition engines employing very ealy injection timing. The model describes the formation of ignitable or combustible fuel-air mixture by turbulent mixing, and includes five chemical reactions, including low-temperature oxidation. The KIVA II computer code was modified with the present ignition and combustion model. The numerical results obtained by the modified code indicate that the model developed in this work reproduces major features of two-stage autoignition, as well as experimentally observed trends in NOx and unburned fuel emissions. The computational results showed that NOx emissions are significantly influenced by fuel injection timing. The results also indicated that fuel droplets which enter the squish region possibly become unburned fuel emissions. The relationships among the in-cylinder fuel spray distributions, fuel-air equivalence ratio, temperature, and mass fractions of NO and unburned fuel can be demonstrated by the graphical results included in this work.