Combustion and Emission Modeling for a Direct Injection Diesel Engine

In order to improve the predicting capability of KIVA-3V code for a diesel engine, various numerical models were reviewed. From the comparison of TAB, wave and χ - square distribution models for atomization of a liquid fuel jet, it was found that the wave model was most suitable for predicting a diesel spray because of proper breakup length. The high pressure evaporation model, which considered the air in a combustion chamber as a real gas, predicted earlier ignition about 0.7 °CA than the low pressure model. For the diesel ignition, the Hardenberg model predicted shorter ignition delay than the Shell model and measurements, and the Hardenberg model showed the spatially uniform ignition. For soot emission, the phenomenological models suggested by Foster, Belardini and Hiroyasu were studied. The Hiroyasu model could be used effectively for the prediction of soot emission although it did not provide detailed information on soot formation. The quite different in-cylinder distributions of soot were predicted by the Foster and Belardini models because of their different activation energies for the formation of particle nuclei. In this study, a reaction constant for C₂H₂ formation in the Belardini model was adjusted to match the measurements and the reasonable trend of soot emission with respect to injection timing could be obtained.