Computational Prediction of NO_x Reduction Characteristics of Premixed Lean Diesel Engine

Three-dimensional computations were carried out to study the effects of engine operating conditions on NO_x emissions from premixed lean diesel combustion in a DI (Direct fuel Injection) engine. A modified version of the KIVA II computer code was used for numerical simulations. Qualitatively good agreement between computational and experimental results of the spatial distribution of impinging fuel sprays, the heat release rate, and the relative NO_x mass have been achieved. The computational results demonstrate that NO_x emissions are significantly influenced by intake air temperature, fuel injection timing, and fuel ignitability. It was also shown that fuel droplets which enter the squish region can later contribute to unburned fuel emissions.