An Investigation of Ignition and Heat Release Characteristics in a Diesel Engine Using an Interactive Flamelet Model

A multidimensional model is employed to model ignition and heat release rates in a Diesel engine. An interactive flamelet model is employed to model combustion. Nheptane is used as a representative fuel for Diesel fuel in the computations. Comparisons of computed and measured results are presented for a range of engine operating conditions: speed 1200 rpm, start of injection 12.5 degrees before top dead center to 9.5 degrees after top dead center and intake air temperature of 340-360 K. The primary objective of this work is to assess the ability of the model to reproduce ignition timings. The flamelet model uses detailed chemical kinetics and it is shown that it can reproduce the qualitative trends of changes in ignition delay and heat release rates with respect to changes in operating conditions of the engine. The capability to reproduce the measured changes in ignition delay is important because changes in injection timing lead to changes in ignition timing. Changes in ignition timing, coupled with changes in injection pressure and EGR, are employed to control NO and soot emissions in the engine. The interactive flamelet model is able to predict these changes.