Comparison of Characteristic Time (CTC), Representative Interactive Flamelet (RIF), and Direct Integration with Detailed Chemistry Combustion Models against Multi-Mode Combustion in a Heavy-Duty, DI Diesel Engine

Three different approaches for modeling diesel engine combustion are compared against cylinder pressure, NOx emissions, and simultaneous optical diagnostic images from a heavy-duty, DI diesel engine. A characteristic time combustion (KIVA-CTC) model, a representative interactive flamelet (KIVA-RIF) model, and direct integration using detailed chemistry (KIVA-CHEMKIN) were integrated into the same version of the KIVA-3v computer code. In this way, the computer code provides a common platform for comparing various combustion models. Five different engine operating strategies that are representative of several different combustion regimes were explored in the experiments and model simulations. Comparison of simulated cylinder pressure and heat-release rates with the experimental results shows that all the models predict the cylinder pressure and heat release rate reasonably well. All the models predict NOx emissions trends very well but the absolute magnitudes are different from the experimental measurements. A comparison of the model predicted and experimentally observed in-cylinder details is also presented. The KIVA-CHEMKIN model better predicted the details of the flame structure and emissions for the LTC conditions.