Effect of the Cetane Number on the Combustion and Emissions of Diesel Engines by Chemical Kinetics Modeling

Abstract

A seven-step chemical reaction mechanism of di-tertiary butyl peroxide (DTBP), a type of cetane number improver, was combined with a reduced diesel surrogate fuel mechanism to model the effect of the cetane number on diesel ignition. The DTBP concentration in diesel fuel was tuned up to modify the cetane number. A chemical reaction solver, SENKIN, was used to display the ignition delay of diesel fuel containing different DTBP concentrations. It was learned that DTBP advances the ignition timing of diesel fuel under different pressures, temperatures, and equivalence ratios. The effect of advancing becomes more evident with a higher DTBP concentration. The combined mechanism of diesel surrogate fuel with DTBP was coupled in KIVA-3 V2 code to model the effect of cetane numbers 50−64 on the ignition timing, in-cylinder pressure, rate of heat release, engine-out NOx, and soot emissions of a Euro 4 diesel engine under different conditions. The simulation results revealed a sound agreement with the experiments. For the engine equipped with a common rail multiple injection, the increase in the cetane number advances ignition for the pilot injection; it has a negligible effect on the combustion process for the main injection and post-injection. The engine-out NOx and soot emissions are almost unchanged.