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The main purpose of this study is to investigate the effects of exhaust gases on different combustion modes in DI, Direct Injection, compression ignited engines in terms of combustion efficiency and emission formations. The conventional parametric Φ -T (Equivalence Ratio-Temperature) emission map analysis has been extended by constructing the transient maps for different species characterizing the combustion and emission formation processes. The results of the analysis prove the efficiency of different combustion modes when EGR loads and injection scenarios.

The main purpose of this study is to apply the parametric φ-T (Equivalence Ratio-Temperature) map analysis coupled with 3D engine simulations to characterize different combustion modes in DI, Direct Injection, compression ignited engines in terms of combustion efficiency and emission formations. The conventional static map analysis has been extended by constructing the parametric maps of a dynamic nature for different species characterizing the combustion and emission formation processes. The results of the analysis prove the efficiency of different combustion modes when injection parameters were varied from early to retarded injections.

The effect of ammoniac deoxidizing agent (Urea) on the reduction of NOx produced in the Diesel engine was investigated numerically. Urea desolved in water was directly injected into the engine cylinder during the expansion stroke. The NOx deoxidizing process was described using a simplified chemical kinetic model coupled with the comprehensive kinetics of Diesel oil surrogate combustion. If the technology of DWI (Direct Water Injection) with the later injection timing is supposed to be used, the deoxidizing reactants could be delivered in a controlled amount directly into the flame plume zones, where NOx are forming. Numerical simulations for the Isotta Fraschini DI Diesel engine are carried out using the KIVA-3V code, modified to account for the “co-fuel” injection and reaction with combustion products. The results showed that the amount of NOx could be substantially reduced up to 80% with the injection timing and the fraction of Urea in the solution optimized.

In order to acquire knowledge about temperature vs. equivalence ratio, T-ϕ, conditions in which emissions are formed and destroyed, T-ϕ parametric maps were constructed for: 1 Soot and soot precursors (C2H2) 2 Nitrogen oxides (NO and NO2) 3 Unburnt intermediates (CH2O, H2 and CO) 4 Important radicals (HO2 and OH) Each map was obtained by plotting data from a large number of simulations for various T-ϕ combinations in a zero-dimensional, 0D, closed Perfectly Stirred Reactor, PSR. Initially, the influences of elapsed reaction time, pressure and EGR level were examined, varying one parameter at a time. Then, since both the elapsed time and pressure change in an engine cycle, the maps were constructed according to engine pressure traces obtained from Computational Fluid Dynamics, CFD, simulations. Since the pressure is changing in elapsed time intervals the maps are called transient.

This paper reports the numerical studies of self-ignition and early combustion process of n-heptane sprays under various diluted air conditions. The numerical simulations employ a detailed chemistry approach, coupled directly with the computational fluid dynamics (CFD). A “subgrid” Partially Stirred Reactor (PaSR) model has been developed to account for the turbulence-chemistry-interaction. This model has been implemented into the KIVA3V CFD code. A detailed chemical mechanism of reduced size (65 species and 273 elementary reactions) for the n-heptane fuel has been derived and applied to the simulations of spray combustion. The studies focus on sprays injected into a high-pressure constant-volume chamber. Firstly, the validation of the current numerical model has been carried out for the case in which the injection and initial conditions are similar to those used in the “classical” Aachen experiments (50bar and 800K).