Application of Transient Temperature vs. Equivalence Ratio Emission Maps to Engine Simulations

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. 1
   Soot and soot precursors (C₂H₂)
2. 2
   Nitrogen oxides (NO and NO₂)
3. 3
   Unburnt intermediates (CH₂O, H₂ and CO)
4. 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. Correlations between the 0D maps and the engine simulation results were then examined by plotting the T-ϕ conditions in all computational cells of the CFD simulation on the maps. The map approach is a useful tool for visualizing the links between in-cylinder T-ϕ conditions and emission levels, and to identify conditions that promote efficient, low-emission engine operation.