Characterization of Partially Premixed Combustion

The influence of charge stratification on the spectral signature of partially premixed combustion in a light-duty optical engine

“…By moving from HCCI to PPC regime, the thermal contribution increases. Most likely, the latter is due to locally increased equivalence ratios (closer to stoichiometric) that give rise to enhanced formation of soot [3]. Furthermore, OH*, CH* and C 2 * chemiluminescence intensities all increase upon increasing charge stratification (as a consequence of moving from HCCI to PPC).…”

“…PPC is a promising combustion concept allowing to reduce both NO x and soot emissions while providing high combustion efficiency. By and large, the low NO x emissions result from the low combustion temperature, whereas the low soot emission is a result of increased premixing (with respect to conventional CI engines) [2][3][4][5][6]. However, many details of the incylinder phenomena are still to be explained and evaluated.…”

“…The broadband chemiluminescence did also correlate with the equivalence ratio quite well in both HCCI and PPC regimes, suggesting that the total emission in the spectral region of 330-400 nm can serve as a proxy of equivalence ratio and the rate of heat release. Regarding C 2 * chemiluminescence, we see two different chemical mechanisms for formation of C 2 * in the PPC regime: first during the early stage of combustion by the breakup of bigger molecules engines, relies on a relatively long ignition delay (ID) to achieve a partially premixed charge [1][2][3][4][5][6]. PPC is a promising combustion concept allowing to reduce both NO x and soot emissions while providing high combustion efficiency.…”

Implementation of the Partially Premixed Combustion concept in a 2-stroke HSDI diesel engine fueled with gasoline

“…This strategy was implemented by Nissan under the name of Modulated Kinetics (MK) [8,9] and also by Lund University [10]. In both cases, simultaneous reductions in NOX and soot emissions were observed for medium-to-high load points.…”

“…In both cases, simultaneous reductions in NOX and soot emissions were observed for medium-to-high load points. Nevertheless, the range for simultaneous reduction of NOX and soot by introducing high EGR rates was very narrow, and a sharp decline in engine efficiency due to high CO and HC emissions and poor combustion phasing was observed in most cases [10].…”