Characterization of partially premixed combustion with ethanol: Egr sweeps, low and maximum loads

Exhaust gas recirculation (EGR) sweeps were performed on ethanol partially premixed combustion (PPC) to show different emission and efciency trends as compared with diesel PPC. The sweeps showed that when the EGR rate is increased, the efciency does not diminish, HC trace is at, and CO is low even with 45% of EGR. NO_x exponentially decreases by increasing EGR while soot levels are nearly zero throughout the sweep. The EGR sweeps underlined that at high EGR levels, the pressure rise rate is a concern. To overcome this problem and keep high efciency and low emissions, a sweep in the timing of the pilot injection and pilot-main ratio was done at ~16.5 bars gross IMEP. It was found that with a pilot-main ratio of 50:50, and by placing the pilot at -60 with 42% of EGR, NO_x and soot are below EURO VI levels; the indicated efciency is 47% and the maximum pressure rise rate is below 10 bar/CAD. Low load conditions were examined as well. It was found that by placing the start of injection at -35 top dead center, the efciency is maximized, on the other hand, when the injection is at -25, the emissions are minimized, and the efciency is only 1.64% lower than its optimum value. The idle test also showed that a certain amount of EGR is needed in order to minimize the pressure rise rate.