Experimental investigation on the effect of EGR rate variation on emissions in optimized PCCI-DI diesel engine

Abstract

Combustion in diesel engines is focusing towards unexplored combustion concepts where innovative combustion ideas are being developed following several engine control factors. Advanced low temperature combustion engines for automotive applications are one of the improvements in this regard. The test was conducted on a single cylinder, four stroke and air cooled diesel engine. The scope of this study is to investigate the impact of EGR rate variation (25%, 35% and 45 % EGR rates) on emission reductions in PCCI-DI diesel combustion approach showing a reduction of NOx–soot trade-offs than the conventional diesel combustion approach. The PCCI-DI diesel combustion in this setup is optimized applying the algorithm of grey relational analysis together with Taguchi method. This investigational setup used a methanol port injection and advanced injection timing for PCCI formation. Emission results from different EGR settings in the optimized PCCI-DI combustion scheme were analyzed and compared using surface and contour plots. From the experiment higher EGR rate resulted a decrease in NOx productions but an increase in HC, CO and smoke due to the combustion mode of the experimental setup. The study indicated that excess EGR application should be avoided to have an optimum PCCI-DI combustion having lower emission results.