A key challenge for the practical introduction of dual-fuel reactivity controlled compression ignition (RCCI) combustion modes in diesel engines is the requirement to store two fuels on-board. This work demonstrates that partially reforming diesel fuel into less reactive products is a promising method to allow RCCI to be implemented with a single stored fuel. Experiments were conducted using a thermally integrated reforming reactor in a reformed exhaust gas recirculation (R-EGR) configuration to achieve RCCI combustion using a light-duty diesel engine. The engine was operated at a low engine load and two reformed fuel percentages over ranges of exhaust gas recirculation (EGR) rate and main diesel fuel injection timing. Results show that RCCI-like emissions of NOx and soot were achieved load using the R-EGR configuration. It was also shown that complete fuel conversion in the reforming reactor is not necessary to achieve sufficiently low fuel reactivity for RCCI combustion. Overall engine brake thermal efficiency (BTE) was found to be slightly lower than for conventional diesel combustion (CDC) at the same overall fueling rate; however, increasing fumigant energy fraction (FEF) was shown to improve BTE. The presented data illustrated that further system optimization could allow R-EGR-based RCCI combustion systems to achieve BTE parity with CDC operation while maintaining extremely low engine-out soot and NOX emissions.
Bibliographical noteFunding Information:
This work was funded in part by The Minnesota Corn Growers Association (grant #1078-16EU) and the National Science Foundation (grant #1350709). The authors would like to thank our colleagues at the Thomas E. Murphy Engine Research Laboratory at the University of Minnesota.
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