Evaluating the emissions and performance of two dual-mode RCCI combustion strategies under the World Harmonized Vehicle Cycle (WHVC)

This work compares the emissions and performance of two dual-mode reactivity controlled compression ignition (RCCI) combustion strategies under the World Harmonized Vehicle Cycle (WHVC), a chassis dynamometer version of the World Harmonized Transient Cycle (WHTC) test proposed by the EURO VI emission regulation for heavy-duty engines. The major difference between the two dual-mode combustion strategies investigated is that, while one of them relies on covering with conventional diesel combustion (CDC) the part of the map that cannot be covered by RCCI regime (RCCI/CDC dual-mode), the other does it relying on dual-fuel diffusion combustion (dual-mode dual-fuel). The influence of the gear shifting strategy on the emissions and performance over the WHVC is discussed first. Later, both dual-mode concepts are compared considering the optimal gear shifting strategy. The results suggest that dual-mode dual-fuel concept allows reducing the specific fuel consumption by 7% in average versus RCCI/CDC concept. Moreover, NOx emissions are around 87% lower with dual mode dual-fuel, meeting the EURO VI requirements without the need for an SCR aftertreatment system. In counterpart, HC and CO emissions are near 2 and 10 times greater, respectively, for dual-mode dual fuel than for RCCI/CDC. (C) 2017 Elsevier Ltd. All rights reserved.