Simultaneous Reduction of NOX and Soot in a Diesel Engine through RCCI Operation with PFI of n-butanol and DI of Cottonseed Biodiesel

This study presents the combustion and emissions characteristics of Reactivity Controlled Combustion Ignition (RCCI) produced by early port fuel injection (PFI) of low reactivity n-butanol (normal butanol) coupled with in cylinder direct injection (DI) of cottonseed biodiesel in a diesel engine. The combustion and emissions characteristics were investigated at 5.5 bars IMEP at 1400 RPM. The baseline was taken from the combustion and emissions of ULSD #2 which had an ignition delay of 13° CAD or 1.5ms. The PFI of n-butanol and DI of cottonseed biodiesel strategy showed a shorter ignition delay of 12° CAD or 1.45ms, because of the higher CN of biodiesel. The combustion proceeded first by the ignition of the pilot (cottonseed biodiesel) BTDC that produced a premixed combustion phase, followed by the ignition of n-butanol that produced a second spike in heat release at 2° CAD ATDC. The addition of n-butanol into the cycle reduced the compression and peak temperature by 100K and resulted in 35% NOx and 90% soot reduction. Adding 20% cooled EGR further reduced the NOx to a total of 50%. The results suggest that early PFI of n-butanol combined with cottonseed biodiesel resulting in RCCI, may be an effective way of reducing emissions of NOx and soot when compared to the baseline of ULSD #2.