Dual-fuel reactivity controlled compression ignition (RCCI) experiments were performed using a single cylinder, light-duty engine. Diesel fuel was direct injected into a premixed charge of port injected gasoline, E10, or E85. By increasing the amount of ethanol content in the port injected fuel, the reactivity gradient was increased. It was found that combustion phasing could be controlled by adjusting the DI to PFI ratio. By increasing the mass percentage of the low reactivity, PFI fuel, combustion phasing was delayed, allowing for higher loads to be attained. Under gasoline and diesel operation at 9 bar IMEP, gross indicated thermal efficiencies over 50% were achieved with NOx below 0.04 g/kW-hr and near zero soot levels using 48% EGR. Operation with PFI E10 performed similarly to gasoline, but higher thermal efficiencies were observed (>51% with 45% EGR). However, by increasing the amount of E10 to 94% by mass, combustion was late but stable enough to support RCCI operation without the use of EGR. Using E85, 14 bar IMEP load conditions were achieved with and without EGR. With EGR, thermal efficiencies were near 49% with NOx and soot below 0.2 g/kW-hr and 0.005 g/kW-hr, respectively.
RCCI was also tested using DI E10 plus 3% by volume 2-ethylhexyl nitrate (EHN) cetane improver and PFI E10. The additized E10 blend performed similarly to diesel fuel and was capable of achieving controlled PCI operation over a range of conditions, with NOx levels below 1 g/kW-hr. The single fuel E10-EHN RCCI strategy demonstrated a peak efficiency of near 50% at a 9 bar IMEP operating condition.