A comprehensive study of fuel reactivity on reactivity controlled compression ignition engine: Based on gasoline and diesel surrogates

Based on three-component gasoline surrogates and five-component diesel surrogates, the effects of fuel reactivity of port injection fuel and direct injection fuel on combustion and emission characteristics of reactivity controlled compression ignition (RCCI) mode were systematically studied. The research octane number of port injection fuels and cetane number of direct injection fuels were modulated by changing the proportions of n-alkanes and iso-alkanes in surrogates. The results show that both the cetane number of direct injection fuel and research octane number of port injection fuel played the key role in the combustion phase of RCCI mode. When port injection fuel with research octane number <= 90, the low temperature heat release would occur. For premixed ratio of 0.8 and with RON70/CN55 as fuel, the CO emissions were the lowest (as low as 1585 ppm). Increasing the premixed ratio was an effective solution for suppressing NOx and particulate matter emissions. For premixed ratio increased from 0.4 to 0.8, the peak value of nuclear mode particulates decreased from 10(9) to 10(7). Increasing the cetane number of direct injection fuels or lowering the research octane number of port injection fuels inhibited the emissions of formaldehyde, acetaldehyde, ethylene, propylene, acetylene and 1,3-butadiene effectively. Port injection of low research octane number was beneficial to reducing indicated specific fuel consumption. Fuel combination with port injection of RON70, direct injection of CN55 and premixed ratio of 0.8 was recommended taking into account of fuel consumption, and regulated/unregulated gas emissions.