Effects of diesel injection strategy on natural gas/diesel reactivity controlled compression ignition combustion

The effects of diesel injection strategies on the combustion and pollutant emission characteristics of amodified heavy-duty reactivity controlled compression ignition engine fueled with natural gas/diesel arestudied. Natural gas with low reactivity is assumed to be inducted into the engine through the intakeport, while diesel fuel with high reactivity is directly injected into the engine using a double injectionstrategy. Several parameters were studied including the premixed natural gas amount, thefirst andsecond injection timings and the injected diesel mass split between the two injections. The resultsshowed improved engine efficiency with reductions in soot and oxides of nitrogen emissions could beachieved with the injection strategies studied, but hydrocarbons and carbon monoxide emissions weredeteriorated. Three factors, namelyfirst start of injection timing, second start of injection timing and thediesel injection fuel fractions, had pronounced effects on reactivity controlled compression ignitionengine combustion performance and emissions. To reduce soot and oxides of nitrogen emissions,increasing the natural gas percentage, advancingfirst and second starts of injection timing beyond acertain point and increasing fuel fraction infirst start of injection timing are preferred, but they had anadverse effect on hydrocarbons and carbon monoxide emissions.