Experimental Study of the Impact of Ethanol Content on Partially Premixed Combustion With Ethanol-Gasoline Blends

As ethanol production increases and the demand for gasoline in spark ignition engines decreases over the next few decades, the use of these fuels in compression ignition systems is expected to increase. This raises the question of how much ethanol-in-gasoline is the right blend for compression ignition. This work experimentally studied E10, E30, E50, E75, and E100 in a split injection partially premixed compression ignition strategy. It was found that, separately, the cool flame reactivity of E10 and the high cooling potential of E75 and E100 enable heat release rate control in partially premixed combustion. E30 and E50 did not show the same control authority. E30 performed the worst due to having a small amount of cool flame reactivity and a low cooling potential. It was found that NOx emissions were not significantly impacted by ethanol content, but the smoke emissions were. E100 produced near zero smoke, but all the ethanol-gasoline blends produced some smoke. When 20% of the fuel was injected during the mid-dle of the compression stroke, E10, E30, E50, and E75 all produced low, but nonzero smoke emissions. When the second injection was moved near top dead center, the smoke emissions of E75 stayed low but the smoke emissions of E10, E30, and E50 all rose to a filter smoke number greater than 0.3. These results indicate that low- and high-ethanol content gasolines are both viable paths forward for partially premixed combustion systems, but medium-ethanol content gasolines should be avoided.