Experimental Investigation of Combustion and Emission Characteristics of Ethanol–Gasoline Blends across Varying Operating Parameters

Ethanol-gasoline is a significant approach to achieving low-carbon combustion engines. In this article, the combustion and emission characteristics of ethanol-gasoline (E22) and ordinary gasoline under varying air-fuel ratios, injection pressures, and ignition timings are experimentally investigated, and the engine performances and combustion characteristics of both fuels are compared under full-load conditions. The results show that the combustion stability of E22 is slightly lower than that of gasoline at different air-fuel ratios, and the ignition delay and combustion duration are slightly longer than that of gasoline, but the thermal efficiency of E22 is higher due to the lower exhaust energy loss. Emission trends with respect to the air-fuel ratio are similar for both fuels, with E22 showing slightly lower carbon monoxide (CO) and nitrogen oxide (NOx) emissions. Moreover, engine performance at medium and high loads is more sensitive to injection pressure compared to low loads. An appropriate increase in the injection pressure can significantly enhance the mixture quality, leading to higher thermal efficiency and lower emissions. Conversely, an excessive injection pressure may result in increased CO and total hydrocarbon emissions (THC). E22 can deliver comparable power to that of gasoline while also achieving an earlier combustion phase and higher thermal efficiency for greater resistance to detonation under full-load conditions. Furthermore, the higher oxygen content of E22 leads to a notable reduction in the intake pressure required.