Emission and combustion performance of anhydrous ethanol jet ignition in an optical single-cylinder gasoline engine

Ethanol and gasoline have long been used as blending fuels, yet their combined application in active pre-chamber (PC) jet ignition systems remains scarcely studied. This work integrates CFD simulations with optical single-cylinder engine (OSCE) experiments to evaluate anhydrous ethanol and gasoline as PC jet-ignition fuels in a port fuel injection spark-ignition engine (2000 rpm, PLFI = 20 MPa, tID = 0.3–0.8 ms). Results show that ethanol yields a lower global excess-air ratio (λPC) but a narrower spatial λ distribution at ignition, indicating more homogeneous in-chamber mixing. Consequently, ethanol promotes earlier jet phasing and shorter main-chamber burn duration, while maintaining comparable jet intensity. Ethanol operation further produces lower combustion temperatures and NO emissions, albeit with higher HC, and its particulate behavior transitions from elevated particle number (PN) at short tID (≤0.4 ms) to substantially lower PN than gasoline when tID ≥0.5 ms. Soot remains negligible in the pre-chamber and primarily originates from gasoline combustion in the main chamber. Overall, the study demonstrates ethanol's potential as a low-carbon jet-ignition fuel that supports efficient, low-temperature combustion and cleaner emissions in spark-ignition engines.