Investigation of the nanostructure and reactivity of soot particulates from diesel/methanol dual-fuel combustion with and without EGR

Abstract

Dual-fuel combustion fueled with diesel and renewable methanol provides a path toward low-carbon transportation in the heavy-duty engine sector. Exhaust gas recirculation (EGR) benefits NO_x reduction in diesel/methanol dual-fuel combustion engines and its introduction may alter soot features. In this work, we therefore examined the impact of EGR on diesel/methanol dual-fuel combustion soot oxidation reactivity and morphological and nanostructural characteristics. The results showed that under a specific experimental setting, the use of EGR increased the primary particle size compared to noEGR conditions. The increment varied from 3.682 nm to 6.609 nm, depending on various methanol substitutions. The soot nanostructure tended toward a more ordered organization by introducing EGR, which is indicated by longer fringe length but smaller fringe tortuosity and separation distance. EGR reduced the fractions of volatile organics and increased the soot ignition temperature. The average activation energies of particle samples with EGR operation increased by 10.2–56.8 kJ mol⁻¹ compared to noEGR operation, indicating a lower soot oxidation reactivity. The reduced oxidation reactivity when applying EGR is highly linked to the more ordered soot nanostructure.