Impact of short-chain alcohols on carbonyl emissions in dual-fuel compression ignition engines

• Total carbonyl emissions remain stable with up to 35% alcohol energy replacement. • Formaldehyde and acetaldehyde were the predominant carbonyls, representing 74–98% of total concentration. • Biodiesel + Methanol yields a broader range and higher concentrations of carbonyl compounds. • Dual-fuel mode with low C alcohols has a minimal effect on specific reactivity. This study investigated the impact of methanol and ethanol on carbonyl emissions from a single-cylinder diesel engine operating under dual-fuel mode. Fourteen carbonyl compounds were investigated, with formaldehyde and acetaldehyde dominating the emissions. Moderate amounts of alcohol did not significantly affect specific carbonyl emissions. However, higher ethanol concentrations increased carbonyl emissions, especially when using ethanol and biodiesel. Specific reactivity, a measure of the potential impact of pollutants on atmospheric ozone formation, was quite similar for all fueling conditions tested, despite some of these conditions notably increased total carbonyl emissions. Thus, contrary to expectations, dual-fuel mode had a minimal effect on specific reactivity, even at high alcohol substitution ratios. This result suggests that using light alcohols in dual-fuel CI engines does not increase the atmospheric reactivity of exhaust gases, and their use in decarbonizing heavy-duty CI engines seems viable, even considering future emission standards for unregulated emissions like carbonyls.