Exploring the effect of methanol and ethanol on the overall performance and substitution window of a dual-fuel compression-ignition engine fueled with HVO

Abstract

All sectors where compression-ignition engines are the predominant technology are undergoing a complex change motivated by the transition to a carbon-free economy. Nevertheless, these engines, if operated under advanced combustion strategies and fueled with low carbon-intensive fuels, are a real opportunity. This work investigates the effect of two renewable short-chain alcohols (methanol and ethanol) on the performance, emissions, combustion pattern and energy substitution window of a dual-fuel engine operated at high and low loads. Diesel-like fuels include a hydrotreated vegetable oil to evaluate the potential of its high cetane number in dual-fuel mode. The work was executed in two stages. In the first, the operating parameters (EGR rate, combustion phasing) were adjusted for attaining the best compromise between engine efficiency and NOx emissions. In the second, the maximum achievable substitutions were sought, achieving higher substitution ratios than those found by others. HVO-ethanol pair led to the highest substitution (84%), although generally methanol showed superior results in NOx and thermal efficiency. HVO and high alcohol ratios broke down the existing trade-off between large and small particles, leading to a simultaneous reduction of large (more than one order of magnitude) and small (three times lower) compared to only diesel or HVO fueling.