Hydrogen Use in a Dual-Fuel Compression Ignition Engine with Alternative Biofuels

Abstract

Recent progress has been made towards decarbonisation of transport, which accounts for one quarter of global carbon dioxide emissions. For the short to medium term, new European Union (EU) and national energy and climate plans agree on a strategy based on the combination of increasing shares of electric vehicles with the promotion of sustainable fuels, especially if produced from residual feedstock and routes with low or zero net carbon emission. Hydrogen stands out among these fuels for its unique properties. This work analyses the potential of using hydrogen in a dual-fuel, compression ignition (CI) engine running with three diesel-like fuels (conventional fossil diesel, advanced biodiesel (BD) and hydrotreated vegetable oil (HVO)) and different hydrogen energy substitution ratios. The results were confronted with conventional diesel operation, revealing that dual-fuel combustion with hydrogen demands higher exhaust gas recirculation (EGR) rates and more advance combustion, leading to a remarked reduction of NOx emission at the expense of a penalty in energy consumption due mainly to unburnt hydrogen and wall heat losses. Unreacted hydrogen was ameliorated at high load. At low load, the use of BD dual combustion permitted higher hydrogen substitution ratios and higher efficiencies than diesel and HVO.