Numerical simulation studies on performance, soot and NOx emissions of dual-fuel engine fuelled with hydrogen enriched biogas mixtures

Abstract

This study analyses the effects of hydrogen concentration enriched biogas on indicated engine cycle work, soot and NOx emissions of dual-fuel engine. The results show that if advance injection angle of the engine is fixed at the same value as biogas only mode operation, peak value of in-cylinder pressure increases significantly but indicated engine cycle work is only slightly improved with an increase in hydrogen concentration. Optimum advance injection angle decreases as increasing hydrogen concentration in the fuel mixture. At a given engine speed, NOx emissions decrease with increasing equivalence ratio whereas soot emissions increase almost proportionally with the equivalence ratio. At a given equivalence ratio, NOx emission increases with the increasing hydrogen concentration in fuel mixture whereas soot emission decreases contrarily. The maximum soot peak value is obtained with slightly rich mixture at equivalence ratio of around 1.1. Lean burn mixture and high hydrogen concentration result in extremely low soot concentration. Soot emission is practically negligible at equivalence ratio of about 0.9 and 20% hydrogen concentration in mixture with biogas. As hydrogen concentration increases, the decrease of optimum advance injection angle reduces simultaneously both soot and NOx emissions.