Effect of hydrogen fumigation on combustion stability and unregulated emissions in a diesel fuelled compression ignition engine

The automotive pollution norms throughout the world are getting increasingly stringent, which has made achieving the emissions regulation significantly challenging for the automakers. Additionally, energy security remains a matter of concern for all the economies due to depleting fossil fuels and fluctuating crude oil prices. These factors have motivated researchers to invest resources in the exploration of alternative fuels. Hydrogen has been consistently pitched and researched upon as a viable fuel for the future, meeting all these requirements. In this context, the presented work explores the dual fuel mode combustion in a single-cylinder constant speed engine. Under variation of engine load (25, 50 and 75%) different levels of hydrogen energy substitution are investigated. This study examines the combustion performance of hydrogen diesel dual-fuel through peak pressure location, cycle to cycle variability and combustion noise. The detrimental effects of hydrogen substitution at lower and mid loads are observed on the stability of combustion as cycle to cycle variability of combustion metrics show an increase. Additionally, the effect of hydrogen energy substitution on unregulated emissions like aldehydes and aromatics is reported. These unregulated emissions at these operating conditions are relatively unexplored despite being reported as carcinogens and precursors for soot formation.