Examining the significance of the ignition characteristics of hydrogen and liquefied-petroleum-gas on the reactivity controlled compression ignition and its interspersed profiles induced in an existing diesel engine: A comparative perspective

The present study highlights the comparative analysis of diesel-hydrogen and diesel- Liquefied-petroleum-gas bi-fuel operation. It investigates the ignition delay criterion and its effects on performance, emission, and stability characteristics under varying injection and reactivity phasings in an existing single-cylinder diesel engine. The experimental analysis-based statistical modelling approach for simultaneous identification of relative optimum parametric combination to improve the performance, emission, and stability has been incorporated in this study through response surface methodology. It is evident from the results that the different parametric combinations of input variables for both Liquefied-petroleum-gas and hydrogen-enriched diesel operation influenced the combustion parameter (ignition delay), performance, and emission significantly. Subsequently, the ignition delay corresponding to the maximum hydrogen enrichment scenario is 41.2% more than the corresponding Liquefied-petroleum-gas operational mode. Similarly, the exergetic efficiency attained with maximum hydrogen substitution is 9.54% higher than the exergetic efficiency of the corresponding Liquefied-petroleum-gas enriched operation. On the other hand, the minimum footprints of soot, total unburnt hydrocarbon, Carbon monoxide, and Carbon dioxide registered with hydrogen enrichment were 15.77%, 72.45%, 38.48%, and 2.37% lower than the corresponding Liquefied-petroleum-gas enriched operation. In contrast, the lowest recorded value of oxides of nitrogen with Liquefied-petroleum-gas enriched diesel operation was 77.93% lower than the corresponding hydrogen-enriched operation. Thus, the study presents itself as a first-of-a-kind strategy for the comparative analysis of the effect of ignition delay on the performance, emission, and stability matrices of existing infrastructure with diesel- Liquefied-petroleum-gas and diesel-hydrogen operation.