Ignition-delay-time/time-resolved CO2-concentration measurements during the combustion of iC4H10/H2 mixtures

This study measured the ignition delay times of iC(4)H(10)/H-2 mixtures in shock-tube experiments at 1310-1450 K and time-resolved CO2 concentrations by combining tunable diode laser absorption spectroscopy. The aim was to determine the performance of using isobutane as additive in changing hydrogen reactivity. The measured data were compared with predictions based on the three mechanism, namely, AramcoMech 2.0, Hychem model and CRECK mechanism. Results showed that data obtained using AramcoMech 2.0 best agreed with the measured data. Formation-path analyses demonstrated that the three mechanism provided different isobutane oxidation and CO2 formation paths at the selected time point. This study did further comparisons between n-butane and isobutane as additives to check the performance of butane and its isomer in changing hydrogen-enriched-fuel reactivity. Adding isobutane was found to prolong the ignition delay times of hydrogen-enriched mixtures more evidently than adding the same amount of n-butane. Isobutane showed similar initial oxidation as n-butane but had fewer channels through direct unimolecular decomposition. CO2 formation-path analyses based on AramcoMech 2.0 demonstrated that CO + OH = CO2 + H occupies a higher proportion in CO2 formation channels during n-butane combustion than during isobutane combustion at the selected time point.

Automated summary

This study compared the performance of different butane isomers as additives in hydrogen-enriched fuel mixtures through experiments and simulations. The results showed that adding isobutane significantly prolonged ignition delay times compared to n-butane, with differences in CO2 formation pathways at selected time points.