High pressure ignition delay times of H2/CO mixture in carbon dioxide and argon diluent

Experimental and modelling study of hydrogen ignition in CO2 bath gas

“…2. Similar observations were reported by Karimi et al [16] for heavily diluted CO2 mixtures. They associated the hotspots formed in the periphery of the shock tube to the increased bifurcation in these mixtures.…”

“…The small ignition kernels are picked up by the sidewall OH* earlier than the endwall emission. The large internal diameter of the shock tube ensures that the core of the mixture remains unaffected, as reported by Karimi et al [16]. Endwall emission thus responds to the ignition of the core gas as it sees the bulk of the volume [20].…”

“…In contrast to the usual practice where time zero is defined as the midpoint of the reflected shock wave, time zero is defined in this work at the start of reflected shock pressure rise. This is based on inferences from the pressure traces of Hargis et al [15] and Karimi et al [16]. Figure 1 shows a representative sidewall pressure trace for an 85% CO2-diluted H2 mixture at 20 bar from the present work.…”

“…This reaction competes with Reaction 2 (forward direction) for H radicals, thus slowing the rate of the branching reaction and reducing the production of OH radicals. Interestingly, Karimi et al [16] did not observe any significant difference in IDTs of syngas in CO2 vs Ar bath gas.…”

“…Time zero identification is challenging for mixtures with high levels of CO2 dilution, as has been reported in literature shock tube studies [15,16]. Non-idealities from CO2 dilution mainly originate due to the interaction of the reflected shock wave (RSW) with an energy-deficient boundary layer behind the incident shock wave (ISW), thus leading to the bifurcation of the reflected shock.…”