A comparative study of chlorine and bromine species addition on the explosion limits of hydrogen-oxygen mixtures

Abstract

In this work, we investigate the effects of chlorine (Cl) and bromine (Br) containing species additions on the pressure-temperature explosion limits of hydrogen-oxygen (H2-O2) mixtures computationally. It is shown that, with the addition of HCl, Cl2, HBr and Br2, the explosion limit evolves from being a non-monotonic Z-shaped curve to monotonic or maintains its non-monotonic response depending on the different types of additives. Specifically, with the addition of HCl to the mixtures, the limit always maintains the non-monotonic structure, while with the addition of around 18% of Cl2, it loses its Z-shaped structure. Compared with HCl and Cl2, more sensitive responses were found for HBr and Br2. With the addition of around 1% of HBr and 0.7% of Br2 to the H2-O2 mixtures, the limit's non-monotonic feature disappears rapidly, and becomes a monotonic curve. Further detailed kinetics analysis explains that after the addition of the halogen species, the radical competitions are different at the low- (P = 1.0 × 102 Pa), intermediate- (P = 1.0 × 104 Pa) and high- (P = 1.0 × 106 Pa) pressures respectively, resulting in the change of the dominant reactions. These findings enhance the understanding of Cl and Br containing species sensitization for the explosion limits of the H2-O2 mixtures and help to understand the kinetic interaction between the H2-O2 system and halogen.