Assessment of non-thermal termolecular reactions on H₂/air detonation cell size

Previous numerical studies by Taylor et al. (Proc. Combust. Inst. 34 (2013) 2009-2016) have shown that thermally equilibrium chemical kinetic models may be insufficient for modeling detonation. The computed detonation cell sizes and cell regularity differ from experimental observations, indicating that the chemical kinetic model overestimates both the rate of energy release and its sensitivity to temperature behind detonation shocks. To resolve this discrepancy between the numerical detonation cell size and experimental observations, numerical simulations were conducted in this work on a two-dimensional adaptive grid with a detailed thermochemical reaction model for a premixed nitrogen-diluted hydrogen-oxygen mixture. Following the procedure described by Tao et al. (Proc. Combust. Inst. 38 (2021) 515–522), non-thermal reactions were included in the macroscopic kinetic model as chemically termolecular reactions facilitated by the H + OH radical-radical recombination and H + O₂ radical-molecule association reactions. Comparison of the simulated detonation cell widths between the different cases suggests that non-thermal reactivity can lead to a noticeable increase in gaseous detonation cell-size. As such, it is important to properly account for non-thermal reactions in simulations of H₂/air detonations.