Features of the Inhibition of Hydrogen-Air Mixtures by Propylene Additive

Small additions of hydrocarbons, such as propylene, which are widely studied as combustion and explosion inhibitors of hydrogen-air mixtures, sometimes exhibit specific properties. The known mechanism of the inhibitory effect of these additives is associated with the intensification of the termination of branching chains due to the addition of hydrogen atoms; however, conditions also exist in which these compounds, instead of inhibiting, have a neutral and even promoting effect. Such conditions and the reasons leading to the fact that inhibition is practically absent have not yet been studied. This article shows the results of numerical modeling, which make it possible to more fully outline the range of conditions where the addition of propylene practically does not inhibit hydrogen-air mixtures and outline possible reasons for this effect. The solution to three model problems is presented: self-ignition in a constant-volume reactor, laminar flame propagation, and gas ignition with a heated wire. The calculations are carried out with the detailed kinetic mechanism of chemical reactions NUIGMech 1.1 (2020). The objects of the study are three air mixtures containing hydrogen in amounts of 15, 29.6, and 50 vol % (lean, stoichiometric, and rich mixtures, respectively) without additives and with the addition of 1% propylene.