The opposite influences of flame suppressants on the ignition of combustible mixtures behind shock waves

Experimental study of chemiluminescence in UV and VIS range at hydrogen-oxygen mixtures ignition

“…In this study, for the first time, a significant increase in the intensity of nonequilibrium radiation in the range of spectra 210-415 nm at ignition of hydrogen in the presence of inhibiting additions of halogenated hydrocarbons, was experimentally observed. Thus, the assumption of a mechanism for inhibiting the ignition of hydrogen by quenching excited radicals [7] is hardly justified, and the real mechanism of inhibition, as shown in [5,6], is the capture of the primary radicals by inhibitors. This work was supported by the grant of the RNF -№ 14-19-00025.…”

“…To analyse the possible mechanisms of amplification of nonequilibrium UV radiation with the addition of inhibitors to the hydrogen-oxygen mixture, numerical simulation of the kinetics of ignition of the investigated mixtures was carried out using the Chemkin code and kinetic mechanisms proposed in [12] for a hydrogen-oxygen mixture without additives and with the addition of CO2, and in a recent paper [5] -for mixtures with CCl4 additions. Both mechanisms are written in the form of "formal" kinetics, suggesting equilibrium in internal degrees of freedom of molecules.…”

“…Therefore, when studying extremely topical problems of inhibiting the ignition of hydrogen, recording of nonequilibrium UV emission is usually one of the main diagnostic methods. In previous works [5,6], it was shown that halogenated hydrocarbons are the effective inhibitors of hydrogen ignition and substantially increase the ignition delay times of hydrogen-oxygen mixtures behind shock waves. In a recent paper [7] it was suggested that the one of the possible inhibition mechanisms is the resonance quenching of excited states of active radicals, in particular, the peroxyl radical HO2*, which plays a key role in chain branching upon ignition of hydrogen-oxygen mixtures H + O2  HO2 *  O + OH, H + O2 + M  HO2 + M [8,9], in collisions with molecules of inhibitors.…”

“…Therefore, the goal of this work is to analyse the effect of halogen-containing combustion inhibitors (CCl4, C2F4Br2) addition, which effect on hydrogen ignition was previously studied in detail by the authors [5,6], as well as inert CO2 addition, on the level of nonequilibrium UV radiation in spectral range from 210 up to 415 nm at ignition of stoichiometric hydrogen-oxygen mixture with additives of combustion inhibitors behind shock waves.…”

Direct measurements of C3F7I dissociation rate constants using a shock tube ARAS technique

“…Note that according to the Montreal Convention, the use of ozone‐depleting compounds, in particular, the most effective bromine‐containing freons, such as 13B1 (CF 3 Br), 114B2 (C 2 F 4 Br 2 ), and 12B1 (CF 2 ClBr), nowadays is forbidden. Therefore, the search for the new chemically active additives to combustible mixtures, well‐inhibiting ignition, and detonation processes in different hydrocarbon–air mixtures, is very topical. Iodine‐containing halogenated hydrocarbons (e.g., CF 3 I, C 2 F 5 I, C 3 F 7 I), because of their complete ozone‐friendly and perfectly suitable physical properties in spite of their high cost, can be a prospective substitute for brominated‐containing freons.…”