Effect of singlet oxygen O2(a 1Δg) molecules produced in a gas discharge plasma on the ignition of hydrogen–oxygen mixtures

Abstract

A kinetic model describing the impact of singlet delta oxygen O2(a 1Δg) produced in a gas discharge plasma on the evolution of hydrogen–oxygen mixture composition is developed. In the framework of this model the possibility of describing all the main experimental data on the dynamics of O2(a 1Δg) quenching in H2 : O2 gas mixtures in the temperature range T0 = 300–1050 K is shown. Most of the collisions between singlet oxygen molecules and atomic hydrogen, O2(a 1Δg) + H, lead to quenching of O2(a 1Δg). The efficiency of this interaction channel is more than 80% and the fraction of the reaction H + O2(a 1Δg) → OH + O(3P) is only 10–20%. The impact of singlet oxygen O2(a 1Δg) admixture on the ignition of H2 : O2 mixtures is investigated. The dominant process determining the degree of O2(a 1Δg) impact is its deactivation by HO2 molecules. As a result, in H2 : O2 mixtures of high pressure, where the number density of the produced HO2 molecules can be sufficiently high, the impact of singlet oxygen on the ignition delay time of these mixtures turns out to be relatively weak. This effect becomes even less noticeable if admixtures of atomic oxygen are present in the mixture. Oxygen atoms produced by the discharge are more efficient in the ignition of hydrogen–oxygen and hydrogen–air mixtures than O2(a 1Δg) molecules. Thus, to reduce the ignition delay time and to decrease the temperature threshold of combustive mixtures, the use of gas discharge systems providing the efficient production of atomic particles is recommended.