Formation of Vibrationally Excited HF Molecules during the Inhibition of Hydrogen and Methane Combustion in Oxygen and Air by Dichlorodifluoromethane

Abstract

For the first time, vibrationally excited HF molecules (v = 2, 3) are observed with the use of hyperspectrometers in the VIS and NIR ranges in the products of the reactions of oxidation of hydrogen and methane in the presence of Difluorodichloromethane (CF2Cl2). The combustion of hydrogen and methane in air and oxygen at atmospheric and reduced pressure is initiated by a spark discharge. The propagation of the flame front is recorded using high-speed color filming. It is found that during the combustion of methane HF (v = 3) molecules are formed at the moment of reaching the maximum rate of the chemical transformation, i.e., reactions involving CF2Cl2 molecules compete directly with the development of reactive chains. It is also found that the concentration limit of the ignition of a premixed hydrogen-air mixture in the presence of Difluorodichloromethane at a pressure of 1 atm exceeds 10% CF2Cl2, while the concentration limit of the ignition of a premixed methane-air mixture is 1% CF2Cl2. This means that the active centers of the combustion of hydrogen and methane, which determine the development of combustion, have a different chemical nature. It is shown that the set of reactions involving Difluorodichloromethane molecules, leading to the formation of HF (v = 2, 3) during methane combustion, should include active centers of methane combustion.