IGNITION DELAY REDUCTION IN THE SYNGAS-O2 MIXTURE DUE TO EXCITATION OF O2 MOLECULES TO THE A1-G STATE

Abstract

Experimental studies of the influence of singlet delta oxygen on the ignition delay of syngas-oxygen mixture are performed in a low-pressure flow reactor at a pressure of 16 mbar in a temperature range of 860-930 K. Glow discharge is used for the production of O2(a1As) molecules. The discharge cell and ducts for oxygen plasma supply are covered by HgO in order to decrease the concentrations of oxygen atoms and ozone molecules which are the effective deactivators of O2(a1As) molecules. Diagnostics of O2(a1 -g) and O3 concentrations both in the mixer and along the flow reactor is executed. It is shown that the presence of a small amount of O2(a1As) molecules (4% of the total oxygen) result in the 10%-20% reduction of the induction length in the temperature range 860-930 K. The effect of such an amount of O2(a1 -g) molecules is equivalent to the 30-kelvin heating of the whole mixture. It is revealed on the basis of combined experimental and numerical studies that at low pressure (at least at ~ 10-20 bar), the deactivation of O2(a1As) molecules on the reactor walls contributes significantly to a decrease in the singlet oxygen concentration along the reactor. This effect should be taken into consideration during modeling of the ignition process at low-pressure conditions.