Enhancement of combustion of a hydrogen-air mixture by excitation of O$_2$ molecules to the $a^1\Delta_g$ state state

The possibility of increasing the laminar flame velocity in a hydrogen-air mixture by excitation of O$_2$ molecules into the $a^1\Delta_g$ singlet state. The presence of 10% of O$_2$($a^1\Delta_g$) molecules in oxygen is demonstrated to result in noticeable (up to 50%) enhancement of mixture burning. The temperature of combustion products and also the concentrations of H$_2$O, NO, and other constituents increase. The greatest effect of O$_2$($a^1\Delta_g$) molecules is manifested in combustion of lean mixtures; the least pronounced effect is observed in rich mixtures. These effects are caused by intensification of the chain mechanism in the presence of a super-equilibrium amount of excited O$_2$($a^1\Delta_g$) molecules in a hydrogen-air mixture.