Effect of alternating electric field on the combustion and no formation of diffusion flames

This paper experimentally studied the effect of high-frequency alternating electric field on the methane/air diffusion flames and their NOx formation. The flame shape, intermediate and final products were assessed over a large-range voltage. As the voltage increased from zero to a certain value at which gas discharge occurred, the volumetric concentrations of OH and CH radicals increased firstly, then decreased and finally remained at a constant. The NO volumetric fraction firstly decreased and then increased when the voltage kept increasing, and sharply decreased when the gas discharge occurred. The CO volumetric fraction shows an inverse trend to NO. The combustion process became incomplete and the flame turned to unstable after the discharge occurred.