OH and O radicals production in atmospheric pressure air/Ar/H₂O gliding arc discharge plasma jet

Atmospheric pressure air/Ar/H₂O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic (OES) diagnostic technique is used for the characterization of plasmas and for identifications of OH and O radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation T_x ≈5550–9000 K, rotational T_r≈1350–2700 K and gas T_g≈850–1600 K temperatures, and electron density n_e ≈(1.1-1.9 )× 10¹⁴ cm^-3 under different experimental conditions. The production and destruction of OH and O radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of OH and O radicals indicate that their production rates are increased with increasing Ar content in the gas mixture and applied voltage. ne reveals that the higher densities of OH and O radicals are produced in the discharge due to more effective electron impact dissociation of H₂O and O₂ molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced n_e. The productions of OH and O are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, T_g significantly reduces with the enhanced air flow rate. This investigation reveals that Ar plays a significant role in the production of OH and O radicals.