Demonstration of NO production in air plasmametallic surface interaction by broadband laser-induced fluorescence

D Studer (1) , P Boubert (1) , P Vervisch (1)

1 CORIA - Complexe de recherche interprofessionnel en aérothermochimie

This paper deals high temperature chemistry of air in interaction with a metallic surface. A subsonic air plasma is created with an inductive torch and is investigated using broadband KrF laser-induced fluorescence. Nitrogen monoxide fluorescence spectra are recorded in the free subsonic plasma jet as well as within the boundary layer above a stainless steel flat plate water-cooled to 300 K. The comparison between calculated and experimental calibrated fluorescence spectra allows the determination of rotational and vibrational temperatures as well as densities of NO ground state. The results demonstrates a strong non-equilibrium between rotational and vibrational temperatures in both the free jet and the boundary layer including very close to the wall. Density determinations show that nitrogen monoxide is in chemical equilibrium on the axis of the free jet but not on its boundaries. The NO results are analyzed together with previous O 2 and N 2 results obtained by Raman spectrosocpy in order to explain the increasing NO densities observed within the boundary layer. The discussion highlights a double production of NO due to catalytic reactions at the wall and to the exothermic reaction N + O 2 −→ NO +O within the boundary layer following O 2 recombination at the wall.

Mots clés: 52.25.Os; 52.40.Hf; 52.50.Qt; 52.70.Kz

D Studer, P Boubert, P Vervisch. Demonstration of NO production in air plasmametallic surface interaction by broadband laser-induced fluorescence. Journal of Physics D: Applied Physics, 2010, 43 (31), pp.315202. ⟨10.1088/0022-3727/43/31/315202⟩. ⟨hal-00569664⟩