CARS diagnostic and modeling of a dielectric barrier discharge

Dielectric barrier discharges (DBD) with planar- and knife-shaped electrode s are operated in N-2-O-2-NO mixtures under a pressure of 20 and 98 kPa. Th ey are excited by means of consecutive unipolar or bipolar high-voltage pul se packages of 10 kV at a pulse repetition rate of I and 2 kHz. The rotatio nal and vibrational excitation of N-2 molecules and the reduction of nitric oxide (NO) in the discharge have been investigated using coherent anti-Sto kes Raman scattering (CARS) technique. Rotational (gas) temperatures near t he room temperature and vibrational temperatures of about 800 K at atmosphe ric pressure and 1400 K at a pressure of 20 kPa are observed. Therefore, ch emical reactions of NO with vibrationally excited N-2 are probably insignif icant. One-dimensional kinetic models are developed that balance 35 chemica l reactions between 10 species and deliver equations for the population den sity of excited vibrational levels of N-2 together with a solution of the B oltzmann equation for the electrons. A good agreement between measured vibr ational temperatures of N-2, the concentration of NO, and calculated data i s achieved. Modeling of the plasma discharge verifies that a DBD operated w ith a N-2-NO mixture reduces the NO content, the simultaneous presence of O -2, already 1%, is enough to prevent the NO reduction.