Study of a non-equilibrium pulsed nanosecond discharge at atmospheric pressure using coherent anti-Stokes Raman scattering

Time-resolved CARS measurements of rotational and vibrational temperatures of nitrogen in nanosecond pulsed discharge at atmospheric pressure are reported. Experiment is first performed with a discharge in pure air where spatial and temporal evolution of temperature distribution is recorded by delaying the probe lasers relative to the discharge pulse in the range 10 ns to 1 ms. The experiments demonstrate that a strong vibrational non-equilibrium can be sustained in N₂ at 1 bar. The effect of different colliding partners on the vibrational relaxation of N₂ is studied for discharges in CH₄/air mixtures with different equivalence ratio. The observed temperature distributions suggest that thermal equilibrium is not fully achieved in this mixture. Effect of the discharge on the ignition of a premixed CH₄/air flame is also investigated for various equivalence ratio.