Thermally-Nonequilibrium Kinetics of Plasma-Assisted Oxidation and Ignition below Self-Ignition Threshold

摘要

Precise control of the direction of energy deposition in the plasma is possible for a relatively short time period when the multiplication of electrons (above the breakdown threshold) or recombination (below the threshold) do not have enough time to change the electron concentration and plasma conductivity significantly. When the plasma conductivity is not very high, it is possible to maintain a desired value of E in the inter-electrode gap. This approach, together in combination with a short high-voltage pulse and constant bias, allows for the selective and extremely nonequilibrium excitation of the gas. The duration of the critical high-voltage pulse depends on the gas parameters (density, composition), but for the practically important range of parameters, it is restricted to few nanoseconds. Present work demonstrates the influence of vibrational excitation on the oxidation and ignition kinetics below self-ignition threshold. It was shown that vibrational excitation of nitrogen leads to HO_2 decomposition and dramatic extension of the self-ignition threshold to low temperature region. The combined effect of nonequilibrium excitation at high E (dissociation of molecules and ionization) and at low E (vibrational excitation) leads to synergetic effect and significantly increases the efficiency of plasma assisted initiation of ignition in the temperature range 400-800 K.