ABSTRACT
The gliding arc is a unique discharge with both thermal and nonthermal plasma characteristics. It has relatively high electron energy (>1 eV) and electron number density as well as moderate heating (1,000–5,000 K), thus offering multiple energy coupling pathways toward combustion enhancement. The high electron energy of a gliding arc compared to thermal plasma enables activation of reactants and produces active radicals to increase fuel oxidation. The moderate heating effect can elevate the reactants’ temperature to further accelerate reactions and extend the lifetime of active radicals produced by the gliding arc. The unique properties of the gliding arc provide great potential to enhance combustion in ultra-lean internal combustion engines and high-speed propulsion systems. In this entry, the dynamics, characterization, temperature, and electron energy distributions of the conventional gliding arc and the magnetic stabilized gliding arc are summarized. The effects of the magnetic stabilized gliding arc on combustion enhancement were studied in both counterflow flames and lifted flames using Rayleigh scattering and OH laser-induced fluorescence. The results showed that the thermal effect extended the flame extinction limit and increased the flame speed and stabilization. In addition, the results showed that the gliding arc-generated nitrogen oxides (NOx) had a strong kinetic effect to increase OH production and reduce ignition temperatures of methane and hydrogen mixtures. Different ignition regimes induced by the NOx production in gliding arcs were computationally modeled. Elementary reactions of kinetic processes are discussed. The results showed that the gliding arc has a strong kinetic enhancement effect for lower temperature ignition, mainly through the NO + HO2 = NO2 + OH reaction pathway.
