Enhancing ignition and inhibiting extinction of methane diffusion flame by in situ fuel processing using dielectric-barrier-discharge plasma

This paper addresses the possibility that dielectric-barrier-discharge (DBD) can provide in situ fuel processing to manipulate methane diffusion flame, and this technology may be extended to other higher-order hydrocarbon fuels. In this work, an in situ fuel processing system, by coupling a DBD generator to the fuel nozzle, was developed to examine the chemical effect of the DBD on enhanced ignition and inhibited extinction of a CH₄/O₂/Ar counterflow diffusion flame. Experimental results show that 25 kHz plasma reduces the ignition temperature by approximately 180 K, and extends the extinction limit by approximately 20% with a moderate stretch rate. DBD sustained in the fuel stream is expected to perform as a pool of radicals and active molecules to promote combustion, which was verified by the diagnosis of several key intermediate species. In situ planar laser-induced fluorescence (PLIF) technique mapped the profile of CH radical, and gas chromatograph measured some stable species, such as hydrogen and higher order hydrocarbons. Hydrogen is more reactive fuel; therefore, this paper gives further insight into hydrogen-enriched ignition by CHEMKIN-PRO, and it is found that the acceleration is approached through more efficient generation of H radical.