Ignition Process of Diesel Spray Based on Behavior of Rotating Gliding Arc in Plasma Reformer

The design of efficient plasma reformers requires both efficient fuel conversion of fuel and chemical energy extraction. In this regard, liquid fuels provide the advantages of high gravimetric and volumetric energy densities, therefore yielding high energy; in particular, diesel is promising for use in plasma reformers. In this study, we investigated the ignition process in a diesel reformer driven by a rotating gliding arc using a high-speed camera. The locations of the flame kernel generated by the arc were clearly identified under different power conditions. At high power, the flame kernel was generated at the nozzle tip, which grew into a fully developed flame. This indicates that the period for fuel vaporization and mixing with air (which is a necessary step prior to chemical reactions and is typically longer than the characteristic chemical reaction time) is extremely short. Moreover, with low oxygen concentrations, we observed a rotating flame kernel. At low power, the flame kernel was generated at a distance from the nozzle tip and the arc. This result indicates that the generation mechanism of the flame kernel in the plasma reformer is not straightforward; flow and arc dynamics also influence the interactions between the arc and fuel droplets.