Glow-to-Spark Transitions in a Plasma System for Ignition and Combustion Control

This paper deals with the investigation of a new regime in a plasma ignition and flame control system as applied to air-hydrocarbon mixtures. The system is based on the design of a classical high-current arc plasmatron. Compared with a thermal plasmatron mode, the average discharge current in the described device has been decreased to about 0.1 A. Although average power dissipated in the discharge does not exceed 200 W and average gas temperature at the plasmatron exit for typical regimes of the discharge operation in air is less than 500 K, the device demonstrates reliable ignition and flame stabilization in a wide range of equivalence ratios. Physical mechanism of ignition is associated with the nonsteady-state properties of discharge. At a low current level, the discharge burns in a kind of glow mode, and because of the glow-to-spark transitions, the high-current nanosecond pulses are superimposed on the glow plasma background. Then, the spark discharge initiates the combustion process, which is efficiently sustained in the glow plasma.