Mode transition and uncertainty analysis of repetitive nanosecond pulsed discharge

Abstract

The interest in plasma as a flame stabilization technique has been growing increasingly in the past decades. Specifically, repetitive nanosecond pulsed (RNP) discharge as a non-thermal plasma has shown some promising results due to its unique characteristics, like low-energy consumption, low gas temperature, and highly activated excited species/radicals. However, depending on the application, the advantages may be limited to specific modes in which the discharge occurs, including corona, diffuse, filamentary, and thermal spark discharge. To investigate the behavior of RNP discharge in a concentric electrode configuration, a series of experiments has been designed and performed. This behavior has been discussed in terms of the discharge modes and their transition as a function of flow condition (i.e., jet velocity) and pulse parameters (i.e., peak voltage and repetition frequency). The effect of the repetition frequency and jet velocity on three transition voltages of “diffuse to filamentary”, “filamentary to thermal spark”, and “diffuse to thermal spark” has been investigated. It is shown that decreasing the frequency or increasing jet velocity delays all three transitions. It is also observed that at frequencies lower than a critical value, the filamentary mode does not occur and the diffuse plasma directly turns into the thermal spark mode. It is also shown that by defining the Plasma Influence number, a more accurate and unified interpretation of the transition process can be provided. For example, for different combinations of the jet velocity and frequency, as long as the Plasma Influence number is smaller than 0.3, filamentary discharge cannot be maintained steadily.