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.

在过去的几十年里，人们对等离子体作为一种火焰稳定技术的兴趣越来越大。具体而言，作为非热等离子体的重复纳秒脉冲（RNP）放电由于其独特的特性，如低能耗、低气体温度和高度活化的激发物种/自由基，已显示出一些有希望的结果。然而，根据应用，其优势可能仅限于发生放电的特定模式，包括电晕、扩散、丝状和热火花放电。为了研究同心电极配置中 RNP 放电的行为，设计并进行了一系列实验。这种行为已经在放电模式及其作为流动条件（即射流速度）和脉冲参数（即，峰值电压和重复频率）。研究了重复频率和射流速度对“扩散到丝状”、“丝状到热火花”和“扩散到热火花”三个过渡电压的影响。结果表明，降低频率或增加射流速度会延迟所有三个转变。还观察到，在低于临界值的频率下，不会出现丝状模式，扩散等离子体直接变成热火花模式。还表明，通过定义等离子影响数，可以提供对过渡过程的更准确和统一的解释。例如，对于射流速度和频率的不同组合，只要等离子影响数小于0.3，就无法稳定地维持丝状放电。