The energy tree: Non-equilibrium energy transfer in collision-dominated plasmas

Abstract

Collision-dominated plasmas (CDPs) possess unique features compared to traditional fluid and collision-free plasmas that arise from frequent collisions among various species. Synergistic effects of mass–momentum–energy exchange are discussed for most common CDP sources including thermal plasmas, cold plasmas and plasmas with reactive gases. The concept of the “Energy Tree” is employed for analysing multiple synergistic effects of the external electric fields, the nature and density of species of the operating gases, and the features of the environment surrounding the discharges. The examples of employing the “Energy Tree” concept include control of plasma properties in nanosecond pulsed discharges for combustion, non-equilibrium flow discharges in a wind tunnel and discharges for CO2 conversion into value-added chemicals and fuels. The remaining challenges and future trends for the development of versatile CDP sources, as well as their potential applications, are also discussed from cross-disciplinary perspective.