Pinpointing energy transfer mechanisms in the quenching process of microwave air plasma

Abstract: A time-dependent multi-temperature quenching model at atmospheric pressure, incorporating chemical and vibrational kinetics, is introduced. The model provides insights into the pathways of NOx formation and destruction in the downstream region of a microwave air plasma. The relaxation of the temperatures during the forced cooling trajectory by the wall is modelled. A Continuous Stirred Tank Reactor model and a Plug Flow Reactor model represent the plasma and quenching regions, respectively. For the non-thermal conditions, where gas and vibrational temperatures differ, most reaction rate coefficients, except those obtained from molecular dynamics methods, are determined based on a generalized Fridman-Macheret scheme. The energy transfer channels involved in the quenching process are tracked across different time scales. By varying the gas temperature in the plasma region and the cooling rate, the reaction pathways for the NOx synthesis mechanism are analysed. This research provides a first step for the further advancement and optimisation of plasma reactors for efficient NOx production.