Triple-T Method for Modeling Plasma-Assisted Ignition with Rich Vibrationally Excited States

Vibrationally excited species play an important role in elevating the gas temperature and reaction rates in fuel-plasma reaction systems. Classical two-temperature models coupled with the well-known Fridman-Macheret α-model have been validated and widely used to describe the plasma and fuel systems. However, the Fridman-Macheret α-model strictly requires the information on elementary reaction rates. This, in conjunction with two-temperature models, may lead to high errors and high computational cost in high-dimensional plasma-combustion coupled modeling due to the enormous vibrationally related reactions and the misuse of overall rates in classical combustion chemistry sets. We propose in this work a three-temperature model (Triple-T model hereafter) as an option for modeling complex plasma-fuel chemistry systems. A new variation, "Reaction Temperature" T_react, is introduced to account for the influence of vibrationally excited states in high-dimensional models. This model has been successfully tested in 3 classical cases: the plasma-assisted ignition of NH₃/O₂/N₂, CH₄/O₂/He, and H₂/O₂/He mixtures. The original chemistry set is reduced by 46%, 33%, and 7%, respectively. The influence of vibrational states on the energy partition and ignition delay time is studied with the help of the proposed model.