A collisional-radiative model for atmospheric-pressure low-temperature air discharges

Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines. The electron density is a key discharge parameter related to the active-particledensity. The latter has been considered playing an important role in the above applications bythe kinetic effect. In this work, an atmospheric pressure air plasma collisional-radiative model con-sidering the excited states of atomic nitrogen and oxygen is built based on previous widely kineticinvestigations of molecules and radicals, as well as their excited states. The excited states, especiallythe atomic nitrogen and oxygen states were less investigated in previous works. The emission inten-sity distributions from the model have a good agreement with those measured in the glide arcplasma with two discharge modes, as well as the microwave plasma. Based on the kinetics of molec-ular and atomic emitting states, the line-ratio method is presented to determine the electron density.The N2（337 nm）/O（844 nm） and N2（337 nm）/NO（γ） line ratios are used for the glide arc plasma andmicrowave plasma torch, respectively. Besides, the kinetics of the excited states involved with twoline-ratios are also investigated in the two types of discharges. Combined with the atmospheric pres-sure actinometry method, the kinetic effect of the plasma-assisted combustion can be revealed quan-titatively in the future.