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Power Transfer to Gas Heating in Pure N 2 and in N 2 –O 2 Plasmas

2016; American Chemical Society; Volume: 120; Issue: 38 Linguagem: Inglês

10.1021/acs.jpcc.6b05463

1932-7455

C. D. Pintassilgo, Vasco Guerra,

Vacuum and Plasma Arcs

A time-dependent kinetic model is developed to study the energy transfer to gas heating in N2 and N2–O2 plasmas. The model is based on the coupled solutions to the gas thermal balance equation and a system of rate balance equations for the most important neutral (including vibrational kinetics) and ionic heavy species produced in these plasmas. A complete set of gas heating mechanisms is taken into account, together with gas cooling by heat conduction to the wall. Calculations are performed for a cylindrical geometry and fractional concentrations of oxygen molecules [O2]/Ng (Ng being the gas number density) up to 80%. Modeling simulations are carried out for fixed values of the reduced electric field E/Ng and electron density ne with the purpose of focusing on the role of adding molecular oxygen O2 into the N2–O2 mixture. It is shown that the fractional discharge power and energy transferred to the translational mode (gas heating) increase with [O2]/Ng. The present work also shows that when the variation of E/Ng and ne with the mixture composition is considered, the gas temperature has a maximum for [O2]/Ng ∼ 20%, which is qualitatively in line with experimental observations. Gas heating mechanisms are identified and discussed in detail.