Electronic Excitation Modeling for Inductively Coupled Plasma Flows

At Japan Aerospace Exploration Agency, a surface catalysis measurement facility has been developed to investigate the catalytic efficiency of atomic oxygen and nitrogen recombination on thermal protection system materials. In the facility, an oxygen-argon inductively coupled plasma (ICP) flow was investigated, and it was found that the development of electronic excitation modeling is crucial since electronically excited particles play an important role in the flow field. In this work, the modeling of electronic transitions as well as ionization reactions using the Quantum-Kinetic (Q-K) model in direct simulation Monte Carlo (DSMC) has been developed. In DSMC, 5 temperatures (translational, rotational, vibrational, electronic excitation and electron temperatures) were computed and compared with the ICP experimental results. The acceptance-rejection (A-R) and accumulated distribution (A-D) schemes for electron-electronic energy transfer have been tested and the A-D scheme was more effective and stable. Using the Q-K model with the A-D scheme, the O2-Ar ICP flows were investigated in DSMC, and it was found that the electronically excited levels of Ar and O have significant impact on the chemistry in the ICP flow field. The production rate of O + ,O + and Ar + is greatly increased, and the degree of ionization is 0.5-0.6 % with the assumption of neutral freestream condition. Besides, the DSMC results lead to our presumption that the consideration of external energy sources is important for the prediction of the ICP flow field. Good agreement between numerical and experimental results is obtained in terms of the electronic excitation temperature while the DSMC predicts higher translational temperature than the experimental one.