Study on the Calculation Method of Nonequilibrium Plasma Composition Considering Phase Transitions of Ablation Products

Accurate prediction of plasma composition during the phase transitions of ablation products remains challenging under thermodynamic nonequilibrium conditions. To address this issue, a plasma composition calculation method based on an electron–heavy-particle–cluster three-temperature assumption is proposed in this work. In the proposed method, condensed-phase clusters formed through the aggregation of gaseous atoms and molecules are treated as independent species, while individual temperatures are assigned to electrons, heavy particles, and clusters to investigate the effects of thermal nonequilibrium on plasma composition. A total Gibbs energy function is then formulated for the three-temperature plasma system and transformed into an objective function compatible with metaheuristic optimization. The proposed method is assessed through comparisons with previously reported gas-phase composition and equilibrium phase-transition results and subsequently applied to investigate the phase transition of Cu-containing ablation species in an air–Cu plasma system. The results reveal that thermodynamic nonequilibrium between heavy particles and clusters can lead to a pronounced difference between the deposition and melting temperatures of ablation products, which significantly modifies the plasma composition across phase transitions. These findings highlight the importance of accounting for heavy-particle–cluster nonequilibrium in plasma composition calculations involving ablation products. Further independent validation of the proposed method under three-temperature nonequilibrium conditions is still required.