Numerical Simulation of the Chemical Combination and Dissociation Reactions of Neutral Particles in a Rarefied Plasma Arc Jet

The expansion of neutral particles in a plasma arc jet is crucial for the distribution of the ions and electrons, especially in an unsteady rarefied plasma arc jet with chemical reactions. A 3-D unsteady investigation of neutral particles in a rarefied flow with chemical combination and dissociation reactions is numerically simulated based on an in-house direct simulation Monte Carlo (DSMC) code. The evolution of the neutral particles flow in vacuum cylinders is presented, and the influence of the chemical reactions has been investigated for the neutral particles. The predicted results imply that the dissociation reaction plays a key role in the expansion of the neutral particles process. In order to study the expansion of the neutral particles in an electric field, an electrostatic particle-in-cell (PIC) and DSMC are combined to simulate the axisymmetric rarefied plasma flows with chemical reactions. Two sets of grids are employed for the DSMC/PIC method by considering the different requirements of both the methods based on the molecule mean free path and the Debye length. The properties of both the flow and electric fields are analyzed in detail. It is found that the electric potential increases if the initial velocity of the ions from the inlet is sufficiently large, and accordingly, the number density of the ions in the flow field increases further.