Search

The target surface to be treated in reality is often not smooth and horizontal and may also be in different tilting angles. The treatment of the tilted dielectric surface by the atmospheric pressure plasma jet (APPJ) undoubtedly increases the complexity of surface modification. Therefore, a two-dimensional fluid model is established to reveal the internal mechanism of the interaction between the He APPJ and the tilted dielectric surface by means of numerical simulation. The distribution of the gas flow in a small angular range (0°, 3°, 5°, 8°, 10°, and 15°) is studied. In addition, the effects of the tilt angle on the jet morphology, discharge dynamic properties, and species distribution of the He APPJ are emphatically discussed. It is found that the jet morphology and parameters are no longer symmetrical under the tilted surface. With the increase in the tilt angle, the enhanced electric field in the upper surface region leads to the increase in the ionization rate and electron density here, and also accelerates the propagation speed of the jet to the dielectric surface in the atmospheric environment. Driven by the electric field force, the jet is closer to the dielectric surface, resulting in a decrease in the thickness of the cathode sheath and an increase in the surface charge density in the area to the right of the central axis. The influence of the gas flow structure leads to the shortening of the jet development distance and a decrease in the jet velocity on the upper surface. N and O also form higher fluxes on the upper surface due to the increase in the electron density. [ABSTRACT FROM AUTHOR]

This paper established a three-dimensional transient MHD model of a high-current multi-component vacuum arc under a transverse magnetic field (TMF) to simulate the dynamic characteristics of plasma parameters in the uniform motion mode of a contracted arc under lower TMF. The model considered the ionization–recombination process among the multi-components and used the P1 model to calculate the thermal radiation losses. The simulation results show that the ion number density of The TMF arc is on the order 1024 m−3, and when the plasma temperature reaches 4.3 eV, the effects of thermal radiation cannot be ignored. The majority of the plasma from the cathode and anode undergo acceleration and then deceleration before finally intersecting at the center of the arc, creating an extreme value of the density and the pressure, where a large amount of kinetic energy is converted into internal energy. The arc will be bent and deflected under the action of the ampere force, and the deflection of Cu3+ is especially obvious. The TMF affects the collision strength of the jet in the intersection area and, thus, affects the ion density, in which the change of Cu2+ is dominant. The ionization–recombination process of ions is mainly determined by the electron temperature, which is affected by the arc current. As the current decreases, Cu1+ increases and Cu2+ and Cu3+ decrease, and the change in ionization rate is the main reason for the change in the proportion of each ionic component; the heat flux density to the anode and cathode is on the order of 1010 W/m2, which heats the front of the arc and ensures the stable movement of the arc. Meanwhile, due to the high ion number density, the ion heat flux accounts for the main part of the heat flux, and the anode exhibits a higher proportion of ion heat flux. [ABSTRACT FROM AUTHOR]