Atmospheric-Pressure Air Plasma Jet and Its Striation Discharge Mode for Treatment of Thermally Sensitive Materials

A hollow inner electrode covered with a dielectric tube was inserted into an outer electrode and airflow was fed through the inner electrode. The electrodes were then connected to a transformer operated at an alternating voltage with sinusoidal waveform at a frequency of 20 kHz. The resulting discharge is ejected out of the outer electrode from a 0.7 mm hole in the form of a plasma jet into ambient air. The attributes of the discharged plasma jet were evaluated by monitoring the voltage and current behavior and by investigating the optical emissions. The discharge patterns in the atmospheric-pressure air plasma jet in the form of striations could be observed by the naked eye. Furthermore, we reported the striation mechanism by ion acoustic wave propagation by utilizing a simple calculation.

In situ study on the influence of bicarbonate, chloride and outer electrode potential on crevice corrosion occurrence and development of X70 steel

Purpose The purpose of this paper is to clarify the influence of bicarbonate, chloride and outer electrode potential on crevice corrosion occurrence and development of X70 steel. Design/methodology/approach The crevice corrosion behavior in NaHCO3 and NaCl solutions was investigated through modeling and experiments. The electrode potential and current density distribution were simulated, and the acidification of crevice solution was monitored in situ. Findings The bicarbonate concentration and outer electrode potential remarkably influenced the occurrence of crevice corrosion. The former changes the passivation curves, and the latter alters the initial potential. Moreover, chloride concentration exerted minimal influence. The location of acidification and pitting occurrences depended on the potential difference between the outer electrode and electrode at the active dissolution current peak. Originality/value This study provides a better understanding of the crevice corrosion behavior and mechanism under natural conditions.

Electrostatically controlled large-amplitude, non-axisymmetric waves in thin film flows down a cylinder

We examine the dynamics of a thin film flowing under gravity down the exterior of a vertically aligned inner cylinder, with a co-aligned, concentric cylinder acting as an outer electrode; the space between the outer cylinder and the film is occupied by an inviscid gas. The stability of the interface is studied when it is subjected to an electric field, applied by imposing a potential difference between the two cylinders. Leaky-dielectric theory is used in conjunction with asymptotic reduction, in the large-conductivity limit, to derive a single, two-dimensional evolution equation for the interfacial location, which accounts for gravity, capillarity, and electrostatic effects. A linear stability analysis is carried out which shows that non-axisymmetric modes become more dominant with increasing electric field strength. Our fully two-dimensional numerical solutions of the evolution equation demonstrate qualitative agreement between the trends observed in the nonlinear regime and those predicted by linear theory. These numerical solutions also show that, depending on the electric field strength and the relative proximity of the outer electrode, the interface either remains spatially uniform, or exhibits either axisymmetric or, importantly, non-axisymmetric travelling waves. The effect of wave formation on the interfacial area is investigated in connection with the use of electric fields to control thin film flows to enhance heat and mass transfer rates.