Atmospheric dielectric barrier discharge containing helium–air mixtures: the effect of dry air impurities on the spatial discharge behavior

Abstract

Air is a typical and arguably unavoidable impurity in atmospheric pressure dielectric barrier discharges (DBDs). The introduction of air may bring rich plasma chemical effects on DBDs and lead to a significant change of discharge characteristics. Here we implement a two-dimensional fluid model to study the spatial discharge behavior in a helium–dry-air DBD under the air impurity level (N air) of 10–200 ppm. The simulation results reveal that under low impurity content (less than 30 ppm), the gas gap cannot be ignited due to the feeble Penning ionization during the breakdown. However, with an elevation in the impurity level, the progressively enhanced Penning ionization makes the DBD experience three different spatial modes, namely uniform, columnar, and complementary quasi-uniform modes. Of particular note is that the improvement of discharge uniformity observed after the second mode transition is not directly controlled by seed electron level—a previously reported qualitative indicator of the discharge uniformity concluded by helium DBDs with only nitrogen traces. And the main contributor to this phenomenon is the complementary spatial structure appearing in successive two discharges induced by the further reinforced Penning ionization with extra oxygen doped. The result suggests the necessity of considering oxygen in helium–air DBDs when the impurity effect of air is concerned.

Cold plasma treatment of porous scaffolds: Design principles

“…The current plasma modeling literature focuses on plasma breakdown in the absence of a structure being treated [40][41][42][43][44][45][46][47]49] . When a porous structure is modeled inside of a plasma-containing vessel [57][58][59] , the computational cost associated with plasma modeling limits researchers to modeling a small fraction of the complex structure.…”

“…[46,47] The development of the COMSOL Multiphysics® plasma module leads to the deployment of 2D axisymmetric full plasma models. [48,49] However, previous works model plasma inside an otherwise empty vessel or flowing around simple structures. Modeling a full nitrogen plasma, which is commonly used in surface engineering, continues to be a computational challenge due to the number of chemical reactions involved.…”

Cyto- and bio-compatibility assessment of plasma-treated polyvinylidene fluoride scaffolds for cardiac tissue engineering

“…The second parameter responsible for the filamentary/ homogeneous behavior is seed electron density (n seed ). Cold atmospheric plasmas generated in dielectric barrier devices supplied with argon or helium commonly have a background of ambient air, i.e., N 2 and O 2 molecules (typically 10-100 ppm) even after a few minutes of purge (Wang et al, 2021). These socalled contaminants can interact with atoms of noble gas in a metastable state (X m ) and potentially induce Penning reaction as shown in Eq.…”

Effect of solid particle type, concentration and size on DC breakdown voltage of short needle‐plate air gap: An experiment and simulation study

“…The discharge characteristics of unclean air has been studied by scholars at home and abroad [12][13][14][15][16]. Dzlieva and others have studied the effect of dust on the DC breakdown voltage of high-pressure gas.…”

“…Ermolenko et al simulated and analysed with the influence of multiphase medium on the electric field of plasma reactor by finite element method, and proposed that water droplets/metal particles in the air gap can seriously distort the surrounding electric field, resulting in the formation of small corona area of air medium [18]. Yi et al found that many haze and haze external insulation discharge accidents in Guangzhou Power Grid include both insulator surface flashover caused by wet settlement and air gap breakdown discharge [10,16]. The air gap discharge is mainly due to the drift dust in the air, that is, the solid particles in the haze ionise the positive and negative ions under appropriate conditions, which reduces the insulation performance of the air medium.…”