1-D fluid model of atmospheric-pressure rf He+O2 cold plasmas: Parametric study and critical evaluation

Abstract

In this paper atmospheric-pressure rf He+O2 cold plasmas are studied by means of a 1-D fluid model. 17 species and 60 key reactions selected from a study of 250+ reactions are incorporated in the model. O2+, O3-, and O are the dominant positive ion, negative ion, and reactive oxygen species, respectively. Ground state O is mainly generated by electron induced reactions and quenching of atomic and molecular oxygen metastables, while three-body reactions leading to the formation of O2 and O3 are the main mechanisms responsible for O destruction. The fraction of input power dissipated by ions is ∼20%. For the conditions considered in the study ∼6% of the input power is coupled to ions in the bulk and this amount will increase with increasing electronegativity. Radial and electrode losses of neutral species are in most cases negligible when compared to gas phase processes as these losses are diffusion limited due to the large collisionality of the plasma. The electrode loss rate of neutral species is found to be nearly independent of the surface adsorption probability p for p > 0.001 and therefore plasma dosage can be quantified even if p is not known precisely.

Hydrogen Peroxide Production in an Atmospheric Pressure RF Glow Discharge: Comparison of Models and Experiments

“…Two methods have been used to determine the gas temperature: optical emission spectroscopy using the rotational bands of N 2 (C-B) at 337 nm and using a thermocouple (Fluke Table 3: Reaction rates used in this study that differ from those of our previous work [10,29]. 80BK-A type K) inserted into the grounded electrode of the reactor (see figure 1).…”

“…Although qualitative agreement with experimental observations has been reported, quantitative discrepancies between experimental and computational results observed during this study have led to an improved model. Namely, vibrational and rotational excitation is considered in the new global model, the input power coupled to ions is also taken into account and electrode and radial losses are refined according to [29]. In addition some reaction rates have been updated as shown in table 3.…”

“…These are incorporated in the third model, a 1-dimensional fluid model. The fluid model is based on the model used in references [11,29] and briefly it solves the continuity equation for each plasma species, the electron energy equation and Poisson's equation. Due to the large collisionality of atmospheric pressure plasmas (ν >> ω r f where ν is the neutral collision frequency and ω r f the angular driving frequency), the particle inertia is neglected and the drift-diffusion approximation is used to determine the mean velocity for each species.…”

A theoretical insight into low-temperature atmospheric-pressure He+H2plasmas

“…In addition, it is noted that a significant amount of power can also be coupled to ions in the bulk plasma of an atmospheric pressure discharge. The ratio of power coupled to ions in the bulk to the total (electrons + ions) power coupled to the bulk plasma is given by [21] :…”

“…Although atmospheric-pressure sheath-dominated discharges in which quasi-neutrality does not hold have been reported in the literature, these occur in discharges with a smaller gap than the 2mm considered in this study [19,20] . Diffusion in the radial direction is neglected here since the mean distance travelled by particles during their lifetime is much shorter than the radius of the electrodes [14,21] : for a typical lifetime () of 1ms and a diffusion constant (D) of 1cm 2 /s, the distance travelled in a lifetime is Reaction rates needed to determine the generation/loss of species in the discharge (G k ) depend on the mean electron energy. This is determined by solving the power equation [11,14] .…”