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A zero-dimensional (volume-averaged) and a pseudo-one-dimensional plug-flow (spatially resolved) model are developed to investigate atmospheric-pressure plasma jets operated with He, He/O2, He/N2 and He/N2/O2 mixtures. The models are coupled with the Boltzmann equation under the two-term approximation to self-consistently calculate the electron energy distribution function. An agreement is obtained between the zero-dimensional model calculations and the spatially averaged values of the plug-flow simulation results. The zero-dimensional model calculations are verified against spatially resolved simulation results and validated against a wide variety of measurement data from the literature. The nitric oxide (NO) concentration is thoroughly characterized for a variation of the gas mixture ratio, helium flow rate and absorbed power. An 'effective' and a hypothetical larger rate coefficient value for the reactive quenching N2(A3Σ, B3Π) + O(3P) → NO + N(2D) are used to estimate the role of the species N2(A3Σ, B3Π; v > 0) and multiple higher N2 electronically excited states instead of only N2(A3Σ, B3Π; v = 0) in this quenching. The NO concentration measurements at low power are better and almost identically captured by the simulations using the 'effective' and hypothetical values, respectively. Furthermore, the O(3P) density measurements under the same operation conditions are also better predicted by the simulations adopting these values. It is found that the contribution of the vibrationally excited nitrogen molecules N2(v ⩾ 13) to the net NO formation rate gains more significance at higher power. The vibrational distribution functions (VDFs) of molecular oxygen O2(v < 41) and nitrogen N2(v < 58) are investigated regarding their formation mechanisms and their responses to the variation of operation parameters. It is observed that the N2 VDF shows a stronger response than the O2 VDF. The sensitivity of the simulation results with respect to a variation of the VDF resolutions, wall reaction probabilities and synthetic air impurity levels is presented. The simulated plasma properties are sensitive to the variation, especially for a feed gas mixture containing nitrogen. The plug-flow model is validated against one-dimensional experimental data in the gas flow direction, and it is only used in case an analysis of the spatially resolved plasma properties inside the jet chamber is of interest. The increasing NO spatial concentration in the gas flow direction is saturated at a relatively high power. A stationary O2 VDF is obtained along the direction of the mass flow, while a continuously growing N2 VDF is observed until the jet nozzle.
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| Release Date | 2022-02-21 |
| Identifier | 88a5bac8-718b-44ca-91db-07f3ddaedbfc |
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| Plasma Source Name | |
| Plasma Source Application | |
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| Plasma Source Properties | Atmospheric-pressure plasma jets of planar electrode configuration in five different sizes [48–54] are simulated for the purpose of benchmarking. The jets are constructed with the cross-field configuration, i.e. the applied electric field is oriented perpendicular to the feed gas flow direction [22, 55]. The specific operation conditions are presented in section 5.1. A plasma jet [50] is investigated as a preliminary test of the model predictive capability to a pulse-modulated discharge. The old versions of the radiofrequency-driven COST-Jet (i.e. μAPPJ) [49, 51, 52, 54] might be insufficiently sealed. The resulting unknown high impurity levels in the experiments [49] may impact the results and need to be considered in the simulations. Furthermore, a power transfer efficiency of around 5% is usually assumed in the modelling of these old versions for converting the provided generator input power to the absorbed power in the plasma. The irreproducible experimental results of a μAPPJ are mainly ascribed to the gas impurity and the power uncertainty. Hence, they are minimized by the COST-Jet [48, 53] with a large amount of effort [35] (e.g. the sealing improvement and the absorbed power measurements with integrated probes).
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| Plasma Source Procedure | The COST-Jet is investigated with a focus in this paper owing to the above-mentioned advantages. The jet chamber structure is illustrated in figure 1 together with a depiction of the used modelling formalisms. More details of this setup are reported in the work of Golda et al [35]. In section 5.2, the operation conditions are rightfully addressed based on the measurements of Preissing et al [34]. In sections 5.3 and 5.4, the jet is simulated with the typical operation conditions provided in [35]: a plasma volume of 1 × 1 × 30 mm3 sustained by an absorbed power of 0.6 W at a pressure of 101 325 Pa and a gas temperature of 345 K, is fed with 1400 sccm He, 1400 sccm He + 0.5% O2, 1400 sccm He + 0.5% N2 or 1400 sccm He + 0.5% N2 + 0.5% O2, unless stated otherwise. |
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| Plasma Medium Name | |
| Plasma Medium Properties | see text in section 5.1 - 5.4 in the paper https://doi.org/10.1088/1361-6595/ac278d |
| Plasma Medium Procedure | The simulation results are obtained based on the steady state (i.e. the variations of all the species density and the electron temperature are smaller than 1%) |
| Public Access Level | Public |
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Data and Resources
- figures_2-14_B1-2 in the published paperzip
MATLAB is needed to access the data, and "mine_plot.m" is used to plot the...
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