maintenance E-field sustaining the discharge comes out as an internal parameter, i.e. it is operator independent, in contrast to what is generally believed whatever the kind of E-field sustained discharges; (ii) the smaller the volume in which power is absorbed with respect to the volume in which it is spent, the higher the intensity of the maintenance E-field: this leads to higher atomic (molecular) excitation rates inside than outside the absorption region (such is the case in microdischarges); (iii) the value of θ L varies significantly with the SW field frequency, decreasing with increasing frequency from the RF domain to that of microwaves; (iv) the power lost θ L , which is the power cost to sustain an electron-ion pair in an SWD, can serve to evaluate the efficiency of the various discharge regimes (diffusion and volume recombination with either single or step-wise ionisation); (v) the EM E-field intensity under the electron cyclotron resonance (ECR) condition passes through a minimum, not a maximum, contrary to what is generally claimed; (vi) similarity laws, originally derived with DC discharges, are generalized to include RF and microwave discharges. For example, θ A /p as a function of pR (p is the gas pressure and R the discharge tube inner radius) replaces advantageously the widely used E/p versus pR similarity law since θ A is more easily measured than E 2 and further it prevents considering the latter as an external parameter, etc. The important EM power loss due to space-wave radiation in the immediate vicinity of the SW launching interstice has escaped the attention of those working with SWDs. This effect is documented experimentally, showing in addition that it can be significantly reduced by using a cylindrical conducting enclosure, coaxial with the discharge tube, having a small enough radius such that it acts as a circular waveguide at cut-off. A survey limited to underlining specific properties and innovative features of SWDs other than plasma columns is conducted, which include planar SWDs and microwave discharges of the torch type sustained at atmospheric pressure, for instance, with the TIA and TIAGO E-field applicators: it is shown that their flame actually results from an SWD.
Results of chemical kinetics modeling in methane subjected to the microwave plasma at atmospheric pressure are presented in this paper. The reaction mechanism is based on the methane oxidation model without reactions involving nitrogen and oxygen. For the numerical calculations 0D and 1D models were created. 0D model uses Calorimetric Bomb Reactor whereas 1D model is constructed either as Plug Flow Reactor or as a chain of Plug Flow Reactor and Calorimetric Bomb Reactor. Both models explain experimental results and show the most important reactions responsible for the methane conversion and production of H 2 , C 2 H 2 , C 2 H 4 and C 2 H 6 detected in the experiment. Main conclusion is that the chemical reactions in our experiment proceed by a thermal process and the products can be defined by considering thermodynamic equilibrium. Temperature characterizing the methane pyrolysis is 1,500-2,000 K, but plasma temperature is in the range of 4,000-5,700 K, which means that methane pyrolysis process is occurring outside the plasma region in the swirl gas flowing around the plasma.
The characteristics of electromagnetic waves propagating along dense plasma filaments, as encountered in atmospheric pressure discharges, are examined in the microwave frequency range; they turn out to be surface waves. Results of numerical calculations of the dependence of the phase and attenuation coefficients on the plasma parameters are presented. In the limit of large electron densities, this guided wave is akin to a Sommerfeld wave and the propagation can be described in an analytical form.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.