Roles of the state-resolved OH(A) and OH(X) radicals in microwave plasma assisted combustion of premixed methane/air: An exploratory study

Wang, Chuji; Wu, Wei

doi:10.1016/j.combustflame.2014.01.019

Cited by 30 publications

(13 citation statements)

References 51 publications

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“…In addition, CH is essential in the present work, since it couples the methane−air reaction mechanism with chemionization, via reaction 65 in Table 2, by which free electrons (e) influence the flame chemistry. Here, seven reactions in Table 19, 12,13,16,17,18, and 19, which deal with CH and CH 2 reactions are added to the SG35 reaction mechanism, resulting in the Z42 reaction mechanism, including 17 species and 42 irreversible reactions. The reactions involving CH and CH 2 were adopted from GRI 3.0, 45 but with minor modifications to the reaction rates.…”

Section: Skeletal Microwave-assisted Methane−air Reaction Mechanismmentioning

confidence: 99%

“…Microwave radiation has been studied for PAC in various configurations. In several of these studies, the microwave radiation has been sufficiently strong to create a dielectric breakdown of the gas and thereby creating a microwave plasma, either for reforming or ignition, − or for direct plasma–flame interaction. − A continuous microwave plasma is typically close to local thermodynamic equilibrium (LTE), where the electrons and molecules have approximately the same temperature. However, if the electric field of the microwave radiation is below the critical field for dielectric breakdown, a state of non-LTE can be achieved with a substantial higher temperature of the electrons, compared to the gas temperature.…”

Section: Introductionmentioning

confidence: 99%

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Skeletal Methane–Air Reaction Mechanism for Large Eddy Simulation of Turbulent Microwave-Assisted Combustion

et al. 2017

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Irradiating a flame via microwave radiation is a plasma-assisted combustion (PAC) technology that can be used to modify the combustion chemical kinetics in order to improve flame stability and to delay lean blow-out. One practical implication is that combustion engines may be able to operate with leaner fuel mixtures and have an improved fuel flexibility capability including biofuels. Furthermore, this technology may assist in reducing thermoacoustic instabilities, which is a phenomenon that may severely damage the engine and increase NO X production. To further understand microwave-assisted combustion, a skeletal kinetic reaction mechanism for methane−air combustion is developed and presented. The mechanism is detailed enough to take into account relevant features, but sufficiently small to be implemented in large eddy simulations (LES) of turbulent combustion. The mechanism consists of a proposed skeletal methane−air reaction mechanism accompanied by subsets for ozone, singlet oxygen, chemionization, and electron impact reactions. The baseline skeletal methane−air mechanism contains 17 species and 42 reactions, and it predicts the ignition delay time, flame temperature, flame speed, major species, and most minor species well, in addition to the extinction strain, compared to the detailed GRI 3.0 reaction mechanism. The amended skeletal reaction mechanism consists of 27 species and 80 reactions and is developed for a reduced electric field E/N below the critical field strength (of ∼125 Td) for the formation of a microwave breakdown plasma. Both laminar and turbulent flame simulation studies are carried out with the proposed skeletal reaction mechanism. The turbulent flame studies consist of propagating planar flames in homogeneous isotropic turbulence in the reaction sheets and the flamelets in eddies regimes, and a turbulent low-swirl flame. A comparison with experimental data is performed for a turbulent low-swirl flame. The results suggest that we can influence both laminar and turbulent flames by nonthermal plasmas, based on microwave irradiation. The laminar flame speed increases more than the turbulent flame speed, but the radical pool created by the microwave irradiation significantly increases the lean blow-out limits of the turbulent flame, thus making it less vulnerable to thermoacoustic combustion oscillations. Apart from the experimental results from low-swirl flame presented here, experimental data for validation of the simulated trends are scarce, and conclusions build largely on simulation results. Analysis of chemical kinetics from simulations of laminar flames and LES on turbulent flames reveal that singlet oxygen molecule is of key importance for the increased reactivity, accompanied by production of radicals such as O and OH.

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Section: Skeletal Microwave-assisted Methane−air Reaction Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Skeletal Methane–Air Reaction Mechanism for Large Eddy Simulation of Turbulent Microwave-Assisted Combustion

et al. 2017

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“…12 Quantitative measurements were performed by using absorption spectroscopy, and the flame propagation speed was determined to be increased by several percentage points. Wang et al 13 reported a novel microwave PAC system with emission spectroscopy and pulsed cavity ring-down spectroscopy (CRDS) and hypothesized that OH(X) radicals play a more prominent role in flame stabilization, but OH(A) radicals play a more dominant role in the ignition enhancement. Although the dominant species can be identified in experiment, the role of species produced by a plasma discharge of the fuel has not been discussed in an elementary reaction.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the hydrogen extraction reactions of isopentane molecules and ions

Gao

Yang

Zhao

2022

Phys. Chem. Chem. Phys.

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“…The current study indicates that the underlying mechanisms of PACs are mainly ascribed to the following effects: the temperature-rising effect caused by joule heating, the chemical effect brought about by active radicals, and the aerodynamic effect induced by the transport of charged particles and newly generated species as well as the shock waves and gas expansion generated by the fast heating of the gas [10,11]. The plasma, flow, and heat and mass transfer are highly coupled together such that the energy conversion efficiencies and exhaust emissions are governed by the combination of chemical and transport processes over multiple scales ranging from the atomic scale to that of turbulent fuel/air mixing [12][13][14][15][16][17]. Studies have shown PACs to be extremely sophisticated, and the mechanisms about many processes that occurr in combustion have remained unclear to date.…”

Section: Introductionmentioning

confidence: 99%

The effect of plasma discharge on methane diffusion combustion in air assisted by an atmospheric pressure microwave plasma torch

Li¹,

Niu²,

Cao³

et al. 2022

J. Phys. D: Appl. Phys.

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The atmospheric-pressure air microwave plasma torch is employed to assist the methane diffusion combustion with combination of the combustor and burner. Experimentally, the effect of air microwave plasma on combustion is demonstrated to be prominent in rich fuel condition by comparison of the plasma-assisted combustion (PAC) and the natural combustion (NC) without plasma application. The combustion degree of CH4 in the PAC is found to be much enhanced in rich fuel combustion than in the NC, which is measured by Fourier Transformation Infrared Spectrometer (FTIR). In the PAC with use of air microwave plasma torch, both the radicals produced in abundance and the high gas temperature induced in plasma discharge play the important role in assisting the combustion.

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Roles of the state-resolved OH(A) and OH(X) radicals in microwave plasma assisted combustion of premixed methane/air: An exploratory study

Cited by 30 publications

References 51 publications

Skeletal Methane–Air Reaction Mechanism for Large Eddy Simulation of Turbulent Microwave-Assisted Combustion

Skeletal Methane–Air Reaction Mechanism for Large Eddy Simulation of Turbulent Microwave-Assisted Combustion

Comparison of the hydrogen extraction reactions of isopentane molecules and ions

The effect of plasma discharge on methane diffusion combustion in air assisted by an atmospheric pressure microwave plasma torch

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