Comparative Study on Microwave Plasma-Assisted Combustion of Premixed and Nonpremixed Methane/Air Mixtures

Wu, Wei; Fuh, Che A.; Wang, Chuji

doi:10.1080/00102202.2014.993032

Cited by 15 publications

(4 citation statements)

References 62 publications

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“…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%

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: Introductionmentioning

confidence: 99%

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

et al. 2017

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“…4 by a dashed line. To make the curve fit the observed front trajectory, the coefficient β exp in (6) has been set to 3.1 (as in equation 6 To test the model against other measurements, the apparent flame speed at the exit of the tube was measured and compared to that predicted by (8).…”

Section: Resultsmentioning

confidence: 99%

“…Many experimental, theoretical and numerical studies have been performed in the past years with a variety of ignition systems such as electric discharge, microwave discharge, and laser radiation [2,3,4] tested to achieve simultaneous ignition at multiple ignition points throughout the combustion chamber. Plasma-assisted combustion is a promising technique to improve engine efficiency, reduce emissions, and enhance fuel reforming [1,5,6] with the use of cold and non-thermal plasmas appearing in microwave discharges becoming a major topic of interest [7,8].…”

Section: Introductionmentioning

confidence: 99%

Ignition of premixed air/fuel mixtures by microwave streamer discharge

Denissenko

Bulat

Esakov³

et al. 2019

Combustion and Flame

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“…According to which species the plasma energy is coupled into, plasma-assisted combustion can be classified into the following four approaches: the discharge in oxidizer, fuel, mixtures and the fuel addition such as water. In terms of the moment that plasma energy exerts, plasma-assisted combustion can be classified into pretreatment of reactants [12][13][14][15], direct in situ plasma discharges [16] and after-treatment of combustion [17]. Studies have devoted extensive efforts toward the pretreatment of reactants and after-treatment of combustion.…”

Section: Introductionmentioning

confidence: 99%

Investigation of flame structure in plasma-assisted turbulent premixed methane-air flame

ZHANG¹,

He²,

Yu³

et al. 2017

Plasma Sci. Technol.

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The mechanism of plasma-assisted combustion at increasing discharge voltage is investigated in detail at two distinctive system schemes (pretreatment of reactants and direct in situ discharge). OH-planar laser-induced fluorescence (PLIF) technique is used to diagnose the turbulent structure methane-air flame, and the experimental apparatus consists of dump burner, plasma-generating system, gas supply system and OH-PLIF system. Results have shown that the effect of pretreatment of reactants on flame can be categorized into three regimes: regime I for voltage lower than 6.6 kV; regime II for voltage between 6.6 and 11.1 kV; and regime III for voltage between 11.1 and 12.5 kV. In regime I, aerodynamic effect and slower oxidation of higher hydrocarbons generated around the inner electrode tip plays a dominate role, while in regime III, the temperature rising effect will probably superimpose on the chemical effect and amplify it. For wire-cylinder dielectric barrier discharge reactor with spatially uneven electric field, the amount of radicals and hydrocarbons are decreased monotonically in radial direction which affects the flame shape. With regard to in situ plasma discharge in flames, the discharge pattern changes from streamer type to glow type. Compared with the case of reactants pretreatment, the flame propagates further in the upstream direction. In the discharge region, the OH intensity is highest for in situ plasma assisted combustion, indicating that the plasma energy is coupled into flame reaction zone.

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Comparative Study on Microwave Plasma-Assisted Combustion of Premixed and Nonpremixed Methane/Air Mixtures

Cited by 15 publications

References 62 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

Ignition of premixed air/fuel mixtures by microwave streamer discharge

Investigation of flame structure in plasma-assisted turbulent premixed methane-air flame

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