Combustion Enhancement and Stabilization: Principles of Plasma Assistance and Diagnostics Tools

Vincent‐Randonnier, Axel

doi:10.1002/9783527628148.hoc077

Cited by 6 publications

(7 citation statements)

References 55 publications

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“…Plasma-assisted combustion (PAC) has triggered scientific attention for decades and several studies reviewed the experimental and numerical works performed on the subject [1][2][3][4]. In a review of PAC experiments performed in a wide range of pressures (0.01-10 atm) and temperatures (300-2000 K), Starikovskaia [1] stressed that kinetic models can predict the shortening of autoignition delay times but fail by several orders of magnitude to predict the absolute concentrations of radicals and active species.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, kinetic models have been developed to predict the chemical and thermal effects of nanosecond discharges in air [16][17][18] or in combustible mixtures [3]. An issue for complete numerical simulations of practical applications is the difference between plasma timescales (picoseconds to nanoseconds) and combustion timescales (nanoseconds to milliseconds) [4]. A simplified model of active species and heat production was successfully developed for NRP discharges in fresh methane/air mixtures [19] and successfully applied to simulate ignition [20].…”

Section: Introductionmentioning

confidence: 99%

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Plasma-assisted combustion with nanosecond discharges. I: Discharge effects characterization in the burnt gases of a lean flame

Minesi

Blanchard

Pannier

et al. 2022

Plasma Sources Sci. Technol.

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The prediction of a flame response to plasma assistance requires extensive knowledge of discharge-induced plasma kinetics. Detailed studies of nanosecond discharges are common in N2/O2 and fresh combustible mixtures but are still lacking in burnt gases. To fill this gap, we define a combustion reference test case and investigate the effects of Nanosecond Repetitively Pulsed (NRP) discharges placed in the recirculation zone of a lean (Φ = 0.8) CH4-air bluff-body stabilized flame at atmospheric pressure. In this zone, the plasma discharge is created in a mixture of burnt gases. Quantitative Optical Emission Spectroscopy (OES), coupled with measurements of electrical energy deposition, is performed to provide temporally (2 ns) and spatially (0.5 mm) resolved evolutions of the temperatures and concentrations of N2(B), N2(C), N2 +(B), OH(A), NH(A), and CN(B) in the discharge. At steady state, the 10-ns pulses deposit 1.8 mJ at a repetition frequency of 20 kHz. Spatially resolved temperature profiles are measured during the discharge along the interelectrode gap. The temperature variations are more pronounced near the electrodes than in the middle of the gap. On average, the gas temperature increases by approximately 550 K. The heat release corresponds to about 20% of the total deposited electric energy. The electron number density, measured by Stark broadening of Hα, increases up to about 1016 cm-3. These characteristics allow to classify the discharge as a non-equilibrium NRP spark, as opposed to the thermal NRP spark where the temperature can reach 40,000 K and the degree of ionization is close to 100%. These measurements will serve (i) as a reference for future studies in the Mini-PAC burner at the same conditions, (ii) to test discharge kinetic models, and (iii) to derive a simplified model of plasma-assisted combustion, which will be presented in companion paper.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Plasma-assisted combustion with nanosecond discharges. I: Discharge effects characterization in the burnt gases of a lean flame

Minesi

Blanchard

Pannier

et al. 2022

Plasma Sources Sci. Technol.

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“…The H α width uncertainty is about ±20%, which leads to a 30% uncertainty on the n e measured with this technique. The Stark broadening HWHM can be calculated 5 with equation ( 4) [59,60]…”

Section: This Workmentioning

confidence: 99%

“…These non-equilibrium plasmas can be sustained at a quasi-steady state by repeating the nanosecond discharge at kHz frequencies. Nanosecond repetitively pulsed (NRP) discharges feature rich non-thermal chemistry and therefore present a broad interest in several fields of engineering [4], such as plasma-assisted combustion [5,6] and plasma medicine [7]. They have been studied in various gas mixtures with the electrodes facing open gaps [8][9][10][11][12][13][14][15][16] or separated by dielectric barriers [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Kinetic mechanism and sub-ns measurements of the thermal spark in air

Minesi

Mariotto

Pannier

et al. 2023

Plasma Sources Sci. Technol.

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This experimental and numerical study is focused on the formation of fully ionized plasmas in ambient air by nanosecond pulsed discharges, namely the thermal spark. The first contribution of this article is the experimental charaterization of the electron number density during the pulse. The increase of the electron number density from 1016 to 101 cm-3 was measured with sub-nanosecond resolution via three techniques based on optical emission spectroscopy (OES): Stark broadening of Hα, Stark broadening of N+/O+, and the continuum emission of electrons. The discharge diameter is measured with sub-nanosecond resolution using calibrated OES of the N+ and O+ lines. All measurements indicate a transition to a micrometric-size filament of fully ionized plasma in approximately 0.5 ns. The second main contribution of this work is the development of a 0D kinetic mechanism to explain this observation. The mechanism includes 100 reactions, 12 species, and 12 excited electronic states. Particular attention is paid to modeling of N2, N2 +, N, and O electronic state kinetics using the electronic states as additional pseudo-species. Our results show that including the electron-impact ionization of the excited electronic states of N and O, in addition to those of N2, is necessary to explain the experimental results, emphasizing the key role of excited state kinetics in the thermal spark formation.

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“…The effects of electric fields on flames have been extensively investigated and shown to improve flame stabilization [1][2][3][4][5][6], change of burnt gas composition [7][8][9], and enhance flame speed [5,6,[10][11][12][13][14] for both premixed and diffusion flames. There are, however, still questions like which effects are mainly responsible for the observed changes; (1) an ionic wind responsible for changing flame shape, (2) a change in the chemical reactions due to ion/electron collisions, and or (3) a conversion of electrical energy into thermal energy.…”

Section: Introductionmentioning

confidence: 99%

Pulsed Current‐Voltage‐Induced Perturbations of a Premixed Propane/Air Flame

Schmidt¹,

Ganguly²

2011

Journal of Combustion

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The effect of millisecond wide sub-breakdown pulsed voltage-current induced flow perturbation has been measured in premixed laminar atmospheric pressure propane/air flame. The flame equivalence ratios were varied from 0.8 to 1.2 with the flow speeds near 1.1 meter/second. Spatio-temporal flame structure changes were observed through collection of CH (A-X) and OH (A-X) chemiluminescence and simultaneous spontaneous Raman scattering from N 2 . This optical collection scheme allows us to obtain a strong correlation between the measured gas temperature and the chemiluminescence intensity, verifying that chemiluminescence images provide accurate measurements of flame reaction zone structure modifications. The experimental results suggest that the flame perturbation is caused by ionic wind originating only from the radial positive space-charge distribution in/near the cathode fall. A net momentum transfer acts along the annular space discharge distribution in the reaction zone at or near the cathode fall which modifies the flow field near the cathodic burner head. This radially inward directed body force appears to enhance mixing similar to a swirl induced modification of the flame structure. The flame fluidic response exhibit a strong dependence on the voltage pulse width ≤10 millisecond.

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Combustion Enhancement and Stabilization: Principles of Plasma Assistance and Diagnostics Tools

Abstract: The sections in this article are Introduction Diagnostics Applied to Plasma‐Assisted Combustion Imaging S chlieren Flow Visualization Interferometry Spectroscopy Laser‐Induced Fluorescence … Show more

Cited by 6 publications

References 55 publications

Plasma-assisted combustion with nanosecond discharges. I: Discharge effects characterization in the burnt gases of a lean flame

Plasma-assisted combustion with nanosecond discharges. I: Discharge effects characterization in the burnt gases of a lean flame

Kinetic mechanism and sub-ns measurements of the thermal spark in air

Pulsed Current‐Voltage‐Induced Perturbations of a Premixed Propane/Air Flame

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