Schlieren imaging and pulsed detonation engine testing of ignition by a nanosecond repetitively pulsed discharge

Lefkowitz, Joseph K.; Guo, Peng; Ombrello, Timothy; Won, Sang Hee; Stevens, Christopher; Hoke, John; Schauer, Frederick; Ju, Yiguang

doi:10.1016/j.combustflame.2015.02.019

Cited by 77 publications

(44 citation statements)

References 32 publications

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“…The wall boundary fluxes for electrons, positive ions, negative ions, and electron energy are given by Eqs. (8)(9)(10)(11), respectively [34], where the secondary electron emission coefficient γ is taken to be 0.05, following [34]. The temperature of secondary electrons ejected from the electrode surface T se is assumed to be 1 eV [34].…”

Section: B Governing Equations and Initial/boundary Conditionsmentioning

confidence: 99%

“…In Eqs. (8)(9)(10)(11), a 1 if E · n s < 0, and a 0 otherwise. A zero flux boundary condition is also imposed for the mass and momentum conservation equations.…”

Section: B Governing Equations and Initial/boundary Conditionsmentioning

confidence: 99%

“…Experiments have demonstrated that plasmas can shorten ignition delay times [5][6][7][8][9][10][11], extend extinction limits [12,13], improve flame stabilization [12,14], increase flame speed [6,15], and suppress soot formation [15,16]. Unfortunately, most of the studies mentioned focus on the phenomenological impacts of plasma assisted combustion (PAC), and the underlying physical and chemical mechanisms of plasma enhancement remain less understood.…”

Section: Introductionmentioning

confidence: 99%

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Nanosecond Pulsed Plasma Activated C2H4/O2/Ar Mixtures in a Flow Reactor

Yang¹,

Gao²,

Yang³

et al. 2016

Journal of Propulsion and Power

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The present work combines numerical and experimental efforts to investigate the effect of nanosecond pulsed plasma discharges on the low-temperature oxidation of C 2 H 4 ∕O 2 ∕Ar mixtures under reduced pressure conditions. The nonequilibrium plasma discharge is modeled using a one-dimensional framework, employing separate electron and neutral gas temperatures, and using a detailed plasma and combustion chemical kinetic mechanism. Good agreement is seen between the numerical and experimental results, and both results show that plasma enables lowtemperature C 2 H 4 oxidation. Compared to zero-dimensional modeling, the one-dimensional modeling significantly improves predictions, probably because it produces a more complete physical description (including sheath formation and accurate reduced electric field). Furthermore, the one-and zero-dimensional models show very different reaction pathways, using the same chemical kinetic mechanism and thus suggest different interpretations of the experimental results. Two kinetic mechanisms (HP-Mech and USC Mech-II) are examined in this study. The modeling results from HP-Mech agree better with the experimental results than those of USC Mech-II because USC Mech-II does not include the OH C 2 H 4 CH 2 CH 2 OH reaction pathway. The model shows that 75-77% of the input pulse energy is consumed during the breakdown process in electron impact dissociation, excitation, and ionization reactions, which efficiently produce reactive radical species, fuel fragments, and excited species. The modeling results using HP-Mech reveal that reactions between O 1 D and C 2 H 4 generate 24% of OH, 19% of HCO, 60% of CH 3 , 63% of CH 2 , and 17% of CH 2 O. These in turn significantly enhance hydrocarbon oxidation, since 83% of CO comes from HCO and 53% of CO 2 comes from CH 2 under the present low-temperature environment and short time scale. Nomenclature E = electric field, V · cm −1 F EHD i = electrohydrodynamic force per unit volume, kg · cm −2 · s −1 Gt = nondimensional heat transfer parameter J e;s = wall boundary flux of electrons, cm −2 · s −1 J k = flux of kth species, cm −2 · s −1 J ϵ = flux of electron energy, eV · cm −2 · s −1 J ϵ;s = wall boundary flux of electron energy, eV · cm −2 · s −1 J ;s = wall boundary flux of positive ions, cm −2 · s −1 J −;s = wall boundary flux of negative ions, cm −2 · s −1 J ;− = net positive and negative charge fluxes, respectively, cm −2 · s −1

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Section: B Governing Equations and Initial/boundary Conditionsmentioning

confidence: 99%

“…In Eqs. (8)(9)(10)(11), a 1 if E · n s < 0, and a 0 otherwise. A zero flux boundary condition is also imposed for the mass and momentum conservation equations.…”

Section: B Governing Equations and Initial/boundary Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nanosecond Pulsed Plasma Activated C2H4/O2/Ar Mixtures in a Flow Reactor

Yang¹,

Gao²,

Yang³

et al. 2016

Journal of Propulsion and Power

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“…Lefkowitz et al have used the schlieren imaging and optical emission spectra to reveal the evolution characteristics during and between the discharge pulses for the nanosecond repetitively pulsed discharge in CH 4 /air. 14 Levko and Raja have studied the active species production by the CH 4 / air streamer discharge and have concluded that steamers initiated by the positive and negative trigger voltage cannot be considered symmetrical. 15 More recently, Qian et al have presented a fluid modeling study of the radical species generation a) Author to whom correspondence should be addressed: sdnupanjie@163.com by a positive streamer in the dense CH 4 /air DBD.…”

Section: Introductionmentioning

confidence: 99%

Reaction pathways of producing and losing particles in atmospheric pressure methane nanosecond pulsed needle-plane discharge plasma

Zhao

Wang

et al. 2018

Physics of Plasmas

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In this work, a two-dimensional fluid model is built up to numerically investigate the reaction pathways of producing and losing particles in atmospheric pressure methane nanosecond pulsed needle-plane discharge plasma. The calculation results indicate that the electron collisions with CH4 are the key pathways to produce the neutral particles CH2 and CH as well as the charged particles e and CH3+. CH3, H2, H, C2H2, and C2H4 primarily result from the reactions between the neutral particles and CH4. The charge transfer reactions are the significant pathways to produce CH4+, C2H2+, and C2H4+. As to the neutral species CH and H and the charged species CH3+, the reactions between themselves and CH4 contribute to substantial losses of these particles. The ways responsible for losing CH3, H2, C2H2, and C2H4 are CH3 + H → CH4, H2 + CH → CH2 + H, CH4+ + C2H2 → C2H2+ + CH4, and CH4+ + C2H4 → C2H4+ + CH4, respectively. Both electrons and C2H4+ are consumed by the dissociative electron-ion recombination reactions. The essential reaction pathways of losing CH4+ and C2H2+ are the charge transfer reactions.

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“…1 Major combustion enhancement pathways of plasma assisted combustion [1] accelerate cool flame ignition. However, many of the kinetic mechanisms governing plasma assisted low temperature chemistry are poorly understood [22].…”

Section: Introductionmentioning

confidence: 99%

Plasma Assisted Low Temperature Combustion

Lefkowitz

Reuter

et al. 2015

Plasma Chem Plasma Process

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139

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This paper presents recent kinetic and flame studies in plasma assisted low temperature combustion. First, the kinetic pathways of plasma chemistry to enhance low temperature fuel oxidation are discussed. The impacts of plasma chemistry on fuel oxidation pathways at low temperature conditions, substantially enhancing ignition and flame stabilization, are analyzed base on the ignition and extinction S-curve. Secondly, plasma assisted low temperature ignition, direct ignition to flame transition, diffusion cool flames, and premixed cool flames are demonstrated experimentally by using dimethyl ether and n-heptane as fuels. The results show that non-equilibrium plasma is an effective way to accelerate low temperature ignition and fuel oxidation, thus enabling the establishment of stable cool flames at atmospheric pressure. Finally, the experiments from both a nonequilibrium plasma reactor and a photolysis reactor are discussed, in which the direct measurements of intermediate species during the low temperature oxidations of methane/ methanol and ethylene are performed, allowing the investigation of modified kinetic pathways by plasma-combustion chemistry interactions. Finally, the validity of kinetic mechanisms for plasma assisted low temperature combustion is investigated. Technical challenges for future research in plasma assisted low temperature combustion are then summarized.

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Schlieren imaging and pulsed detonation engine testing of ignition by a nanosecond repetitively pulsed discharge

Cited by 77 publications

References 32 publications

Nanosecond Pulsed Plasma Activated C2H4/O2/Ar Mixtures in a Flow Reactor

Nanosecond Pulsed Plasma Activated C2H4/O2/Ar Mixtures in a Flow Reactor

Reaction pathways of producing and losing particles in atmospheric pressure methane nanosecond pulsed needle-plane discharge plasma

Plasma Assisted Low Temperature Combustion

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