A ‘frozen electric-field’ approach to simulate repetitively pulsed nanosecond plasma discharges and ignition of hydrogen–air mixtures

Nagaraja, Sharath; Yang, Vigor

doi:10.1088/0022-3727/47/38/385201

Cited by 9 publications

(24 citation statements)

References 22 publications

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“…To tackle the multiscale nature of the problem, adaptive time stepping is implemented with small time steps (10 −13 − 10 −12 s) during each voltage pulse and larger time steps (10 −10 s) in the gap between two consecutive pulses. More details about the numerical methods can be found in the work by Nagaraja et al [30,31] and Yang et al [36].…”

Section: Fitting Of Voltage Waveformmentioning

confidence: 99%

“…Recently, Nagaraja et al [7,30,31] and Yang et al [6,32] developed a self-consistent, one-dimensional (1D) numerical framework to simulate pulsed nanosecond discharges in fuel/air mixtures. The model is capable of resolving the transient electric field during each nanosecond discharge pulse as well as calculating the cumulative effects of multiple pulses on fuel oxidation and combustion.…”

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: Fitting Of Voltage Waveformmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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 "frozen electric field" strategy takes advantage of the quasi-periodic behaviors of the electrical field to avoid the re-calculation of the electric field for each pulse. [25,28] show that the electrical characteristics are not exactly periodic, but approach pure periodicity after a certain number of pulses, when the input energy per pulse becomes stable (that is, the field achieves quasi-equilibrium). After the plasma has reached quasi-equilibrium, the accumulated input energy is linearly proportional to the number of pulses.…”

Section: "Frozen Electric Field" Strategymentioning

confidence: 99%

“…After the plasma has reached quasi-equilibrium, the accumulated input energy is linearly proportional to the number of pulses. Based on this observation, a "frozen electric field" strategy [25] is implemented. Simulation conducted in H2/air mixture at 114 Torr and 473 K initial pressure and temperature, respectively, at 40 kHz repetition rate.…”

Section: "Frozen Electric Field" Strategymentioning

confidence: 99%

Multiscale modeling and general theory of non-equilibrium plasma-assisted ignition and combustion

Yang¹,

Nagaraja²,

Sun³

et al. 2017

J. Phys. D: Appl. Phys.

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A self-consistent 1D theoretical framework for plasma assisted ignition and combustion is reviewed. In this framework, a "frozen electric field" modeling approach is applied to take advantage of the quasi-periodic behaviors of the electrical characteristics to avoid the recalculation of electric field for each pulse. The correlated dynamic adaptive chemistry (CO-DAC) method is employed to accelerate the calculation of large and stiff chemical mechanisms.The time-step is updated dynamically during the simulation through a three-stage multitimescale modeling strategy, which takes advantage of the large separation of timescales in nanosecond pulsed plasma discharges. A general theory of plasma assisted ignition and combustion is then proposed. Nanosecond pulsed plasma discharges for ignition and combustion can be divided into four stages. Stage I is the discharge pulse, with timescales of O(1-10 ns). In this stage, most input energy is coupled into electron impact excitation and dissociation reactions to generate charged/excited species and radicals. Stage II is the afterglow during the gap between two adjacent pulses, with timescales of O(100 ns). In this stage, quenching of excited species not only further dissociates O2 and fuel molecules, but also provides fast gas heating. the remaining gap between pulses, with timescales of O(1-100 μs). The radicals generated during Stages I and II significantly enhance the exothermic reactions in this stage. Stage IV is the accumulative effects of multiple pulses, with timescales of O(1 ms -1 sec), which include preheated gas temperatures and a large pool of radicals and fuel fragments to trigger ignition. For plasma assisted flames, plasma significantly enhances the radical generation and gas heating in the pre-heat zone, which could trigger upstream auto-ignition.Keywords: plasma assisted combustion, plasma fluid modeling, nanosecond plasma discharge, low temperature chemistry, ignition. Nomenclature

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“…Because of the lack of reliable experimental measurements for the permittivity and sheath formation in plasma-assisted combustion, the solution of Poisson equation for the electric field distribution becomes difficult without appropriate boundary conditions and plasma properties [1], [15]- [17]. Tomography by definition refers to a method of producing a multidimensional image of the internal characteristics of a specified region by observation and recording of the differences in the effects on the passage of waves of energy impinging on those structures.…”

Section: Introductionmentioning

confidence: 99%

Direct Measurements of Permittivity of Plasma-Assisted Combustion Using Electrical Capacitance Tomography

Chen

Jia

Mao

et al. 2016

IEEE Trans. Plasma Sci.

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The permittivity distribution and the flame development in a closed plasma-assisted combustor were investigated using an electrical capacitance tomography system. The experiments were conducted at a pressure of 1 atm and at different equivalence ratios. I-V curves measured by the Langmuir probe were utilized to estimate the floating potential (−40 to −10 V) and the electron local parameters (T e and n e ) in the plasma-assisted flames. The results showed that the electron concentration reached the maximum at a location close to the plasma injection point where the primary reaction region of the CH 4 -air premixed flame was located. Major species measurement by emission spectrometer combined with the probe measurement revealed that the kinetic enhancement was more significant than the thermal enhancement in the plasma-assisted combustion. Moreover, the dependence of combustion kinetics including electron/ion concentration and temperature on the flame permittivity was verified. The quantitative permittivity data obtained in this study provide a good validation target for modeling of the electric field in plasma-assisted combustion.

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A ‘frozen electric-field’ approach to simulate repetitively pulsed nanosecond plasma discharges and ignition of hydrogen–air mixtures

Cited by 9 publications

References 22 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

Multiscale modeling and general theory of non-equilibrium plasma-assisted ignition and combustion

Direct Measurements of Permittivity of Plasma-Assisted Combustion Using Electrical Capacitance Tomography

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