Calculation and analysis of the mobility and diffusion coefficient of thermal electrons in methane/air premixed flames

Bisetti, Fabrizio; Morsli, Mbark El

doi:10.1016/j.combustflame.2012.08.002

Cited by 51 publications

(32 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ion transport is modeled according to a mixture-average approach with potentials adequate for charged species [7]. The mobility of the electron is constant and equal to µ e = 0.4 m 2 V −1 s −1 [17]. Einstein's rela-tion is used to obtain diffusion coefficients from mobilities and vice versa.…”

Section: Configuration Models and Methodsmentioning

confidence: 99%

“…(4). In reality, while µ − = µ e ≈ const in the burnt gases [17], the cation mobility µ + does vary significantly across the preheat zone ahead of the flame.…”

Section: Analytical Model For the I -V Curvementioning

confidence: 99%

“…Recall that the conservation equation for the number density n i is dJ i /dx =ω i [7,17], where J i is the number flux of species i, andω i is the source term due to reactions. By contrast with neutral species, J i consists of three terms for charged species [7,17]: (a) the convective flux due to the number-averaged bulk velocity, (b) the diffusive flux due to gradients in the number density, and (c) the drift diffusion flux ±µ i En i , where µ i is the mobility of the charged species, E is the electric field strength, and + (−) denotes positive (negative) charges. Note that in this work we consider the case of singly charged species only.…”

Section: Electrical Aspects Of Burner-stabilized Flames Under Appliedmentioning

confidence: 99%

See 2 more Smart Citations

The i−V curve characteristics of burner-stabilized premixed flames: detailed and reduced models

Han

Belhi

Casey

et al. 2017

Proceedings of the Combustion Institute

Self Cite

View full text Add to dashboard Cite

The i -V curve describes the current drawn from a flame as a function of the voltage difference applied across the reaction zone. Since combustion diagnostics and flame control strategies based on electric fields depend on the amount of current drawn from flames, there is significant interest in modeling and understanding i -V curves. We implement and apply a detailed model for the simulation of the production and transport of ions and electrons in one-dimensional premixed flames. An analytical reduced model is developed based on the detailed one, and analytical expressions are used to gain insight into the characteristics of the i -V curve for various flame configurations. In order for the reduced model to capture the spatial distribution of the electric field accurately, the concept of a dead zone region, where voltage is constant, is introduced, and a suitable closure for the spatial extent of the dead zone is proposed and validated. The results from the reduced modeling framework are found to be in good agreement with those from the detailed simulations. The saturation voltage is found to depend significantly on the flame location relative to the electrodes, and on the sign of the voltage difference applied. Furthermore, at sub-saturation conditions, the current is shown to increase * Corresponding author Email address: fbisetti@utexas.edu (Fabrizio Bisetti)Preprint submitted to Proceedings of the Combustion Institute July 17, 2016linearly or quadratically with the applied voltage, depending on the flame location. These limiting behaviors exhibited by the reduced model elucidate the features of i -V curves observed experimentally. The reduced model relies on the existence of a thin layer where charges are produced, corresponding to the reaction zone of a flame. Consequently, the analytical model we propose is not limited to the study of premixed flames, and may be applied easily to others configurations, e.g. nonpremixed counterflow flames.

show abstract

Section: Configuration Models and Methodsmentioning

confidence: 99%

“…(4). In reality, while µ − = µ e ≈ const in the burnt gases [17], the cation mobility µ + does vary significantly across the preheat zone ahead of the flame.…”

Section: Analytical Model For the I -V Curvementioning

confidence: 99%

Section: Electrical Aspects Of Burner-stabilized Flames Under Appliedmentioning

confidence: 99%

See 1 more Smart Citation

The i−V curve characteristics of burner-stabilized premixed flames: detailed and reduced models

Han

Belhi

Casey

et al. 2017

Proceedings of the Combustion Institute

Self Cite

View full text Add to dashboard Cite

show abstract

“…Two extreme cases-α = 0 (all negative charges were carried by negative ions) and α = 1 (all negative charges were carried by electrons)-were examined to test the effect of different mobility. For both positive and negative ions, mobility was adopted at 2.9×10 -4 m 2 /s-V [27,30], while electron mobility was set at 0.4 m 2 /s-V [36]. The width parameter a of the ion generation profile g was set at 1 mm to approximate typical flame thickness.…”

Section: The Ionized Layer At the Center Of A Gapmentioning

confidence: 99%

DC field response of one-dimensional flames using an ionized layer model

Xiong

Park

Lee

et al. 2016

Combustion and Flame

View full text Add to dashboard Cite

Abstract:We develop a simplified model to better explain electric current response when direct current (DC) is applied to a flame. In particular, different current responses have been observed by changing the polarity of the DC in a sub-saturated current regime that results from the presence of ions and electrons in the flame zone. A flame zone was modeled as a thin, ionized layer located in one-dimensional DC electric fields. We derived simplified model-governing equations from species equations by implementing mobility differences dependent on the type of charged particle, particularly between ions and electrons; we performed experiments to substantiate the model. Results showed that the sub-saturated current and local field intensity were significantly influenced by the polarity of the DC because of the combined effect of unequal mobility of charged particles and the position of the ionized layer in the gap relative to two electrodes. When an energized electrode is close to the ionized layer, applying a negative DC causes a more rapid increase in current than by applying a positive DC to the same electrode.Results from our experimental measurement of current using counterflow diffusion flames agreed qualitatively well with the model predictions. A sensitivity analysis using dimensional and non-dimensional parameters also supported the importance of the mobility difference and the relative location of the ionized layer on the electric current response.

show abstract

“…Meanwhile, the impact of electrons in this model is also small, because the applied voltages on the mesh electrodes are negative in this paper, so the direction of the electric field was from the ignition electrodes to the mesh electrodes (to the right in the simulation part of Figure 4). For this reason, only positive ions were driven to the premixed zone to produce the ionic wind effect, while electrons would be removed to the burned zone rapidly, due to their low number density and extremely high mobility (K = 4000 cm 2 /s/V) [36], which is at least three orders of magnitude higher than that of ions (K = 1.0 cm 2 /s/V) [28,37]. Although some research had shown that electrons may produce the excitation of nitrogen and other molecules by collisions [19,20], however, these chemical activation steps ocurred in the burned zones in this paper, so they would not have an obvious effect on the outward flame propagation.…”

Section: Numerical Assumptionmentioning

confidence: 99%

Deformation Study of Lean Methane-Air Premixed Spherically Expanding Flames under a Negative Direct Current Electric Field

et al. 2016

Energies

View full text Add to dashboard Cite

This paper compares numerical simulations with experiments to study the deformation of lean premixed spherically expanding flames under a negative direct current (DC) electric field. The experiments, including the flame deformation and the ionic distribution on the flame surface were investigated in a mesh to mesh electric field. Besides, a numerical model of adding an electric body force to the positive ions on the flame surface was also established to perform a relevant simulation. Results show that the spherical flame will acquire an elliptical shape with a marked flame stretch in the horizontal direction and a slight inhibition in the vertical direction under a negative DC electric field. Meanwhile, a non-uniform ionic distribution on the flame surface was also detected by the Langmuir probe. The simulation results from the numerical model show good agreement with experimental data. According to the velocity field analysis in simulation, it was found the particular motion of positive ions and neutral molecules on the flame surface should be responsible for the special flame deformation. When a negative DC electric field was applied, the majority of positive ions and colliding neutral molecules will form an ionic flow along the flame surface by a superposition of the electric field force and the aerodynamic drag. The ionic flow was not uniform and mainly formed on the upper and lower sides, so it will lead to a non-uniform ionic distribution along the flame surface. What's more, this ionic flow will also induce two vortexes both inside and outside of the flame surface due to viscosity effects. The external vortexes could produce an entraining effect on the premixed gas and take away the heat from the flame surface by forced convection, and then suppress the flame propagation in the vertical direction, while, the inner vortexes would scroll the burned zones and induce an inward flow at the horizontal center, which could be the reason for the pitted structure at the horizontal center when a high voltage was applied.

show abstract

Calculation and analysis of the mobility and diffusion coefficient of thermal electrons in methane/air premixed flames

Cited by 51 publications

References 12 publications

The i−V curve characteristics of burner-stabilized premixed flames: detailed and reduced models

The i−V curve characteristics of burner-stabilized premixed flames: detailed and reduced models

DC field response of one-dimensional flames using an ionized layer model

Deformation Study of Lean Methane-Air Premixed Spherically Expanding Flames under a Negative Direct Current Electric Field

Contact Info

Product

Resources

About