Modelling of the effect of DC and AC electric fields on the stability of a lifted diffusion methane/air flame

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

“…Lastly, the boundary conditions proposed in Ref. [9] were adopted for the balance equations describing the transport of charged species.…”

Section: Configuration Models and Methodsmentioning

confidence: 99%

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

“…The resulting spatial discretization is second-order accurate with low numerical dissipation. As pointed out by Sommerer and Kushner [31] and more recently by Belhi et al [21], the high drift velocity developed by the ions, even when exposed to weak electric fields, increases the stiffness of the problem requiring a time-step much smaller than that needed to advance the Navier-Stokes equations in time. In fact, the Courant-Friedrichs-Lewy (CFL) condition for the k th drifting scalar is reformulated to provide the integration time-step (∆t) as…”

Section: Numerical Proceduresmentioning

confidence: 99%

An efficient flamelet progress-variable method for modeling non-premixed flames in weak electric fields

et al. 2017

View full text Add to dashboard Cite

Combustion stabilization and enhancement of the flammability limits are mandatory objectives to improve nowadays combustion chambers. At this purpose, the use of an electric field in the flame region provides a solution which is, at the same time, easy to implement and effective to modify the flame structure. The present work describes an efficient flamelet progress-variable approach developed to model the fluid dynamics of flames immersed in an electric field. The main feature of this model is that it can use complex ionization mechanisms without increasing the computational cost of the simulation. The model is based on the assumption that the combustion process is not directly influenced by the electric field and has been tested using two chemi-ionization mechanisms of different complexity in order to examine its behavior with and without the presence of heavy anions in the mixture. Using a one-and two-dimensional numerical test cases, the present approach has been able to reproduce all the major aspects encountered when a flame is subject to an imposed electric field and the main effects of the different chemical mechanisms. Moreover, the proposed model is shown to produce a large reduction in the computational cost, being able to shorten the time needed to perform a simulation up to 40 times.

show abstract

“…Furthermore, replacing one Poisson-like velocity equation with the continuity equation will break the favourable second-order ellipticity of the governing equations and will compromise its advantageous convergence properties for fully implicit solvers. This deficiency is especially severe for flame simulations, because complicated and highly nonlinear models for chemical kinetics [44][45][46][47][48][49], radiation [50,51], diffusion [52], droplets [53][54][55], particles [56], soot [57][58][59][60][61] and electric fields [62][63][64] are often employed. In order to circumvent this difficulty, Ern and Smooke [33] suggested that the converged solution of the Poisson approach can be used as the initial guess in the hybrid approach [23,24].…”

Section: Introductionmentioning

confidence: 99%

MC-Smooth: A mass-conserving, smooth vorticity–velocity formulation for multi-dimensional flows

Cao

Bennett

Smooke

2015

Combustion Theory and Modelling

View full text Add to dashboard Cite

A novel vorticity-velocity formulation of the Navier-Stokes equations -the MassConserving, Smooth (MC-Smooth) vorticity-velocity formulation -is developed in this work. The governing equations of the MC-Smooth formulation include a new secondorder Poisson-like elliptic velocity equation, along with the vorticity transport equation, the energy conservation equation, and N spec species mass balance equations. In this study, the MC-Smooth formulation is compared to two pre-existing vorticity-velocity formulations by applying each formulation to confined and unconfined axisymmetric laminar diffusion flame problems. For both applications, very good to excellent agreement for the simulation results of the three formulations has been obtained. The MC-Smooth formulation requires the least CPU time and can overcome the limitations of the other two pre-existing vorticity-velocity formulations by ensuring mass conservation and solution smoothness over a broader range of flow conditions. In addition to these benefits, other important features of the MC-Smooth formulation include: (1) it does not require the use of a staggered grid, and (2) it does not require excessive grid refinement to ensure mass conservation. The MC-Smooth formulation is a computationally attractive approach that can effectively extend the applicability of the vorticity-velocity formulation.

show abstract

Modelling of the effect of DC and AC electric fields on the stability of a lifted diffusion methane/air flame

Cited by 60 publications

References 38 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

An efficient flamelet progress-variable method for modeling non-premixed flames in weak electric fields

MC-Smooth: A mass-conserving, smooth vorticity–velocity formulation for multi-dimensional flows

Contact Info

Product

Resources

About