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Articles

Electric field influence on the stability and the soot particles emission of a laminar diffusion flame

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Pages 325-338 | Received 30 Oct 2017, Accepted 17 Apr 2018, Published online: 01 May 2018
 

ABSTRACT

Influence of electric fields on flames has been studied for many years and the ionic wind constitutes the main explanation of the observed effects on the flame structure and pollutant emissions. However, previous works have been limited to small flames. The interaction mechanisms of an electric field with longer flames, involving both ionic wind and buoyancy are not fully identified. In the present paper, the effects of a D.C. electric field on a laminar 88-mm-long ethylene diffusion flame burning in ambient air are investigated. Based on the calculated electric field configuration, the influence of both downward and upward electric field is compared via imaging, electrical diagnostic and soot measurements. The application of a negative (directed downstream) electric field triggers a flickering instability and an electric instability at higher field strength, in which self-sustained flame oscillations of flame length directly affect ion current. Conversely, the flame is stabilized by a positive electric field. In-situ soot volume fraction measurements show that the electric field decreases the average soot volume fraction measured on a stable flame axis, whereas flame oscillations lead to a sooting flame.

Nomenclature

fv=

mean soot volume fraction

HAB=

height above burner

I=

intensity of the extinguished beam

I0=

intensity of the reference beam

λ=

laser wavelength

E(m)=

function of the refractive index of the soot

L=

laser path length through the flame

Subscripts

0=

reference

Superscripts

+=

positive electric field

=

negative electric field

Acknowledgments

The authors appreciate the technical contributions of L. Peilleron and N. Gouillon.

Additional information

Funding

This work was supported by the Labex CAPRYSSES-ANR from the French Government [Convention n° ANR-11-LABX-0006-01].

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