An experimental study on laminar CH4/O2/N2 premixed flames under an electric field

This work investigates the electric field effect on gas temperature, radiative heat flux and flame speed of premixed CH4/O-2/N-2 flames in order to gain a better insight into the mechanism of controlling the combustion process by electro-physical means. Experiments were performed on laminar Bunsen flames (Re<2200) of lean to rich mixture composition (phi=0.8-1.2) with slight oxygen enrichment (Omega=0.21-0.30). The Schlieren flame angle technique was used to determine the flame speed, and thermocouple measurements at the post flame gas were conducted. The radiative heat flux was measured by using a heat flux meter. At high field strengths, coincident with the appearance and enhancement of flame surface curvatures, an apparent change in flame speed and gas temperature was observed. However, the application of an electric field had no significant effect on flame speed and temperature when the flame geometry was unaltered. This was supported by radiative heat flux showing negligible electric field effects. The modification in flame temperature and flame speed under electric field was attributed to the field-induced flame stretch due to the body forces produced by the ionic winds. This additional flame stretch, coupled with the influence of non-unity Lewis number, accounts for such changes. This reinforces the idea that the action of an electric field on flames with a geometry that remains practically undeformed produces very minimal effect on flame speed, temperature and radiative heat flux. A possible mechanism of combustion control by the application of flame stretch using electric field was introduced.