The Effect of Uniform and Non-Uniform Electric Field on Flame Propagation

Abstract

The purpose of this study is to elucidate flame propagation behavior under the application of uniform and non-uniform electric fields by using a constant volume vessel. Two electrodes were attached to the ceiling and the bottom of the cubic shaped combustion chamber and electric fields were applied in the direction of the chamber's vertical axis. A Nd:YAG laser was used to apply laser-induced breakdown for igniting the mixture at the center of the combustion chamber. A homogeneous propane-air mixture was supplied at three equivalence ratios of 0.7, 1.0 and 1.5 and ignited under atmospheric pressure and room temperature. Under a uniform electric field, the premixed flame rapidly propagated both upward and downward, forming a cylindrically shaped flame front. The maximum combustion pressure decreased with increasing input voltage because the flame front reached the chamber wall rapidly and the heat loss to electrodes increased. However, the combustion duration was little affected by the input voltage. In a non-uniform electric field, the flame propagation velocity in the downward direction increased. The leftward and rightward flame propagation velocities were almost the same and were slightly larger than those of conventional combustion. Combustion was markedly enhanced when the input voltage was larger than 12 kV because a brush corona discharge occurs and intense turbulence was generated at the flame front. This indicated that both the electrical potential and corona wind affected combustion. The brush corona discharge caused by a non-uniform electric field enhanced combustion, and the enhancement effect was clearly seen for both lean and rich mixtures.