Abstract
It was explored that the flame propagation behavior of hydrogen-air mixture under the application of positive and negative non-uniform electric field by using a constant volume vessel. For applying a non-uniform electric field, a needle-shaped electrode was attached to the center of the combustion chamber ceiling and a plate electrode was attached to the bottom of the chamber. A Nd:YAG laser was used to apply laser-induced breakdown for igniting the mixture at the center of combustion chamber. A homogeneous hydrogen-air mixture was supplied at three equivalence ratios of 0.4, 1.0 and 3.5 and ignited under atmospheric pressure and room temperature. The flame propagation process was visualized with a conventional Z-shaped schlieren system. In case of lean mixture and applying positive polarity non-uniform electric field, the wrinided flame appeared by the effect of preferential diffusion and the wrinkle was enhanced when the input voltage was larger than 12 kV because a brush corona discharge occurred and turbulence was generated at the flame front. However, for the stoichiometric mixture, the pre-mixed combustion process was not influenced by the positive polarity non-uniform electric field and, for rich mixture, the flame front was merely moved toward downward by corona wind. When a negative polarity non-uniform electric field was applied, for any cases, the combustion was not affected because the corona wind was not generated. Therefore, the electric field hardly affects the flame propagation of hydrogen-air mixture and the corona wind which is generated by the positive brash corona only influences the combustion process.
