Role of hydrogen addition in propane/air flame characteristic and stability in a micro-planar combustor

For combustion occurring under micro-scale conditions, how to enhance the flame stability is of significance. For this, a micro-planar quartz combustor with transparent main walls is designed to experimentally shed lights on the flame stabilization mechanism of premixed propane flame with hydrogen added in terms of flame dynamics. Experimental results show that as far as the pure propane combustion is concerned, there are six types of flame structures with varying the gaseous inlet velocity, i.e., flame repetitive extinction and ignition (FREI flame), cellular flame, planar flame, U-shaped flame, inclined flame and spinning flame. Furthermore, blending hydrogen is found to significantly extend the flame stability. This is due to the fact that the addition of hydrogen can overcome the inlet velocity inertia and restrain flame instability caused by hysteresis. For the inlet velocity considered in this work, hydrogen addition can inhibit transformation of flame type from U-shaped flame to inclined flame. Finally, the flame position, thickness and curvature of U-shaped flame are shown to be significantly affected by hydrogen addition ratio. Specifically, the larger the hydrogen addition ratio, the smaller the flame thickness, indicating that hydrogen addition is conducive to maintaining symmetry of the flame back and forth. In general, this work has an implication of designing a high stability micro-power system by reasonably considering the inlet parameter.