Progress in miniature liquid film combustors: Double chamber and central porous fuel inlet designs

One of the key limits to miniaturizing the size of liquid fueled combustors is the atomization process applied in meso-scale systems. A single-wall fuel-film combustor was introduced recently as one of the successful liquid fuel combustors at the meso-scale. Instead of atomizing the fuel, film combustors spread out a liquid film along the wall and absorb the heat transferred from the flame for vaporization. With a single-wall film design, however, there are some unexpected and disadvantageous combustion phenomena. This paper attempts to improve the single-wall film combustor by exploring separately a double chamber concept and a central porous fuel delivery concept. These two configurations help describe the limits and the potential of liquid fuel-film miniature combustors. The double chamber design demonstrates how heat transfer issues can be overcome by injecting the fuel-film on the outside of the primary combustor wall rather than on the inside, and the second design demonstrates a flame-holding mechanism using a porous material set on the bottom of the chamber. The combustion behavior in these two configurations is compared with that in the original single-wall miniature fuel-film combustor, revealing new aspects that are relevant to portable power generation with high specific energy and power.