Flame structure in smal-scale liquid film combustors

Recent advances in technology for commercial, medical, military, and governmental applications have increased the demand for portable power systems. One solution is to design a small-scale liquid-fueled combustion system, which takes advantage of volumetric reactions for quick energy release and a nonvolatile fuel that provides high specific energy. To make use of the high surface-to-volume ratios with decreasing size that generally increase heat loss, an innovative concept is to inject the fuel as a liquid film on the inner combustor surface, effectively reducing losses by redirecting heat towards film vaporization. This film is generated and stabilized in a tubular chamber by introducing swirling airflow, and investigation of the resulting flames has demonstrated that flame ignition and stability are dependent upon wall temperature and film location, and do not require recirculation or a physical flameholder. Attempts to investigate flame structures in a low thermal conductivity quartz chamber have revealed that poor wall heat transfer compromises the stability of the flame. Chemiluminescence measurements of the OH*, CH*, and C-2* intensities, and an Abel transform of the integrated images to obtain the radial distribution of these radical species within a sapphire chamber supports the theory that the fuel-film flame is composed of two structures: a double flame at the exit rim and a central triple flame within the chamber. (c) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.