Experimental Facility for Laminar, Heterogeneous Flame Propagation in a Nano-Aluminum Aerosol
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Research with heterogeneous mixtures involving solid particulate in closed, constant-volume bombs is typically limited by the powder dispersion techniques. This work details the development of an experimental apparatus that promotes ideal conditions, namely a quiescent atmosphere and uniform particle distribution, for measuring laminar, heterogeneous flame propagation. In this work, two methods of dispersing particles were investigated. In the first, heterogeneous mixtures were made in a secondary vessel that is connected to the main experiment. Particles are dispersed into the secondary vessel by adapting a piston-driven particle injector, which has been shown to produce uniform particle distributions. The heterogeneous mixture is then transferred to the main bomb facility and ignited after laminar conditions are achieved. In the second method of dispersion, particles were directly injected into the main experimental facility using a strong blast of compressed air. As with the first approach, enough time was given (~4 minutes) for the mixture to become quiescent before ignition occurs. An extinction diagnostic was also applied to the secondary mixing vessel as well as the primary experimental facility (for both dispersion methods) to provide a qualitative understanding of the dispersion technique. Aluminum nano-particles with an average diameter of 100 nm were used in this study. A hybrid mixture of Al/CH4/O2/N2was employed to achieve the project goal of demonstrating a system for controlled laminar flame speed measurements in aerosol mixtures. With the hybrid mixture, the combustion characteristics were studied both with and without the presence of nano-Al particles. Based on experimental results, the simplicity of the direct-injection methodology compared to that of the side-vessel is desirable and will be further investigated as a viable alternative, or improvement, to the side-vessel technology. 2013 by the authors.
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51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition
