Correlating flame geometry in opposed-flow flame spread over thin fuels |
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Authors: | Subrata Bhattacharjee Shuhei Takahashi Kazunori Wakai Christopher P. Paolini |
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Affiliation: | 1. Mechanical Engineering Department, Stanford University, Stanford, CA 94305-3032, United States;2. Department of Fire Protection Engineering, University of Maryland, College Park, MD 20742, United States;1. Department of Mechanical Engineering, University of California - Berkeley, Berkeley, CA 94720, USA;2. NASA Glenn Research Center, 21000 Brookpark Rd., Cleveland, OH 44135, USA;1. University of Maryland, Department of Fire Protection Engineering, College Park, MD 20742, United States;2. University of New Haven, Department of Fire Science and Professional Studies, West Haven, CT 06516, United States |
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Abstract: | Numerical analysis and scale analysis are combined in a novel manner in this work to develop closed-form expressions for flame geometry in opposed-flow flame spread over condensed fuels. A scale analysis is used to relate different geometric attributes to appropriate non-dimensional parameters. A comprehensive numerical model is then used to generate a large set of numerical data for flame height, flame length, and pyrolysis length as functions of different fuel and oxidizer parameters for flame spread in the thermal, kinetic, and radiative regimes. The numerical data is then correlated to scaled expressions and the unknown coefficients are numerically determined. It is shown that flame length, flame height, and pyrolysis length can be expressed in terms of the preheat length in different regimes of flame spread. An experimental approach is outlined to measure the preheat length necessary for accurately predicting the flame structure. Experimental images obtained from interferometry in two different regimes – downward spreading configuration and quiescent microgravity environment – are consistent with the proposed flame height correlation. |
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