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Original Articles

Effect of Non-Luminous Flame Radiation During Methanol Droplet Combustion

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Pages 546-564 | Published online: 23 Jan 2008
 

Abstract

The effect of non-luminous thermal radiation on the combustion of a suspended methanol droplet in a low temperature (300 K) and low pressure (1 atm) environment is discussed in detail. Numerical results are obtained using a predictive, transient, two-phase, axisymmetric numerical model that includes surface tension effects. Radiation is modeled using the optically thin approximation with the product species CO2 and H2O as the radiating species. Results for combustion in a nearly quiescent atmosphere (initial Reynolds number 0.01) and initial droplet diameters in the range of 0.43 mm to 3 mm are presented. In agreement with the reported literature, it is shown that the effect of flame radiation is negligible when the initial droplet diameter is less than approximately 1 mm and becomes increasingly important for larger droplets. As a result, the average evaporation constant decreases with the initial droplet diameter. Radiation and surface tension combined as well as surface tension alone have a significant effect on the predicted extinction diameters of methanol droplets. However, when surface tension is neglected, radiation alone has a negligible effect on the prediction of the extinction diameter. The extinction diameter presents a non-linear variation with the initial droplet diameter for initially large droplets. The agreement with experimental results available in the literature is very good.

This research was funded by NASA EPSCoR under grant NCC5-572. Computational resources were provided by the Thermal-Fluids computational facility and the Research Computing Facility at the University of Nebraska – Lincoln.

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