Abstract
Reduced gravity experiments were performed to investigate droplet combustion behaviors in environments with He, N2, or Xe as diluents. These diluents have significant differences in molecular weight, allowing investigation of Soret transport (species diffusion from temperature gradients) and differences in binary diffusion coefficients. The droplets, which were initially about 1 mm in diameter, were composed of decane/hexadecane mixtures with initial hexadecane mass fractions of 0, 0.05 and 0.20. Individual fiber-supported droplets were burned at 0.1 MPa with an ambient oxygen mole fraction of 0.21. Use of He produced the largest burning rates, while burning rates for N2and Xe were similar to each other. Flame standoff ratios were unsteady for all inert species investigated. Flame unsteadiness was largest when the inert was He, with N2and Xe producing successively more quasisteady flames, respectively. Using He as an inert did not produce any visible soot, while N2and Xe produced successively brighter radiant soot emissions, respectively. This behavior is interpreted in terms of variations in O2 Lewis numbers between the flame and the environment. The data suggest that Soret transport effects and differences in binary diffusion coefficients were important when He or Xe were used as inerts, but not when N2was used as an inert.
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Shaw, B.D., Dee, V. Influence of the gas phase inert on reduced-gravity combustion of decane/hexadecane droplets. Microgravity Sci. Technol 17, 26–34 (2005). https://doi.org/10.1007/BF02870972
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DOI: https://doi.org/10.1007/BF02870972