Effects of Varying Forced Convection on Single and Twin Droplets Combustion in Microgravity

Paper number

IAC-05-A2.7.06

Author

Dr. Hideaki Kobayashi, Tohoku University, Japan

Coauthor

Mr. Masaki Mitsuya, Japan

Coauthor

Dr. Hironao Hanai, Japan

Coauthor

Mr. Satoru Sakurai, Tohoku University, Japan

Coauthor

Dr. Yasuhiro Ogami, Tohoku University, Japan

Year

2005

Abstract

A new microscopic interaction model between a droplet flame and a vortex tube which composes flow turbulence was proposed. Three non-dimensional numbers were introduced to extend the length scale and time scale to fit for the microgravity experiment using droplets of about 1 mm in diameter. An experimental apparatus for a single droplet and twin droplets combustion in varying air flow was developed, and experiments were performed in microgravity using the MGLAB drop-shaft facility and in normal gravity at pressures up to 2.0 MPa for n-nonane and ethanol as fuels.
 Variations of the instantaneous burning rate constant, Ki, responding the varying flow velocity was successfully measured by back-lit imaging using a high-speed video camera. At high pressure, the effects of droplet Reynolds number, Re, on Ki, was clearly seen, while the effects of natural convection, which increases Ki, was seen in normal gravity even in the forced air flows.
 As for the experiments of the twin droplets combustion, Ki reduction of the downstream droplet was weak when the flow direction was varied. However, the Ki reduction of the downstream droplet for flow direction variations was clearly seen for n-nonane droplets compared to ethanol droplets. The interaction mechanism between upstream and downstream droplet is considered to be the elimination of oxidizer supply to the downstream droplet. Therefore, the strong interaction effects of n-nonane droplets due to larger stoichiometric oxygen-fuel ratio of n-nonane (i.e., 14.0) than that of ethanol (i.e., 3.0).

Abstract document

IAC-05-A2.7.06.pdf

Manuscript document

IAC-05-A2.7.06.pdf (🔒 authorized access only).

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