Opposed Flame Flow Spread on Cylindrical Surfaces (OFFS) - MGBX

Objectives

The objective of this experiment was to enhance the understanding of flame spreading over solid fuel surfaces in the presence of low-speed opposed flows; especially considering effects of radiation heat transfer from cylindrical fuels. Seek flammability limit in terms of air velocity for cylindrical samples.

Shuttle-Mir Missions
NASA-4

Approach
In the Microgravity Glovebox, four of eight samples successfully ignited and burned. Remaining samples judged to be not flammable under the test conditions. Two large diameter solid samples were burned in varying air flow in order to establish the flammability limit. The remaining six samples were each burned in a steady flow ranging from 2 cm/sec to 9 cm/sec. A grid on each exit screen collected soot for later analysis. Grids were analyzed by Transmission Electron Microscopy (TEM) for soot morphology. Flames were imaged with video and still photography and surface and gas temperatures were measured with thermocouples. Video recording captured the anemometer display, thermocouple meters, and fan speed. Four gas samples were collected for post-mission analysis of the combustion products. Oxygen concentration was recorded using a sensor located within the glovebox.

Results
Video and film images obtained for four samples. Change in flame spread characteristics observed with change in air flow velocity. Observed flammability limit for thick cylindrical sample. Exit screens indicate symmetric burning and uniform flow during the tests.

Glovebox environment useful for flame spread tests at the lowest airflow velocities. Differences between flame spread characteristics for flat and cylindrical samples attributed to differences in radiative heat losses.

Earth Benefits
Buoyant flows, a phenomena where less dense air molecules rise over the more dense molecules, induced in normal gravity prevent the study of low speed air flows. In microgravity, combustive mechanisms such as radiative heat transfer control flame spread rates and flammability. Better understanding of these mechanisms contribue to fire safety in spacecraft and in extraterrestrial environments. The knowledge gained from studying radiative effects and material flammability contribute to fire safety science on Earth.

Publications
Ferkul, P.V., et al. "Combustion Experiments on the Mir Space Station," AIAA 37th Aerospace Sciences Meeting, AIAA-99-0439, January 1999.

Principal Investigators
Robert A. Altenkirch
Mississippi State University

Co-Investigators
Dr. Kurt Sacksteder
Prof. Subratta Bhattacharjee
Dr. Michael A. Delichatsios

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Page last updated: 07/16/1999

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