The implication of experimentally controlled gravitational accelerations for combustion science

• Published in: Symposium, International, on Combustion Vol. 23; no. 1; pp. 1589 - 1596
• Main Author: Sacksteder, Kurt R.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1991
• ISSN: 0082-0784
• DOI: 10.1016/S0082-0784(06)80430-3

Explorations of fundamental combustion phenomena under reduced gravitational conditions have multiplied during the last decade with improved access to Earth-based testing facilities. Under conditions where buoyant convection is suppressed, classical combustion theories that neglect body forces have been tested—frequently with unexpected results. New fundamental insight has been achieved concerning laminar premixed flames; stabilized gaseous diffusion flames; flame propagation over condensed fuels; droplet combustion; and other areas. Modifications of the corresponding theoretical structures to include behavior observed in reduced-gravity are being formulated and should enhance the fundamental basis of combustion science. Reduced-gravity facilities also provide experimental access to low-momentum-flux reacting-flows where external flow potentials can be varied continuously. Low-speed combustion tunnels in microgravity and variable-gravity facilities provide the capability to isolate the effects of buoyant and forced flows and observe behavior at characteristic velocities below the magnitudes possible under normal-gravity conditions. Earth-based testing facilities provide very limited testing times; more complete testing is possible only in orbiting spacecraft. The expense of space-based experiments provides a motivation for the combustion community to carefully choose the most appropriate experiments for flight, and to seek innovation in the apparatus design to accommodate multiple users. Incorporating advanced diagnostic methods into flight experiments is essential for scientific productivity but introduces a significant engineering challenge. Applications of reduced-gravity results to Earth-based technology are not currently obvious, but would follow from the improved fundamental understanding of the underlying phenomena. In return for access to space-based testing facilities, however, combustion science can contribute significantly to fire safety aboard spacecraft.