**Studies of premixed-gas flames at microgravity**

Click here for results on the SOFBALL experiment on
the STS-107 mission…

Gravity affects
flames through buoyancy-induced natural convection. Prof. Ronney has conducted
experiments on flames at low gravity, obtained in drop towers and aircraft
flying parabolic trajectories, since 1981. These experiments have demonstrated
a variety of new phenomena which are "masked" at earth gravity due to
buoyancy. Most seem to result from interactions between radiant heat loss,
unequal rates of diffusion of thermal energy and reactants (i.e. Lewis number
effects), and flame front curvature and stretch. Such studies are relevant to
spacecraft fire safety applications and the development of clean, lean-burning
combustion engines on earth.

One of the most
remarkable findings of these experiments is the discovery of "flame
balls," which are stable, stationary, spherically symmetric flames that
occur in combustible gas mixtures having low Lewis number (ratio of thermal
diffusivity of the bulk mixture to the mass diffusivity of the
stoichiometrically limiting reactant). An experiment entitled "Structure
Of Flame Balls At Low Lewis-number," or "SOFBALL" was performed
on the MSL-1 Space
Shuttle mission , April 4 - 8, 1997 and the reflight of this mission,
STS-94/MSL-1R, July 1 - 16, 1997. Prof. Ronney served as the Alternate Payload
Specialist Astronaut for both missions. These experiments used a combustion
apparatus, called CM-1,
developed by NASA-Glenn.

Official
NASA website about SOFBALL

Short description of the results from
the SOFBALL experiments

Some pictures
of flame balls in space

View on-line presentation
about SOFBALL results

Much longer, more detailed text-based
version

Information about the
CM-1 experimental facility

Download .pdf version of AIAA Journal paper (2.4 MB)

Download powerpoint presentation on SOFBALL (810 KB)

Download entire set of SOFBALL movies and powerpoint
presentation engine (30 MB!)

A reflight of
this experiment using the Combustion
Module-2 facility on STS-107 was flown in January 2003 to complete the test
matrix and test the new hypotheses developed based on the results from the
MSL-1 missions. Click here for results…

In addition, we
are studying the effects of radiation in the "optically thick"
regime, where reabsorption of emitted photons cannot be neglected. This regime
can be studied through the use of different gas mixtures, pressures and the
addition of inert solid particles. Under optically thick conditions, theory
predicts that flame propagation rates can be increased over those of non-absorbing
mixtures. Our g experiments have indeed demonstrated this effect.

Radiation effects of
premixed-gas flames (on-line version)

Download .pdf version of paper (3.1 MB)

Download powerpoint presentation (504 KB)

**Publications**

__Book
Chapters __(3)

Ronney, P. D., “Understanding Combustion Processes Through Microgravity
Research,” to appear in *Physics of Fluids in Microgravity* (R. Monti, Ed.), Gordon
and Breach, Reading, U.K.

Ronney, P. D., “Premixed-Gas Flames,” in: *Microgravity
Combustion:*
*Fires in Free Fall*
(H. Ross, Ed.), Academic Press, London, U.K., 2001, pp. 35-82.

Wu, M. S.,
Ronney, P. D., Colantonio, R., VanZandt, D., "Detailed Numerical
Simulation of Flame Ball Structure and Dynamics," *Combustion and Flame*, Vol. 116, pp. 387-397*
*(1999).

Ju, Y., Masuya,
G. and Ronney, P. D., "Effects of Radiative Emission and Absorption on the
Propagation and Extinction of Premixed Gas Flames" *Twenty-Seventh
International Symposium on Combustion*, Combustion Institute, Pittsburgh, 1998, pp.
2619-2626.

View on-line version

Download .pdf version (3.1 MB)

Download powerpoint presentation (504 KB)

Buckmaster, J.
D. and Ronney, P. D., "Flame Ball Drift in the Presence of a Total
Diffusive Heat Flux," *Twenty-Seventh International Symposium on
Combustion*,
Combustion Institute, Pittsburgh, 1998, pp. 2603-2610.

Ronney, P. D.,
"Understanding Combustion Processes Through Microgravity Research," *Twenty-Seventh
International Symposium on Combustion*, Combustion Institute, Pittsburgh, 1998, pp.
2485-2506 (**invited paper).**

View on-line version

Download .pdf version (8.7 MB)

Download powerpoint presentation (2.4 MB)

Ronney, P. D.,
"Premixed Laminar and Turbulent Flames at Microgravity," *Space
Forum*,
Vol. 4, pp. 49-98 (1998).

Ronney, P. D.,
Wu, M. S., Weiland, K. J. and Pearlman, H. G., "Flame Ball Experiments in
Space: Preliminary Results from STS-83," *AIAA Journal, *Vol. 36, pp. 1361-1368
(1998).

View on-line version

Download .pdf version (2.4 MB)

Download powerpoint presentation (810 KB)

Download entire set of SOFBALL movies and powerpoint presentation
engine (30 MB!)

Pearlman, H.
G., Ronney, P. D., "Near-Limit Behavior of High Lewis-Number Premixed
Flames in Tubes at Normal and Low Gravity," *Physics of Fluids*, Vol. 6, pp. 4009-4018
(1994).

Pearlman, H.
G., Ronney, P. D., "Self-Organized Spiral and Circular Waves in Premixed
Gas Flames," *Journal of Chemical Physics*, Vol. 101, pp.
2632-2633 (1994).

Lozinski, D.,
Buckmaster, J. D., Ronney, P. D., "Absolute Flammability Limits and Flame
Balls in Optically Thick Mixtures," *Combustion and Flame*, Vol. 97, pp. 301-316
(1994).

Ronney, P. D.,
Whaling, K. N., Abbud-Madrid, A., Gatto, J. L., Pisowicz, V. L.,
"Stationary Premixed Flames in Spherical and Cylindrical Geometries,"
*AIAA Journal*,
Vol. 32, pp. 569-577 (1994).

Abbud-Madrid,
A., Ronney, P. D., "Premixed Flame Propagation in an Optically-Thick
Gas," *AIAA Journal,* Vol. 31, pp. 2179-2181 (1993).

Buckmaster, J. B.,
Gessman, R., Ronney, P. D., "The Three-Dimensional Dynamics of Flame
Balls," *Twenty-Fourth International Symposium on Combustion*, Combustion Institute,
Pittsburgh, 1992, pp. 53-59.

Buckmaster, J.
D., Joulin, G., Ronney, P. D., "Structure and Stability of Non-adiabatic
Flame Balls: II. Effects of Far-Field Losses," *Combustion and Flame*, Vol. 84, pp. 411-422
(1991).

Abbud-Madrid,
A., Ronney, P. D., "Effects of Radiative and Diffusive Transport Processes
on Premixed Flames Near Flammability Limits," *Twenty Third Symposium
(International) on Combustion*, Combustion Institute, 1990, pp. 423-431.

Farmer, J. N.,
Ronney, P. D., "A Numerical Study of Unsteady Nonadiabatic Flames," *Combustion
Science and Technology*, Vol. 73, pp. 555-574 (1990).

Ronney, P. D.,
"Near-Limit Flame Structures at Low Lewis Number," *Combustion and
Flame*,
Vol. 82, pp. 1-14 (1990).

Buckmaster, J.
D., Joulin, G., Ronney, P. D., "Effects of Heat Loss on the Structure and
Stability of Flame Balls," *Combustion and Flame*, Vol. 79, pp. 381-392
(1990).

Ronney, P. D.,
Sivashinsky, G. I., "A Theoretical Study of Propagation and Extinction of
Nonsteady Spherical Flame Fronts," *SIAM Journal on Applied Mathematics*, Vol. 49, pp. 1029-1046
(1989).

Ronney, P. D.,
"On the Mechanisms of Flame Propagation Limits and Extinction Processes at
Microgravity," *Twenty Second Symposium (International) on Combustion*, Combustion Institute,
1988, pp. 1615-1623.

Ronney, P. D.,
"Effect of Chemistry and Transport Properties on Near-Limit Flames at
Microgravity,"* Combustion Science and Technology*, Vol. 59, pp. 123-141
(1988).

Ronney, P. D.,
"Effect of Gravity on Halocarbon Flame Retardant Effectiveness," *Acta
Astronautica*,
Vol. 12, pp. 915-921 (1985).

Ronney, P. D.,
"Effect of Gravity on Laminar Premixed Gas Combustion II: Ignition and
Extinction Phenomena," *Combustion and Flame*, Vol. 62, pp. 120-132
(1985).

Ronney, P. D.,
Wachman, H. Y., "Effect of Gravity on Laminar Premixed Gas Combustion I:
Flammability Limits and Burning Velocities," *Combustion and Flame*, Vol. 62, pp. 107-119
(1985).