Fifth International Microgravity Combustion Workshop
Kurt R Sacksteder
Experiments: CFI
On behalf of the NASA Headquarters Microgravity Research Division and the Microgravity Combustion Science Discipline Working Group, we are pleased to present these proceedings of the Fifth International Microgravity Combustion Workshop. At the time we go to press we expect to welcome to the workshop over 250 presenters and participants from U.S. academia, industry, and government; and from at least 8 international partner countries. We come together for this workshop at the beginning of the International Space Station era, where the future of microgravity combustion science programs will unfold over the next few years. As we accelerate our preparations for the ISS, this book and the growing literature base cited herein provide a summary of the accomplishments of approximately forty space-flight experiment-missions (plus nearly countless drop tests and aircraft parabolas) and a valuable resource for the new experiment ideas of the future.
Test conditions.
Extracted from the paper by AI · “Verified” means a person checked it
| Fuel | O₂ | Pressure | Airflow | Sensors | Source | AI conf. | Status |
|---|---|---|---|---|---|---|---|
| Ethanol Pool |
— | — | — | Interferometer | p. 73 | 95% | Pending |
| Ethylene and Propane Laminar jet diffusion flame |
— | 35-130 kPa | Still air | Video camera, Laser extinction imaging, Multiline emission imaging, Thermophoretic sampling, TEM analysis, Thermocouple rake | p. 147 | 98% | Pending |
| Candle wax (Paraffin and other hydrocarbons) Candle |
— | — | — | Visual observation | p. 184 | 90% | Pending |
| Heptane Spray (droplets in fuel vapor inner stream) |
— | — | Co-flow configuration | Visual observation | p. 184 | 90% | Pending |
| Liquid fuel (unspecified) Droplets (up to 5 mm diameter) |
— | — | Acoustic levitation field | Acoustic levitator | p. 297 | 85% | Pending |
Findings.
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01
Flame spread is more rapid in microgravity than in normal gravity due to the absence of buoyant convection diverting thermal expansion away from the direction of flame spread.
Other · p. 73 · AI confidence 95% · Extracted · Pending
“In microgravity, the plume is absent, so the thermal expansion is directed in the direction of flame spread, and raises the speed of spread in agreement with the experiment conducted with ethanol.”
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02
Buoyancy forces in normal gravity create a vortex above the pool surface, yielding high velocities in both vertical and axial directions which divert thermal expansion.
Other · p. 73 · AI confidence 95% · Extracted · Pending
“This creates a vortex above the pool surface, yielding high velocities in both the vertical and axial directions. More importantly, buoyancy forces divert some of the thermal expansion that accompanies combustion away from the direction of flame spread.”
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03
The combination of heat loss and slowly diffusing fuels (high Lewis number) is responsible for the onset of oscillations in spray flames.
Other · p. 184 · AI confidence 90% · Extracted · Pending
“The combination of heat loss and slowly diffusing fuels is also responsible to the onset of oscillations observed in spray flames.”
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04
Microgravity droplet combustion allows for the variation of residence time over a wide range by changing droplet size and/or environmental parameters.
Other · p. 256 · AI confidence 90% · Extracted · Pending
“Isolated droplet combustion in microgravity provides the flexibility to vary the residence time over a wide range (residence time is an important and desirable parameter adjustment for studying soot processes) by changing the droplet size and/or environmental parameters (pressure, inert, oxygen index).”
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05
Laser optogalvanic (LOG) spectroscopy can be used for nonintrusive measurements of absorption spectra of atomic and molecular species in flames.
Detection · p. 218 · AI confidence 90% · Extracted · Pending
“Absorption spectra of atomic and molecular species in flames can be obtained via LOG spectroscopy by measuring the voltage and current changes induced by laser irradiation.”