Recent Research on Flames of Gaseous Fuel Aboard the International Space Station
Dennis P Stocker
Research for a set of six independent experiments with flames of gaseous fuels has been carried out on the International Space Station (ISS) since 2017 using the Combustion Integrated Rack (CIR) and a set of modular hardware. While ISS testing has been completed for most of the studies in the Advanced Combustion via Microgravity Experiments (ACME) project, it is expected to continue into 2022. The objectives and selected findings for each investigation are briefly discussed after a short review of the advantages of studying combustion in microgravity, previous research conducted in space, and the experimental hardware and its operation.
Test conditions.
Extracted from the paper by AI · “Verified” means a person checked it
| Fuel | O₂ | Pressure | Airflow | Sensors | Source | AI conf. | Status |
|---|---|---|---|---|---|---|---|
| Ethylene | elevated | — | still | radiometers, photomultiplier tubes, Thin Filament Pyrometry (TFP) | p. 4 | 95% | Pending |
| Methane | elevated | — | still | radiometers, photomultiplier tubes, Thin Filament Pyrometry (TFP) | p. 4 | 95% | Pending |
| Gaseous fuels (general) | < ~25% (by volume) | — | still | radiometers, photomultiplier tubes, Thin Filament Pyrometry (TFP) | p. 4 | 95% | Pending |
| Gaseous fuels (general) larger flames |
elevated | — | still | radiometers, photomultiplier tubes, Thin Filament Pyrometry (TFP) | p. 4 | 95% | Pending |
| Gaseous fuels (general) smaller flames |
elevated | — | still | radiometers, photomultiplier tubes, Thin Filament Pyrometry (TFP) | p. 4 | 95% | Pending |
| Gaseous fuels (general) spherical |
— | — | — | Intensified camera imaging with filter for formaldehyde emissions | p. 7 | 95% | Pending |
| Methane (CH4) spherical |
— | — | high flow rates | Thin Filament Pyrometry (TFP) | p. 9 | 90% | Pending |
| Methane (CH4) spherical |
— | — | low flow rates | Thin Filament Pyrometry (TFP) | p. 9 | 90% | Pending |
Findings.
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01
Low-momentum microgravity flames can burn for minutes in the absence of an air flow or flame spread.
Prevention · p. 4 · AI confidence 95% · Reported · Pending
“Hazard! Low - momentum microgravity flames can burn for minutes in the absence of an air flow or flame spread.”
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02
Microgravity flames self-extinguish in oxygen concentrations below approximately 25% by volume.
Prevention · p. 4 · AI confidence 95% · Reported · Pending
“they were found to self - extinguish in concentrations below ~25% (by volume).”
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03
Sooty microgravity flames are taller and wider and contain 5x to 8x more soot than equivalent 1G flames.
Other · p. 5 · AI confidence 95% · Reported · Pending
“Sooty microgravity flames are taller & wider and contain 5x to 8x more soot than equivalent 1G flames.”
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04
Microgravity increases the limits of fuel dilution, allowing for lifted flames at lower fuel concentrations.
Other · p. 5 · AI confidence 95% · Reported · Pending
“Microgravity increases the limits of fuel dilution. Near limits, microgravity flames are more stable, allowing for lifted flames at lower fuel concentrations.”
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05
Highly-diluted flames can be stabilized with very weak electric fields.
Suppression · p. 7 · AI confidence 90% · Reported · Pending
“Highly - diluted flames can be stabilized with very weak electric fields.”
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06
Large flames increase in size over time until they extinguish due to radiative heat loss.
Suppression · p. 8 · AI confidence 95% · Reported · Pending
“Large flames increase in size over time until the flame extinguishes due to radiative heat loss .”
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07
Before total extinction, large flames experience an unstable, oscillatory mode where they partially extinguish and reform.
Detection · p. 8 · AI confidence 90% · Reported · Pending
“Before total extinction, these flames experience an unstable, oscillatory mode, in which they partially extinguish and reform .”
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08
Very small flames have low radiative loss and asymptotically approach steady-state behavior.
Other · p. 8 · AI confidence 95% · Reported · Pending
“Very small flames have low radiative loss and asymptotically approach steady - state behavior .”
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09
Radiative extinction of spherical flames occurs at high flow rates, while kinetic extinction occurs at low flow rates.
Suppression · p. 9 · AI confidence 90% · Reported · Pending
“Radiative extinction seems to occur at high flow rates and kinetic extinction at low flow rates.”