Particle Morphology and Size Results from the Smoke Aerosol Measurement Experiment-2
Urban, David L., Ruff, Gary A., Greenberg, Paul S., Fischer, David, Meyer, Marit, Mulholland, George, Yuan, Zeng-Guang, Bryg, Victoria, Cleary, Thomas, Yang, Jiann
Results are presented from the Reflight of the Smoke Aerosol Measurement Experiment (SAME-2) which was conducted during Expedition 24 (July-September 2010). The reflight experiment built upon the results of the original flight during Expedition 15 by adding diagnostic measurements and expanding the test matrix. Five different materials representative of those found in spacecraft (Teflon, Kapton, cotton, silicone rubber and Pyrell) were heated to temperatures below the ignition point with conditions controlled to provide repeatable sample surface temperatures and air flow. The air flow past the sample during the heating period ranged from quiescent to 8 cm/s. The smoke was initially collected in an aging chamber to simulate the transport time from the smoke source to the detector. This effective transport time was varied by holding the smoke in the aging chamber for times ranging from 11 to 1800 s. Smoke particle samples were collected on Transmission Electron Microscope (TEM) grids for post-flight analysis. The TEM grids were analyzed to observe the particle morphology and size parameters. The diagnostics included a prototype two-moment smoke detector and three different measures of moments of the particle size distribution. These moment diagnostics were used to determine the particle number concentration (zeroth moment), the diameter concentration (first moment), and the mass concentration (third moment). These statistics were combined to determine the diameter of average mass and the count mean diameter and, by assuming a log-normal distribution, the geometric mean diameter and the geometric standard deviations can also be calculated. Overall the majority of the average smoke particle sizes were found to be in the 200 nm to 400 nm range with the quiescent cases producing some cases with substantially larger particles.
Test conditions.
Extracted from the paper by AI · “Verified” means a person checked it
| Fuel | O₂ | Pressure | Airflow | Sensors | Source | AI conf. | Status |
|---|---|---|---|---|---|---|---|
| Teflon | — | — | quiescent to 8 cm/s | Transmission Electron Microscope (TEM), prototype two-moment smoke detector, particle number concentration sensor (zeroth moment), diameter concentration sensor (first moment), mass concentration sensor (third moment) | p. 1 | 95% | Pending |
| Kapton | — | — | quiescent to 8 cm/s | Transmission Electron Microscope (TEM), prototype two-moment smoke detector, particle number concentration sensor (zeroth moment), diameter concentration sensor (first moment), mass concentration sensor (third moment) | p. 1 | 95% | Pending |
| cotton | — | — | quiescent to 8 cm/s | Transmission Electron Microscope (TEM), prototype two-moment smoke detector, particle number concentration sensor (zeroth moment), diameter concentration sensor (first moment), mass concentration sensor (third moment) | p. 1 | 95% | Pending |
| silicone rubber | — | — | quiescent to 8 cm/s | Transmission Electron Microscope (TEM), prototype two-moment smoke detector, particle number concentration sensor (zeroth moment), diameter concentration sensor (first moment), mass concentration sensor (third moment) | p. 1 | 95% | Pending |
| Pyrell | — | — | quiescent to 8 cm/s | Transmission Electron Microscope (TEM), prototype two-moment smoke detector, particle number concentration sensor (zeroth moment), diameter concentration sensor (first moment), mass concentration sensor (third moment) | p. 1 | 95% | Pending |
Findings.
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01
The majority of average smoke particle sizes were found to be in the 200 nm to 400 nm range.
Detection · p. 1 · AI confidence 95% · Reported · Pending
“Overall the majority of the avera ge smoke particle sizes were fo und to be in the 200 nm to 400 nm range”
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02
Quiescent airflow cases produced some instances with substantially larger particles than the 200-400 nm range.
Detection · p. 1 · AI confidence 90% · Reported · Pending
“with the quiescent cases pro ducing some cases with substantially larger particles”
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03
Smoke was held in an aging chamber for times ranging from 11 to 1800 seconds to simulate transport time.
Other · p. 1 · AI confidence 95% · Reported · Pending
“This effective transport time was varied by holding the smoke in the aging chamber for times ranging from 11 to 1800 s”
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04
The experiment used three discrete instruments to measure separate moments of the size distribution (number, diameter, and mass concentration).
Detection · p. 2 · AI confidence 95% · Reported · Pending
“used three discrete instruments to measure separate moments of the size distribution”
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05
ISS smoke detectors use near-IR forward scattering and are most sensitive to particles larger than a micrometer.
Detection · p. 2 · AI confidence 95% · Reported · Pending
“The International Space Station (ISS) smoke de tectors use near-IR forward scattering, rendering them most sensitive to particles larger than a mi crometer”
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06
Space Shuttle detectors used an inertial separator designed to eliminate particles larger than 1-2 micrometers.
Detection · p. 2 · AI confidence 95% · Reported · Pending
“used an inertial separator designed to eliminate particles larger than 1-2 micrometers”
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07
The target for spacecraft fire detection systems is the early phase (pyrolysis products) rather than established flaming fires (soot).
Detection · p. 2 · AI confidence 90% · Reported · Pending
“the target for the fire detection system is necessarily the early phase and not es tablished flaming fires; consequently, the primary target for detection is the pyrolysis products and not the soot”