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Explosion Mechanics

Measurements of the Temperature Inside an Explosive Fireball

[+] Author and Article Information
Luke S. Lebel

Department of Chemistry and Chemical Engineering,
Royal Military College of Canada,
P.O. Box 17000, Stn. Forces,
Kingston, ON, K7K 7B4, Canada
e-mail: luke.lebel@rmc.ca

Patrick Brousseau

Energetic Material Section,
Defence Research and Development
Canada—Valcartier,
2459 Pie-XI North,
Québec, QC, G3J 1X5, Canada
e-mail: patrick.brousseau@drdc-rddc.gc.ca

Lorne Erhardt

Radiological Analysis and Defence Group,
Defence Research and Development
Canada—Ottawa,
3701 Carling Avenue,
Ottawa, ON, K1A 0Z4, Canada
e-mail: lorne.erhardt@drdc-rddc.gc.ca

William S. Andrews

Department of Chemistry and Chemical Engineering,
Royal Military College of Canada,
P.O. Box 17000, Stn. Forces,
Kingston, ON, K7K 7B4, Canada
e-mail: andrews-w@rmc.ca

1Corresponding author.

Manuscript received June 29, 2012; final manuscript received November 23, 2012; accepted manuscript posted February 6, 2013; published online April 19, 2013. Assoc. Editor: Bo S. G. Janzon.

J. Appl. Mech 80(3), 031702 (Apr 19, 2013) (6 pages) Paper No: JAM-12-1279; doi: 10.1115/1.4023561 History: Received June 29, 2012; Revised November 23, 2012; Accepted February 06, 2013

This paper discusses the development of a fiber optic probe that can obtain temperature measurements from the interior of explosive fireballs, which are generated when unreacted detonation products react with oxygen in the surrounding air. Signatures of the thermochemical environment and chemical species involved can often be deduced from their light emissions, but the limited optical depth of fireballs means that remote sensing techniques can only sample emissions from the outer shell. By developing a protected fiber optic probe that can be placed adjacent to an exploding charge, giving it the ability to become enveloped by the fireball, the thermal radiation from the interior of the fireball can be sampled. Measurement from five shots using Detasheet-C explosives were carried out and could be obtained over the course of about 20 ms. Blackbody-type radiation with temperatures in the 1600 K to 1900 K range were observed, peaking at about 1850 K after 12 ms. The magnitude and time behavior of the temperature was not significantly different when taken at different locations within the fireball, indicating that temperature is fairly uniform throughout. The lack of specific spectral emission lines implies that in the interior of the fireball any combustion that occurred was probably primarily with carbonaceous soot, though differences in optical depth at different locations in the fireball indicate that it was much more fuel-rich closer to the center.

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References

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Figures

Grahic Jump Location
Fig. 1

Assembly of fiber optic probe for measuring the emission spectra from an explosive fireball

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Fig. 3

Typical raw spectrum of fireball light emissions, as collected by the Ocean Optics USB2000+ VIS-NIR spectrometer

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Fig. 4

Time series of spectrometer response from green, red, and (2) infrared channels, for measurement taken 51 cm from original position of the charge. (a) shot 1 and (b) shot 2. See online figure for color.

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Fig. 5

Time series of spectrometer response from green, red, and (2) infrared channels, for measurement taken 34 cm from original position of the charge. (a) shot 3, (b) shot 4, and (c) shot 5. See online version for color.

Grahic Jump Location
Fig. 6

Signal intensity in spectrometer and real spectral irradiance of LS-1-CAL radiometric calibration standard

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Fig. 7

Spectral irradiance of fireball during shot 3 at 12 ms after detonation, as well as best fit of a Plank's law distribution through the data

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Fig. 8

Time series of fireball temperature estimates for measurements taken at 51 cm from the original position of the charge

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Fig. 9

Time series of fireball temperature estimates for measurements taken at 34 cm from the original position of the charge

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