Optical Spectroscopy of Fireballs from Metallized Reactive Materials

Glumac, Nick; Krier, Herman; Lynch, Patrick T.; Peuker, Jennifer Mott

doi:10.2514/6.2010-695

Cited by 7 publications

(2 citation statements)

References 3 publications

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“…Given the high opacity of fireballs of fuel-rich and metalized explosives, non-intrusive collection of the emitted light by optical sensors placed outside fireballs probe only temperatures in the outer layer of the fireball. Since radiant emission is strongly dependent on temperature, optical emission measurement techniques are always biased towards the highest temperature in a fireball [8]. For a homogeneous, oxygen-deficient explosive such as nitromethane, the highest temperature is associated with the diffusive flamelets at the mixing interfaces of detonation products with air.…”

Section: The Challenge Of Temperature Measurements In Explosive Fireballsmentioning

confidence: 99%

Thermocouple Temperature Measurements in Metalized Explosive Fireballs

Frost

Clemenson

Goroshin

et al. 2021

Propellants Explo Pyrotec

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The detonation of a metalized explosive generates a fireball that has a spatially non-uniform distribution of particle concentration and gas temperature. The transient gas temperature field must be probed with ruggedized spatially-and temporally-resolved diagnostics. The use of in-situ thermocouples for temperature measurements within multiphase fireballs is demonstrated. Although the thermocouple temperature lags behind the local gas temperature, the transient gas temperature is assessed by modeling the sensor assuming first-order response and using two analysis methods: (1) when the thermocouple temperature trace reaches a local extrema, the thermocouple temperature is instantaneously equal to the local gas temperature, and (2) reconstructing the gas temperature trace using multiple co-located thermocouples of different lag responses. The temperature history within the fireball at various distances is presented for charges consisting of packed beds of particles saturated with liquid nitromethane. The results for reactive particles (Al, Ti, Zr) are compared with non-reactive particles (Fe), as well as homogeneous NM charges. For NM charges, a maximum gas temperature of about 1100 K occurs at times on the order of 100's of milliseconds, less than the temperature of the burning soot in the fireball (~1900 K). With Al particles, the gas temperature is spatially non-uniform due to particle jetting and non-uniform particle combustion, but gas temperatures up to about 1800 K are recorded for times up to 0.5 s, less than the temperature of the burning particles (2 700 K). Inert particles act as a heat sink and the thermocouple temperatures recorded did not exceed 400 K.

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Section: The Challenge Of Temperature Measurements In Explosive Fireballsmentioning

confidence: 99%

Thermocouple Temperature Measurements in Metalized Explosive Fireballs

Frost

Clemenson

Goroshin

et al. 2021

Propellants Explo Pyrotec

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“…Optical depth is often discussed in the context of the challenges it poses researchers or the limitations it places on optical data from post-detonation high explosive fireballs. Previous studies have discussed the impact optical depth has on the interpretation of optical diagnostic data, citing not only the broadband attenuation of light, but also self-absorption of chemical species and increased uncertainty in temperature fitting [1]. Lewis et al compared visible emission spectra collected both outside and inside aluminized HMX explosive fireballs, illustrating that pathaveraged optical diagnostics on optically thick fireballs provide misleading data [2].…”

Section: Introductionmentioning

confidence: 99%

Spectrally‐ and Temporally‐Resolved Optical Depth Measurements in High Explosive Post‐Detonation Fireballs

Lodes

Krier

Glumac

2019

Propellants Explo Pyrotec

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Temporally‐and‐spectrally‐resolved‐optical‐depth‐measurements were made in fireballs from five common high explosives. Chambered explosive detonations were probed with 405 nm, 532 nm, 650 nm, 1310 nm, and 9600 nm laser light to quantify optical attenuation during the first 5 ms after initiation. Attenuation lengths are reported for each wavelength and high explosive as a function of time. Two charge sizes were studied to show optical depth scaling for charge mass. Trends in optical depth between type of explosive and probe wavelength are presented and discussed. The spectral dependence of attenuation departed strongly from the λ4 prediction from Rayleigh scattering, indicating significant absorption in addition to scattering. Beam steering effects were determined to be of minimal influence for the scale of explosives tested. Blast scaling is considered in attempt to generalize the results presented.

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Early time spectroscopic measurements during high-explosive detonation breakout into air

Glumac

2012

Shock Waves

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Optical Spectroscopy of Fireballs from Metallized Reactive Materials

Cited by 7 publications

References 3 publications

Thermocouple Temperature Measurements in Metalized Explosive Fireballs

Thermocouple Temperature Measurements in Metalized Explosive Fireballs

Spectrally‐ and Temporally‐Resolved Optical Depth Measurements in High Explosive Post‐Detonation Fireballs

Early time spectroscopic measurements during high-explosive detonation breakout into air

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