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Symposium (International) on Combustion | 1982

Detonation tube studies of aluminum particles dispersed in air

Allen J. Tulis; J. Robert Selman

A 5.487-m vertical detonation tube of 152-mm inside diameter instrumented to monitor both shock front (piezoelectric transducers) and reaction front (fiber-optic/light-detector probes) was used to study the detonation of both flake and atomized aluminum powders dispersed in air. Effects of concentration, surface-to-mass ratio, aluminum oxide coating, and type of initiation were evaluated. Flake-aluminum powder with a surface-to-mass ratio of 3 to 4 m 2 /g was readily detonated with detonation velocities as high as 1.65 km/sec and detonation pressures of about 5 MPa (compared to the Chapman-Jouguet values of 1.85 km/sec and about 2.5 MPa). The nominal 5-μm, 0.34 m 2 /g atomized-aluminum powder was also detonated, but with greater difficulty and some loss in detonation characteristics; i.e. maximum detonation velocities of 1.35 km/sec and detonation pressures of at most 3 MPa. Furthermore, in the case of the flake aluminum the induction times between shock and reaction fronts were often in the range characteristic of homogeneous detonations, approaching the limits of the instrumentation (about 1 μsec) whereas the atomized aluminum consistently gave substantially higher values: e.g., 14 μsec being the lowest. Increasing the aluminum oxide coating of either powder caused deterioration of detonation characteristics and tended to decouple, the shock and reaction fronts. Detonability and detonation characteristics were very sensitive to surface-to-mass ratio and rather insensitive to overall concentration. Spinning detonation was identified in all instances investigated for this phenomenon. Initiation of detonation in all cases required shock wave energy as obtained from the detonation of small charges of high explosive.


Journal of Hazardous Materials | 1980

Flowability techniques in the processing of powdered explosives, propellants, and pyrotechnics

Allen J. Tulis

Abstract A very effective flowability additive developed by Dow Corning Corporation is obtained by converting a hydrophilic silica aerogel to a hydrophobic colloidal silica by reacting with hexamethyldisilazane. This additive has been used to prepare homogeneous powder mixtures with a minimum of mixing, to mil difficult materials, and to obtain amazing flow properties in troublesome powders. This hydrophobic silica has an exceedingly light bulk density of about 0.05 g/cc, and a particle size of about one millimicron. It can be premixed before milling and will allow milling of waxy materials. After treatment the powder becomes water repellant and the bulk density increases. Hydrophobic silica additive in amounts less than one percent by weight has often proven effective.


Journal of Hazardous Materials | 1980

Effect of ammonium perchlorate particle size on its detonation characteristics when sensitized with small amounts of nitroguanidine

Allen J. Tulis

Abstract Sympathetic detonation has already been achieved in ammonium perchlorate by adding small amounts of nitroguanidine. Although it appeared that the ammonium perchlorate was detonating at the ideal detonation velocity of the nitroguanidine additive, the effects of confinement, charge diameter, and ammonium perchlorate particle size were not assessed. The effects of confinement and charge diameter were subsequently investigated. In all these studies, however, the particle size of the ammonium perchlorate remained unchanged--nominally 200 micron Class C mil spec ammonium perchlorate. The present effort investigated the effect of variable ammonium perchlorate particle size upon the detonation characteristics of a typical ammonium perchlorate composite system: one sensitized with 5 percent nitroguanidine. Three particle size ranges--designated coarse (149 to 500 micron), medium (44 to 149 micron), and fine (0 to 44 micron)--were investigated. Screen-sieve separation was used. Although the results did confirm a general increase of detonation velocity with a decrease in ammonium perchlorate particle size, some anomalous behavior was also identified. A more comprehensive study will be needed to elucidate the effects of particle size or, more generally, the particle size distribution.


Review of Scientific Instruments | 1982

Characterization of shock and reaction fronts in detonations

Allen J. Tulis; J. Robert Selman

An instrumental technique has been developed which allows the concomitant measurement of the arrival times of both shock and reaction (flame) fronts in propagating detonations. A combination of fiber‐optic probes and light detectors is used to monitor the arrival of the reaction front, whereas piezoelectric pressure gauges monitor the arrival of the pressure pulse from the preceding shock wave. Both signals provide the measurement of the detonation velocity; variance between shock and reaction front velocities implies nonstable detonation (growing or dying detonation) which can be attributed to variation in density, concentration, or homogeneity of the detonating media. This technique is straightforward in the case of pressed or cast formulations but presents difficulties when gas‐phase or two‐phase detonations are involved. The detonation of near‐stoichiometric ethylene–air mixtures in a detonation‐tube facility was used to refine the technique and calibrate the instrumentation. The technique was then us...


Symposium (International) on Combustion | 1994

Phenomenological aspects in explosive powder/gas two-phase detonations

Allen J. Tulis; William K. Sumida; Richard P. Joyce; David C. Heberlein; Divyakant L. Patel

Attempts were made to detonate a special ball-milled TNT powder of about 30-μm particle size thatwas dispersed in air, oxygen, and nitrogen at nominally 1 kg/m 3 in a highly instrumented 152-mm-diameter 7.31-m-long horizontal detonation tube. Results were successful in both air and oxygen, but not in nitrogen. New modifications to the detonation tube for this work included implementation of two-color temperature-measuring instrumentation, and the repositioning of some piezoelectric pressure transducers and fiberoptic light-detector probes so that phenomena such as spinning detonation and multiple-front detonations could be better identified and quantified. TIGER Code Chapman-Jouguet (CJ) computations were made for TNT, RDX, and mixtures of TNT and RDX in air, oxygen, and nitrogen at concentrations up to 100 kg/m 3 . The computed results for TNT in air and oxygen at a concentration of 1 kg/m 3 for the detonation velocities, pressures, and temperatures were 2.00 km/s, 4.00 MPa, 3250 K in air and 2.05 km/s, 4.40 MPa, 3740 K in oxygen. Experimental results for TNT powder were 1.82 km/s, 4.06 MPa, 3245 K in air and 1.90 km/s, 4.61 MPa, 4240 K in oxygen; the experimental concentrations, which were monitored with laser optics, were determined to be 1 kg/m 3 with an estimated error of ± 10%. Subsequent experiments were conducted with RDX, alone and in mixtures with TNT, in attempts to achieve detonation in nitrogen. These were successful except when the RDX percentage fell below 20% by weight. Results of sucessful detonations of RDX/TNT mixtures indicated multiple-front detonations, suggesting that the TNT was reacting behind the RDX detonation front in such a manner that it supported the overall detonation.


High Speed Photography, Videography, and Photonics I | 1984

High Speed Photographic Observation Of The Initiation Of Detonation In Explosives By Imploding Shock Waves

James L. Austing; Allen J. Tulis; David C. Heberlein

This paper is concerned with the use of a Beckman & Whitley Model 189 framing camera to observe the initiation of detonation in cylindrical explosive charges by the detonation of a concentric outside layer of sheet explosive initiated at one end. Experiments were con-ducted with nitromethane, which is a transparent liquid explosive, and aluminum-potassium perchlorate, which is a binary mixture of fuel and oxidizer powders. The use of the transparent explosive permitted viewing along the entire length of the charge axis, so that the time of the nitromethane initiation as a function of the position of the concentric sheet explosive detonation could be observed. In the case of the binary charge, the experiment involved the simultaneous viewing of both the side and the end of the charge by a judicious positioning of two front-surface mirrors. One of these was oriented at the end of the charge at an angle of 45° with respect to the charge axis. The second mirror, larger in size, viewed the entire system, and was destructed at 656 psec by an explosive backing charge to preclude the possibility of film rewrite. Framing rates for both experiments were approximately 250,000 frames/sec. The induction time to initiation of detonation in the nitromethane was measured to be about 20 psec. However, the induction time for the aluminum-potassium perchlorate charge was too long to be recorded by the Beckman and Whitley camera. For this and other pyrotechnic dharges, it was necessary to use a slower writing Fastax camera recording at a rate of 2000 frames/sec; the induction times for the pyrotechnic systems were in the neighborhood of 1 to 3 msec, which is two orders of magnitude longer than for the nitromethane.


Journal of Hazardous Materials | 1982

Open matrix very low density explosive formulations

Allen J. Tulis; James L. Austing; Douglas E. Baker

Abstract In this paper, we have established the feasibility of preparing open-cell matrix explosive charges by two entirely different techniques, one based on a


Fiber Optics in Adverse Environments I | 1982

Fiber Optics As Light-Detector Probes In The Accurate Measurement Of Detonation Velocities In Two-Phase Fuel-Air Explosions

Allen J. Tulis

Fiber-optic probes can be placed directly into solid explosives in order to obtain accurate measurement of the detonation velocity. In the case of two-phase fuel-air explosions, however, such measurements become difficult as the fiber optics can receive radiant energy from the reaction front well before and after the passage of the reaction front. Nevertheless, appropriate design and placement of the fiber-optic probes and discrimination of the signals makes this technique useful. Furthermore, a5 the distance between the shock and reaction fronts becomes significant in two-phase fuel-air detonations, the concomitant measurement of arrival times at co-located fiber-optic probes and piezoelectric pressure gages of the reaction and shock fronts, respectively, allows characterization of induction time/distance information as a function of the system parameters. Application of this technique to the detonation of aluminum powder in air resulted in induction times of 14 to 48 lisec. Such variation was attributed to variations in the concentration of aluminum powder in air. This compares with an induction time of about 3 psec in the case of ethylene-air homogeneous gas-phase detonations.


Journal of Hazardous Materials | 1977

Characterization of detonation in confined charges of ammonium perchlorate sensitized with small amounts of nitroguanidine

Allen J. Tulis

Abstract In previous work sympathetic detonation was achieved in ammonium perchlorate by adding small amounts of nitroguanidine. Although it appeared that the ammonium perchlorate was detonating at the ideal detonation velocity of the nitroguanidine additive, the effect of confinement was not adequately assessed. In the present work we investigated the variation of detonation velocity and detonation output characteristics of the ammonium perchlorate-nitroguanidine composite, under steel confinement, as functions of charge diameter and the amount of NQ additive. Additionally, most tests were conducted with materials and test devices prepared over one year ago and compared to freshly prepared materials and devices.


Propellants, Explosives, Pyrotechnics | 1991

Carbon resistor gauges for measuring shock and detonation pressures. I. Principles of functioning and calibration

James L. Austing; Allen J. Tulis; Donald J. Hrdina; Douglas E. Baker; Ricardo Martinez

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J. Robert Selman

Illinois Institute of Technology

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E. Urbanski

IIT Research Institute

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J. A. Mosora

Wright-Patterson Air Force Base

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