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Materials Science Forum Vols. 465-466 (2004) pp 475-0
Online available since 2004/Sep/15 at www.scientific.net
© (2004) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/MSF.465-466.475
Detonation Propagation in Packed Beds of Aluminum Saturated
with Nitromethane
Yukio Kato 1,a, Yuichi Nakamura 1,b, Kenji Murata 1,c, Kouhei Inoue 2,d
and Shigeru Itoh 2,e
1
NOF CORPORATION
61-1 Kitakomatsudani, Taketoyo-cho, Chita-gun, Aichi 470-2398, Japan
2
Shock Wave and Condensed Matter Research Center, Kumamoto University
2-39-1 kurokami, kumamoto 860-8555
a
[email protected], b [email protected], c [email protected]
d
[email protected],
e
[email protected]
Keywords: Detonation, Nitromethane, Aluminum, Heterogeneous explosive
Abstract. Detonation velocity and pressure measurements were performed for heterogeneous
mixtures consisted of packed beds of aluminum particles saturated with pure nitromethane using
aluminum particles of 3 different sizes. In case of packed beds of aluminum particles of 30 and
110µm size, critical diameter was greatly decreased as in case of nitromethane containing small
concentration of aluminum particles. Measured detonation velocity and pressure were compared with
calculated values obtained by KHT code. Difference between measured and calculated detonation
properties provides the evidence for lack of equilibrium between aluminum particles and detonation
products of nitromethane.
Introduction
The addition of solid particles to liquid explosive changes detonation propagation mechanism of the
explosive from homogeneous to heterogeneous. The effect of the addition of solid particles to liquid
nitromethane (NM) has been the subject of many studies [1-9]. Many experiments with mixtures of
NM and solid particles have been performed at small particle concentration. The experiments with
small concentration of micron-sized solid particles were performed by Kato and Brochet [3] using
aluminum (Al) particles and by Engelke [5] using glass spheres. The results of these experiments
shows that the addition of small amount of solid particles drastically changes detonation properties;
sensitivity increase and critical diameter decrease caused by particle induced hot-spots. The
photographic observation by Kato and Brochet [3] revealed bright re-initiation sites formed around Al
particles and lent qualitative support to particle induced hot-spots.
Very limited data exist for heterogeneous mixtures consisting of densely packed beds of solid
particles saturated with liquid NM. Campbell et al. [1] measured detonation velocity and initiation
pressure of heterogeneous mixture consisting packed bed of carborundum saturated with pure NM.
Kato [2] measured detonation velocity of heterogeneous mixtures consisting packed beds of Al
saturated with pure NM using Al of 3 different size, and observed detonation velocity dependence on
Al particle size. Lee et al. [6,7] performed systematic study of heterogeneous mixtures consisting
packed beds of spherical glass beads of different size saturated with chemically sensitized NM, and
showed the effect of glass beads size on critical diameter of these mixtures. Recently, Haskins et al.
[9] measured detonation velocity of heterogeneous mixtures consisting packed beds of Al saturated
with pure NM, and showd that significant reaction of Al was not observed even with nanometric
grade Al.
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Explosion, Shock Wave and Hypervelocity Phenomena in Materials
In this work, we measured detonation velocity and pressure of heterogeneous mixtures consisting of
packed beds of Al of 3 different sizes saturated with pure NM, and showed the effect of Al particle
size on detonation properties of these heterogeneous mixtures.
Experimental results were compared with calculated results obtained using KHT code.
Experimental
Commercial grade NM and 3 types of Al particles with mean diameter 30, 110 and 350 µm were used
in this series of experiments. Properties of heterogeneous mixtures consisting packed beds of Al
particles saturated with NM (NM/Al) were presented in Table 1. The initial density and mass fraction
of Al of these mixtures were respectively 1.83-1.97g/cm3 and 66-72%. The ambient temperature
throughout the tests was between 10~15 degrees.
Fig.1 shows experimental arrangement of detonation velocity measurements. NM/Al mixtures were
contained in PVC tubes of different inner diameter 13, 16, 20 and 31mm , and 250mm in length.
Detonation velocity was measured by 4 optical fiber probes placed at 50mm interval. First optical
fiber probe was set at 90mm from booster explosive to assure steady detonation propagation.
Fig.2 presents experimental arrangement of detonation pressure measurements. NM/Al mixture
contained in PVC tube of 31mm in diameter and 150mm in length was placed on PMMA plate of
1mm thick. PVDF pressure gauge of 9µm thick was placed between 1mm thick PMMA plate and
PMMA block. PVDF pressure gauge measured pressure transmitted into PMMA plate and block, and
detonation pressure was calculated using impedance match method. To confirm steady detonation
propagation, detonation velocity was also measured using optical fiber probe in detonation pressure
measurements.
Table 1 Properties of NM/Al Mixtures
Type of Aluminum
A
B
C
Mean Diameter of Al (µm)
30
110
350
Density of Mixture (g/cm3)
1.84
1.97
1.83
66
72
66
Mass Fraction of Al (%)
Fig.1 Exprimental arrangement of
detonation velocity measurements.
Fig.2 Exprimental arrangement of
detonation pressure measurements.
Materials Science Forum Vols. 465-466
477
Results and Discussion
Fig.3 presents the relation between detonation velocity and reciprocal of charge diameter. In case of
Al particle A and B, detonation velocity decreases lineally with increase of reciprocal of charge
diameter, and critical diameter is estimated to be smaller than 10mm as in the case of NM/Al mixtures
containing small concentration of Al particles [5]. In case of Al particle C, detonation could not
propagate at charge diameter 20mm, and detonation velocity at charge diameter 31mm was more than
1000m/s lower than the case of Al particle A and B.
Fig.4 shows pressure-time profiles measured by PVDF pressure gauge. In case of NM detonation,
pressure profile in reaction zone is not observed because of very short reaction zone length of NM,
and only pressure decay in Taylor wave can be measured.
Pressure profile in reaction zone behind leading shock and following pressure decay in Taylor wave
can be measured in case of Al particle A and B. The increase of reaction zone length can be explained
by shock diffraction/expansion effects due to the presence of Al particles and energy and momentum
losses in the acceleration of Al particles. In case of Al particle C, pressure peak of reaction zone is not
observed. A possible explanation is that shock diffraction/expansion effects and energy and
momentum losses are much more important because of much larger Al particle size. For all NM/Al
mixtures, the effect of Al reaction was not observed in measured pressure-time profile.
Fig.5 shows Hugoniot curves for unreacted NM and PMMA, and Rayleigh lines for detonation in NM
and NM/Al mixture containing Al particle A. Detonation pressure was determined using impedance
match method. Table 2 summarizes the results of detonation pressure measurements. Detonation
pressure of NM/Al mixtures containing Al particle A and B is 2~3GPa higher than that of NM,
although detonation velocity of these mixtures is about 1000m/s lower than that of NM. Detonation
pressure of NM/Al mixture containing Al particle C is 3GPa lower than that of NM, and its detonation
velocity is 2300m/s lower than that of NM.
Detonation properties of NM/Al mixtures were calculated by KHT code assuming Al totally inert or
reactive. Experimental results were compared with calculated results in Fig.6,7,8. Measured
detonation velocities of NM/Al mixtures containing Al particle A and B agree well with calculated
detonation velocity assuming Al inert, but measured detonation velocity of NM/Al mixture
containing Al particle C is more than 1000m/s lower than calculated value (Fig.6). Measured
detonation pressures of NM/Al mixtures containing Al particle A and B are 5~6.5GPa higher than
calculated detonation pressure assuming Al inert, and measured detonation pressure of NM/Al
mixture containing Al particle C agrees with calculated value (Fig.7). For all NM/Al mixtures,
particle velocities calculated using measured detonation velocity and pressure are higher than
calculated particle velocity assuming Al inert (Fig.8). Difference between measured and calculated
detonation properties provides the evidence for lack of equilibrium between Al particles and
detonation products of NM.
Table 2 Summary of the results of detonation pressure measurements.
Sample Explosive
NM
A
B
C
Detonation Velocity (m/s)
6260
5230
5350
3940
ρ o・D２/4
(GPa)
11.1
12.6
14.1
7.1
Detonation
Pressure (GPa)
11.6
13.4
14.6
8.5
1640
1390
1400
1180
Particle Velocity (m/s)
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Explosion, Shock Wave and Hypervelocity Phenomena in Materials
Fig.3 Relation between detonation velocity
and reciprocal of charge diameter
Fig.4 Pressure-time profiles measured by PVDF pressure gauge.
Materials Science Forum Vols. 465-466
Fig.5 Hugoniot curves for unreacted
NM(
) and PMMA(
), and Rayleigh
lines for detonation in NM (
) and
NM/Al mixture containing Al particle
A(
).
Fig.7 Compairson of measured detonation
pressure with caluclated detonation
pressure by KHT code.
479
Fig.6 Compairson of measured detonation
velocity with calculated detonation vlocity
by KHT code.
Fig.8 Compairsion of measured particle
velocity with caluculated particle velocity
by KHT code.
480
Explosion, Shock Wave and Hypervelocity Phenomena in Materials
Conclusions
Detonation velocity and pressure measurements were performed for heterogeneous mixtures
consisted of packed beds of Al saturated with NM using Al particle of 3 different sizes. The addition
of Al particle of 30 and 110µm greatly decreased critical diameter, but the addition of Al particle of
350µm did not. Measured pressure-time profile revealed that reaction zone length of NM/Al mixtures
was increased by the effects of shock diffraction / expansion and energy / momentum losses. The
effect of Al reaction in detonation products of NM was not observed in measured pressure-time
profile for all NM/Al mixtures. Measured detonation velocity and pressure were compared with
calculated values obtained using KHT code. In case of Al particle of 30 and 110µm, measured
detonation velocities agree well with calculated value assuming Al inert, but measured detonation
pressures are much higher than calculated value. Difference between measured and calculated
detonation properties provides the evidence for lack of equilibrium between Al particles and
detonation products of NM.
References
[1] A.W. Campbell, W.C. Davis, J.B. Ramsay and J.R. Travis: Phys. Fluids Vol. 4 (1961), p.511
[2] Y. Kato: Rapport de DEA, Universite de Poitiers (1974)
[3] Y. Kato and C. Brochet: Proc. of 6th Symposium on Detonation (1976), p.124
[4] R. Engelke: Phys. Fluids Vol.22 (1979), p.1623
[5] R. Engelke: Phys. Fluids Vol.26 (1983), p.2420
[6] J.J. Lee, D.L. Frost, J.H.S. Lee and A. N. Dremin: Shock Waves Vol.5 (1995), p.115
[7] J.J. Lee, M. Brouillete, D.L. Frost and J.H.S. Lee: Combustion and Flame Vol.100 (1995),p.292
[8] A.M. Milne: Shock Waves Vol.10 (2000), p.351
[9] P.J. Haskins, M.D. cook and R.I. Briggs: Proc. of 12th APS Shock Compression of Condensed
Matter (2001), p.890
Explosion, Shock Wave and Hypervelocity Phenomena in Materials
10.4028/www.scientific.net/MSF.465-466
Detonation Propagation in Packed Beds of Aluminum Saturated with Nitromethane
10.4028/www.scientific.net/MSF.465-466.475
DOI References
[1] A.W. Campbell, W.C. Davis, J.B. Ramsay and J.R. Travis: Phys. Fluids Vol. 4 (1961), p.511
doi:10.1063/1.1706354
[4] R. Engelke: Phys. Fluids Vol.22 (1979), p.1623
doi:10.1063/1.862821
[5] R. Engelke: Phys. Fluids Vol.26 (1983), p.2420
doi:10.1063/1.864427
[6] J.J. Lee, D.L. Frost, J.H.S. Lee and A. N. Dremin: Shock Waves Vol.5 (1995), p.115
doi:10.1007/BF02425043
[8] A.M. Milne: Shock Waves Vol.10 (2000), p.351
doi:10.1007/s001930000062

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