Influence of mixture sensitivity and pore size on detonation velocities in porous media |
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Authors: | A Makris H Shafique J H S Lee R Knystautas |
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Institution: | (1) Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canada |
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Abstract: | Experiments have been carried out to determine the dependence of the detonation velocity in porous media, on mixture sensitivity
and pore size. A detonation is established at the top end of a vertical tube and allowed to propagate to the bottom section
housing the porous bed, comprised of alumina spheres of equal diameter (1–32 mm). Several of the common detonable fuels were
tested at atmospheric initial pressure. Results indicate the existence of a continuous range of velocities with change in
Φ, spanning the lean and the rich propagation limits. For all fuels in a given porous bed, the velocity decreases from a maximum
value at the most sensitive mixture near Φ≈1 (minimum induction length), toV/V
CJ≈0.3 at the limits. A decrease in pore size brings about a reduction inV/V
CJ and a narrowing of the detonability range for each fuel. For porous media comprised of spherical particles, it was possible
to correlate the velocity data corresponding to a variety of different mixtures and for a broad range of particle sizes, using
the following empirical expression:V/V
CJ=1–0.35 log(d
c
/d
p)]±0.1. The critical tube diameterd
c
is used as a measure of mixture sensitivity andd
p denotes the pore diameter. An examination of the phenomenon at the composition limits, suggests that wave failure is controlled
by a turbulent quenching mechanism. |
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Keywords: | Detonations Velocity deficits Porous media |
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