Dynamics study of detonation-wave cellular structure 1. Statistical properties of detonation wave front |
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Authors: | OV Achasov OG Penyazkov |
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Institution: | (1) Heat & Mass Transfer Institute, 15 P. Brovki str., 220072 Minsk, Belarus , BY |
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Abstract: | We have investigated the evolution of cellular detonation-wave structure as a gaseous detonation travels along a round tube
and measured cell lengths as a function of the initial pressure of the gas. We have tested acetylene-containing combustible
gas mixtures with different degrees of regularity. Along with the smoked-foil technique, an emission method has been used
to the measure current and average values of the detonation cell length. The method is based on the detection of an emission
spectrum behind the detonation front in the spectral range corresponding to local gas temperatures that are much higher than
those for the Chapman-Jouguet equilibrium condition. This technique provides quasi-continuous cell-length measurements along
the normal to the detonation front over the length of several factors of ten times the tube.
Our study has experimentally identified the steady states of detonation structure in round tubes, referred to here as the
single detonation modes. When the state of a single mode is fully established, then both the flow structure and the energy
release at detonation front develop strictly periodically along the tube at a constant frequency inversely proportional to
the cell length of the mixture. The mixture regularity has had no influence on the occurrence of the detonation mode, which
is defined by the value of initial pressure or the total energy release of the mixture. Outside of the pressure range where
a detonation mode was most likely to occur, the detonation front is unstable and may exhibit an irregular cellular pattern.
Monitoring the evolution of cells over a long distance revealed that the local gas emissivity, which is time dependent and
corresponds to axial pulsations of the detonation structure, has the appearance of a superposition of separate harmonics describing
the states of emissivity oscillations and cell structure of single detonation modes.
Received 18 October 1999 / Accepted 10 June 2001 |
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Keywords: | : Detonation Cellular structure |
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