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Physics
The development of three-dimensional approaches for description of flow structure and energy release associated with a gaseous detonation are actual from theoretical point of view and practical applications, which have began to develop recently. The taking into account of three-dimensional phenomena and interactions is also extremely important under considerations of reacting flows accompanied with shock waves. In this work we have attempted to study initiation mechanisms of combustion and detonation at nonuniform flow and boundary conditions modeling the gas auto-ignition and interaction of flows in detonation wave front in propane/hydrogen/air mixtures within the pressure range of 2 – 25 atm, temperatures of 850 –1850 К and stoichiometries of 0.5 - 2.
The flow inhomogeneities were produced by changing the geometry of reflecting wall at interactions with an incident shock wave in shock tubes. The measurements at nonuniform flow conditions were compared with a reference data obtained behind normally reflected shock waves. Induction times and auto-ignition modes of the mixtures (strong, transient and weak) were determined for different two- and axsymmetrical ducts, and Mach numbers of incident shock wave. Particular attention has been paid in experiments to determining the critical ISW intensity required for initiation of different self-ignition regimes.
It was shown that the shock wave focusing in two-dimensional and axisymmetric profiles significantly decrease the ignition thresholds of the mixture as compared with the case of the normal reflection. For self-ignition of the mixture, axisymmetric reflectors are much more efficient than two-dimensional ones. Parametric diagrams, characterizing auto-ignition of propane/air mixture at shock wave reflection from a plane wall, similar two-and axisymmetrical profiles show the significant influence of three-dimensional effects and interactions on the transformation local and integral regimes of combustion. It was demonstrated that in comparison with a normal reflection case the shock wave focusing can provide the auto-ignition of propane at extremely low level of mean temperature of the mixture (» 500 К).
Note. Abstracts are published in author's edition
Last update: 06-Jul-2012 (11:52:45)