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- Bubble explosion (4)
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Experimente der vergangenen 15 Jahre haben bestätigt, dass sauerstoffhaltige Blasen in einer organischen Flüssigkeit durch eine Stoßwelle zur Explosion gebracht werden können. Obwohl dieses Phänomen für die Risikoanalyse entsprechender chemischer Prozesse in der chemischen Industrie von großer Bedeutung ist, ist die Zahl der Lösemittel, an denen Blasenexplosionsuntersuchungen durchgeführt worden sind, stark begrenzt. In der vorliegenden Arbeit wird das Explosionsverhalten von Sauerstoffblasen in reinem Cyclohexan unter der Einwirkung einer Stoßwelle untersucht. In diesem Beitrag werden Hochgeschwindigkeitsfotos vorgestellt, die die Existenz von Rußbildung an der Position der Sauerstoffblasen nach dem Durchgang der Stoßwelle andeuten. Die vorgestellten Untersuchungen sind Teil eines von der Deutschen Forschungsgemeinschaft geförderten Forschungsprojektes.
Heterogene Explosionen
(2002)
Modelling of detonation wave parameters, initiation and hazard of chemically active bubble systems
(2002)
The detonation processes in chemically active bubble systems at high initial pressures are calculated numerically. The dependences of detonation wave velocity at sub- and supersonic regimes of propagation on molar fraction of gas in the mixture and on initial pressure have been calculated for the first time. The Chapman-Jouguet condition for supersonic bubble detonation wave is obtained. The principal possibility for a different detonation wave structure in the case of propagation in the mixture with high initial pressure and longitudinal gradient of bubble volume fraction is predicted.
The dynamics and ignition of a chemically active bubble in a field of external pressure is analyzed. It is shown, that an inert diluent addition can increase the explosion hazard of heterogeneous gas - liquid systems. Calculations demonstrate the possibility of chemically active bubble ignition on the second pulsation. It is shown, that single chemically active bubble ignition is possible also owing to a decompression impulse.
An algorithm for the calculation of thermodynamic parameters of chemically equilibrium hydrocarbon gas with soot particles has been suggested. It is shown, that soot formation can have an essential influence on the dynamics of single bubble in chemically active hydrocarbon-oxygen (organic solvent (liquid) - oxidizer (gas)) heterogeneous systems.
The detonation processes in chemically active bubble liquids under elevated initial pressures are investigated theoretically. It is shown, that supersonic regimes of wave propagation can exist, if the initial pressure is relatively high and the volume fraction of the bubbles is relatively small. Characteristic values of the bubble detonation wave pressure at sub- and supersonic regimes differ by an order of magnitude.
The principal possibility of detonation wave structure transformation in the case of propagation in the mixture with high initial pressure and longitudinal gradient of bubble volume fraction is predicted. The leading shock may transform into a smooth wave of compression.
The Chapman-Jouguet conditions for self-sustaining supersonic bubble detonation wave is obtained.
A model of shock induced single bubble dynamics and ignition taking into account the real properties of the liquid, inter-phase transition processes, mechanical mixing of phases, ignition delay and continuous shift of chemical equilibrium have been described. Calculations for the oxygen containing bubble in liquid cyclohexane have been performed.