Shock induced condensation in a fuel-rich oxygen containing bubble in a flammable liquid

Shock induced dynamics and explosion of a single oxygen containing bubble in liquid cyclohexane is calculated. The possibility, in principle, of fuel vapor condensation during bubble compression is shown. This condensation takes place, if the gas inside the bubble has a relatively high initial temperature or a low initial pressure. As a result of fuel vapor condensation the bubbles, which have an initial gas composition above the upper flammability limit, can, nevertheless, explode. It is shown that the fuel vapor condensation in fuel-rich bubbles is possible during compression stages of oscillations and during a few milliseconds after the end of bubble dynamics. The rate of the condensation process is estimated. According to estimations, this process is fast enough to significantly change the chemical composition of the bubble and shift it into the flammable range even during the compression stage of the first bubble oscillation. Explosion limits of a single bubble as a function of initial temperatures and pressures are calculated. It is shown that condensation processes extend the explosion range. The influence of a chemically inert gas (argon), on the bubble ignition threshold and parameters of bubble explosion is analyzed. It is shown that argon addition in a bubble can reduce the ignition threshold and therefore increase the explosion hazard. On the other hand, such additions reduce explosion pressure and can be used for mitigation of explosions in bubbly liquids. (C) 2007 Elsevier Ltd. All rights reserved.