ICMS'2000

The International Conference on Multiphase Systems, ICMS'2000
Ufa, RUSSIA, June 15-17, 2000

Hai D. N.

Institute of Mechanics, NCNST, 264 Doi-Can Str., Hanoi, VIETNAM

Muller U.

Institut fur Angewandte Thermo- und Fluiddynamik, Postfach 3640, D-76021, Karlsruhe 1, GERMANY

One process that is able to produce fast fine scale fragmentation is called thermal fragmentation or violent boiling. There are indications that this type of fragmentation is due to the explosive vaporization (a micro explosion) of small amounts of coolant that are injected into the fuel drop by some hydrodynamic instability developed when the bubble surrounding the fuel drop collapses under the action of a sharp pressure increase in the surrounding coolant.

Previously two types of models had been applied to the problems:

1. Models that describe the thermal conditions in the vapor film but assume spherical symmetry which is quite obviously inappropriate and

2.A model that allows for ellipsoidal droplets and bubbles with an arbitrary height of the droplet within the bubble but does not take into account thermal effects and thus vaporization at the bubble wall.

Improving existed models, taking into account thermal effects and vaporization at the bubble wall and rotational symmetric shape of droplet and bubbles, in the paper the equation set for considered bubble - inside drop system dynamic description and result of numerical investigation are presented. The initial relative location of drop in the bubble is determined by equilibrium condition between drop weight and lift - the force due to the pressure distribution in gas/vapor. Calculations are implemented for the cases of ellipsoidal bubble, drop without and with vaporization and for the experimental case with alumini hot drop in water in pressure wave.