Nowadays, more and more industrial sites include storage
facilities of tanks filled with hydrocarbons or compressed
liquids that can be either toxic or flammable. In case of an
accident, these vessels can rupture explosively and lead to
generation of BLEVE or Boilover phenomenon depending
on the type of reservoir and liquid.
Allowing secure small scale experiments, the VKI BABELs
facility (Bleve And Boilover ExperimentaL setup) consists of
a cylindrical chamber of 2m diameter and 3m high, with
round shape flanges, made out of steel with a rated pressure
of 0.5 MPa. It has 3 series of 7 optical accesses, an
entrance door, and an optional air venting system.
© von Karman Institute for Fluid Dynamics, Waterloosesteenweg
72, B-1640 Sint-Genesius-Rode, Phone: +32 (0)2 359 96 04
EXPERIMENTAL CHARACTERIZATION AND MODELLING OF HAZARDS:
BLEVE AND BOILOVER
BOILOVER
A Boilover is a violent ejection of fuel due to the vaporization
of a
water sublayer, resulting in an enormous fire enlargement
and
formation of fireball and ground fire. Small scale experiments
with
cylindrical reservoirs of 0.08 to 0.3m diameter in glass or
metal,
filled with a mixture of diesel and oil have been performed.
At Boilover onset, high speed visualizations in glass reservoir
show
that the growth of one big vapour bubble leads to a water
boiling
front that spreads radially all along the fuel-water interface.
That
results in the ejection of the fuel layer and the increase of
the flame
size. Such an experimental finding confirms that the
vaporization of
the water layer is homogeneous and produces a piston effect.
Contact
Jean-Marie Buchlin
[email protected]
Phone: +32 (0)2 359 96 14
Shadowgraph of BLEVE rupture
with 80mm weakness (left),
40mm (middle) and 10mm (right)
This research project is carried out in theframe of a
collaboration between the von Karman Institute (VKI), the École
desMines d’Allès (EMA) and the CEAGramat.
BABELs
Flame enlargement
during Boilover (Dt=0.2s)
BLEVE phenomenon (Wikipedia)
Bottom visualization of evaporation front at Boilover onset for
lamp oil experiment
BLEVE
A BLEVE (or Boiling Liquid Expanding Vapour Explosion) is an
explosion resulting from the catastrophic failure of a vessel
containing
a liquid at a temperature significantly above its boiling point
at
normal atmospheric pressure. BLEVE accidents appear mostly
when the tank is engulfed in fire. The heat increases wall
temperature
and internal pressure and induces wall-thinning and/or formation
or
fissures. The vessel then fails; vapour is ejected and the
pressure
drop caused by the rupture is superheating the liquid that
boils
rapidly and violently. This rupture generates a blast wave and
if the
liquid is flammable, it could ignite and form a fireball.
The study is based on small scale experiments performed with
cylinders of propane, laid horizontally and heated from the
bottom
by an electrical resistor. A weakening of the reservoirs on the
upper
part allows better reproducibility of the rupture. High speed
visuali-
sation and shadowgraphy techniques help the tracking of the
rupture
and content release. These experiments show that the fluid
behaviour
during rupture depends on the size of the weakened part and
there-
fore on the rupture pressure.
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