EXPERIMENTAL CHARACTERIZATION AND MODELLING OF … · 2013. 1. 24. · A Boilover is a violent...

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

buchlin@vki.ac.be

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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