Affiliations: Wolfson School of Mechanical and Manufacturing
Engineering, Loughborough University, Loughborough, Leicestershire, UK. e-mail:
g.k.hargrave@lboro.ac.uk
Abstract: Flow visualization data is presented to describe the structure of
flames propagating in methane-air explosions in semi-confined enclosures. The
role of turbulence is well established as a mechanism for increasing burning
velocity by fragmenting the flame front and increasing the surface area of
flames propagating in explosions. This area increase enhances the burning rate
and increases the resultant explosion overpressure. In real situations, such as
those found in complex process plant areas offshore, the acceleration of a
flame front results from a complex interaction between the moving flame front
and the local blockage caused by presence of equipment. It is clear that any
localised increase in flame burn rate and overpressure would have important
implications for any adjacent plant and equipment and may lead to an escalation
process internal to the overall event. To obtain the information required to
quantify the role of obstacles, it is necessary to apply a range of
sophisticated laser-based, optical diagnostic techniques. This paper describes
the application of high-speed, laser-sheet flow visualization and digital
imaging to record the temporal development of the flame structure in
explosions. Data is presented to describe the interaction of the propagating
flame with a range of obstacles for both homogeneous and stratified mixtures.
The presented image sequences show the importance of turbulent flow structures
in the wake of obstacles for controlling the mixing of a stratified
concentration field and the subsequent flame propagation through the wake. The
data quantifies the flame speed, shape and area for a range of obstacle
shapes.