Visualization of the unburned gas flow field ahead of an accelerating flame in an obstructed square channel

Journal Article · Sun Feb 15 00:00:00 EST 2009 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2008.07.010· OSTI ID:21137925

Johansen, Craig T; Ciccarelli, Gaby ^[1]

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1. Mechanical and Materials Engineering, Queen's University, McLaughlin Hall, 130 Stuart Street, Kingston, ON K7L 3N6 (Canada)

The effect of blockage ratio on the early phase of the flame acceleration process was investigated in an obstructed square cross-section channel. Flame acceleration was promoted by an array of top-and bottom-surface mounted obstacles that were distributed along the entire channel length at an equal spacing corresponding to one channel height. It was determined that flame acceleration is more pronounced for higher blockage obstacles during the initial stage of flame acceleration up to a flame velocity below the speed of sound of the reactants. The progression of the flame shape and flame area was determined by constructing a series of three-dimensional flame surface models using synchronized orthogonal schlieren images. A novel schlieren based photographic technique was used to visualize the unburned gas flow field ahead of the flame front. A small amount of helium gas is injected into the channel before ignition, and the evolution of the helium diluted unburned gas pocket is tracked simultaneously with the flame front. Using this technique the formation of a vortex downstream of each obstacle was observed. The size of the vortex increases with time until it reaches the channel wall and completely spans the distance between adjacent obstacles. A shear layer develops separating the core flow from the recirculation zone between the obstacles. The evolution of oscillations in centerline flame velocity is discussed in the context of the development of these flow structures in the unburned gas. (author)

• OSTI ID: 21137925
• Journal Information: Combustion and Flame, Vol. 156, Issue 2; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
FLAMES
HELIUM
GAS FLOW
ACCELERATION
VELOCITY
TIME DEPENDENCE
PHOTOGRAPHY
VORTICES
DUCTS
MACH NUMBER
FLAME PROPAGATION
SIMULATION
IGNITION
IMAGES
LAYERS
OSCILLATIONS
SHAPE
SHEAR
BAFFLES
COMBUSTION KINETICS
Flame acceleration
Schlieren photography
Obstacle flow