Flame Propagation in a Narrow Closed Channel: Effects of Aspect Ratios, Blockage Ratio, and Mixture Reactivity on Flame Speed and Pressure Dynamics

Abstract

ABSTRACT A set of experiments is conducted to study flame acceleration in a narrow rectangular cross-section channel in order to examine the effects of mixture reactivity, channel height, and blockage ratio (BR). The channel had an ignition chamber at one end and a dump chamber at the opposite end. The initial conditions are mixtures of hydrogen-air at 1 bar and 293 K. Five different compositions of 10, 20, 30, 40, and 50% hydrogen volume fraction in air are studied. The rectangular chamber is 500 mm long and 40 mm in width, with an adjustable height from 2 to 10 mm. To study the relation between channel height and BR, combustion behaviors with three different B.R. (BR of 0.1, 0.5, and 0.9), 5 different obstacle sizes, and different channel heights (from 2–10 mm) are presented. Pressure waves are monitored with seven fast response pressure transducers placed along the chamber, and the flame propagation is observed with a high-speed Schlieren imaging system. There was no detonation observed during this series of experiments. The results show that the flame propagation is affected by both the channel dimensions and the obstacles, with a maximum flame velocity achieved for partially obstructed channels. The evolution of the flame’s propagation and the pressure dynamics through the various obstructed and unobstructed channels, including the dynamics contributed by the ignition and dump chamber, are discussed.