Flame propagation and flow field measurements in a Hartmann dust explosion tube

In this paper both the flame structure and propagation velocities of zirconium and lycopodium dusts are studied experimentally in air. The measurements were conducted in a Hartmann tube and a high-speed CMOS camera was used to record the images of the flame. The results show that the zirconium flame has a spherical shape, whereas the lycopodium flame has a very complex structure which makes flame speed calculation difficult and the lycopodium flame speed needs to be determined through statistical averaging of multiple measurements. This discrepancy between the flame structure of lycopodium and zirconium is attributed to the flame speed. In case of lycopodium, the flame speed is much lower, which makes the flame structure and propagation very sensitive to turbulent fluctuations of the flow field at the time of ignition. To reveal the structure of the flow field in the Hartmann tube prior to ignition, Time-Resolved Particle Image Velocimetry (TR-PIV) was used. The data of the PIV measurement shows the existence of large turbulent zones, which decay in time. These turbulent structures have a large influence on the flame propagation and therefore, it was concluded that flame speed measurements in a Hartmann tube can only be reliable for powders with a high flame speed. (C) 2017 Elsevier B.V. All rights reserved.