Flame propagation of corn starch in a modified Hartmann tube with branch structure

Abstract

Branch structure is used widely in network of dust extraction systems for dust processing and collection. However, flame propagation mechanisms of dust explosion in branch pipes are rarely investigated. In this study, the Hartmann tube was modified with four branch configurations, and both the dust cloud motion behavior and corn starch flame propagation were studied. A high-speed camera was used and an image processing procedure was developed based on the YCbCr color model, by which the luminous intensity distribution was observed and the flame speed was calculated. The results indicate that only a small amount of dust enters the branch pipe during the dispersion process. A variety of flame propagation phenomena were observed, including vortex groups, smooth flame front, increased luminance area behind the front and backward flows, implying complex flame behaviors owing to the effects of branch configuration and primary pipe deflagration. The fluctuation of flame speed in the branch region implies that the deceleration of dust deflagration is reduced by the internal combustion in the branch pipes. The discrepancy of the average flame speed for four configurations indicates that the energy losses in the primary pipes result in the flame speed decline; meanwhile, according to the correlations of flame speed peaks between those in the branch pipes and the primary pipes, the flame propagation in the branch region is influenced not only by the internal combustion but also by the deflagration in the primary pipes.