Abstract: Taking food grade corn starch after vacuum drying as example, particle shape and size were analyzed by laser particle size analyzer and SEM. High speed camera technology was used to study explosive flame propagation behavior of corn starch dust cloud in a 1.2 m long vertical half-open tube, and the influence of dust cloud concentration on flame propagation with or without obstacle was investigated. The results showed that the flame speed overall increases at first and then decreases. Both dust cloud concentration and obstacle have significant influence on the flame propagation pattern and flame speed of corn starch dust cloud. With the increase of dust cloud concentration, the dust combustion is not sufficient, resulting in the gradual decrease of the maximum flame speed and flame brightness and unclear flame contour and flame segment phenomenon. The turbulence effect of obstacles will accelerate the combustion of dust, increase the speed of dust flame propagation, improve the flame brightness and contour clarity. However, an increase in the concentration of dust clouds will reduce the accelerated effect of obstacles on flame propagation, and promote the maximum flame speed to increase at first and then decrease.

Key words: corn starch, dust cloud concentration, flame velocity, obstacle, flame propagation pattern