Flame behaviors and pressure characteristics of vented dust explosions at elevated static activation overpressures

• Two kinds of flame regimes during dust explosions venting were observed.
• Three types of dust explosion venting process were observed.
• Larger diameters and smaller static activation overpressures were beneficial to the occurrence of the secondary explosions.

Dust explosion venting experiments were performed using a 20-L spherical chamber at elevated static activation overpressures larger than 1 bar. Lycopodium dust samples with mean diameter of 70 μm and electric igniters with 0.5 KJ ignition energy were used in the experiments. Explosion overpressures in the chamber and flame appearances near the vent were recorded simultaneously. The results indicated that the flame appeared as the under-expanded free jet with shock diamonds, when the overpressure in the chamber was larger than the critical pressure during the venting process. The flame appeared as the normal constant-pressure combustion when the pressure venting process finished. Three types of venting processes were concluded in the experiments: no secondary flame and no secondary explosion, secondary flame, secondary explosion. The occurrence of the secondary explosions near the vent was related to the vent diameter and the static activation overpressure. Larger diameters and lower static activation overpressures were beneficial to the occurrence of the secondary explosions. In current experiments, the secondary explosions only occurred at the following combinations of the vent diameter and the static activation overpressure: 40 mm and 1.2 bar, 60 mm and 1.2 bar, 60 mm and 1.8 bar.

Dust explosion venting experiments were performed using a standard 20-L spherical chamber at elevated static activation overpressures larger than 1 bar. The explosion overpressure in the chamber and the flame in the surroundings near the vent were recorded simultaneously. Flame regimes and the secondary explosions near the vent were discussed.Figure optionsDownload as PowerPoint slide