Flame propagation characteristics and flame structures of zirconium particle cloud in a small-scale chamber

Flame propagating through zirconium particle cloud in a small-scale vertical rectangle chamber was investigated experimentally. In the experiments, the zirconium quoted 99% purity was used and the diameter of particles was distributed 1–22 μm. The zirconium dust was dispersed into the chamber by air flow and ignited by an electrode spark. A high-speed video camera was used to record the images of the propagating flame. Micro-thermocouples, schlieren optical system and microscopic lens were used to obtain temperature profiles and flame structure, respectively. Based on the experimental results, flame propagation characteristics and flame structure of zirconium particle cloud were analyzed. The propagation velocity of the flame is quite slow in the initial 14 ms and then accelerates to maximum value. Subsequently, the propagation velocity of the flame almost keeps constant. The combustion zone width of zirconium particle cloud is 5–6 mm. Smaller particles burn mainly at the leading edge of combustion zone in the width of 1.4 mm followed by larger particles burning 1.4–6 mm behind the leading edge of the combustion zone. Gas phase flame is not seen in zirconium particle cloud and the combustion time of single zirconium particle is 1–5 ms, which depends on its original size. The preheated zone is 7–8 mm thickness ahead of the combustion zone and intensive chemical reaction takes place at 490 K. The maximum flame temperature increases at lower concentrations, reaches the maximum value, and then decreases slightly at higher concentrations.