Abstract:
The explosion process of the flake aluminum powder-air two-phase flow is experimentally studied in a large-scale long straight horizontal tube with a length of 32.4 m and an inner diameter of 0.199 m. The deflagration-to-detonation transition (DDT) of the aluminum powder-air mixture is analyzed after being ignited by a 40-J electric spark, and the DDT of the mixture at different mass concentrations is compared. The results show that self-sustained detonation can be achieved in the range of 286 $\div$ 532 g/m$^3$ of the flake aluminum powder concentration, and the DDT process of the aluminum powder-air mixture at the concentration of aluminum particles 409 g/m$^3$ (optimal concentration) is analyzed in detail. The detonation velocity and detonation pressure at the optimal concentration are 1690 m/s and 58 bar, respectively. During the self-sustained detonation stage, the detonation overpressure of the multiphase fuel-air mixture exhibits a typical constant oscillation characteristic, while the detonation velocity remains stable. In addition, a double-headed mode helical detonation phenomenon is observed in the detonation wave front of the aluminum powder-air mixture. The structure of the detonation wave, the flow field parameters, and the interaction between the shock wave and the three-wave point trajectory are analyzed. The detonation cell size at the optimal concentration is approximately 486 mm.
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