Influence of chemical reaction mechanism on turbulent jet flame

Explosion experiments utilizing a 20 L spherical explosion apparatus were conducted to investigate the explosion characteristics of aluminum and aluminum-silicon alloy powders, prevalent in additive manufacturing. The tested samples included Al, Al-12Si, and Al-20Si. Various parameters were measured under different influencing factors, including the lower explosion limit, maximum explosion pressure, maximum pressure rise rate, explosion temperature, and time to reach peak temperature. Thermogravimetric analysis-differential scanning calorimetry was employed to analyze the thermal oxidation properties of the samples. The results indicated that an increase in the silicon content within the alloy corresponded with a lower explosion limit. Conversely, the maximum explosion pressure and peak temperature showed a downward trend. Meanwhile. a reduction in the maximum pressure rise rate was observed. The exothermic amount of the oxidation process reduced, and the oxidation rate slowed down. The concentrations at which the three samples reached the maximum explosion pressure and peak temperature were 300 g/m³ for Al, 750 g/m³ for Al-12Si, and 900 g/m³ for Al-20Si, respectively. When the ignition energy increased, the rate of increase in maximum explosion pressure for the aluminum-silicon alloys was lower than that for aluminum powder. The effect of environmental temperature changes on the lower explosive limit was less significant compared to that of particle size variations. As the environmental temperature increased, the explosion pressure did not show a significant change, while the pressure rise rate increased slightly. X-ray diffraction analysis of the explosion products revealed that, in addition to Al₂O₃ and Al, the explosion products of the aluminum-silicon alloys also contained SiO₂ and Si. This indicates that the Si element in the alloy participated in the explosion reaction. It confirms that the explosion of aluminum-silicon alloy powder is caused by the heating and vaporization of the particles, leading to the formation of a combustible gas composed of gaseous aluminum and silicon, which then combusts with oxygen.