Study on the mechanism of explosion flame propagation of aluminum powder coated with stearic acid
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摘要: 为了探究包覆铝粉爆炸火焰的发展演化规律与传播机理，采用溶剂蒸发法制备了壳-核结构硬脂酸包覆铝粉（SA@Al），利用改进的哈特曼管进行实验，研究了粉尘云浓度对5%、10%与15%包覆浓度SA@Al粉尘爆炸火焰传播特性的影响；同时采用CHEMKIN模拟分析其气相爆炸反应动力学特征，从而揭示SA@Al爆炸火焰传播机理。结果表明，随着粉尘云浓度的增大，5%、10%和15%包覆浓度SA@Al粉尘爆炸火焰的饱满度和连续性均先增强后减弱，平均火焰传播速度均呈先增大后减小的趋势，当粉尘云浓度为500 g/m3时火焰传播速度均达到最大。相比而言，纯铝粉爆炸火焰传播速度在750 g/m3时达到最大，表明硬脂酸包覆层促进了铝粉爆炸火焰的传播。此外，各粉尘云浓度下，10%包覆浓度SA@Al爆炸火焰最剧烈，平均火焰传播速度最大。SA@Al爆炸火焰升温主要包括快速升温和缓慢升温2个阶段，快速升温阶段R2、R11和R10的温度敏感性较高，缓慢升温阶段R5、R11的温度敏感性较高。粉尘云浓度对缓慢升温阶段的温升速率影响显著，使得500 g/m3时SA@Al的爆炸平衡温度最高。硬脂酸包覆层的燃烧促进了铝核的氧化，使爆炸反应得以强化，但过高的粉尘云浓度会导致O自由基受限，在一定程度上削弱反应强度。Abstract: To investigate the explosion flame development and propagation mechanism of coated aluminum powder, a shell and core structure of stearic acid-coated aluminum powder (SA@Al) was prepared using the solvent evaporation method. The influence of dust cloud concentration on the explosion flame propagation characteristics of SA@Al dust with coating concentrations of 5%, 10%, and 15% was experimentally studied using an improved Hartmann tube. Flame propagation behavior was observed through high-speed photography, and the flame propagation speed was calculated. The kinetic characteristics of the gas-phase explosion reaction were analyzed using CHEMKIN-PRO software to reveal the mechanism of SA@Al dust explosion flame propagation. The results indicated that as the dust cloud concentration increased, the fullness and continuity of the explosion flames for 5%, 10%, and 15% SA@Al dust first increased and then decreased, with the average flame propagation speed showing a trend of first rising and then falling. The flame propagation speed reached its maximum at a dust cloud concentration of 500 g/m³. In contrast, the explosion flame propagation velocity of pure aluminum powder reached its maximum at 750 g/m³, suggesting that the stearic acid coating layer promotes the propagation of the aluminum powder explosion flame. Additionally, under each dust cloud concentration, the explosion flame of 10% coating concentration SA@Al was the most intense, with the highest average flame propagation speed. The temperature rise of the SA@Al explosion flame with different dust cloud concentrations mainly consisted of two stages: a rapid heating stage and a slow heating stage. The rapid heating stage exhibited higher temperature sensitivity for reactions R2, R11, and R10, while the slow heating stage exhibited higher temperature sensitivity for reactions R5 and R11. The dust cloud concentration significantly affected the rate of temperature rise in the slow heating stage, resulting in the highest explosion equilibrium temperature for SA@Al at 500 g/m³. The combustion of the stearic acid coating promoted the oxidation of the aluminum core, thereby strengthening the explosion reaction. However, high dust cloud concentration led to limitations in O radicals, which weakened the reaction intensity to some extent.
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图 2 铝粉和10% SA@Al的扫描电子显微镜图像
Figure 2. Scanning electron microscope images of Al and 10% SA@Al dust
图 4 纯铝粉及10% SA@Al粉尘的粒度分布
Figure 4. Particle size distribution of Al and 10% SA@Al dust
图 6 不同粉尘云浓度的Al粉尘云爆炸火焰传播行为
Figure 6. Flame propagations of Al dust clouds with various dust cloud concentrations
图 7 不同粉尘云浓度的5% SA@Al粉尘云爆炸火焰传播行为
Figure 7. Flame propagations of 5% SA@Al dust clouds with various dust cloud concentrations
图 8 不同粉尘云浓度的10% SA@Al粉尘云爆炸火焰传播行为
Figure 8. Flame propagations of 10% SA@Al dust clouds with various dust cloud concentrations
图 9 不同粉尘云浓度的15% SA@Al粉尘云爆炸火焰传播行为
Figure 9. Flame propagations of 15% SA@Al dust clouds with various dust cloud concentrations
图 10 不同粉尘云浓度下Al、5% SA@Al、10% SA@Al和15% SA@Al粉尘云的爆炸火焰传播速度
Figure 10. Explosion flame propagation velocity of Al, 5% SA@Al, 10% SA@Al, and 15% SA@Al dust clouds under different dust cloud concentrations
图 11 Al和10% SA@Al粉尘爆炸火焰中主要物种的摩尔分数分布
Figure 11. Mole fraction distribution of major components in the explosion flame of Al and 10% SA@Al dust
图 12 Al和10% SA@Al粉尘爆炸温度变化曲线
Figure 12. Variation curves of explosion temperature for Al and 10% SA@Al dust
图 13 不同粉尘云浓度的10% SA@Al粉尘爆炸过程中的温度敏感度变化
Figure 13. Variation of temperature sensitivity during explosion of 10% SA@Al dust at different dust cloud concentrations
图 14 不同粉尘云浓度的10% SA@Al粉尘爆炸过程中的O自由基含量变化
Figure 14. Variation of O radical content during the explosion of different dust cloud concentrations of 10% SA@Al dust
图 15 不同粉尘云浓度下10% SA@Al粉尘爆炸过程中的O自由基敏感度分析
Figure 15. O radical sensitivity analysis during explosion of 10% SA@Al dust under different dust cloud concentrations
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