Comparative study on the inhibition effect of three inhibitors on the flame propagation of aluminum alloy dust cloud

To investigate the inhibitory effects of NH4H2PO4, NaCl, and CaCO3 on the flame propagation of aluminum alloy dust, an orthogonal experimental approach was employed. The concentrations(C) and particle sizes of the inhibitors were systematically altered to explore variations in inhibitory effects across different scales and to investigate their thermal decomposition characteristics. The results indicate that increasing inhibitor concentration and decreasing particle size serve to decelerate and shorten the flame propagation of aluminum alloy dust. During the inhibition process, the "concentration effect" and the impact of particle "size effect" of the inhibitors become more prominent, resulting in a non-linear reduction in both flame propagation distance and flame velocity. Notably, inhibitory effects are more pronounced when the concentration of NH4H2PO4 exceeds 80%, compared to NaCl. Conversely, when the concentration falls below this threshold, NH4H2PO4 is less effective than NaCl. However, in terms of the "concentration effect," both NH4H2PO4 and NaCl outperform CaCO3. A crucial transition in inhibitory effects is observed at particle sizes near 20 μm, with a significant increase in inhibition efficacy below 20 μm. Among the inhibitors, NH4H2PO4 exhibits the highest level of inhibition, followed by NaCl, while CaCO3 displays the weakest inhibitory effect.