Effects of nano-aluminum particle size on the explosion behaviors of aluminum/methanol nanofluid fuel spray

Aluminum/methanol nanofluid fuel, as a modified methanol-based fuel, demonstrates promising application potential. However, the elucidation of its spray explosion disaster's evolution process remains elusive. This paper clarifies the influence of aluminum powder particle size on the behavior of aluminum/methanol nanofluid fuel spray explosions by examining changes in explosion parameters. On this basis, the microstructure of the explosion flames was observed, and the explosion residues were analyzed using SEM and XRD. The results indicate that when the solid content is less than 8 wt%, the maximum explosion pressure and maximum flame propagation speed of nanofluid fuel spray explosions mixed with 50 nm aluminum powder are higher than those mixed with 100 nm and 200 nm aluminum powder. The maximum explosion pressures for the three particle sizes of aluminum powder are 9.59 bar, 8.94 bar, and 8.25 bar, respectively. When the solid content exceeds 8 wt%, the differences in aluminum powder particle size no longer significantly affect the intensity of the spray explosion and flame speed, mainly due to the agglomeration behavior of the nanosized aluminum powder. The reaction combustion zone of aluminum/methanol nanofluid fuel spray explosion flames is characterized by the gas-phase combustion of methanol and the heterogeneous/homogeneous combustion of aluminum, manifested as the white tail-like light and the quasi-spherical gaseous flame. The study also found that nano-aluminum particles increase their initial size through reactive sintering before combustion, while the agglomeration behavior of nano-aluminum powder mainly occurs before reactive sintering.