Explosion characteristics and reaction mechanism of nano-aluminum/methanol fuel spray in a square closed vessel

Abstract

Nano-aluminum/methanol fuel has broad application prospects in the field of ship and automobile energy, but disasters caused by its spray explosion tend to be ignored. In this study, a 16.2-L visualization sealed chamber was employed to assess the impact of varying aluminum powder blending ratios (from 2 wt% to 15 wt%) on the flame morphology, flame speed, and explosion overpressure of nano-aluminum/methanol fuel spray explosions. The results show that, compared with pure methanol, the spray explosion flame of nano-aluminum/methanol fuel is more continuous and brighter. Within the microscopic flame structure, the agglomeration and combustion of aluminum particles become more evident as the mass fraction of nano-aluminum powder increases. When the aluminum powder mass fraction surpasses 8 wt%, the flame's instantaneous velocity showcases oscillatory propagation patterns similar to those observed in dust explosions. The Pmax and (dP/dt)max of the nano-aluminum/methanol fuel spray explosion initially increase, then decrease with the rise in nano-aluminum powder mass fraction, peaking at 4 wt%. Compared to pure methanol, the enhancements in Pmax and (dP/dt)max are over 23.1 % and 73.3 %, respectively. By integrating the TG analysis of reactants with the SEM analysis of explosion residues, a combustion mechanism for the single droplet explosion of the nano-aluminum/methanol fuel was established. Numerical simulations suggest that nano-aluminum augments the generation rate and quantity of O free radicals via elemental reactions R2 (Al + O2 <=> AlO + O), R4 (AlO + O2 <=> AlO2 + O), and R8 (AlO2 <=> AlO + O). This amplifies combustion reactivity, expedites fuel consumption, and bolsters flame propagation. The research provides empirical evidence supporting the safe application of nano-aluminum/methanol fuels.