Combustion and micro-explosion mechanisms of magnesium-based gel fuels and comparison study with Al-based gel

Magnesium (Mg)-based gel fuels, formulated by incorporating Mg particles and gellants into liquid hydrocarbon fuels, hold significant potential for future aviation propulsion systems. In this study, single droplet combustion experiments were conducted on Mg-based JP-10 gel fuels under ambient temperature and pressure to investigate the effects of particle addition and size on the combustion and micro-explosion characteristics. The results indicate that the addition of Mg particles significantly alters the combustion mode of droplets. At a particle addition of 20 wt%, the micro-explosion intensity peaks, significantly enhancing the combustion and reducing the residues of droplets. Conversely, at 25 wt%, micro-explosions are suppressed; however, the high-temperature combustion of Mg agglomerates is occasionally observed in the late combustion stage, leading to the complete oxidation of Mg particles. Mg droplets exhibit intense micro-explosions across the entire particle size range (20–100 μm). Specifically, small-to-medium particles (20–50 μm) promote disruptive burning through abundant heterogeneous nucleation sites, while large particles (100 μm) trigger violent global fragmentation driven by gravity-induced sedimentation and localized bottom heating. A comparative analysis with prior studies on aluminum (Al)-based gels indicates that the micro-explosions of Mg-based gels are primarily triggered by localized internal superheating. This mechanism more effectively ejects metal particles into the flame zone to participate in gas-phase combustion, thereby mitigating the issue of metal agglomeration. These findings offer an experimental foundation for optimizing the formulation and elucidating the combustion enhancement mechanisms of Mg-based gel fuels.