Breakup and atomization of gel fuels induced by shock waves and under-expanded flow

The viscoelastic cohesion of gel fuels is resistant to aerodynamic breakup, posing challenges for effective atomization in propulsion. This study investigated the breakup and atomization behaviors of aluminum-loaded gel fuels subjected to under-expanded flows. High-speed schlieren imaging revealed that effective atomization is primarily governed by the high-speed flow behind the contact surface, with shear and entrainment associated with vortex structures promoting rapid breakup. A distinctive plume morphology was observed in high-Mach-number flows, providing direct evidence of the link between viscoelasticity and aerodynamic fragmentation in non-Newtonian systems. Quantitative fitting of the cloud displacement established breakup thresholds linked to the Mach number and gel rheology, demonstrating that an increased aluminum content enhances the structural robustness but suppresses secondary atomization. These results advance the understanding of gel-fuel fragmentation dynamics and provide a physical framework for optimizing atomizer designs and gel formulations in aerospace propulsion.