A Post-combustion reaction model for aluminum in thermobaric effects field

The post-combustion effect is recognized as a critical factor responsible for the sustained high temperature and slow pressure decay in the blast field of thermobaric explosives. Focusing on CL-20 based thermobaric explosives, this study elucidates the underlying mechanism of the post-combustion effect through systematic experimental and theoretical investigations, and explores effective strategies for its enhancement. High-speed thermography is employed to record fireball morphology and temperature evolution, while a blast overpressure testing system is used to measure and compare shockwave parameters of thermobaric explosives with different post-combustion characteristics. The results demonstrate that thermobaric explosives exhibit a unique volumetric explosion mechanism characterized by a concentrated fireball, in stark contrast to the fragmented combustion observed in TNT. A higher oxidizer content yields a higher initial fireball temperature. After 30 ms, the post-combustion reaction of excess metallic fuel becomes dominant, causing TBX5% to exceed TBX30%, which has a higher oxidizer content. Secondary post-combustion reaction analysis also reveals that TBX5% exhibits more pronounced post-combustion fireball features. After 60 ms, the post-combustion temperatures of the two thermobaric explosive systems converge. The proposed post-combustion reaction model indicates that a higher fireball temperature broadens the particle size range of reactive aluminum powder, thereby improving combustion completeness. Notably, the hotter fireball (3001 K) driven by elevated oxidizer concentration leads to near-complete (>95%) and rapid combustion of aluminum powder, thus clarifying the enhancement of the thermobaric effect. Shockwave parameters correspond well with fireball evolution. In the near field, TBX5% shows higher overpressure and impulse, while in the far field, the supplementary effect of post-combustion on shockwave parameters becomes evident.