Abstract:To investigate the influence of the structure of a laminated composite charge on its energy release during the afterburning process of aluminum powder， a composite charge with a multiple sandwich structure of uniform layer thickness was prepared by introducing two types of explosives namely high explosive and thermobaric explosive. The high explosive with a higher detonation velocity than that of the thermobaric explosive by 1.8 km·s^-1. The evolutionary process of the fire ball and the mechanical energy in different ambient environment during various reaction stages were independently investigated in free-air and confined explosion experiments. Additionally， the distribution characteristics of aluminum powder throughout the explosion were assessed through integrated numerical simulation. The results showed that the thermobaric explosive layer was axially compressed by the high explosive layer， resulting in an increase in the radial diffusion rate of both detonation products and aluminum powder. Furthermore， the average concentration of the aluminum powder cloud was reduced to 60%-80% of that in a homogeneous thermobaric charge， and even to 50% in the tail region， finally resulting in a reduction of anaerobic combustion rate of aluminum powder， as well as the mechanical energy released by aluminum powder. In the laminated composite charge， the total mechanical energy released by thermobaric explosive in detonation and anaerobic combustion process was about 81% of that in a corresponding homogeneous thermobaric charge. However， the mechanical energy produced during the aerobic combustion stage increased significantly， leading to the total mechanical energy remained approximately stable. This study indicated that the laminated composite charge structure could efficiently regulate the afterburning reaction and energy release of thermobaric explosives in different reaction stages by adjusting the spatial distribution of aluminum powder without losing the total energy of the charge.

Abstract:In order to explore the application prospects of a new high-energy oxidizer ammonium dinitramide （ADN） in thermobaric explosives， ammonium perchlorate （AP） was replaced by ADN to prepare five formulations of thermobaric explosives with different ADN/AP mass ratios （AP， ADN∶AP=1∶3， 1∶1， 3∶1， ADN）. The mechanical sensitivity and thermal stability of the formulations were tested by impact sensitivity instrument， friction sensitivity instrument and differential scanning calorimetry （DSC）. The energy level of five different formulations was calculated by Explo5 software， meanwhile relevant energy parameters were measured by combustion calorimeter and detonation calorimeter. The results indicated that the characteristic drop height of impact sensitivity and the explosion probability of friction sensitivity of the fomulation using pure AP as oxidizer were 17.9 cm and 12%， respectively. But as soon as AP was replaced by ADN in various mass fraction， the characteristic drop height of impact sensitivity and the explosion probability of friction sensitivity of the corresponding formulations increased by 7.9-12.0 cm and 20%-28%， respectively. As the ADN/AP mass ratio increased， the peak temperature of exothermic reaction initially increased and then decreased. The highest exothermic peak temperature was observed when the mass ratio of ADN∶AP=1. When the mass ratio of ADN/AP≥1， the components in the formulations interacted intensely， resulting in a single sharp exothermic peak in a DSC curve. When the mass ratio of ADN∶AP=1， the formulation exhibited an impact sensitivity of 28.1 cm， a friction sensitivity of 32%， and a thermal decomposition temperature of 277.9 ℃. The combustion heat and detonation heat of the formulation were 13874.4 and 7666.9 kJ∙kg^-1， respectively.

Abstract:To study the evolution laws and its suffered influential factors of thermal effect and shock wave generated by thermobaric explosive （TBX） explosion around the tunnel entrance， explosion experiments were carried out by varying the initial location of TBX relative to the tunnel entrance. Thermal effect parameters （e.g. fireball size and temperature）， and shock wave parameters （e.g. overpressure peak value， positive pressure duration， specific impulse and waveform）， were analyzed. Moreover， the propagation trace of shock wave inside the tunnel was analyzed in conjunction with the results of Trinitrotoluene （TNT） explosion experiments. The results indicated that， when the TBX charge was initiated at the tunnel entrance， both the thermal effect and shock wave effect in air explosion was better than that in a ground surface explosion. Regarding thermal effect， the height and peak temperature of the fireball generated by the explosion were approximately 2 and 1.41 times higher than that of a ground surface explosion， respectively. The peak temperature measured inside the tunnel was about 2.42 times higher than that of a ground surface explosion， and the heat flux density could exceed 19.3 times that of the ground surface explosion. The temperature increasement generated by the afterburning process of TBX indicated a positive correlation with the weight of TBX charge. Concerning shock wave， the overpressure generated by the afterburning process of TBX in air explosion at the tunnel entrance was stronger than that of the ground surface explosion. For air explosion， the reflection and superposition paths of shock wave were more sufficient. Compared to the ground surface explosion， the equivalent coefficients of overpressure peak value， positive pressure duration and specific impulse of the shock wave in air explosion were approximately 1.3， 1， and 1.1， respectively. The evolution laws of thermal effect and shock wave effect were influenced by the combination of the constraint from tunnel and the intervention of the ground. In air explosion， the constraint effect of tunnel was much more significant， so as to the afterburning effect. However， in a ground surface explosion， the intervention effect of the ground could weaken the constraint function of tunnel， so that the mixing between Al particles and air could be suppressed， resulting in a reduction of afterburning intensity.

Abstract:The cloud detonation devices typically form a fuel air mixture cloud with an approximate cylindrical shape. The morphological parameters of the cloud closely related to the charge structure strongly affect the spatiotemporal evolution law of its detonation overpressure field， which in turn has a significant impact on its detonation overpressure damage power. In order to explore the morphological effects of cloud， through the numerical calculation method for ideal detonation in cylindrical cloud， the complex dynamic process of waves during its detonation process was analyzed. The evolution and distribution law of the cloud detonation overpressure field was investigated. A similar decay law of the radial far-field peak overpressure with scaled distance was established．The dependence relationship between the detonation overpressure damage radius and the morphological parameters （ratio of radius to height） of the cloud was provided. The research results indicated that there was a significant bimodal phenomenon in the radial far-field overpressure field， due to the complex detonation process inside the cylindrical cloud. The pursuit of two peaks resulted in a characteristic mutation phenomenon of small amplitude and small range in the variation curve of the peak overpressure of detonation with scaled distance， and the larger the morphological parameter， the closer the certain position was to the detonation point．Furthermore， when the morphological parameters within the range of 2-4.5， the decay law of the detonation far-field peak overpressure with scaled distance satisfied the same similarity law. The maximum error of the overpressure damage radius obtained based on that similarity law was less than 8%. When the morphological parameters within the range of 0.5-2， the detonation overpressure damage radius decreased with the increase of morphological parameters.

Abstract:The content and particle size of aluminum powder in thermobaric explosives （TBXs） directly influence the energy output structure of explosions， significantly affecting the characteristic “post-combustion effect” of TBXs， which is crucial to the formation of the “thermobaric effect.” This paper discusses the influence of aluminum powder content and particle size on the explosive energy， pressure effect， thermal damage effect， and asphyxiation effect of TBXs. It also analyzes the mechanism by which aluminum influences the post-combustion reaction， identifying the optimal content and particle size range for aluminum addition in TBXs. Looking ahead， future research should focus on the reaction kinetics of energy release from aluminum powder， develop corresponding testing methods， and thoroughly analyze the energy release process of TBXs， providing a foundation for the precise control of formulation design and energy output structure.

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