1.School of Civil Engineer, Tianjin University;2.Beijing Institute of Space Launch Technology
The effects of different duration blast waves on the structure and protection engineering are obviously different. Long duration blast wave is often needed in experimental studies and numerical simulations. However, it is difficult to prolong the duration of the positive pressure in the practice experiment of studying the structural responses under long duration blast load. A multi-point delayed detonation model with multiple small charge TNT explosives in a long tube explosion chamber is established by computational fluid dynamics software AUTODYN with remapping technique. Compared with the corresponding experimental data, the feasibility of numerical simulation is verified. Cylindrical explosion chamber with a radius of 1.5m is adopted, and the explosive interval of 1m is arranged on the longitudinal axis of the explosion chamber. And the propagation law of blast wave in the long tube is analyzed. On this basis, the influences of the length of explosion chamber, the delay detonation time and the initiation sequence on the blast wave form are further investigated. The results show that, as the distance increases, the peak value of overpressure decreases and the duration of positive pressure increases. The overpressure time-history curve with full and continuous attenuation of the waveform can be obtained by selecting the delay detonation time rationally according to the amount of explosive and the length of the explosion chamber. Detonating from the bottom of the explosion chamber and controlling the delay detonation time interval reasonably can form a long-duration blast wave which is similar to the continuous attenuation produced by a large equivalent charge long distance explosion. The parameters such as the length of explosion chamber, amount of explosive and delay detonation time are adjusted repeatedly, and the detonation schemes of 100ms explosion duration and 200ms explosion duration are provided, which provides technical support for the design of long duration explosion simulation device.