Study Of Detonation Characteristic Of Combustible Nanoparticles

With the rapid development of nanotechnology, the nano-materials become so increasingly involved in peoples life that its safety raises concerns. In the material preparation and application processes, the flammable nanometer-sized particles prone to cause explosion because of its own characteristics, such as small size effect. Thus, the security of flammable nano-size particles is of great significance.The simulation of gas-solid two-phase is used by means of discrete random track model (DRT), and the simulation of heterogeneous reaction is used by combustion Model, while the homogeneous reaction is simulated by eddy diffusion concept (EDC) model.The detonation of industrial carbon dust and explosion TNT dust in the 7:1 Hartmann is numerically studied in this thesis. The explosion processes as well as the main influence factors are studied, in which the particle concentration, oxygen mass concentration, ignition energy, as well as environmental factors, ambient humidity and ambient temperature are analyzed. Moreover, comparing to carbon and explosion TNT, the modeling results showed the similar detonation characteristic, but different influence at different parameters.The injecting process is simulated in this thesis, and the results show that the particles distribution is most uniform at such parameters for 5m/s gas velocity and 10ms injecting time. The detonation process is simulated, and the results show that flame front and the pressure wave transmit at the same time, and then shock wave is generated. Through the study of the pressure wave, it was found that the explosion process could be divided into three stages, the rise stage, the peak stage and the drop stage. The influences of particle concentration, oxygen mass concentration, ignition energy are studied. The simulation result shows that there is a lower explosion limit. Similarly, when oxygen was insufficient, the explosion could not take place. The detonation will never generate unless the ignition energy is bigger than 5000J. With the increase of environment humidity, the explosion is less drastic. While as the increase of environment temperature, the explosion is more drastic. The detonation of explosive TNT particles is simulated. The results show the similar detonation process as the detonation of carbon particles. But the maximum explosive pressure and temperature are higher than that, as well as the propagation velocity of the pressure wave and flame front are higher. TNT belongs to explosive powders, so it contains oxygen. Therefore, the concentration of oxygen had no influence on the detonation. But it has still the lower explosion limit and minimum ignition energy.