Research On Propagation Law Of Shock Wave Of Coal Dust Explosion In Confined Space

Based on the dust explosion theory, adopting methods of experimental study, theoretical analysis, numerical simulation, the dissertation studies characteristics of coal dust explosion and the propagation law of shock wave of coal dust explosion in one-way, two-way bifurcation pipeline and cross-section pipeline. The results offer important theoretical and technological support for preventing and controlling the damage of explosion shock wave and decision-making in coal dust explosion accidents.On the basis of former researches, the characteristics of coal dust explosion and the propagation character of explosion shock wave were analyzed, and the process of explosion, structure of the explosion shock wave, the propagation law and factors of two-phase flow of gas and solid when detonation and air shock wave in coal dust explosion were introduced and discussed in detail.The 20L spherical explosion test apparatus was adopted to test and analyze characteristics of test coal explosion, and the perfect concentration was confirmed to be 500g/m3. By making a proximate analysis on coal dust sample, it is concluded that 95% of the volatile and 85% of fixed carbon participate in the combustion. With a microscopic analysis, it is found that the surface of the text coal was covered with fracture before the explosion, while after the explosion the surface was smooth. The energy spectrum analysis showed that the mass of carbon and oxygen reduced by 7% and 9%, correspondingly, the mass of inorganic elements, such as Sodium, Magnesium, aluminum, silicon increased.By adopting the self-designed-and-manufactured coal-dust explosion propagation experiment system, the propagation law of shock wave in general air area of coal dust explosion in one-way or two-way bifurcation pipeline and cross-section pipeline was studied. The results showed that attenuation coefficient raised with the increase of initial pressure, but the increase was slight. In one-way bifurcation pipeline, the coefficient decreased with the increase of angle in the straight line, and the increase was bigger than the decrease. In two-way bifurcation pipeline, the attenuation coefficient of each bifurcation raised with the angle increasing, and the two branches interacted in the opposite direction because of the difference of angle of each branch. The final attenuation coefficient raised with increase of the angle between the two branches. In cross-section pipeline, the attenuation coefficient varied with initial pressure and the variation rate of load area changing.Based on hydrodynamics, according to mass, momentum and energy conservation, by simplifying properly and reasonably hypothesizing propagation progress of the dust explosion in pipeline, the formulas of the overpressure in different pipeline was established. With the initial pressure, the bifurcation angle and the intensity of the incident shock wave being given, the shock wave pressure could be calculated, and the propagation law of shock wave in the bifurcation entry could be got. And the results based on the formulas conformed to the experiment results.By making numerical simulation analysis on the law of overpressure change of dust shock wave in bifurcation pipeline and cross-section pipeline in general air zone, pressure distribution diagram and the overpressure peak of each measured point in the propagation progress of shock wave were obtained. The simulation result was identical with the experiment result, which showed that the result of numerical simulation was correct, therefore a new method was provided for the further study. The simulation results, as a beneficial supplement, also settled some phenomena and results in the experimental study and theoretical analysis.