| Based on the theory of gas dust explosion and the research methods of experiment,theoretical derivation and numerical simulation,this paper systematically studies the characteristics of gas dust mixed explosion and the propagation law of shock wave in different forms of pipeline,which can supply technical and theoretical guidance for avoiding the occurrence of explosion accident in coal mine and the decision-making of accident rescue.Based on the existing research results,this paper analyzes the characteristics of gas and coal dust mixed explosion and the propagation law of shock wave in the pipeline,introduces and discusses in detail the process of mixed explosion,the reflection process of blast wave,the wave's modality in the pipeline,the propagation characteristics of shock wave in the general air area and its influencing factors.In this paper,the explosion characteristics of gas coal dust mixture explosion are studied by using the spherical explosion system.The function relationship between the lower limit of gas explosion and the change of coal dust concentration and the lower limit of coal dust explosion with the change of gas concentration is obtained.Under different gas concentration,the influence of coal dust on the maximum explosion pressure and the maximum pressure rise rate is different.When the gas concentration is10% and 12%,with the increase of coal dust concentration,the maximum explosion pressure and the maximum pressure rise rate of gas show a downward trend.When the gas concentration is 6% and 8%,the coal dust can promote the maximum explosion pressure and the maximum pressure rise rate first and then restrain it.The lower the gas concentration,the more obvious the promotion of coal dust.A test system of coal dust and gas mixed explosion propagation with different cross-section shapes is designed and manufactured by ourselves.By using this system,the propagation law of shock wave of coal dust and gas mixed explosion in general air area of three different cross-section shapes of pipes with various forms is studied.The test results show that in the explosion with the same concentration of gas and coal dust,the attenuation coefficient of shock wave overpressure in the bifurcated pipeline is the largest in the rectangular section pipeline,the second in the trapezoid section pipeline,and the smallest in the arch section pipeline,but the decrease amplitude is not obvious;in the unidirectional bifurcated pipeline,the attenuation coefficient of shock wave overpressure in the straight section and the branch section decreases with the increase of bifurcated angle respectively The decreasing trend is smaller than the increasing trend;for the double bifurcated pipe,fix the bifurcated angle of one pipe,and the decreasing coefficient of internal shock wave overpressure of the other pipe increases with its own bifurcated angle.For the pipe with the same bifurcated angle,the decreasing coefficient of internal shock wave overpressure decreases with the increasing of the bifurcated angle of the other pipe,The increase is greater than the decrease.In the pipeline with abrupt section,when the shock wave enters the large section from the small section,the attenuation coefficient of shock wave overpressure in the pipeline with different section shapes increases with the increase of the change rate of section area,and the section shape changes from arch to trapezoid and then to rectangle,the attenuation coefficient of shock wave overpressure also increases;when the shock wave enters the small section from the large section,the attenuation coefficient of shock wave overpressure in the pipeline with different section shapes increases With the increase of the change rate of the cross-section area,the attenuation coefficient of the shock wave in the pipeline decreases,and the cross-section shape changes from rectangle to trapezoid and then to arch.In the above two cases,the change amplitude of the attenuation coefficient caused by the change of the cross-section area of the pipeline is larger than that caused by the different cross-section shape,which is the main factor affecting the attenuation of shock wave.According to the basic principle of hydrodynamics,the propagation process of gas and coal dust mixed explosion in bifurcated pipeline and cross-section abrupt pipeline is reasonably assumed and simplified.By using the laws of mass conservation,momentum conservation and energy conservation,the calculation formula of the pressure in the pipeline is established,and the propagation attenuation formula of the shock wave in the bifurcated pipeline and the abrupt section pipeline is obtained.The attenuation coefficient of shock wave overpressure in the bifurcated pipe and the pipe with abrupt section can be calculated when the pressure of incident shock wave,initial pressure,bifurcation angle and change rate of section area are known.The results calculated by the formula are consistent with the experimental results.In this paper,the numerical simulation of the overpressure of the blast wave in the general air area of the bifurcated pipeline with different cross-section and the pipeline with abrupt cross-section is carried out.The pressure distribution,the peak value of overpressure and the attenuation coefficient of the explosion shock wave in the bifurcated pipe with different cross-section and the pipe with abrupt cross-section are obtained.The reflection effect of shock wave in the case of pipe bifurcation and section mutation is found,and the quantitative conclusion of reflection effect is obtained.The results of numerical simulation also give a reasonable explanation for some phenomena and conclusions in experimental research and theoretical analysis.The test results are consistent with the numerical simulation results,which verify the reliability of the model used in this paper.The results of numerical simulation also give a reasonable explanation for law and some phenomena in theoretical derivation and experiment. |
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