| The danger and destructive effect of gas explosion in coal mine are very serious.After a gas explosion,a high concentration of disaster gas will be generated instantly,which will seriously threaten the life and health of underground workers.Highconcentration noxious gas diffuses and dilutes along the underground tunnel under the action of airflow,thereby expanding the scope of disasters.Based on this,this paper adopts a combination of theoretical analysis and numerical simulation to focus on studying the diffusion law of noxious gas after a gas explosion in underground roadway,and then explores the migration characteristics of noxious gas in the dangerous area.Based on the multi-physical field coupling software COMSOL,the diffusion and transport model of noxious gas was established according to the flow field and the dilute material transfer field,and the diffusion law of noxious gas under different airflow and gas explosion concentration in the straight roadway was studied.The study found that the airflow mainly affects the residence time of the noxious gas in the roadway,and the gas explosion concentration mainly influences the diffusion speed of the noxious gas.Finally,the relationship between the peak concentration of noxious gas and the airflow and gas explosion concentration is obtained.Through the establishment of roadway with different structure types(turning,bifurcation and abrupt change of cross section),the diffusion law of noxious gas along the local complex roadway was analyzed.In the turning roadway,the relationship between the sudden increase coefficient of noxious gas and the corner Angle at the corner and before the corner was obtained;In the bifurcation roadway,the relationship between the attenuation coefficient of noxious gas and the bifurcation Angle at straight lane and branch lane was obtained;In the roadway with cross section change,the relationship between the attenuation coefficient of noxious gas and the cross section mutation ratio at roadway with enlarged cross-section was obtained,the relationship between the sudden increase coefficient of noxious gas and the cross section mutation ratio at roadway with reduced cross-section was obtained.It is found that there is a positive correlation between airflow and these coefficients.The emergency response planning guidelines(ERPG)developed by the American Industrial Hygiene Association were selected to determine the boundary concentration in the hazardous area of noxious gases.In this paper,the migration characteristics of the dangerous area of noxious gases are analyzed,including the variation law of the length of the dangerous area with time and the variation law of the migration speed of the dangerous area.It reveals the variation characteristics of dangerous area along the length of different types of roadways.It is found that the length of the dangerous area along straight roadways changes with time in an inverted U shape.The speed of airflow mainly affects the change speed of the length of the dangerous zone,and the concentration of gas explosion affects the maximum length of the dangerous zone.The migration velocity of the dangerous area in the straight roadway decreases gradually at first,and then it moves steadily at the speed close to the wind speed.The concentration of gas explosion mainly affects the time when the migration velocity in the dangerous area decreases to a steady change.The influence of turning,bifurcation,and abrupt cross-section roadways on the length and migration speed of dangerous areas is further explored.The research results provide a theoretical basis for the judgment of the toxic gas in the roadway,the rapid recovery of the ventilation system after the disaster,and the emergency evacuation decision-making of personnel. |
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