| After gas explosion accident in goaf caused by coal spontaneous combustion,great damage and loss are often accompanied.Based on previous research results,this paper studies the influence of coal spontaneous combustion heat and gas production characteristics on gas distribution in goaf.Considering the complexity and danger of the environment inside the goaf,similar simulation experiment method is used to carry out the research.Focusing on the research theme of coal spontaneous combustion and gas,based on the similarity simulation theory,this paper independently designs and constructs the three-dimensional flow field simulation experimental system in goaf.Relying on this experimental system,the simulation experiments of coal spontaneous combustion under heat generation characteristics,gas generation characteristics and heat and gas generation characteristics are carried out,rich data of temperature and gas concentration are obtained,and the distribution characteristics of temperature field and gas concentration field under different characteristics are obtained,The influence process and characteristics of three characteristics on gas distribution in goaf are further analyzed.The research work and results of this paper are as follows:(1)The three-dimensional flow field simulation experimental system in goaf is designed and constructed,and the experimental parameters are determined.The basic structure of the experimental system is determined,including cavity structure,ventilation subsystem,heating subsystem,temperature acquisition subsystem,gas release subsystem and gas acquisition and detection subsystem.The heating system is used to simulate heat release,helium is used to replace gas in goaf,and nitrogen is used to replace carbon monoxide to simulate gas production.A layer of measuring point network is arranged on the planes with a height of 4cm,13 cm and 23 cm,with 56 measuring points on each layer.The gas release room is designed to fully diffuse the gas and then inject it into the goaf.(2)The heat production experiment was carried out.The distribution characteristics of temperature field and three factors affecting the distribution of temperature field are obtained.The distribution characteristics of gas concentration field are obtained,that is,gas accumulation area will be formed at the position of spontaneous combustion point,and low concentration area will be formed outside the spontaneous combustion point.The analysis shows that the heat production characteristics of coal spontaneous combustion affect the gas in goaf by generating buoyancy along the vertical direction and entrainment from the outside to the inside.(3)The gas production experiment was carried out.The distribution characteristics of gas concentration field are obtained,that is,the gas in the caving zone(layers I and II)accumulates in the deep part of the return air side,while the gas in the fracture zone(layer III)accumulates in the deep part of the inlet air side,forming a low concentration area near the inlet air roadway and return air roadway,and reducing the gas concentration to a certain extent.The analysis shows that the gas production characteristic of coal spontaneous combustion is to interfere with the gas distribution structure and reduce the gas concentration through the generated index gas.(4)The experiment of heat and gas production was carried out.The distribution characteristics of temperature field and four factors affecting the distribution of temperature field are obtained.The distribution characteristics of gas concentration field are obtained,that is,the gas accumulation area is formed at the spontaneous combustion point,the low concentration area is formed outside the spontaneous combustion point,and the gas concentration is reduced to a certain extent.The analysis shows that the heat and gas production characteristics are the result of the organic combination of heat and gas production characteristics,in which the heat production characteristics mainly affect the gas distribution,and the gas production characteristics mainly affect the gas concentration.The influence of coal spontaneous combustion heat and gas production characteristics on gas distribution obtained in this paper improves the theoretical system of mutual influence between coal spontaneous combustion and gas,provides an experimental basis for gas disaster prevention,and has a certain reference value for practical work. |
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