| Due to the expansion of coal mining scope and the transformation of mining technology,goafs have become the main prone areas for coal spontaneous combustion disasters.The actual fire site in the goaf is extremely complex and dynamic,and its spontaneous combustion high-temperature points are difficult to monitor and difficult to determine,which makes it more difficult to effectively prevent and control coal spontaneous combustion.Therefore,this thesis uses the coal spontaneous combustion experiment to study the migration law of high-temperature points;based on the theory of heat transfer,the COMSOL Multiphysics software is used to simulate the spontaneous combustion experiment,and the experimental results are compared and analyzed;Finally,according to the control equations of multi-field coupling theory in the goaf and the changes of various physical fields with the dynamic advancement of the working face during the process of coal spontaneous combustion,considering the influence factors of the working face such as different air supply and advancing speed,the coal in the goaf is developed.Numerical simulation study of spontaneous combustion and oxidation heating,analyzed the evolution mechanism of oxygen concentration field,temperature field and flow field during the spontaneous combustion of the goaf.The research results have important guiding significance for the prevention and control of spontaneous combustion in the goaf.Using the coal spontaneous combustion experiment system,the whole process of the spontaneous combustion of the Dafosi coal sample was tested,and the temperature and index gas changes during the entire combustion process were tracked and measured.The experimental results showed that the high-temperature point in the furnace was always near the central axis.And continue to migrate to the air inlet;then based on the theory of heat transfer,use COMSOL Multiphysics software to establish a numerical model of the temperature field of the coal spontaneous combustion experiment system,and analyze the migration law of the high-temperature point of the coal spontaneous combustion under the conditions of different oxygen volume fraction and air leakage intensity.Finally,by comparing the migration law of high-temperature points in the simulation and experiment,a good theoretical foundation is laid for the migration law of high-temperature points in the goaf.Based on the control equation of multi-field coupling theory of goaf and the dynamic evolution process of spontaneous combustion,the dynamic evolution model of goaf with coal spontaneous combustion was established by using the method of deformation geometry,and the distribution of oxygen concentration and temperature field in Dafosi 40106 working face under different working conditions(different propulsion speed and different air supply)was simulated.With the increase of the advancing speed of the working face,the distribution law of the oxygen concentration field in the goaf tends to be stable,and the high-temperature point in the goaf gradually decreases with the increase of the advancing speed,and there is also a certain tailing phenomenon in the high-temperature area.In addition,under certain quantitative conditions,the temperature change in the goaf is positively correlated with the air supply volume.When the air supply is larger,the high-temperature point in the goaf area is larger,and the more it extends to the deep suffocation zone of the goaf area.Finally,the dynamic superposition effect of the high-temperature area and the width of the oxidation zone in the goaf is deeply analyzed,and compared with the field measured data,the research results have important guiding significance for the prevention and control of coal spontaneous combustion in the goaf. |
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