Numerical Simulation Of Temperature Field Of Coal Spontaneous Combustion

Coal spontaneous combustion affects the coal industrial development seriously, andbrings great safety hidden trouble to the production of the mine. It is very difficult to describethe actual conditions clearly of the coal spontaneous combustion process, which makes itseverely restricted of the development of prediction technology of coal seam spontaneouscombustion. The urgent task is to establish an effective and complete mechanism of predictionof coal spontaneous combustion. Based on the mechanism of the formation mechanism ofcoal spontaneous combustion, there are three necessary conditions of coal spontaneouscombustion:1The coal has the spontaneous combustion tendency and in the state of brokenand accumulation;2With continuous ventilation oxygen supply conditions;3Heat is easy toaccumulate. The sufficient conditions are: Certain heat storage duration. The college of coalscience professionals use small experimental furnace to simulate large coal mines and collectexperiment data, with a simple curve fitting the approximate solution of coal temperaturechanges, when fully exposed into oxygen and reaches a certain temperature, the coalspontaneous combustion will occur (Different coal samples have different ignition points). Byusing optimization algorithms and computer numerical simulation we can explore thecombustion process of coal and the temperature changes more accurately. Significance of thethesis lies in switching the actual furnace ignition experiment into the numerical simulation,to makes it more intuitive of the coal spontaneous combustion process.This paper commenced from two dimensional mathematical model of coal spontaneouscombustion experiment, based on the coal spontaneous combustion test furnace of Xi ’anuniversity of science and technology, through the determination of the furnace’s main datastructure, wind conditions and coal samples conditions, etc, and the basic hypothesis of lessinfluence factors on the model, we established a three-dimensional mathematical model of coal spontaneous combustion. The established three dimensional mathematical model ofcoal spontaneous combustion is a three-dimensional multi field coupling conditions ofconvection diffusion reaction equations, after the initial conditions and boundary conditionsare added, summarized as a convection dominated diffusion reaction equation underthree-dimensional unsteady condition. Take the experience exothermic intensity and oxygenconsumption rate into the three-dimensional convection-diffusion equation, numericalsimulation process is mainly using the finite element method, in order to improve thecalculation accuracy and convergence rate, this paper introduces the characteristic finiteelement method two-grid algorithm. This paper through the experimental of furnacehierarchical traversal solution to numerical simulated under certain experimental conditions ofZaoquan coal sample temperature changes.After using characteristic finite element method to solve the trend of natural variationfield control equation and simulate the temperature of coal spontaneous combustion of coaltemperature under certain boundary conditions, numerical simulate a group of spacecorresponding temperature value with dynamic variation. Visualization software has achievedwho designed an interface to import data, it can import ACCESS, EXCEL simulation andexperimental data directly and reproduce the experiment process by virtual platform of coalspontaneous combustion. The software achieved an interface of dynamic change temperaturefield of three-dimensional furnace by OpenGL, and can realize the export of highest coaltemperature data at a time point.Coal temperature test device was measured some specific points after the transienttemperature change in coal pile, the simulation temperature and the experimental temperaturewas compared. Feasibility analysis shows that numerical simulation of temperature field andcombustion period on the change process of coal spontaneous combustion can well reflect thereal experimental conditions’ situation. According to the simulation results, we can evaluatethe model, and lay a foundation of the establishment of fast and accurate prediction of coalspontaneous combustion system.