Experimental And Applied Research On The Influence Of Temperature On Air Flow Characteristics In Coal Field Fire Area

Coal field fires are one of the common disasters faced by coal mining countries all over the world,and coal field fires in my country are particularly serious.Coal fires not only burn down and sluggish a large amount of coal resources,but also produce toxic and harmful substances,such as SO₂ and mercury,causing immeasurable air pollution and environmental damage.While the air flow in the loose coal rock in the coal fire area provides oxygen to the high temperature area of the coal fire,it is also affected by the temperature of the coal rock.There are few researches on the influence of loose medium temperature on air flow.For this reason,the thesis carried out an experimental study on the influence of temperature on air flow law in loose medium to reveal the air flow characteristics in variable temperature loose medium.The main research results obtained are as follows:1)A variable temperature loose medium air flow experiment system with intelligent temperature control,flow control and pressure measurement is developed independently.The system is mainly composed of an air compressor,a pressure reducing valve,a mass flow controller,a differential pressure gauge and a loose medium heating device.The developed experimental system was used to carry out air flow experiments in loose media with different single particle sizes under normal temperature conditions,and the corresponding relationship between flow velocity and pressure drop was obtained.Combined with the Fochheimer equation,the equivalent permeability and non-Darcy factor of the loose media with different particle sizes are obtained,and the functional relationship between them and the particle size and porosity is established.The results show that compared with the effect of porosity on the equivalent permeability and non-Darcy factor of loose media,the particle size has a greater impact on it;the equivalent permeability,non-Darcy factor and particle size and porosity are in power Functional relationship.2)The developed variable temperature loose medium air flow experiment system was used to test the pressure drop of the air flowing through the loose medium at different temperatures.Combining the equivalent permeability and non-Darcy factor of the loose medium obtained from the room temperature experiment,the permeability coefficient,the non-Darcy coefficient and the turning flow rate(Re=10)change with the temperature of the loose medium are obtained.The coefficient of the viscosity term and the coefficient of the inertia term are defined,and the functional relationship between them and the temperature of the loose medium is obtained,and the quantitative characterization of the air flow characteristics in the variable temperature loose medium is realized.The results show that the pressure drop of the air at both ends of the loose medium with the same equivalent permeability increases with the increase of temperature,while for the same temperature,the pressure drop of the air at both ends of the loose medium increases with the decrease of the equivalent permeability;The permeability coefficient,non-Darcy coefficient,and turning flow velocity change with temperature in loose media with different permeability;the viscosity term coefficient and inertia term coefficient of air flowing in loose media with different equivalent permeability are in quadratic function relationship with temperature.3)Taking Xinjiang's Daquan Lake fire area as a prototype,based on the multi-field coupling mathematical model of coal field fire area constructed by the research team,the momentum equation is optimized according to the obtained gas flow law in the variable temperature loose medium.The unoptimized and optimized mathematical models were used to simulate the evolution process of the temperature field in the fire zone(simulation 1 and simulation 2 respectively)and compared.The results show that the maximum temperature of the fire area simulated by the two mathematical models gradually increases and tends to be constant with the increase of time,and the constant values are basically the same;In the early stage of coal fire evolution,the maximum temperature increase rate in simulation 2 is higher than that in simulation 1.In the same time,the temperature range of simulation 1 is wider than that in simulation 2,and with the passage of time,the temperature of the bottom of the coal seam in simulation 2gradually decreases.But simulation 1 still maintains a higher temperature.The paper has 66 figures,12 tables,and 86 references.