Study On Microwave Propagation Characteristics Of Coal-gangue In Fully Mechanized Caving Face

Fully mechanized caving mining is one of the important methods of thick coal seam mining.Automatic control of top coal caving process is of great significance to realize intelligent mining of fully mechanized caving face.Identification of gangue rate in coal and gangue mixture is an important basis for automatic control of top-coal caving process.The accuracy and efficiency of identification are the key factors affecting the safe and efficient production of top-coal caving mining.This thesis takes coal-gangue mixture as the research object.And uses non-contact microwave detection technology as the means to carry out the simulation analysis and experimental study of microwave radiation detection of coal-gangue mixture.Those coal-gangue mixture with different frequencies,different sizes of coal and gangue,and different rates of gangue.so as to reveal the changing rules of microwave propagation characteristics of different mixing states of coal and gangue.It lays the theoretical foundation for realizing the intellectualized caving of fully mechanized caving face based on electromagnetic wave signal.The main research work of this paper is as follows:(1)The basic theory of electromagnetic wave numerical simulation is studied.Then,the mathematical model of electromagnetic wave numerical simulation in coal-gangue mixture medium is established,and the stable operation conditions of numerical simulation are discussed.Considering the boundary reflection of the simulation region,the absorbing boundary layer was added,and the iterative formula of electromagnetic wave propagation with time and space was derived under the condition,which provided theoretical basis for the subsequent simulation.(2)Based on the physical characteristics and the electromagnetic parameters of coal-gangue mixture,the spatial distribution characteristics of coal-gangue mixture after top coal drainage are analyzed.And the autocorrelation function and characteristic parameters of coal-gangue mixture are calculated.On this basis,the two-dimensional numerical models of coal and gangue mixtures with different gangue ratios and different particle sizes were established based on the multiphase discrete random media,and the effectiveness of the modeling was verified.In order to further study,a 3D model was established by SOLIDWORKS and the electromagnetic parameters of coal and gangue were assigned in CST software to obtain a three-dimensional model of coal and gangue mixture.(3)Based on the theory of electromagnetic wave numerical simulation,using the MATLAB editor on the 2D mixture of coal and gangue forward modeling.At the same time,using CST software simulation results contrast analysis,discusses the electromagnetic wave reflection signal,transmission signal and frequency of electromagnetic wave,coal-gangue,medium type and size of coal waste mixture containing gangue rate of inner link.(4)An experimental system for microwave detection of coal-gangue mixture was set up.The electromagnetic parameters of different coal and gangue were measured by using vector network analyzer as signal source,transmitting antenna and receiving antenna.On this basis,microwave irradiation was carried out on the mixture of coal and gangue with different granularity,different rate of gangue and different coal types.The experimental results show that: under the same mixture of coal and gangue,the attenuation degree of electromagnetic wave is positively correlated with the frequency.At the same frequency,when the granularity of coal-gangue is between3 and 10 cm,the amplitude of the transmitted wave signal is inversely proportional to the granularity of the medium,while when the granularity is between 10 and 20 cm,and it was the opposite between 10 and 20 cm.At the same frequency and the same granularity,when the electromagnetic parameters of coal and gangue differ greatly,the intensity of electromagnetic wave and the amplitude of transmitted wave signal are inversely proportional to the rate of gangue in coal and gangue mixture.When the difference is small,there is no regularity.The reflected signals are not intrinsically related to the above parameters and show irregularity.The experimental results are basically consistent with the simulation results,which verifies the correctness and rationality of the simulation analysis.The research results provide a new idea for the identification of gangue rate in coal and gangue mixture.This thesis has 74 figures,10 tables,and 96 references...