| The basic operation parameters of gas extraction pipe network(negative pressure and flow rate)are the important material for evaluating mine extraction effect and discovering problems of extraction pipe network.Currently the pressure maladjustment of gas extraction pipe is a common problem encountered by gas mine extraction pipe network,and the best way to solve the maladjustment is to build the hydraulic condition model of gas extraction pipe network and use the computer to simulate and analyze the operation condition of each branch of gas extraction pipe network under different regulation status.Therefore,to further understand the operation rules of gas extraction pipe network,this thesis conducted the following research:(1)The study of the rule of gas flow in gas drainage pipelineTo simplify the analysis of the rule of gas flow in gas drainage pipeline,the paper makes the basic hypothesis of the gas flow in gas drainage pipeline:(1)Insider of gas drainage pipeline is the stable flow of one dimensional compressible gas;(2)The flow of the gas in gas drainage pipeline is isothermal flow;(3)The gas pressure of node(including the testing point and branch mixing point)is the same.Based on the formula of gas continuity equation,energy equation and gas state equation,the stable flow of one dimensional compressible gas is set up.According to the formulas,it is found that,as to the same gas drainage pipeline,square of absolute pressure of gas of the gas in the pipe is linear decrease change under the normal operation situation;when there is any blockage or leakage in the middle of the pipe,the change slope absolute value of square of absolute pressure of the gas will be large rapidly with the increasing transportation distance,while under the blockage situation,the change slope absolute value of square of the absolute pressure of the gas in the lower section of the pipe will be covered to the same as the upper section's with the change of transportation distance.When the pipe is leaking,the change slope absolute value of square of the absolute pressure of the gas in the lower section of the pipe will be more than the upper section's with the change of transportation distance.There is a simulated calculation of the rule of gas flow in gas drainage pipeline through the Fluent simulation software.The result of simulated calculation shows that the coefficient of friction ? back out by the simulated calculation is small when using the K-SST equation of turbulent flow to do the simulated calculation,which explains that there is error with the Fluent simulation software.To get more precise simulation result,boundary condition,the pipe wall roughness should be input to the simulated calculation.Finally,the simulated calculation result with corrected numerical value analyzes the efficiency and reliability.(2)The Establishment of Experimental Platform of Gas Drainage and Experimental StudyType of mine gas drainage pipe network is branch pipe network and the distance of underground gas drainage pipe is very long and it is difficult testing as well as the measurement is difficult.Hence,opening the actual measurement of mine gas drainage pipe network is complex and the experience in the lab is convenient to do the testing measuring of the pipeline operating parameters.This part is mainly the running test under the operating condition of single pumping pipeline,the influence of leaking of main pipe to the negative pressure of branch pipe,the influence of leaking of branch pipe to the negative pressure of adjacent pipe and the influence of connection between the temporary pumping station and ground pumping station in series to the running state of the pipe net.To test the gas flow in the experimental pipe precisely,the paper will inject the tracing smoke to experimental pipe firstly,and then the flow will be measured with the camera by image correlation method.To delete the effect of background value,the paper will extract the background value of the experimental pipe with Matlab software then calculate the released tracing smoke at the real time.The monitoring window will cut the change of gray value of background information.Through the real time analysis from gray value 2 monitoring windows,the final gas flow of experimental pipe is counted with cross correlation algorithm.The experiment result shows that the error of this method is less than 3%.The study lays a foundation of the precise measurement of experimental parameters of gas drainage pipe network.The experiment of gas drainage pipe network shows that pressure variation law in the gas drainage gas pipeline is parabolic situation and the square of pressure will be linear attenuation law with the change of distance.The leaking and blocking situation of the pipe can be identified effectively through the relationship between square pressure and distance.The place more close to vacuum pump will be leakage.The decrease of negative pressure of the pump becomes faster;the influence on the negative pressure of drilling will be less.The connection between pumping system for temporary underground pumping station and the pumping system of ground permanent pumping station will seriously affect the negative pressure and flow quantity of the temporary pumping station adjacent pipes,which may lead to the positive pressure existing in the adjacent pumping pipe.(3)The simulation study of the gas extraction pipeline operationThe type of mine gas extraction pipe type is branched network.The most different thing from the most common dendritic pipeline gas delivery system is negative pressure extraction.The pressure of the gas from extraction pipe changed a lot,the density and velocity of which change severely with the change of negative pressure.The gas flow in the gas extraction pipeline needs to be analyzed as the Compressible gas flow.As for the difficulties of mine gas extraction pipe in the distance,debugging and measurement,it is complex to carry out the actual measure mine gas extraction pipeline.It is convenient for the laboratory experiments to measure debugging of pipeline operation parameters.This part is mainly to run the test operation of single extraction pipe,the influence of the air leakage of the main pipe to the manifold pressure,the influence of manifold air leakage to the adjacent pipe pressure,the influence to the network running state for the series of the temporary pumping station and the ground station.The experimental research results indicate that the pressure change rules of the gas extraction gas pipe is a parabola form.But the square of pressure presents the linear attenuation rule with the change of distance.The pipe state of air leakage and clogging can be effectively identified through the relationship between Pressure square and distance.The closer the location of the vacuum pump air leakage,the faster the vacuum negative pressure decreases,but less impact on negative pressure drilling,however,The closer the air leakage hole position,The smaller influence on the operation condition of the vacuum pump,but with a very big impact on the borehole pressure.When the temporary pumping station underground extraction pump system and ground permanent extraction system are in series,the negative pressure and rate of flow with the temporary pumping station adjacent pipe will be adversely affected.When something is serious,positive pressure will exist in the adjacent extraction pipe.(4)The Onsite Application of the Optimized Operation of Gas Drainage Pipe NetworkOn the view of the present situation of gas drainage in Yuwu Coal,the leakage area and blocking area of the gas drainage pipe is confirmed by the diagnosis of the running state of the North Wing mining area of gas pipeline based on the pressure gradient method,which lays a foundation of operation optimization of gas drainage pipeline.Then the rationality of the application of the calculation of gas drainage pipe network is proved through the fluid network solution module based on compressible flow of Ventsim software to do the theoretical analysis.Finally the simulated analysis of Yuwu Coal's optimum operation of gas drainage pipe network is carried on with the software. |
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