| Coal mine is the basic energy of China and it has a long-term support to the orderly development of national economy.These years,the imbalance of national economic structure cause a severe impact to mining and utilizing of coal,it is urgent to find a scientific,efficient and energy-saving coal mining method in this new situation.A good ventilation cindition is the premise of mine safe production,and the efficient operation of mine fan is the foundation of mine ventilation.The diffuser plays a vital role in the efficient operation of the mine fan.The optimization of the diffuser and mine ventilation system of the main fan is not only required for mine safety production,but also necessary for improving the production capacity and efficiency of the mine.It has important scientific significance and application value.Based on current situation of coal mining,this paper conducts an in-depth study on the reconstruction and optimization of the vertical diffuser of the main fan and the ventilation system of the mine.The main research contents include:firstly,do simulation analysis on internal flow characteristics of diffuser device when different forms of guide plate installed in vertical diffuser elbow.On the basis of numerical simulation results,the energy recovery rate and diffusion efficiency is evaluated,as well as the layout of optimal diffuser elbow guide plates for specific wind conditions are determined.Secondly,according to the results of numerical simulation,the vertical diffuser simulation experiment is designed.Thirdly,according to simulation and experimental results,the reasonable renovation project is determined,and it helps the transform construction to carry out.Fourthly,the research puts forward a new method about mine ventilation resistance calculation and measurement,and a new graphics of mine ventilation network calculation software is developed independently.Fifthly,according to the existing production situation of a coal mine in Shanxi province,the measurement route and measurement plan are selected,and the assessment of wind resistance calculation method is carried out.Fifthly,when the ventilation system of mine ventilation changes form forcing type ventilation to exhaust ventilation,the ventilation system of mine ventilation network by using graphic calculation software,combined with the ventilation network solution and the mine actual production situation,a reasonable reconstruction scheme is put forward to optimize the ventilation system after transformation.Based on the research contents and study scheme,the paper firstly conducts the analysis of transformation and optimization of new main fan mine diffuser.In consideration of the importance of CFD method to calculating internal flow field of ventilator diffuser,the paper firstly utilizes five universal turbulence models(k-?,RNG k-?,Realizable k-?,k-??SST k-?)in CFD software to simulate the aerodynamic characteristics of diffuser with gradient of 60°and 45°respectively.With the comparison and analysis,it finally determines the turbulence k-?model simulate the inner air flow of diffuser,the turbulence k-?model has a accurately predicted result to aerodynamic performance of diffuser.With the help of the above study,the FLUENT software is used to simulate the diffuser device with different forms of guide plate at the elbow.By analyzing the gas flow law of diffuser,it is including that analyzing the distribution law of pressure field and velocity field of flow.According to the result of numerical simulation,a better structure form of guide plate is determined.The simulation results show that when two or four guide plates are installed at the elbow,the vertical diffuser device has a better energy saving effect.In order to further verify the results of numerical simulation,this paper carries out the simulation experiment research of vertical diffuser,when the elbow is provided with two or three plates,four plates,five plates and six plates respectively,the performance measurement on diffuser is carried out.The diffusion efficiency of diffuser under different working conditions were determined by measuring the cross-section parameters on the diffuser entrance section and air outlet section,The analysis shows that when elbow with four or two pieces of guide plates,the performance work of diffuser is the highest,when elbow with five or three guide plates,the performance of diffuser is lower.According to the simulation results and experimental results,considering the field conditions of the coal mine,the guide plate at bottom of elbow is removed to optimize the mine vertical diffuser,as a result,the static pressure at the inlet of diffuser changes,the mine negative pressure changes and power of fan changes,after the transformation,the dynamic pressure recovery effect is improved obviously,and the reduce on the energy consumption of the main fan is 7kw.In addition,the paper also proposal a working-face resistance computing method based on hectometer resistance.The paper take advantage of section element method to select the research objects and make sure the research tunnel sections keep a regular fracture surface and there is a small parameters change in different location,in this way,using the value of hectometer resistance to estimate measurement error of working face ventilation resistance could be more accurate and reliable.According to the method to measure hectometer resistance,the paper measures the windage resistance of two ventilation route of two different mining area of a mine in Shanxi province,which includes 120 measure points,and the method and instruments which adopted are completely reach the requirement.Finally,the measured results are reliable and the accurate.Simultaneously,researcher proposals a reliability assessment method of mine ventilation system based on Probabilistic neural network(PNN).By referring the reliability research status and evaluation index of mine ventilation system,researcher takes various factors which influence the ventilation system into account and determine12 major factors as reliability evaluation indexes to evaluate the ventilation system.Finally,establishing a reliability evaluation model of ventilation system based on PNN theory.The 12 major factors are as follows:complexity of ventilation networks,reasonability of mine air pressure,stability of mine main fan,overall efficiency of mine main fan,acceptability of mine ventilation equipment,required ratio of mine air quality,acceptability of blast capacity in place using mind,acceptability of air quality in place using wind,acceptability of temperature in place using wind,acceptability of disaster prevention facility,flexibility of mine reverse ventilation system and tons of coal electricity.According to practice and previous studies and the related experts‘opinion,the reliability status of ventilation system can be divided to three layers.That is layer one with safety,layer two with moderate security,layer three with insecurity.The structure ventilation system reliability evaluation method based on PNN can be divided to four layers,and the numbers of input and output nodes of nerve cell is twelve and three respectively.By applying trained data set to train PNN and then using tested data set to verify trained PNN.The results show that identification method based on PNN has strong generalization ability.The practice indicates the trained PNN can be used to evaluate other sample,and the results by using this method have a consistency to engineer practice.The fast calculating method on natural air distribution and requisite air distribution in mine ventilation network is conducted based on computer programming skills(C++and Qt)and graphical theory,which helps to develop the graphical calculating software for mine ventilation network.The dissertation combines the ventilating resistance data of in Shanxi X mine and the reliability evaluation methods of ventilation system based on PNN theory,and with the help of 3-D simulation software of Ventsim,a simulating and optimizing analysis of transforming the ventilation system from forcing to exhausting of Shanxi X mine is performed.There are one(Nanyang road)downcast shaft and five return air shafts(dumping vertical shaft?Xinzhuang return air shaft?Nanyang road materials inclined shaft?vice vertical shaft and main inclined shaft)before the ventilation method is changed,the simulated results are basically consistent to the measured results.After changing the mine ventilation method,there are five downcast shafts(vice vertical shaft?main inclined shaft?Nanyang road materials inclined shaft?dumping vertical shaft and Nanyang road vice vertical shaft)and a return air shaft(Nanyang road return air shaft).By simulating,the researcher finds that the supply of air is too much in vice vertical shaft,which has a large discrepancy to the initial imagination that is with 4000 m~3/min,while the supply air of vice vertical shaft located in Nanyang road is 3462 m~3/min and it is less than the imagination,which needs to be adjusted,the vice vertical shaft also located in Nanyang road is easy to court-circuited,which needs add some ventilation facilities to adjust the air flow to reach the demand in place using wind.With the combination of several problems of the overall production arrangement,wind demand after transform ventilation system and the calculated results of ventilation network,researchers design several air control measurements on reducting and increasing the resistance.By using Ventsim to perform simulation,a set of optimal ventilation system optimization scheme is obtained.The mine ventilation system is optimized based on above scheme,and the final engineering practice shows that the results of the calculation is similar with reorganized ventilation system on operating conditions in Shanxi X mine.In general,the main innovations of this dissertation in theory and application research are as follows:1)Conducting systematic simulation analysis in set quantity of guide plate and structure form of diffuser elbow of axial fan of vertical diffuser,the research identified the effect of dynamic pressure recovery and diffusion effect of different number of short arc,long arc(90°)guide plate setting to vertical diffuse.2)The dissertation puts forward the similar simulation experiment on arranging short arc,long arc(90°),elliptic arc guide plate in diffuser elbow of axial flow fan,which confirmed arrangement of quantity and structure of guide plate to make better diffusion effect,and successfully applied in system optimization of vertical diffuser‘s device in Shanxi X mine.3)The method of calculating working face resistance is proposed based on hectometer wind resistance,which is applied to the actual measurement in Shanxi X mine that makes the data more reliable.The dissertation also puts forward a method for evaluating ventilation system reliability based on PNN theory.With the help of 3-D simulation software of Ventsim,the problem of ventilation system in the early and late stage after changing was analyzed,and a variety of control measures and schemes of reducing resistance and increasing resistance were designed.Finally,a reasonable optimization scheme of mine ventilation system is formed,which provides data support for main fan warm-up in winter and fan model selection. |
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