| At present,the cross-section size,excavation speed and roadway length of coal mines arc continuously increasing,which caused the unreasonable air distribution and the severe hidden danger of gas accumulation.However,the"extensive" control of total ventilation cannot be used to change the air state of air duct outlet in fully mechanized heading face,resulting in unable to meet the vcniilation requirements.In view of the ventilation problems in fully mechanized heading face,this paper combines the fluid techanics theory,finite element numerical simulation and test verification methods to analyze the the distribution laws of airfield and gas field under changing the distance from outlet to heading face,the caliber and the angle of outlet.Then the associated data of air outlet parameter changing relates velocity and gas concentration were obtained.The velocity and gas conccntration forecasting models were established by using linear regression methods.Besides,the effect of the velocity control and gas exhausted.The specific research contents are as follows:(1)llieorctical Analysis of Hydrodynamics in airfield and gas-field.The actual distribution of airflow and gas in the fully mechanized heading face and the formation and airflow distribution characteristics in cach area were analyzed.Cornbining the mass conservation.conservation of momentum,and conservation of energy.aiming to analyse the airflow and gas characteristics.Ensuring the turbulence calculation model of the airflow and gas distribution in the attached jet.The component transfer models was used to analysis thegas distribution.(2)Study on the law of the airtlow distribution under the duct outlet parameter changing.A numerical simulation scheme for the airflow field was cstablished.The FLUENT was used to established the finite element model and calculated the numerical simulation.Comparing with the actual measured data of air velocity at the underground,the accuracy of the scheme was verified.Based on the analyzed of original airflow field distribution and existing problems,the airflow simulation schemes under the outlet parameters changing were designed.The influence laws of air velocity and eddy current distribution were analyzed under the air outlet parameter changing.Besides,associated data between outlet parameter changing and velocity were obtained.(3)Establishing the gas numerically simulation schemes.The gas field numerical simulation schemes were established after analyzing the existing problems of original gas field.Then the influence laws on gas concentration were obtained under the outlet parameter changing.The data associated of gas concentration were also obtained when the outlet parameter changing.(4)The establishment of forecast models for the effect of air outlet parameter changing on air velocity and the analysis on air adjustment effect.Utilizing the associated data of air outlet parameters and air velocity obtained,a multiple linear regression analysis was used to establish the air velocity predicting model on the key points of the high speed zone of the roadway when the distance from outlet to heading face is 5m.Besides,the air speed predicting model on the key points in the low speed zone when the distance from outlet to heading face is 10m.The actual data of air speed in underground were measured,which is used to verify the accuracy of the air velocity predicting model,and the wind speed regulation effect was analyzed.The airflow distribution is reasonable.(5)Establishment of predictive model and the analyse on the effect of outlet parameter changing on gas concentration.Using the associated data of outlet parameters changing and gas concentration,the forecast model for the gas concentration in the upper corner of the roadway was established by using the multiple linear regression.It is obviously that the gas concentration and gas accumulated in the upper corner were significantly decreased,which provides the theoretical foundation for achieving the optimal gas concentration distribution. |
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