| The accumulation and overrun of mine gas has always been an important factor that threatens the safety of coal mine production.In the normal production process of the coal mine,the regular pouring process of the mine ventilation system will directly cause the whole mine ventilation system and the underground flow field intermittent ventilation.The frequent occurrence of this unstable factor will directly affect the distribution of gas concentration in the underground flow field and increase the probability of gas accumulation in the mine.This paper is based on the actual production of intermittent ventilation in mines,and studied the influence of ventilation velocity on the gas penetration in the near-wall surface of the downhole working face under different flow velocities in the process of start-stop ventilation,and the external coal face and coal mining face after gas penetration.And the effect of gas concentration distribution on the flow field in the goa.At the same time,the practical application of continuous ventilation technology was realized in Jinhui Wan Feng coal mine in Shanxi,based on the research on the “Preventing the Local Coal Mines from Transient Exceeding of Mine Limits and Uninterrupted Ventilation of Mines”of Shanxi Jinhui coal mine.The main contents and results of this paper are as follows:(1)This article summarizes all the causes of intermittent ventilating in mines.Taking the ventilation of mines caused by the main ventilator in the mine as the research background,this paper makes a detailed analysis of the fluid dynamics characteristics of downhole roadways under intermittent ventilation conditions.A conceptual physical model of gas-air mixing flow in the coal wall structure near the coal face was constructed.For the intermittent ventilation,the flow characteristics of the dynamically changing mine ventilation airflow on the coal wall near the wall face of the coal face were scientifically described.(2)On the basis of microstructural analysis of coal bearing coal rock,the basic parameters and pore structure of the coal samples of 1#,5#,9# and 10+11# coal seam in Wan Feng coal mine were analyzed in the laboratory.At the same time,in combination with the field measured data,the existence of the coal seam in the Wan Feng coal mines,the motive force of the gas flow and the seepage resistance were comprehensively analyzed..(3)Taking the experimental working face located in the 1# coal seam of Wan Feng coal mine as the background of the engineering research,the numerical calculation model was constructed.Through the measurement of the underground working face and the mathematical analysis,the unsteady air flow conditions were determined,and the method of the intercepting the characteristic analysis line of the inner and outer parts of the coal wall surface was carried out,and the gas permeation in the coal wall under the different ventilation velocity conditions was carried out,too.The gas air mixed flow in the near wall flow field near the coal wall was studied.The results of numerical calculation and analysis on the change of the outer and internal gas concentration of the near wall surface of the coal mining face show that the law of the gas and gas seepage flow is concluded under the condition of intermittent ventilation.(4)The numerical simulation analysis method was used to analyze the gas distribution law in the downhole goaf and corner area.The calculation results show that with the decrease of the ventilation velocity,the eddy current zone formed in the goaf gradually weakened,and gradually fused with the surrounding flow field,the gas concentration gradually tended to the surrounding area gas concentration,and the gas concentration in the eddy region rose slightly,but the high concentration gas area was slightly increased.In the gradual diffusion,the vortex area is gradually integrated into the ventilation flow field,and the gas concentration shows an overall upward trend.(5)According to the numerical calculation results,the two main ventilators in the mine ventilation system of No.1 coal seam of Wanfeng Coal Mine were modified by the method of adding air-to-air dampers,and the mine uninterrupted ventilation technology was reformed for the main ventilator system of the experimental mine.The stability and effectiveness of the system were verified.The application of the system can complete the main ventilation switching process within 50 s.The maximum fluctuation amplitude of ventilation flow is 11.95%.The minimum airflow velocity in the downhole working face is 0.98m/s.There is no stoppage state;the system vibration is normal,which can effectively improve the discontinuous ventilation of the mine,and provide a reliable technical solution for the underground gas accumulation and overrun. |
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