Study On Air Leakage And Pressure Balance For Air Control Of High Gas Isolated Fully Mechanized Caving Face Goaf

Flow distribution of isolated fully mechanized caving face goaf which is under the ventilation of“U+II”is different from the goaf which is under the other ventilation forms.It will be important to study on the technology of ventilation,gas drainage and air leakage control for the isolated fully mechanized caving face safety production.According to the characteristics of momentum equation in numerical simulation and the law of ventilation resistance in working face,a new method was adopted.With this method,momentum source term was used to adjust the resistance of the working face,so that the ventilation resistance of working face could coincides with actual level without changing the physical model of the working face.Steady and transient numerical simulation were used to analyze the diffusion law of SF₆ tracer gas in roadway.Result displayed that the shortest fully-mixed distance and stabilizing time of SF₆,under the actual condition.At the same time,these results were used to be reference of releasing the SF₆,in the 8410 air entry roadway.Analysis results show that the low-level gas drainage roadway could take away partial air volume of caving face,also,it would reduce the air volume of goaf leakage from the upper corner into the caving face.Based on the results of the above study,adjusting ventilation resistance of caving face closed to the measured level during the numerical simulation of 8410 isolated fully mechanized caving face and its goaf.The distribution of air volume along the face is in good agreement with the measured results.With this model,variation law of flow field distribution in goaf with air intake was analysed by numerical simulation.The results showed that local high concentration of gas distribution area appeared in coal pillar in the rear of goaf with the increase of air intake.Also orthogonal numerical simulation test scheme with 4 factors and 5 levels was designed to analyze the influencing factors of ventilation and gas drainage in 8410 isolated caving face.The 4 factors included air intake of caving face,horizontal distance between low-level gas drainage roadway and return air roadway,specific value of extraction quantity of low-level gas drainage roadway and air intake of caving face,specific value of extraction quantity of high-level gas drainage roadway and air intake of caving face.Then 8indicators were set up to evaluate the results of 25 CFD numerical simulations.In the end,optimal fuzzy partition matrix elements were plugged in the orthogonal test table to select the best scheme of ventilation and gas drainage in 8410 isolated caving face,and this scheme was simulated to checkout its superiority.Using the data of mine ventilation resistance,network calculating which is based on the change of air density was adopting.Then the second network calculating was adopting with the result of fuzzy optimal selection.Reasonable measures of pressure balance were put forward by several network calculating,and its effects was checked out by the network calculating.Also the method of dynamic simulation was used to analyze the variation situation of pressure balance when the caving face was moving forward.