Numerical Simulation Of Gas Accumulation Condition In Diagonal Tunnel Between Parallel Return Roadway

Along with the expiation of ida area and increase quantity of gas emission, more than tow inlet and return tunnels are used in coalmining. A plurality of return air roadways connection through connection form "grid". The lane between inlet, air return roadway and contact Lane belongs to the diagonal roadway, the direction and quantity of diagonal roadway is instability, which has an influence on the reliability of a mine ventilation system, causing the accumulation of gas, coal natural accident. Therefore research on airflow characteristics and gas accumulation conditions for diagonal tunnels has important effect to prevent coal mine accidents.There are few researches on the romantic movements and gas concentration distribution characteristics within low speed of the diagonal branch at present. A simplified model of airflow in contact lane between parallel connection tunnels (basic symmetric diagonal) is built based on Yamei Daning real produce. Combined with the fluid mechanics, the law of conservation mass and energy conservation, along with other mathematical equations, the mathematical equations of wind flow movement in contact lane are established, studying the following aspects:(1) The relationship between wind velocity in contact lane and air return roadway. The wind of contacting lane can’t be obtained directly. The Fluent software is powerful, we can directly change the wind speed of three return air roadways to obtain the wind speed of connection road. When the wind speed of two adjacent air return roadway of the absolute value of the difference are respectively0.3m/s,0.4m/s,0.5m/s,1.0m/s,1.5m/s,2.0m/s,3.0m/s,4.0m/s, we design8sets of data to compare, concluding that the wind speed of the contacting lane is only related to the two returning road absolute value. To make the connection speed lane was higher than that of0.25m/s, the wind speed at both ends of the return air roadway in the absolute value of the difference is greater than0.5m/s.(2) The contact characteristics of airflow in contact lane. Through the wind changed return air roadway It is acquired air velocity of contact lane such as0.25m/s,0.5m/s,0.7m/s,1.15m/s,3.0m/s,1.5m/s,1.8m/s,2.05m/s,3.7m/s,4.5m/s,through change the wind speed of return air road. Using graphic processing function of FLUENT software to get the wind conditions contact Lane distribution of wind speed every5meters of roadway center in horizontal section, concluding the characteristics of the wind speed of contacting lane is that romantic from the return air roadway into contact Lane first experience the recirculation zone, then the water level section from the connection side to the other side wind velocity increases linearly, the air outlet of linear increase more slowly. From the Lane entrance airflow after10meters wind tunnel at the center the change is very small, which can be used to represent the average wind speed.(3) The connection between return air roadway and contact Lane in model basically is vertical, airflow from air return roadway into contact lane when suddenly change direction. It simulated reflux regional variation characteristics when the average wind speed is0.25m/s,0.5m/s,0.7m/s,1.15m/s,3.0m/s,1.5m/s,1.8m/s,2.05m/s,3.7m/s,4.5m/s.It finds that the bigger the average wind speed in contacting lane is, the smaller the return region exists, the higher the wind speed of return road is, the higher the return air inlet crosswind velocity is.(4) Simulate of gas accumulation conditions. With the gas emission conditions, the following data is obtained by changing the wind speed of return air road (1)0.18m/s,0.3m/s,0.38m/s,0.5m/s;(2)0.09m/s,0.18m/s,0.24m/s,0.33m/s;(3)0.16m/s,0.28m/s,0.36m/s,0.46m/s. The concentration of methane cloud and methane concentration curve every5meters is obtained by fluent, from which the rules are follows:when the wind speed is less than0.3m/s, the methane concentration on the vertical section is in layered distribution obviously, high concentration of gas to accumulate in the tunnel top0.5meters away from the roof. When the wind speed is0.3-0.5m/s, within a range of about15meters of air outlet,vertical section on the roof of methane concentration is in layered distribution, high gas concentrated on the top. When the wind speed is larger than0.5m/s of methane concentration distribution in vertical stratification phenomena on the section does not exist.