Study on the Characteristics of Flow Field and Gas Migration in Gas Tunnels

Abstract

In order to improve the ventilation efficiency and gas dilution effect in the gas tunnel, the main source and formation mechanism of the gas in the tunnel were analyzed, and the hydrodynamic calculation model is established for the gas tunnel ventilation with the auxiliary vertical shaft. The k-ε two-equation turbulence model was used to simulate the ventilation effect under different wind velocity, the flow field distribution characteristics and gas migration regularity under the auxiliary ventilation conditions were obtained. The results indicate that the internal space of the tunnel can be divided into different zones in the longitudinal direction according to the distribution characteristics of the flow field in the tunnel. The distribution of gas concentration in the tunnel is closely related to the flow field characteristics of each zone. The ventilation of the gas tunnel must meet both the requirements of the gas concentration dilution and the cross section wind velocity. When the cross section wind velocity is greater than 0.5m/s, the airflow reaches full turbulence state in tunnel. There is obvious effect on eliminating accumulation of gas at the top of the tunnel by the cross section wind velocity controlling. Under the condition of cross-section wind velocity is 0.5∼1.0m/s, the methane zone is prone to accumulate at the top of the tunnel, which can be diluted when the cross-section wind velocity is greater than 1.0m/s.