Parameters Optimization for External Nozzle of Reverse Circulation Sampling Drill Bit in Underground Coal Mine

The underground coal mine air reverse circulation sampling technique is important to improve accuracy of determining gas content by direct method. Numerical modeling is used to study and optimize the angle and position of coal mine air reverse circulation sampling drill bit nozzle. The research results show that when the external nozzle angle is 15 ° and the arrangement is appropriately away from the drill teeth, it can make drill bit produce better reverse circulation effect; increasing the sampling depth and improving the quality of sampling can prevent drill bit damage and drill burying accidents.