Research On The Jet Characteristics And Gas Outburst Prevention Mechanism Of Hydraulic Releasing Hole For Coal-gas Outbursts Control In Coal Bed

High-pressure water jet cutting technology is a new cold-cutting process and developed in the past 30 years, compared to the other thermal cutting process, such as the laser beam, electron beam and plasma, etc. It has good cutting, grinding, erosion, grinding function, and no cutting heat, to get rid of thermal metamorphism, the possibility of thermal deformation, While water-jet cutting is more economical and effective than other conventional cutting method. As the water-jet cutting is carried out at normaltemperature, when cutting without sparks, dust-free, tasteless, non-gas production, processing safety, little vibration, low noise, therefore it is particularly suitable for water-proof, explosion-proof, anti-reaction, anti-gas and other dangerous situations.Because China's coal geology conditions are complicated, existed condition complicated, gas outburst is extremely serious, and the number of occurrence is more, the number of gas emission is also great, the event of a gas explosion will cause a great loss of human and financial resources. Coal Seam Gas pre-pumping rate increase is a strong measure to combat the powerful coal and gas outburst in one of the measures, the pre-drainage can reduce the counter of gas and gas pressure in the dust, so that the coal seam permeability increase and coal stress reduce,thereby eliminating the outstanding risks of coal and gas. Hydraulic releasing hole measure is making before exposing coal or mining work, using high-pressure water jet, highlighting the risk of coal seam, out of a number of large diameter holes, the process of releasing hole discharges a large number of gas and a number of coal, so a certain degree of pressure relief and emission gas area forms in coal, can prevent the occurrence of gas outburst in this region.In the course of the topic study, designed a novel structure for hydraulic releasing hole nozzles firstly, then, using theoretical analyses,numerical simulation and experimental researches to optimize its structure parameters. By analyzing the relationship between the structure and the characteristic parameters of the nozzle, established the corresponding theoretical model, and made use FLUENT software on the internal and external flow field simulation of nozzle, study on the structural parameters influence to punching nozzle performance, provided a theoretical basis for the optimized parameters. Based on the numerical simulation, carried hydraulic releasing hole nozzle testing, and verified the simulation results. The results show that the flushing effect of the optimized hydraulic releasing hole nozzles is good.