In order to optimize the parameters of pre-mixed abrasive water jet cutting technology, make it more efficient in the coal mine gas environment and solve the problem of hard coal and the difficulty of rock drilling, FLUENT software was used to get the isothermal, incompressible, steady flow field out of a submerged abrasive water jet nozzle through numerical simulation, with different particle sizes and different confining pressures under submerged conditions. The results show that, under submerged conditions, the maximum velocity of the abrasive particle outside the pre-mixed abrasive water jet nozzle is about 6 mm far away from the nozzle; the abrasive particle diameter has little influence on the velocity outside the nozzle. The external confining pressure of the nozzle has an important influence on the velocity, which is that the jet velocity of the same position decreases with the increase of confining pressure and the relationship between the confining pressure of different distance from the nozzle exit and the abrasive velocity is exponential function. The results of the simulation laid the foundation for optimizing the nozzle structure, improving efficiency and developing the abrasive water jet nozzle.

In order to optimize the parameters of the pre-mixed abrasive water jet cutting technology and make it more efficient in the coal mine gas environment, finite element analysis software LS-DYNA is used to simulate single abrasive particle of rock erosion rule and analyze the influence of different particle size, different grinding particle impact velocity, different abrasive particle shape on rock erosion effect. The results show that under the same conditions, the greater the impact velocity, the better the erosion effect, and the erosion rate of abrasive particles is almost linear with the erosion rate of rock. With an increase in velocity of abrasive particles, the erosion rate of cube shape of abrasive particles is gradually higher than that of spherical particles of abrasive. The larger the particle size of abrasive particles, the bigger the kinetic energy of them and also the erosion depth and erosion volume on the rock and steel. But when the particle size increases, the erosion rate of abrasive particles on the rock will decrease gradually. The research results provide theoretical basis for optimizing the parameters of pre-mixed abrasive water jet cutting.