Nozzle Characteristic Research Of The High Pressure Hydraulic Cutting Gap Machine For Coal Rock

As a new type of cutting, the high pressure water jet cutting technology is an important application branch of high pressure water jet, which is characterized by strong cutting ability, good controllability and small pollution. Therefore, it has been widely used in the engineering field gradually. Based on the above characteristics and the selection principles of mine equipment, which are low risk and high explosion-proof property, by cutting coal rock to form artificial fissures, the high-pressure water jet cutting technology is widely used in the release of coal gas, to ensure the safety of coal mining. In order to improve the high-pressure water jet cutting technology and the coal seam gas drainage rate, the paper focuses on the core component of the high pressure hydraulic cutting gap machine——nozzle.In the process of high pressure water jet cutting the coal seam, the nozzle is not only the occurrence component of the high-pressure water system, but also the implementation component of cutting the coal seam. Therefore, the nozzle cutting performance will directly affect the energy distribution of high pressure water jet and the quality of cutting seam. On the basis of the high pressure water jet technology, the subject takes the cone straight nozzle as the center to discuss.The geometric parameters of the nozzle and jet pressure affect the flow field of high pressure water jet. At present, the analysis of theoretical knowledge of the high pressure water jet is not mature enough and experimental methods will cost long cycle. So this paper has taken a computer simulation technology to analyze and explore the internal and external flow field of high pressure water jet cutting nozzle.This paper designs separately three scenarios, including different nozzle contraction angle, nozzle outlet diameter and length diameter ratio of nozzle. What’s more, it analyses the influence of the above geometric parameters on the internal and external flow field of high-pressure water jet cutting nozzle. According to the analysis and research on the simulation results:the nozzle exit velocity decreases gradually in the process of the contraction angle gradually increasing, but the jet core segment is gradually increasing in the process of contraction angle from0°to12°. When the contraction angle increases to12°the jet core segment remains basically unchanged. In order to maintain a longer segment of the jet core and a higher velocity of the nozzle exit, the nozzle contraction angle is determined to be about12°. The smaller the diameter of the nozzle outlet is, the greater the exit velocity is. Combined with the maximum working pressure provided by the system, the nozzle outlet diameter is identified as1.5mm. According to simulation analysis of the different length diameter ratio of nozzle, we obtain that the outlet velocity of nozzle decreases gradually with the increase of the ratio of length to diameter ration. In order to maintain that outlet velocity of nozzle is becoming much bigger and jet core section is becoming longer, the nozzle length diameter ratio is identified as3. In addition, according to the simulation data obtained and the principle of numerical analysis, the function equation is coupled between the nozzle outlet velocity and nozzle geometric parameters and jet pressure.Finally, based on the theory of high pressure water jet, the paper analyzes the high pressure water jet cutting performance from three aspects, which are structure design of nozzle, geometry parameters of nozzle and jet parameters, and it obtains the related research results. It provides important theoretical basis and valuable engineering application for the performance analysis, reasonable design, and structural optimization of this cutting nozzle type.