Study On Crushing Coal Rock And Its Flow Field Characteristics By Straight-swirling Intergrated Jet

China's current domestic coalbed methane resources urgently need to be developed to alleviate domestic resource shortages.Exploitation of coalbed methane by extremely small radius radial drilling technology is one of the main trends for current exploration and development.In the radial drilling technology,the core component is a water jet drill bit,which has a decisive influence on the drilling efficiency and mining effect of the radial drilling technology.Among the many types of jet bits,the straight-rotating mixed jet bit has the advantages of reliable stability and strong drilling ability,so it is suitable for the technical requirements of radial drilling,but it is aimed at the rock breaking mechanism of coal rock and its flow field characteristics.The current research needs further research.In this paper,the methods of theoretical analysis,numerical simulation,and rock-breaking and punching tests are mainly used to carry out jet-crushing coal-rock breaking mechanism,bit structure design,internal structure optimization of drills,and drilling and punching tests on straight-rotating mixed-jet drill bits for coal and rock breaking And other research.The results achieved are:1)In theoretical analysis,research the basic structure of jet flow,basic properties and structural characteristics of coal rock,explore the main stages of impacting coal rock masses,and classify the damage forms of water jet impacting coal rock,so that the general process of broken coal rock is roughly divided into:Formation of initial crushing pit,micro-crack stage;micro-crack propagation stage;formation of macro-crack stage.2)The structure optimization design of the radial drilling technology drill bit was carried out,and the core component,the impeller,was mainly analyzed through simulation.Some parameters of the impeller were optimized through comparative analysis of the results:the number of impeller grooves was 6;the inclination angle of the groove was 45°;the width of the groove was 0.7;the length of the impeller was 5mm;the angle of the cavity contraction section was 60°.And the structural division of the jet is roughly divided in the radial direction into:a direct jet zone,a strong swirling jet zone,a weak swirling jet zone,and a peripheral jet zone;in the axial direction,it is roughly divided into a filtering section and a uniform mixing section.3)Punching tests are performed on three types of jets,the punching characteristics are analyzed,and the advantages of the direct-rotating mixed jets are established,and some simulation results are verified by experiments.According to the test results,the influence between the jet flow field and the rock breaking effect is analyzed:the rock breaking effect of the jet is not only related to the impact velocity of the jet,but also has a greater relationship with the way the jet acts on the rock mass.Rotary jets are more likely to generate cracks on their surfaces,which is conducive to the diffusion of cracks on the surface of coal rocks and internal surfaces under the static action of jets,forming fractured rock bodies on a macro level.The research results of this thesis provide a certain theoretical guidance for water jet radial drilling technology,which enriches the research on flow field characteristics and rock breaking mechanism,etc.,and has certain significance.Figure[59]Table[8]Reference[91]...