| At present, the horizontal well and branch well technology is considered to be an effective solution to CBM exploitation in our country in the production of single well and poor economic benefits and serious pollution problems of the reservoir. Traditional drilling technology in the implementation of horizontal well broken coal drilling process in the presence of drill clamp, the perforations and irregular high energy consumption, slow speed problem, high-pressure rotating water jet technology due to its high energy transmission convenient and rock breaking efficiency, more and more attention. However, the research on the mechanism of high pressure water jet coal and high pressure rotary water jet technology supporting equipment-rotary jet nozzle is still not deep enough.In view of the above questions, this paper with high pressure water jet breaking coal mechanism and rotary jet nozzle as the object of study, knowledge of the field of comprehensive utilization of petroleum and natural gas engineering, mechanical engineering, engineering fluid mechanics and rock dynamics, materials engineering, the combination of experimental research, theoretical research and numerical simulation of analysis method, mainly completed the following work:(1) The composition of the coal rock structure, physical and mechanical properties of SEM and three axis rock experiment study, obtained:Coal overall is relatively compact, with small cracks and pore distribution. Coal rock has high elastic modulus, low Poisson's ratio, high compressive strength and low tensile strength.(2) Based on the smoothed particle flow (SPH) coupled finite element (FEM), the algorithm of high pressure water jet breaking coal process numerical simulation of simulated coal and rock dynamic fragmentation process,:coal and rock damage larger area concentrated in the crushing pit near, the bottom around coal and rock damage and crack development is the most active, and the formation of a composite crack system composed of radial cracks and layered crack. Jet velocity of coal and rock damage failure region formed by the impact and as well as of the initiation and propagation of cracks greatly, improve the jet velocity can significantly improve the jet rock breaking efficiency, and breaking process of rock has a threshold of jet velocity, the study of coal and rock threshold jet velocity for 150 m/s. The damage range of water containing defects is larger than that of coal and rock.(3) Combined with the advantages of direct flow and swirling jet, designs a new type of rotary jet nozzle suitable for CBM horizontal well drilling rock breaking, and the strength and rigidity check.(4) Based on the method of computational fluid dynamics on rotary jet nozzle jet flow field numerical simulation distribution laws of the jet flow field are obtained, and the different process parameters (jet pressure, jet distance) effect of jet and jet structure were studied:when the nozzle structure, under the condition of different jet pressure of the jet flow field structure is similar. The attenuation law of jet velocity and dimensionless jet distance L/d.(5) Between the orthogonal experiment design and variance analysis method based on rotary jet nozzle structure optimization, the dimensionless length of the angle of rotation jet nozzle different structure parameters (leaf conductance process, shrinkage, straight tube section was established) and job performance relationship and get the blade guide process, cylindrical part dimensional length and shrinkage angle and the optimum range of free:16mm-24mm,0.6-1, 55°?60°. |
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