Design And Mechanical Analysis Of Large Diameter Reaming Drill Bit For Drilling Coal Guiding Shaft

Chinses energy distribution is "less oil, less gas, rich coal". There are 5.9 trillion tons of coal reserves in our country, and 230 million tons of proven reserves, representing a 94.22% of the total energy resources while oil and gas less than 6%, so it can be said coal is China's most abundant energy resource. As the energy needs increase, era of deep coal resources development is going to come, uscing drilling technology to achieve coal mining is feasible, and petroleum engineering drilling technology has been used widely. We call this mining method as "Drilling Mining Technique", the mining method based on drilling process, it uses the drill bit to break the scam, and coal particles ara carried to the ground by liquid circulating, then using ground equipment to separate coal particles out from the multiphase fluid, and recycling the separated liquid again. This paper systematically presents the basic principles of Drilling Mining Technique, finished well structure design and hydraulic carrying coal pipeline parameter calculation for single-well Drilling Mining Technique, this paper designed a large adjustable reaming drilling mining bit for special requirements of Drilling Mining Technique, after analyzed and summarized the advantages and disadvantages of existing reaming drill bit, based on extensive research literature related to reaming bit home and abroad. The large adjustable reaming drilling mining bit can pass through the small size well with the inside diameter of 215.9mm, then expanding the hole diameter after arriving to coal seam, it can expand the borehole size to 395mm.this paper made a detailed structural design for the large adjustable reaming drilling mining bit, and focus on the motion analysis and mechanical analysis about reaming assembly and lock assembly, and did the research for working principle and movement mechanism of the large adjustable reaming drilling mining bit. The paper do the fluid dynamics analysis for mandrel and the throttle mouth, determined the inner diameter of the mandrel and the throttle mouth, then checked the strength and stiffness of mandrel.Secondly, the paper made a theoretical calculation for cutting teeth's cutting resistance and the axial resistance, obtained the large adjustable reaming drilling mining bit was under the cutting torque of r= 7845N-m, axial resistance of Fz=4.3t, cutting power of P= 123kW, the above parameters are whin the ratings of PDM which cooperated with the large adjustable reaming drilling mining bit. Thirdly, the paper established a finite element model of the reaming assembly in Abaqus software, did the analysis of the mechanical properties of reaming shell, mandrel, reaming blades, support arm and the pin. Then,thc paper did the research for reaming shell and mandrel's mechanical properties and deformation in the assembly environment, next, did the research for reaming shell and mandrel's mechanical properties and deformation in the Independent Environment.In conclusion, mandrel strengthened the reaming assembly's overall strength significantly.Finally, the paper established a finite element model of the lock assembly in Abaqus software, did the analysis of the mechanical properties of the ball, mandrel, central tube and unlocking sleeve. Contact stress is too large because of the point contact between the ball and other parts, so the paper did some improvements for the lock assembly. Changing the point contact to line contact, did the analysis of the mechanical properties of the improved Lock assembly, and ensured the reliability of the structure.