Key parameters and experimental study of hydraulic driven flexible tool for borehole reaming and increase permeability
To solve the problems of hole collapse and poor engagement of cutter arm in hydraulic punc-hing and mechanical cutter arm reaming and permeability enhancement,hydraulic driven flexible tool expansion and permeability enhancement technology are proposed.Theoretical analysis of torque and speed variation of hydrodynamic motor under different pressure conditions,the calculation model of rota-tional inertia of flexible tool and kinetic energy is established and the key factors affecting the coal brea-king of flexible tool are determined.Based on the self-developed hydraulic driven flexible tool coal brea-king system,the coal samples from Zhaogu No.2 Mine are selected to carry out the torque and speed measurement experiments and experiment of influence of different factors on coal breaking efficiency,and determine the friction loss coefficient k and b respectively 0.67 and 0.447.The influence law of jet pressure,breaking time and contact length on the effect of breaking mass,average breaking depth and kinetic energy of flexible tool are studied,revealing the key factors for improving coal breaking efficien-cy.The results have shown that:The coal breaking of flexible tools can be divided into two stages:im-pact damage and grinding damage.The impact damage determines the volume of breaking pit,and the grinding damage can prepare for the expansion of breaking pit volume.The jet pressure has a significant effect on the coal breaking efficiency,25 MPa has 11 times higher breaking mass,4 times higher average breaking depth and 3 times higher kinetic energy of flexible tool than 10 MPa.Due to the limitation of actual conditions,it is more effective to prolong the breaking time properly to improve the efficiency of coal breaking.The influence of contact length on breaking mass and average breaking depth increases in-itially,then decreases and tends to be stable.The hydraulic driven flexible tool coal breaking technology is improved on the basis of hydraulic punching,which provides a new method and insight for reaming and permeability enhancement of low permeability coal seams.
reaming and permeability enhancementhydraulic drivehydrodynamic motorflexible toolcoal breaking