自驱修孔钻头动力参数及钻齿结构研究

Exploring dynamic parameters and tooth structure of self-propelled borehole repairing drill bits

自驱修孔钻头是修复失效长钻孔的有效技术手段,为进一步提高修孔速度和瓦斯抽采效果,本文基于射流反冲理论,分析了射流反冲力与喷嘴参数的关系,构建了自驱修孔钻头旋转力学理论模型。采用LS-DYNA开展不同结构钻齿破煤过程,分析了不同钻进压力和扭矩作用下钻齿对煤体破坏形式和钻齿破煤体积变化规律,并开展了破煤实验验证数值模拟结果。形成了自驱修孔钻头参数确定方法,设计了自驱修孔钻头,并在郑煤集团超化煤矿22煤柱面底抽巷进行了工程实验。研究结果表明:(1)喷嘴张角α和偏心角β是决定钻进压力和扭矩分配的关键参数,通过调控张角和偏心角可实现钻进压力和扭矩的最优匹配。(2)相同钻进参数条件下,钻齿结构对破煤体积影响较大,阶梯钻齿破煤效果最优。在钻进压力为120N、扭矩0.6N·m时,阶梯型钻齿结构的修孔钻头能够实现钻进压力和扭矩最优匹配。(3)确定了最优修孔钻头结构参数为:钻头外径28 mm;后置喷嘴张角20°,偏心角90°;前置喷嘴张角90°,偏心角0°。(4)工程应用结果表明:瓦斯抽采纯量提高了1.96倍,瓦斯抽采体积分数提高了3.98倍,修孔速度提高了1.2倍。通过改进钻头动力参数及优化钻齿结构,设计的自驱修孔钻头在工程实践中达到了提高修孔速度和瓦斯抽采效果的目的。

Self-propelled borehole repairing drill bits provide an effective technique for repairing long boreholes that have failed.In order to further improve the borehole repair speed and gas drainage efficiency,based on the theory of jet recoil,the relationship between the jet recoil force and nozzle parameters was analyzed,and a theoretical model was established for rotational mechanics of self-propelled borehole repairing drill bits.Subsequently,the coal-breaking processes of drill bits with different tooth structures were simulated using LS-DYNA,the failure modes in coal mass broken by cutting teeth and the rules of variation in the volume of coal broken by cutting teeth(coal-breaking volume)were analyzed under different drilling force and torque conditions,and coal-breaking experiments were conducted to verify the numerical simulation results.In addition,a method for determining the parameters of self-propelled borehole repairing drill bits was established,and a self-propelled borehole repairing drill bit was designed and used in the methane drainage roadway at the working face of No.22 Coal Pillar in Chaohua Coal Mine(Zhengzhou Coal Industry(Group)Co.,Ltd.)for experimental purposes.The results show that(1)the nozzle opening angle(α)and eccentric angle(β)are key parameters that determine the distribution of drilling force and torque,and the optimal distribution of drilling force and torque can therefore be achieved by adjusting these two parameters.(2)Under the same drilling conditions/parameters,tooth structure has a great impact on the coal-breaking volume,stepped teeth have the best coal-breaking performance,and when the drilling force is 120 N and the torque is 0.6 N·m,a drill bit with stepped teeth can achieve the optimal distribution of drilling force and torque.(3)The optimal parameters determined for borehole repair drill bits are as follows:drill bit OD(outer diameter):28 mm;opening angle of rear nozzles:20°;eccentric angle of rear nozzles:90°;opening angle of front nozzles:90°;eccentric angle of front nozzles:0°.(4)The results of engineering applications show that the scalar drainage rate,gas concentration and borehole repair speed have been increased by 1.96 times,3.98 times and 1.2 times,respectively.By improving the dynamic parameters of the drill bit and optimizing the structure of the drill teeth,The self-propelled borehole repair drill bit designed with optimized dynamic parameters and tooth structure has improved the borehole repair speed and gas extraction efficiency in engineering practice.