可切换式反循环潜孔锤钻头设计及优化

Design and optimization of switchable reverse circulation DTH air hammer bits

针对现有气动贯通式潜孔(DTH)锤反循环钻探技术在推广应用过程中遇到的岩矿心(样)丢失、卡钻埋钻事故时有发生等问题,提出一种可切换式反循环潜孔锤钻头的新结构,该结构在正常碎岩钻进和"强吹孔"时,可以通过花键套的辅助配合,从而实现反循环原理上的切换。与此同时,采用正交试验设计的方法,运用计算流体动力学(CFD)分析技术对该钻头中备用内喷孔的6个主要结构参数进行优化设计。研究结果表明:备用内喷孔个数(N)对钻头的反循环效果影响最大,其次依次是备用内喷孔直径(D)、倾角(Θ_s)、备用内喷孔与常开内喷孔间距(L)、水平偏角(Θ_d),而备用内喷孔距孔底高度(H)对钻头的反循环效果影响最小。当N=2,D=5 mm,Θ_s=30°,Θ_d=10°,L=0 mm,H=230 mm时,钻头备用内喷孔结构参数组合最优。

According to the drilling accidents such as cores lost or sticking of drilling tools in the process of popularization and the application of reverse circulation drilling technology with a hollow through Down-the-Hole（DTH） air hammer, a structure of the switchable reverse circulation drill bit was proposed. The structure can achieve the switch of reverse circulation both in normal drilling process and blowing hole operations with the assistance of spline sleeve theoretically. Meanwhile, 6 main structural parameters of the auxiliary suction nozzles in the switchable reverse circulation drill bit were optimized by computational fluid dynamics（CFD） analysis and orthogonal design method. The results show that the number of auxiliary suction nozzle（N） has the maximum influence on the performance of reverse circulation drilling, which is followed by the diameter of auxiliary suction nozzle（D）, the inclination angle（Θ_s）, the deflection angle（Θ_d） and the distance between auxiliary and normal suction nozzle（L）. However, the distance between auxiliary suction nozzle and the bottom face of borehole（L） has the minimum effect on the performance of reverse circulation. In conclusion, the optimal parameter combination of auxiliary suction nozzle in the switchable reverse circulation drill bit is N=2, D=5 mm, Θ_s=30°, Θ_d=10°, L=0 mm and H=230 mm.