大直径反循环钻头流道结构的设计

Structural design of flow channel of large-diameter reverse circulation drill bit

基于反循环钻头孔底流动模拟实验器,对比研究了两种典型的底喷孔布置方式所对应的反循环形成效果,并通过流场数值模拟揭示了不同底喷孔布置方式对反循环形成效果的影响机理,确定了大直径反循环钻头底喷孔的合理布置方式;基于该实验器研究了内喷孔与底喷孔流道截面积分配比例,得到了流道截面积不同分配比例对反循环形成效果的影响规律;此外,提出了一种中心孔底面入口新的结构设计形式。结果表明,流道设计研究对改善和提高大直径反循环钻头的性能具有重要意义。

The flow channel of large-diameter reverse circulation drill bit is relatively complex,and its structure design is closely related to the performance of reverse circulation flow.The research on the structure design of flow channel of large-diameter reverse circulation drill bit was done in this paper.Firstly,the relationship between two typical kinds of arrangement mode of bottom jet nozzles and the forming effects of reverse circulation was studied with the experimental apparatus for hole-bottom flow field simulation of special reverse circulation drill bit.In order to reveal the mechanism that arrangement mode of bottom jet nozzles affects the forming effect of reverse circulation,numerical simulation of down-hole flow field was done,then,the reasonable arrangement mode of bottom jet nozzles of large-diameter reverse circulation drill bit was determined.Secondly,using the experimental apparatus for hole-bottom flow field simulation,the distribution ratio of overflow area of inner jet nozzles and bottom jet nozzles was studied,the influence law of the distribution ratio of overflow area on the forming effect of reverse circulation was obtained.In addition,the structure design of bottom entrance of center hole was studied too,and a new type of structure design was proposed.The research on the structure design of flow channel is meaningful for improving the performance of large-diameter reverse circulation drill bit.