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

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.