Experimental and Numerical Study on Air Flow Behavior for a Novel Retractable Reverse Circulation Drill Bit of Casing-while-Drilling (CwD)

Figure 2

Geometric models of the retractable drill bit. 1: upper drill bit body; 2: lower drill bit; 3: carbide inserts; 4: kidney-shaped groove; 5: pin shaft; 6: snap rings; 7: inner jet nozzles; 8: suction channel; 9: kidney-shaped axis; 10: spiral slots; 11: flushing nozzles; 12: central channel.

(a) Drilling status

(b) Folded status

(c) Drill bit structure