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

Figure 1

Drilling system using DTH hammer with air reverse circulation. 1: air compressor; 2: air inlet hose; 3: casing; 4: DTH hammer; 5: drill bit with reverse air circulation; 6: casing shoe; 7: central passage of dual-wall drill pipes; 8: annular space of dual-wall drill pipes; 9: cyclone separator; 10: discharge hose; 11: swivel with double channels.