The Structural Ddesign And Experimental Studies Of Inner Cuttings Removal PDC Bit

The design and research of Inner cuttings removal PDC bit is a new task,it’s a key link to realize the badger drilling.Based on the work demands of Inner cuttings removal PDC bit,the CAD aided design technology is used for innovative design of bit structure,finally the four types of PDC bit are designed,including the Inner spiral blade PDC bit,the outer spiral blade PDC bit,the crop PDC bit and positive and the positive and negative spiral blade PDC bit.Meanwhile the working principle of each Inner cuttings removal PDC bit is analyzed.By analyzing the cuttings migration theory of the PDC bit with spiral blade,the force analysis expressions are gained of the cuttings particles on the spiral blade surface and the inner cone.To ensure the cuttings which went into the inner bit be conveyed upward by screw in time,the mathematical expression between bit drilling rate and the spiral throughput are established,this work provides theoretical reference and will contribute to the optimization design of parameters in the future.Using EDEM discrete element analysis software,the four types of PDC bit are analyzed in the simulation,the effectiveness of the bit structure design is verified,the velocity vector diagram of cuttings and the average speed on z under different spiral angles and such as visual result are obtained,these provides a lot of help for design work.Through the indoor 8¹/₂"full size rock breaking experiments of four types of Inner cuttings removal PDC bit,the correctness of the bit structural design is verified,the irrelevant structures are discharged,the structures and parameters which have important influence on inner cuttings removal are obtained;According to the experimental results,the necessity of initiative balling prevention device is verified,and it points out the direction for the back of the design work.