| The hollow-through DTH hammer reverse circulation (RC) continuous coringdrilling technology is integrated capturing cores continuously while drilling, highefficiency and reverse circulation. It is drilling efficiency higher than traditionaldrilling methods. Capturing cores continuously while drilling can reduce auxiliaryoperating time of mentioned for cores in traditional drilling methods; Reversecirculation will never damage the wall, is conducive to the application of thetechnology in broken strata. And it will never be restricted by weather, fragmentingstratum, water due to its unique drilling mechanism. Lots of drilling problems in ourcountry have been solved with it and research on this drilling technology is aninternational leader.The RC bit is the most important one of units in the hollow-through DTHhammer reverse circulation, whether a reasonable relationship of structure types andgeometry parameters to the continuous coring reverse circulation drilling normal.However, it is found that the RC Performance is not satisfactory enough when drillingunder heavy air input working condition or in extremely cracked tratumor. There isstill a little bit air with small cuttings escape into the annulus under that circumstanee.As a result, a small scale of dust appears on the ground and this causes a partial lossof samples. RC bit direct impact on whether formation of reverse circulation is goodor bad, its structure type, parameters, the flow field channel in the RC bit design is thekey factor for reverse circulation drilling, depth study of the structure of RC bit moreconducive to improve reverse circulation drilling is extremely necessary. This articledesign and optimize structure of the reverse bits. It can form a rotational flow fieldwith the strength pumping action when the compressed-air run through the bit. Aftersimulating and analyzing the flow field around the new type reverse circulation bitusing the hydrodynamics calculation software, we can get the laws of pressure andflow distribution, etc. To improve and perfect the structure of the reverse circulation sample drilling bit. The drawing of a new Swirl-flow type reverse bit is designed outfinally. More details about research and conclusions as follows:1、The drill bit structure is designed to split up and down, and the threadedconnection, small the drill body strength change to meet the strength requirements ofreverse circulation drill design; the split drill structural design allows the lower part ofthe drill serious wear and tear, only replace the lower part, do not have to replace thewhole bit, drill consumption savings effectively, and reduce drilling costs;2、Finite Element Analysis of the internal flow field of RC bit, optimize thestructure of existing RC bit and make it more effective to reverse circulation drillingto improve the applicability of fragmenting stratum, improve drilling efficiency.Tapered drill bit center channel optimization, better internal structure of gas flowchannel, in the negative pressure a small part of the flow after the rock surfacereflection flow to the drill bit center channels, most of the airflow carrying rocksamples without the hole bottom reflected directly along the center channel reversecirculation, more conducive to the formation of reverse circulation;3、Eccentric cited perforating designed in the central bore of lower RC bit, use ofcyclone formation negative pressure to produce a significant pressure gradient withthe ambient pressure in the hole bottom, more effective suction cuttings at the end ofhole, and its percentage of traffic on the back is1.288; diffuser slot on the top of theeccentric hole, the airflow upward flow pressure quickly restored, the pressureincreases, the gas lift slagging prevent card blocking; the air flows carrying cuttingsthrough the open part center of the spiral grooves on the drill bit channels swirl role tostrengthen the flow speed, reverse circulation form more thorough. |
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