Improvement of drill bit efficiency by bottom-hole temperature reduction in air blast drilling

Removal of drilling chips takes place when the lifting force of the upward air current exceeds the weight of rock particles. The size of particles is of no less importance. When the size of drill chips exceeds the size of the annulus clearance, the chips are incapable to move upward, and their additional crushing is required. On the other hand, if the annulus clearance size is too big, compressed air velocity decreases and the chips become unremovable. Thus, the main drilling parameters are the air flow rate and pressure which greatly govern the technical and economic performance indicators of drilling. When the cleaning agents (compressed air, aerated liquid) have low heat capacity and thermal conductivity, the influence of the temperature factor jumps. For this reason, prediction and rating of the temperature factor is currently in focus of numerous scientific studies. The influence of the temperature regime at bottom-hole during air blast drilling is investigated, and the related research papers are reviewed in brief. The mathematical model of heating of a tricone bit tooth at bottom-hole during compressed air blast drilling is described: the model proves expediency of compressed air cooling down to negative temperatures toward the temperature factor normalization. The experimental test data of a developed two-stage cleaning air cooling facility, which enhances the bottom-hole cleaning efficiency, are described. The recommendations on selection of an efficient temperature regime are given.

Djuraev R. U., Merkulov М. V., Khatamova D. N., Normayev Q. H. Improvement of drill bit efficiency by bottom-hole temperature reduction in air blast drilling. MIAB. Mining Inf. Anal. Bull. 2025;(6):125-138. [In Russ]. DOI: 10.25018/0236_1493_2025_6_0_125.

R.U. Djuraev¹, Dr. Sci. (Eng.), Professor, e-mail: r.u.djuraev@yandex.ru, ORCID ID: 0000-0003-2712-3003,
M.V. Merkulov, Dr. Sci. (Eng.), Professor, Sergo Ordzhonikidze Russian State University for Geological Prospecting (MGRI), 117997, Moscow, Russia, e-mail: mvm.07@mail.ru,
D.N. Khatamova¹, Dr. Sci. (Eng.), Assistant Professor, e-mail: dilyon_hat@bk.ru, ORCID ID: 0009-0002-8336-9884,
Q.H. Normayev¹, PhD, Assistant Professor,
¹ Navoi State University of Mining and Technology, 210100, Navoi, Uzbekistan.

D.N. Khatamova, e-mail: dilyon_hat@bk.ru.

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