Performance of large-diameter pneumatic down-the-hole (DTH) hammers: A focus on influences of the hammer structure  

作　　者：Pin-Lu Cao Hong-Yu Cao Jin-E Cao Cheng-Da Wen Bao-Yi Chen Shan-Shan Yao 

机构地区：[1]College of Construction Engineering,Jilin University,No.938 Ximinzhu Str,Changchun,Jilin,130061,China

出　　处：《Petroleum Science》2023年第4期2399-2412,共14页石油科学(英文版)

基　　金：This work was supported by the Natural Science Foundation of Jilin Province(YDZj202101ZYTS143);National Key Research and Development Project of China(project No.2018YFC1505303).

摘　　要：Pneumatic down-the-hole (DTH) hammer has been extensively used in air drillings through hard and ultra-hard geological formations. Numerical modeling can offer close observation on the working behaviors by visualizing internal pressure status as well as provide reliable performance predictions for large-diameter DTH hammers to which conventional empirical and experimental approaches cannot be applied. In this study, CFD simulations coupled with dynamic meshing are utilized to simulate the air flow and piston movement inside the large-diameter DTH hammers. The numerical modeling scheme is verified against a theoretical model published in literature. Effects of structural parameters on hammer performance, including piston mass, piston upper-end diameter, piston groove diameter, and lengths of intake and exhaust stroke in both front and rear chambers, are analyzed in detail by virtue of sets of numerical simulations. The simulations suggest that changing the intake stroke of front chamber has a negligible influence on hammer performance while increasing the piston groove would lower all the four indicators of hammer performance, including impact energy, impact frequency, maximum stroke, and air consumption rate. Changing the other structural parameters demonstrates mixed effects on the performance indicators. Based on the numerical simulations, a large GQ-400 DTH hammer has been designed for reduced air consumption rate and tested in a field drilling practice. The air drilling test with the designed hammer provided a penetration rate 1.7 times faster than that of conventional mud drilling.

关 键 词：Pneumatic down-the-hole(DTH)hammer Computational fluid dynamics Dynamic mesh Gas turbulent flow Piston impact performance 

分 类 号：TE357.1[石油与天然气工程—油气田开发工程]