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권기범(K. B Kwon),송창헌(C. H. Song),이재욱(J. W. Lee),박진영(J. Y. Park),오주영(J. Y. Oh),조정우(J. W. Cho) 유공압건설기계학회 2013 유공압건설기계학회 학술대회논문집 Vol.2013 No.6
A drill bit, which directly impact into the rock, is operated by percussive force and torque. In order to increase the drilling efficiency, the buttons on drill bit head should be designed under the optimum arrangements. Thus, the drilling efficiency should be investigated. In this study, percussion tests were carried out to assess the fragmentation performance of a drill bit. To investigate the drilling efficiency with testing conditions (i.e., blow speed and spacing), single and multiple piston-drop tests were performed on the granitic rock in Korea. After the tests, the drilled volumes of rock were measured by laser scanner. The drilling efficiency was eventually evaluated by calculating the percussive energy and the drilled volume.
권기범(K. B. Kwon),윤용현(Y. H. Yoon),홍승규(S. K. Hong) 한국전산유체공학회 2004 한국전산유체공학회 학술대회논문집 Vol.2004 No.-
In this study the numerical analysis on staging flow with forward ejector is conducted. The forward ejector plays a vital role in staging, which jets out from aftbody. This staging environment needs careful flow analysis for securing staging safety. Present study investigates the steady inviscid staging flow phenomena with variation of separation distance. The performance index is forebody base pressure coefficients. The three dominant flow phenomena are observed according to separation distance which could be told as impinging stage, cavity vortex dominancy stage, and pure base flow characteristics stage. Impinging stage shows high thrust for forebody as one might think. However, important point is that cavity vortex dominancy stage can be more favorable for separation than impinging stage as one simply think in certain separation distance.