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선구원(Guwon Seon),황원태(Wontae Hwang) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Cooling jets exiting a multi-hole annular pattern around an optical window of a gas turbine IR measurement device mix with the oncoming main hot flow and form a complicated vortex structure. This flow affects heat transfer on the optical window. This problem was analyzed both experimentally and numerically. The window temperature was measured using an IR camera, and was used to verify the Reynolds-averaged Navier Stokes (RANS) simulation results. The cooling performance from the numerical analysis was consistent with the experimental results at the upstream section of the optical window, but underestimated the mixing at the far downstream section. The flow formed two pairs of counter-rotating vortex pairs (CVP), and the CVP generated by the main flow penetrating between the upstream holes was the main factor in the increase of optical window temperature.
선구원(Guwon Seon),안준(Joon Ahn) 대한설비공학회 2016 대한설비공학회 학술발표대회논문집 Vol.2016 No.6
A numerical analysis was performed to design the shape of the cyclone type oil separator in the refrigeration system, which can increase the separation efficiency and decrease the pressure drop at the same time. The total length of the oil separator, the length of outlet port, the number of the inserted pitch rotation in the oil separator were decided by the result of previous research. This study focus on the analyzing the oil separator"s separation efficiency and pressure drop depending on the change of the inlet port. The result of the numerical analysis show that separation efficiency was distributed from 95% to 100% and pressure drop was distributed from 2.33 kPa to 19.8 kPa according to the location of the inlet port. As a result, in the case of the figure whose inlet port is on the edge, we can get most excellent performance; Separation efficiency is 100% and pressure drop is 2.33 kPa.
입수하는 구에서 발생하는 cavity 에 대한 레이저 유도 캐비테이션 기포를 이용한 제어 메커니즘
최규성(Kyuseong Choi),김나영(Nayoung Kim),선구원(Guwon Seon),황원태(Wontae Hwang),박형민(Hyungmin Park) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
We investigate the effect of continuous-wave laser irradiation on the cavity evolution behind a falling (rough) sphere in water entry (in shallow and deep seals). By tuning the irradiation time, the surface temperature (T<SUB>s</SUB>) of the sphere is varied as 105-355℃. We change the radius and impact velocity of the sphere. In the shallow-seal case, the cavity expands up to 5 times as Ts increases, in which nucleate boiling occurs on the sphere surface and bubbles merge into the cavity. If T<SUB>s</SUB> increases above a critical Ts, however, the cavity is reduced by up to 60%, in which the cavity is destroyed into microbubbles as it contacts water, owing to a highly subcooled water condition. The same phenomena happen for the deep-seal case, but the details of cavity expansion and destruction is different. Finally, we investigate the effects of modified cavity on the hydrodynamic forces on the sphere.