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다수의 공동 배열을 가진 가이드 그릴 형상이 공진기 흡입 유동에 미치는 영향
배현우(Hyunwoo Bae),성재용(Jaeyong Sung),이동훈(Dong Hoon Lee) 한국가시화정보학회 2016 한국가시화정보학회 학술발표대회 논문집 Vol.2016 No.12
In this study, the intake flows through guide grills consisting of multi cavities above a resonator have been investigated by 3-D numerical simulations. The flows are assumed to be compressible, unsteady, and turbulent. To analyze the effect of the cavity array structures on the guide grill, aligned and staggered structures are considered. For each structure, the amount of intake mass flow rate through the cavity is compared. The results show that the net mass flow rate through the cavity has a positive or negative value depending on the position of cavity, which denotes intake and outtake flows through a cavity. These intake and outtake flows are sequentially generated in the array of the cavity. In case of the aligned cavity array, there are also found cavities which have neither intake nor outtake flow.
공기유입구를 가진 벤츄리 형상의 기포발생기에서 토출되는 기포 유동 특성의 가시화 측정 분석
배현우(Hyunwoo Bae),이승민(Seungmin Lee),송문수(Moonsoo Song),성재용(Jaeyong Sung) 한국가시화정보학회 2019 한국가시화정보학회지 Vol.17 No.1
Flow visualizations have been carried out to analyze the characteristics of bubby flows exhausted from a venturi-type bubble generator with an air vent. For various design parameters and operating conditions of the bubble generator, the images of bubbly flows was recorded using a high-speed camera and a microscope. Then the amount and size distribution of bubble was evaluated by an image processing technique. The results show that for increasing the amount of bubble, it is more effective to reduce the venturi throat than to enlarge the air vent diameter. If the water flow rate increases, the bubble generation rate increases but reaches a status of saturation, whose condition depends on Reynolds number at a given air vent diameter. The bubble size increases as the diameter of venturi throat decreases and Reynolds number increases. However, the air vent diameter is not a significant factor on bubble size.
열차 주행 시 터널 벽면에서의 속도장 및 압력분포 해석
배현우(Hyunwoo Bae),성재용(Jaeyong Sung) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.10
열차가 터널 내부에서 주행할 때, 터널 벽면에 높은 속도를 가지는 유동장과 강한 압력파가 발생하게 된다. 이는 진동 및 소음을 발생시키고, 터널 내에서 발생하는 먼지를 플랫폼으로 이동시켜 승객들에게 불편을 유발한다. 본 연구에서는 진동 및 소음문제를 개선하고자 터널에서 열차가 주행 시 벽면에서 생기는 속도장 및 압력분포를 해석하였다. 터널내 유동은 2차원 압축성 난류 모델을 이용하여 수치해석 하였다. 난류모델로는 RNG모델을 사용하였고, 움직이는 열차에는 sliding method와 layering method를 적용하였다. 그 결과 터널내 열차 주행에 의해 열차 속도의 2배 이상의 유체 속도장이 벽면 근처에 형성되었으며, 강한 음압이 나타남을 알 수 있었다. When the train passes through a tunnel, high velocity and strong pressure fields are formed on the tunnel wall. These effects generate vibration, noise and make dust transported to platform. And then, the effects cause inconvenience to passengers. In this study, for improving vibration and noise problem, velocity and pressure fields on the tunnel wall during passing through tunnel are solved using Ansys-Fluent software. Flow in the tunnel is computed by using two-dimensional, compressible, turbulence model. As a turbulence model, RNG k-ε model is applied. To implement the train motion, sliding meshes are used. As a result, there forms strong flow velocity more than twice the train speed accompanying with strong negative pressure by the subway train passing.
공명 흡음판 위 가이드 그릴의 형상이 공진기 흡입 유동에 미치는 영향
배현우(Hyunwoo Bae),성재용(Jaeyoung Sung),이동훈(Dong Hoon Lee) 한국생산제조학회 2016 한국생산제조학회지 Vol.25 No.3
This study investigates cavity flows through a guide grill above a resonator. Vortex distributions and intake flows are simulated for various shapes of the guide grill. The flows are assumed to be compressible, unsteady, and turbulent. Numerical simulations are conducted using a large eddy simulation (LES) model. To analyze the effect of the guide grill shape, three cavity lengths (0.2H, 0.6H, and 1.0H) and cavity angles (30°, 45° and 60°) are considered based on resonator height (H). The results show that the vortex generated in the resonator by cavity flow increases with cavity length. Thus, the intake flow is minimum at the smallest cavity length and angle. However, when cavity length is equal to resonator height, the intake flow decreases. The maximum intake flow occurs at a cavity angle 45° at higher cavity lengths owing to the interaction between the vortex in the resonator and intake flow.
압축 공기를 사용한 소형 이젝트의 진공 흡입 성능 평가 요인에 관한 연구
김준현(Joon Hyun Kim),배현우(Hyunwoo Bae),성재용(Jaeyong Sung) 한국생산제조학회 2020 한국생산제조학회지 Vol.29 No.4
This study analyzed the internal flow structure of a small ejector and the major design factors that affect suction force. The ejector had a limited total length of 45 mm, and the primary nozzle had a diameter of 1 mm. This study investigated the effect of the main parameters on optimum nozzle opening ratio based on injection flow as well as the influence of the mixing chamber design on vacuum suction performance. The second nozzle had a significant effect when the diameter was 18 mm. Other parameter values were studied to identify design elements that determine the shape of the mixing chamber. The effect of the pad opening gap and the change in ambient pressure on the control state of the inflow ratio and the possibility of non-contact gripping were also examined.