• 반도체디스플레이기술학회지
• /
• 제8권2호
• /
• pp.31-35
• /
• 2009

In the silicon wafer polishing process, the mounting stage of silicon wafer on the ceramic carrier block has been using the polishing template which utilizes the porous surface instead of traditional wax mounting method. Here in this article, the experimental study is carried out in order to study the wafer demounting by water jet and the effects of operating conditions such as the water jet flowrate and the number of water jet nozzles on the wafer demounting time. It is found that the measured wafer demounting time is inversely proportional to the water flowrate per nozzle, regardless of number of nozzles used; implying that the stagnation pressure by the water jet impingement is the dominant key factor. Additionally, by using the transparent disk instead of wafer, the air bubble formation and growth is observed under the disk, making the passage of water flow, and subsequently demounting the wafer from the porous pad.

• 대한기계학회논문집B
• /
• 제41권1호
• /
• pp.29-36
• /
• 2017

본 논문은 환형노즐 이젝터를 이용하여 세정수 공급과 기포생성을 동시에 할 수 있는 세정기술 개발을 위한 기초연구를 목적으로 한다. 환형노즐 이젝터의 피치변화에 따른 구동 및 부유체의 정량적 유동특성과 세정수조에 분출되는 분류의 정성적 가시화 이미지를 분석하였으며, 세정물의 농약 잔류물 성분의 농도를 검증하였다. 피치가 증가하면 구동유량은 증가하는 반면에, 유량비는 감소하였다. 피치가 증가하면 분류는 부력분류나 평형분류 거동을 나타내며, 잔류농약의 농도는 감소 후 증가하였다.

• 한국항공우주학회지
• /
• 제33권9호
• /
• pp.1-8
• /
• 2005

이차원 타원형 날개꼴에서 펄스제트 브로잉에 의한 박리 제어 효과에 대하여 연구하였다. 박리 유동의 능동제어기술 개발을 위하여 압축공기를 사용하는 연속제트/간헐제트 엑츄에이터를 설계제작하여 타원형 날개 풍동 실험 모델에 장착하였다. 아음속 유동에서 날개 주위 유동장의 PIV 측정과 유동의 가시화을 통하여 간헐제트 브로잉의 타원형 날개의 실속제어 효과와 실용성에 대해 실험연구를 수행하였다. PIV 실험 결과 제트 브로잉에 의해 난류 후류 영역과 박리 버블의 크기를 현저하게 감소시킴으로써 박리제어가 가능함을 보였다. 간헐제트는 연속제트보다 박리제어에 보다 효과적이었다. 간헐제트의 주파수를 증가시키면 보다 높은 받음각에 이르기까지 난류 박리 후류를 효과적으로 억제할 수 있었다.

• 대한기계학회논문집B
• /
• 제28권8호
• /
• pp.895-901
• /
• 2004

Single-phase convection and nucleate boiling heat transfer were locally investigated for confined planar water jets. The detailed distributions of the wall temperature and the convection coefficient as well as the typical boiling curves were discussed. The curve for the single-phase convection indicated the developing laminar boundary layer, accompanied by monotonic increase of the wall temperature in the stream direction. Boiling was initiated from the furthest downstream as heat flux increased. Heat transfer variation according to the streamwise location was reduced as heat flux increased enough to create the vigorous nucleate boiling. Velocity effects were considered for the confined free-surface jet. Higher velocity of the jet caused the boiling incipient to be delayed more. The transition to turbulence precipitated by the bubble-induced disturbance was obvious only for the highest velocity, which enabled the boiling incipient to start in the middle of the heated surface, rather than the furthest downstream as was the case of the moderate and low velocities. The temperature at offset line were somewhat tower than those at the centerline for single-phase convection and partial boiling, and these differences were reduced as the nucleate boiling developed. For the region prior to transition, the convection coefficient distributions were similar in both cases while the temperatures were somewhat lower in the submerged jet. For single-phase convection, transition was initiated at $x/W{\cong}2.5$ and completed soon for the submerged jet, but the onset of transition was retarded to the distance at $x/W{\cong}6$ for the fee-surface jet.

• Journal of Astronomy and Space Sciences
• /
• 제1권1호
• /
• pp.23-34
• /
• 1984

A bubble trapped in the liquid manifold of INTELSAT IV F-7 spacecraft caused a mass imbalance between the System 1 propellant tanks and a wobble half angle of 0.38 degree to 0.48 degree. A maneuver on May 14, 1980 passed the bubble through the axial jet and allowed propellant to redistribute. A 0.2 rpm change in sin rate was observed with an exponential decay time constant of 6 minutes. In this paper, moment of inertia, tank geometry and hydrodynamic models are derived to match the observed spin rate data. The values of the total mass of propellant considered were 16, 19 and 20 kgs with corresponding mass imbalances of 14.3, 15 and 15.1 Kgs, respectively. The result shows excellent agreement with observed spin rate data but it was necessary to assume a greater mass of hydrazine in the tanks than propellant accounting indicated.

• 한국물환경학회지
• /
• 제20권1호
• /
• pp.78-85
• /
• 2004

As an ozone contactor, we newly adopted HJLR (High-performance Jet Loop Reactor) for the decolorization of Reactive black 5 and the mineralization of oxalic acid, which has been applied exclusively in biological wastewater treatments and well-known for high oxygen transfer characteristics. The ozonation efficiency for organic removals and ozone utilization depending on the mass transfer rate were compared to those of Stirred bubble column reactor, which was controlled by varing energy input in the HJLR and Stirred bubble column reactor. The results were as follows; first, the decolorization rate of Reactive black 5 in the HJLR reactor was nearly proportional to the increasing $k_La$. When the $k_La$ was increased by 25 % from $13.0hr^{-1}$ to $16.4hr^{-1}$, 30 % of the k' (apparent reaction rate constant) was increased from 0.1966 to $0.2665min^{-1}$ (Stirred bubble column; from 0.1790 to $0.2564min^{-1}$). Ozone transfer was found to be a rate-determining step in decolorizing Reactive black 5, which was supported by that no residual ozone was detected in all of the experiments. Second, the mineralization of oxalic acid was not always proportional to the increasing $k_La$ in the RJLR reactor. The rate-determining step for this reaction was OH(OH radical) production with ozone transfer, because residual ozone was always detected during the ozonation of oxalic acid in contrast with Reactive black 5. This result indicates that the increase of $k_La$ in the HJLR reactor is beneficial only when there are in ozone transfer limited regions. In addition, regardless of $k_La$, the mineralization of oxalic acid was nearly accomplished within 60 minutes. It was interpreted as that the longer staying of residual ozone by whirling liquid in the HJLR reactor contributed to an high ozone utilization(83-94%), producing more OR radicals.

• 설비공학논문집
• /
• 제13권7호
• /
• pp.595-601
• /
• 2001

We applied PIV method to obtain instantaneous and ensemble averaged velocity fields from the first row to the fifth row of a staggered tube bundle. The Reynolds number based on the tube diameter and the maximum velocity was set to be 4,000. Remarkably different natures are observed in the developing bundle flow. Such differences are depicted in the mean recirculating bubble length and the vorticity distributions. The jet-like flow seems to be a dominant feature after the second row and usually skew. However, the ensemble averaged fields show symmetric profiles and the flow characteristics between the third and fourth measuring planes are not so different. comparison between the PIV data and the RANS simulation yields severe disagreement in spite of the same Reynolds number. It can be explained that the distinct jet-like unsteady motions are not to be accounted in th steady numerical analysis.

• International Journal of Aerospace System Engineering
• /
• 제2권1호
• /
• pp.6-11
• /
• 2015

An active flow control technique using blowing and distributed suction on low Reynolds airfoil is investigated. Simultaneous blowing and distributed suction can recirculate the jet flow mass, and reduce the penalty to propulsion system due to avoiding dumping the jet mass flow. Energy is injected into main flow by blowing on the suction surface, and the low energy boundary flow mass is removed by distributed suction, thus the flow separation can be successfully suppressed. Aerodynamic lift to drag ratio is improved significantly using the flow control technique, and the energy consumption is quite low.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 1998년도 제10회 학술강연회논문집
• /
• pp.18-18
• /
• 1998

평판에 충돌하는 초음속 세트에 관한 연구는 수직/단거리 이·착륙기의 발진, 미사일 발사시스템, 다단계 로켓 분리 등 실제적인 분야에 응용되고 있으며 고온의 충돌제트와 화염에 의한 가열문제와 관련된 산입분야에서도 많은 연구가 이루어지고 있다. 과소팽창하는 초음속 제트가 평판에 충돌할 때 Barrel shock, exhaust gas boundary, Mach disk, contact surface, reflected shock, plate shock, stagnation bubble 등 매우 복잡한 유동 구조가 표면에 나타나는데 이것은 평판으로부터 반사된 shock과 free jet의 충격파 구조 사이에서의 상호간섭 때문이다. 노즐로부터 방출되는 고속, 고온가스가 주변 장비 등에 부딪힐 때 발생하는 이러한 복잡한 간섭현상의 연구는 관련 주변장비 설계 및 상황예측에 필수적인 자료를 제공하며 이해를 도와준다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.706-711
• /
• 2003

A numerical method is presented for computing unsteady incompressible two-phase flows with immersed solids. The method is based on a level set technique for capturing the phase interface, which is modified to satisfy a contact angle condition at the solid-fluid interface as well as to achieve mass conservation during the whole calculation procedure. The modified level set method is applied for numerical simulation of bubble deformation in a micro channel with a cylindrical solid block and liquid jet from a micro nozzle.