• Journal of Advanced Marine Engineering and Technology
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• 제34권1호
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• pp.84-91
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• 2010

The centrifugal oil purifier is used in ships for purifying the engine lubrication oil. The momentum needed for the rotation of the cylindrical chamber is obtained by jet injections. The dust particles in the oil are separated by the centrifugal forces moving to the inner wall of the rotating cylindrical chamber body. The dust particles are eliminated when the particles are adsorbed onto the surface of the inner wall of the chamber body. The flow characteristics and the physical behaviours of particles in this centrifugal oil purifier have been investigated numerically and the filtration efficiencies have been evaluated. For the calculations, a commercial code has been used and the SST k-${\omega}$ turbulence model has been adopted. The MRF (Multiple Reference Frame) method has been introduced to consider the rotating effect of the flows. Under various variables, such as particle size, particle density and rotating speed, the filtration efficiencies have been evaluated. It has been verified that the filtration efficiency is increased with the increments of the particle size, the particle density and the rotating speed of the cylindrical chamber.

• 한국군사과학기술학회지
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• 제6권4호
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• pp.124-131
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• 2003

When a secondary gaseous flow is injected vertically into a supersonic flow through circular nozzle, a complicated structure of flow field is produced around the injection area. The interaction between the two streams produces a strong bow shock wane on the upstream side of the side-jet. The results show that bow shock wave and turbulent boundary layer interaction induces the boundary layer separation in front of the side-jet. This study is to analyze the structure of flow fields and distribution of surface pressure on the flat plate according to total pressure ratio using a supersonic cold-flow system and also to study the control force of affected side-jet. The nozzle of main flow was designed to have Mach 2.88 at the exit. The injector has a sonic nozzle with 4mm diameter at the exit of the side-jet. In experiments, The oil flow visualization using a silicone oil and ink was conducted in order to analyze the structure of flow fields around the side-jet. The flow fields are visualized using the schlieren method. In this study, a computational fluid dynamic solution is also compared with experimental results.

• 대한기계학회논문집B
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• 제26권9호
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• pp.1267-1275
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• 2002

An experimental study was performed to investigate adiabatic wall temperature and heat transfer coefficient around a module cooled by forced air flow. The flow angle of attack to the module were 0$^{\circ}$and 45$^{\circ}$. In the first method, inlet air flow(1~7m/s) and input power.(3, 5, 7W) were varied after a heated module was placed on an adiabatic floor(320$\times$550$\times$1㎣). An adiabatic wall temperature was determinated to use liquid crystal film. In the second method to determinate heat transfer coefficient, inlet air flow(1~7m/s) and the heat flux of rubber heater(0.031~0.062W/$m^2$) were varied after an adiabatic module was placed on rubber heater covering up an adiabatic floor. Additional information is visualized by an oil-film method of the surface flow on the floor and the module. Plots of $T_{ad}$ and $h_{ad}$ show marked effects of flow development from the module and dispersion of thermal wake near the module. Certain key features of the data set obtained by this investigation may serve as a benchmark for thermal-design codes based on CFD.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2003년도 추계학술대회 논문집
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• pp.87-90
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• 2003

In this paper, flow characteristics of plasma flow in a micro-tube were investigated experimentally using Micro-PIV. For comparision, the experiments were repeated for DI-water instead of plasma. Both velocity profiles of Plasma and DI-water are well agreed with the theoretical velocity distribution of newtonian fluid. We also carried out generating plasma-in-oil droplet formation at a Y-junction microchannel. In order to clarify the hydrodynamic aspects involved in plasma droplet formation. Rhodamin B were mixed with plasma only for visualization of plasma droplet.

• 한국가시화정보학회지
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• 제21권1호
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• pp.94-102
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• 2023

Three design parameters were considered in this study: outlet nozzle angle (30°, 60°, 80°), neck length (1 mm, 3 mm), and flow rate (0.5, 0.6, 0.7, 0.8 lpm). A neck diameter of 0.5 mm induced cavitation flow at a venture nozzle. A secondary transparent chamber was connected after ejection to increase bubble duration and shape visibility. The bubble size was estimated using a Gaussian kernel function to identify bubbles in the acquired images. Data on bubble size were used to obtain Sauter's mean diameter and probability density function to obtain specific bubble state conditions. The degree of bubble generation according to the bubble size was compared for each design variable. The bubble diameter increased as the flow rate increased. The frequency of bubble generation was highest around 20 ㎛. With the same neck length, the smaller the CV number, the larger the average bubble diameter. It is possible to increase the generation frequency of smaller bubbles by the cavitation method by changing the magnification angle and length of the neck. However, if the flow rate is too large, the average bubble diameter tends to increase, so an appropriate flow rate should be selected.

• 설비공학논문집
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• 제16권5호
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• pp.452-458
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• 2004

The major cause of compressor failure is the decrease of oil viscosity due to floodback. In most previous researches on the compressor reliability, the relationship between oil circulation rate and performance or oil viscosity has been studied. Another research topic is flow visualization by using a sight glass on the bottom of a compressor sump area and accumulator. Both oil film thickness and oil level through the sight glass should be assessed for compressor reliability if the oil content of the mixture is small and low viscosity raise poor lubrication of pump bearing. In this study, the compressor reliability was assessed by measuring the viscosity of the mixture and calculating oil film thickness. The analysis of the relationship between bottom shell super heat and oil film thickness at heating operation was peformed. It is concluded that bottom shell superheat does not perfectly stand for the mixture's behavior for a low ambient heating operation and oil film thickness can give more detailed and direct criteria for compressor reliability.

• 한국해양환경ㆍ에너지학회지
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• 제1권2호
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• pp.40-51
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• 1998

유벽에 의하여 가두어진 오일의 조류중 거동을 회류수조에서 2차원적인 실험설비를 이용하여 살펴보았다. 유벽을 적정 깊이의 수직판으로 대치하고 레이저 광원을 이용하여 오일과 물과의 경계면 변형을 2 종류의 오일 (콩기름과 경유)에 대하여 관찰하였다. 적용된 조건으로 조류의 속도는 10 cm/s - 35 cm/s, 유벽의 깊이는 4 cm 와 8 cm, 그리고 유량은 2 liter - 8 liter 의 변화를 주었다. 다양한 경계면의 거동과 조건에 따른 누유의 손실 방식을 차원해석을 통하여 정리하고 유적누유와 연속누유의 발생 메카니즘을 설명하였다.

• 한국가시화정보학회지
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• 제13권3호
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• pp.20-23
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• 2015

In this experiment, a heterogeneous droplet consisted of de-ionized water and olive oil was made through two 31G injection needles. The injection flow rate was $50{\mu}{\ell}/min$ and the droplet size was 2 mm. The droplet was impinged onto a sapphire plate which was heated up to $300^{\circ}C$ by a heater. Two high speed cameras were used for visualization, and the frame rate was 20,000 fps. A 150W metal halite lamp was used for illumination. The dropping height was fixed to 20 mm and the corresponding Weber number was 10.6 based on water. Due to different boiling points of two liquids, partial boiling features of heterogeneous droplet was observed. At the Leidenfrost condition, micro explosion phenomenon has occurred.

• 한국항공우주학회지
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• 제34권10호
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• pp.61-70
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• 2006

마하 4 비행 조건에서 작동하는 고성능 램제트와 듀얼모드 스크램제트 엔진의 초음속 공기 흡입구 모델을 설계하였다. 배압, 받음각, 요각 등 비행 변수의 변화에 따른 내부 유동 특성을 파악하기 위하여 규슈대학교의 불어내기식 초음속 풍동을 이용한 실험을 수행하였다. 유동 가시화를 위하여 쉴리렌 기법, 오일 가시화 기법을 이용하였으며, 정량적 성능 분석을 위하여 표면 압력 및 전압력을 측정하였다. 실험의 결과는 전산 유체 해석과 비교하였다. 본 연구는 기본적이지만 찾기 힘든 고 마하수 초음속 공기 흡입구 유동의 실험 결과를 제시한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.159-160
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• 2002

New S-shaped aeroelastic mesoflaps are utilized to control normal shock/boundary-layer interactions. New generation of the mesoflaps is designed f3r a better rigidness and a good flow uniformity across the ulteractions. ,Major advantages of the mesoflap system can be a better total pressure recovery downstream of the interactions due to the lambda shock structure over the flap system, and a rehabilitation of the thickened boundary layer due to bleeding through a cavity underneath the flap system. Skin friction has been measured downstream of the interactions, using the laser interferometer skin friction (LISF) meter, which optically detects the rate of thinning of an oil film applied to the test surface. Various flap-thicknesses of the S-shaped mesoflap arrays are tested, and the results are compared to the solid-wall reference case. Overall, not much difference in the level of skin friction is noticed for the S-shaped flap arrays of various thicknesses, and its level is lower than the skin friction downstream of the solid-wall interaction