• 한국전산유체공학회지
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• 제10권1호
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• pp.107-112
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• 2005

A cross-flow fan is generally used on the region within the low static pressure difference and the high flow rate. It relatively makes high dynamic pressure at low rotating speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. At off-design points, there are a rapid pressure head reduction, a noise increase and an unsteady flow. Those phenomena are remarkably influenced by the setting angle of a stabilizer. Therefore, it should be considered how the setting angle of a stabilizer affects on the performance and the flow fields of a cross-flow fan. It is also required to investigate the effect of the volumetric flow rate before occurring stall. Two-dimensional, unsteady governing equations are solved using a commercial code, STAR-CD, which uses FVM. PISO algorithm, sliding grid system and standard k - ε turbulence model are also adopted. Pressure and velocity profiles with various setting angles are graphically depicted. Furthermore, the meridional velocity profiles around the impeller are plotted with different flow rates for a given rotating speed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.365-370
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• 2000

A computational study on the effect of sweep angle of axial fan on its noise is performed in the present paper. The forward swept axial fan was designed by numerical optimization method incorporated with three dimensional flow analysis. The objective function was defined by the ratio of generation rate of turbulent kinetic energy to pressure head. And, two variables related with sweep angle distribution are used for design variables. The swept fan has better performance characteristics and noise level. The experimental result shows that spectrums of no-sweet and swept fans have differences in the blade passage frequency, especially in the broadband. And the overall noise level of swept fan is lower 10dB(A) than that of no-sweep fan. For the comparison of flow fields between no-sweep fan and swept fan, CFX-TASCflow computational fluid dynamics software is used. Standard k-${\varepsilon}$ model is used for the turbulence model. Distributions of pressure and turbulent kinetic energy distributions are compared in order to find what happen in the low-noise swept fan.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.851-856
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• 2003

A cross-flow fan consists of an impeller, a stabilizer and a rearguider. When it applied for an air conditioner, an evaporator should be added. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. Therefore, the performance of a cross-flow fan is influenced 25% by the impeller, 60% by the rearguider and the stabilizer, 15% by the heat exchanger. At the low flow rate, there are a rapid pressure head reduction, a noise increase and an unsteady flow against a stabilizer and a rearguider. Moreover, the reciprocal relation between the impeller and the flow passage is the important factor for performance improvement of the cross-flow tan because each parameter is independent. The performance characteristics in the cross-flow fan are graphically depicted with various impeller outlet angles and rearguiders.

• 한국항공우주학회지
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• 제37권2호
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• pp.121-130
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• 2009

전진 비행중인 자동회전 로터에 대한 비정상 수치해석 기법이 개발되었다. 자동회전 로터의 플래핑과 회전운동 방정식은 주어지는 시간간격에 따라 연속적으로 적분되며 이 때 회전면에서의 유도 속도장은 동적 유도흐름 이론(dynamic inflow theory)에 의해 계속 업데이트 되면서 블레이드의 모든 요소에서 유효 받음각을 결정하여 비정상 상태를 모사한다. 로터의 임의의 초기 회전속도 및 플래핑각에서 정상상태로 천이(transition)되는 과정을 시뮬레이션 하였고 블레이드 에어포일 공력 데이터들을 이용하여 방정식들의 수치해인 자동회전의 정상상태를 예측하였다. 2차원 Navier-Stokes 솔버로 받음각과 레이놀즈수에 따라 해석된 에어포일 데이터를 이용하여 자동회전의 비정상 시뮬레이션을 수행한 해석 결과는 풍동실험 결과와 잘 일치하였다

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.173-179
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• 2012

본 논문에서는 부분 흡입형 초음속 터빈의 로터 블레이드에 ${\pm}15^{\circ}$의 스윕 각도를 적용하여 그에 의한 효과와 공력 특성을 살펴보기 위해 정상상태 유동해석과 비정상상태 유동해석을 동시에 수행하고 그 결과를 비교해 보았다. 3차원 Navier-Stokes 유동해석에는 상용 코드인 FLUENT 6.3 Parallel을 사용하였다. 모든 계산 케이스들에서 정상상태 유동해석에 비해 비정상상태의 경우가 손실이 더욱 크게 나오는 결과를 나타내었다. 후방스윕(BSW)모델은 기준모델(NSW)에 비해 팁 간극으로 빠져나가는 누설 손실량을 줄이는데 큰 효과가 있었고 비정상상태 유동 해석에서는 로터 출구면 정효율의 증가현상이 더욱 뚜렷하게 나타났다.

• Journal of Biosystems Engineering
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• 제36권1호
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• pp.9-14
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• 2011

This study was carried out to develop a vine crusher for harvesting sweet potato. The experimental two-row vine crusher attachable to agricultural tractor composed of vine crushing part with frail type vine crushing blades and vine lifting blades, power transmission part with chain and gear transmission mechanism, crushing height control part with two control wheels and manual levers, and implement frames, was designed and fabricated. And this vine crushing performance was also analyzed. From vine crushing tests, backward travel direction (i.e., rotational direction of the vine crushing blades) showed better vine crushing performance than forward travel direction. Crushing ratio of remained vine was increased, and length of remained vine and length of crushed vine were decreased as working speed was decreased and rotational speed of vine crushing blades was increased. At a working speed of 0.27 m/s and rotational speed of vine crushing blades of 800 rpm, crushing ratio of remained vine was 98%, length of remained vine was 104 mm, and length of crushed vine was 327 mm. But, when crushing vine on irregular ridges, vines and mulching vinyl were wound in the vine crushing part. Therefore, change of location of power transmission chain mechanism, and an automatic control device for controlling crushing height were needed.