• Title/Summary/Keyword: Cross-flow Fan

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Experimental Study on the Three Dimensional Unsteady Flow in a Counter-Rotating Axial Flow Fan (엇회전식 축류팬의 3차원 비정상 유동에 관한 실험적 연구)

  • Park, Hyun-Soo;Cho, Lee-Sang;Cho, Jin-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.9
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    • pp.1005-1014
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    • 2004
  • Experiments were done for the three dimensional unsteady flow in a counter-rotating axial flow fan under peak efficiency operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the 45$^{\circ}$ inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. It has been found that the radial and tangential velocity components disappeared, while the axial velocity component highly increased as soon as the tip vortex was generated. It has been observed that secondary flow and turbulence intensity which were increased by the front rotor were dissipated passing through the rear rotor. As the result the energy loss of the counter rotating axial flow fan decreased at the downstream of rear rotor. Also, it has been verified that tip vortex pattern of the rear rotor was dampened because the tip vortex generated by front rotor was mixed with that of the rear rotor.

Flow Noise in the Outdoor Unit of an Air-conditioner (에어컨 실외기에서의 유동소음)

  • 이승배;이재환;김휘중;최진규;진성훈;박윤서
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.594-601
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    • 1997
  • Propeller fans are commonly equipped in outdoor units of air-conditioners to provide effective cooling in a dried heat exchanger. A new design technique was developed to satisfy requirements of aerodynamic and aeroacoustic performance, which employs the intersection method of two cylinders for mean camber line. Three proto-types of propeller fan including Palm-Shaped, Highly-Swept(PSHS) fan (proto 3)were not only to provide low lift forces for dipole sound, but also to reduce the organized tip vortices interacting with the fan guide causing narrow-banded rotating instabilities. Cross-correlation technique was applied to study flow noise source characteristics for three proto-type fans designed. The cross-correlations between a microphone at far field and a hot-wire sensor at near field show that flows near hub region of proto 3 fan are less organized and the flow structures especially at high flow rate coefficients for proto 3 fan are less correlated with noise generated than other proto-types fans.

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Experimental Study on the Aerodynamic Characteristics of the Ducted Fan for a Small UAV (소형 무인기 추진용 덕티드 팬의 공력특성에 관한 실험적 연구)

  • Kim, Jae-Kyeong;Choi, Hyun-Min;Cha, Bong-Jun;Lee, Sang-Hyo;Cho, Jin-Soo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.251-256
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    • 2008
  • The experimental analysis on a ducted fan for the propulsion system of a small UAV were performed. To investigate the aerodynamic characteristics of the ducted fan, flow fields at inlet and outlet were measured using a hot-wire anemometry. Thrusts were measured with the six-component balance with due regard to the cross wind. To reproduce the cross wind effect, the ducted fan was aligned to $90^{\circ}$ rotated direction against flow direction in the wind tunnel. In this paper, the variation of the flow fields and thrust according to the cross wind were analyzed.

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Prediction of Frequency Modulation of BPF Tonal Noise for Random Pitch Cross-Flow Fans by Unsteady Viscous Flow Computations (비정상 점성유동 해석에 의한 부등피치 횡류홴의 BPF 순음 주파수 변조 특성 예측)

  • Cho, Yong;Moon, Young J.
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.3
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    • pp.286-293
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    • 2003
  • The unsteady flow characteristics and associated blade tonal noise of a cross-flow fan are predicted by computational methods. The incompressible Navier-Stokes equations are time-accurately solved for obtaining the pressure fluctuations between the rotating blades and the stabilizer. and the sound pressure is predicted using Curie's equation. The discrete noise characteristics of three impellers with a uniform and two random pitch (type-A and -B) blades are compared by their SPL (Sound Pressure Level) spectra. and the frequency modulation characteristics of the BPF (Blade Passing Frequency) noise are discussed. Besides. a mathematical model is proposed for the prediction of discrete blade tonal noise and is validated with available experimental data. The fan performance is also compared with experimental data. indicating that the random pitch effect does not significantly alter the performance characteristics at ${\phi}$ 〉 0.4

Computational Flow Analysis on the Flow Field Improvement of an Indoor RAC by LES (LES에 의한 RAC 실내기의 유동장 개선에 관한 전산유동해석)

  • Kim, J.K.;Oh, S.H.
    • Journal of Power System Engineering
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    • v.16 no.3
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    • pp.29-36
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    • 2012
  • The computational flow analysis using LES technique was introduced to investigate the flow field improvement of an indoor RAC chassis consisting of a rear-guider, a stabilizer and a cross-flow fan. This unsteady three-dimensional numerical analysis was carried out by the commercial SC/Tetra software. The edge blocks were adopted in this study as a tool for the flow field improvement of an indoor RAC. In view of the results so far achieved, the edge blocks cause the center of an eccentric vortex to be stable along all length of a cross-flow fan, and then, the static pressure and the velocity vector show a stable distributions. In consequence, because the edge blocks eliminate a reverse flow near the edges, an exhausting flow becomes to be stable and uniform.

Frequency Characteristics of Fluctuating Velocity According to Flow Rates in a Tip Leakage Vortex and a Wake Flow in an Axial Flow Fan (축류 홴의 익단누설와류 및 후류에서 유량에 따른 변동속도의 주파수 특성)

  • Jang, Choon-Man;Kim, Kwang-Yong;Fukano, Tohru
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.2
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    • pp.181-188
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    • 2004
  • The frequency characteristics in an axial flow fan operating at a design and three off-design operating conditions have been investigated by measuring the velocity fluctuation of a tip leakage vortex and a wake flow. Two hot-wire probe sensors rotating with the fan rotor. a fixed and a moving ones, were introduced to obtain a cross-correlation coefficient between two sensors as well as the fluctuating velocity. The results show that the spectral peaks due to the fluctuating velocity near the rotor tip are mainly observed in the reverse flow region of higher flow rates than those in the peak pressure operating condition. However, no peak frequency presents near the rotor tip for near stall condition. Detailed wake flow just downstream of the rotor blade was also measured by the rotating hot-wire sensor. The peak frequency of a high velocity fluctuation due to Karman vortex shedding in the wake region is mainly observed at the higher flow rate condition than that in the design point.

Study on Flow Structure inside Room Air Conditioner Using Visualization Technique (가시화기법을 이용한 룸 에어컨 내부의 유동 구조에 관한 연구)

  • Lee, Soo-Hong;Na, Seon-Uk;Kang, Geun;Ko, Han-Seo
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2713-2717
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    • 2008
  • Whole flow fields of a room air conditioner (RAC) have been visualized by a Particle Image Velocimetry (PIV) technique to analyze the flow structure with various inlet and outlet angles, and to control an eccentric vortex which affects an efficiency and noise of the RAC. A test model with 5 stages of a cross flow fan has been manufactured and a transparent acryl has been installed at the side of the test model for the PIV experiment. The inlet and outlet flows and the flow inside the cross flow fan have been analyzed by varying the inlet grill angles and outlet blade angles. The movement of the eccentric vortex has been investigated experimentally by developing the measurement technique for the inner flow field of the cross flow fan. From the visualization of the inner flows, the origins of the noise inside the RAC and the condensation points around the outlet parts of the cold air have been observed and the solution of the problems can be proposed in this study.

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Unsteady Nature of a Tip Leakage Vortex in an Axial Flow Fan (축류팬 익단누설와류의 비정상 특성)

  • Jang, Choon-Man;Kim, Kwang-Yong
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.845-850
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    • 2003
  • Unsteady nature of a tip leakage vortex in an axial flow fan operating at a design and off-design operating conditions has been investigated by measuring the velocity fluctuation in a blade passage with a rotating hotwire probe sensor. Two hot-wire probe sensors rotating with the fan rotor were also introduced to obtain the cross-correlation coefficient between the two sensors located in the vortical flow as well as the fluctuating velocity. The results show that the vortical flow structure near the rotor tip can be clearly observed at the quasi-orthogonal planes to a tip leakage vortex. The leakage vortex is enlarged as the flow rate is decreased, thus resulting in the high blockage to main flow. The spectral peaks due to the fluctuating velocity near the rotor tip are mainly observed in the reverse flow region at higher flow rates than the peak pressure operating condition. However, no peak frequency presents near the rotor tip for near stall condition.

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A Numerical Study on Solidity Characteristics of the Cross-flow Power Turbine(CPT) (횡류형 파워 터빈(CPT)에서 솔리디티 영향에 관한 수치해석 연구)

  • Chung, Kwang-Seop;Kim, Chul-Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.22 no.8
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    • pp.562-566
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    • 2010
  • Wind energy is one of the most general natural resources in the world. However, as of today, generating electricity out of wind energy is only available from big wind generator, Furthermore, an axial-flow turbine is the only way to produce electricity in the big wind generator. This paper is for the guidance of drawing impact fact about power turbine using cross-flow type transferring wind energy to electricity energy. It will find the ideal value which enables to make cross-flow power turbine(CPT) using computational fluid dynamics(CFD) code. This study tries to analyze the "Solidity" characteristics. We can find out turbine-blade number through CFD. CFD is using "Fluent_ver 6.3.16", and the data from its result will judge fan-blade performance through specific torque and specific power from each "Solidity" model. Based upon the above, we will make cross-flow power turbine of multi-blade centrifugal fan instead of axial-flow type.