• Title/Summary/Keyword: Square duct

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Kinetic energy of Laminar Steady flows in the Exit Reguon Connected to the straight Square-sectionnal $180^{\circ}$ curved Duct by using PIV (PIV 계측에 의한 $180^{\circ}$곡관 출구에 연결된 직관에서 층류정상유동의 운동에너지)

  • Lee J.G.;Lee H.G.;Sohn H.C.;Lee H.N.;Park G.M.
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.521-524
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    • 2002
  • In the present study, kinetic energy of laminar steady flow in the exit region connected to the square-sectional $180^{\circ}$curved duct was investigated experimentally. The experimental study for air flows was conducted to measure kinetic energy distributions by using the Particle Image Velocimetry(PIV) system with the data acquisition and processing system of Cactus 2000 software. The results obtained from experimental studies are summarized as follows : (1) The critical Reynolds number for a change from laminar steady flow to transitional steadt flow was about 1910, in the 50 region of dimensionless axial position (x/Dh) whirh was considered as a fully developed flow region. (2) Maximum kinetic energy of laminar steady flow was gradually increased as the Reynolds number increased.

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Optimization for Flow Uniformity on the Selective Catalytic Reduction (SCR) System of a Steam Supply Boiler (열병합 보일러 SCR 장치의 유동 균일화를 위한 최적화 연구)

  • Park, Young-Bin;Jang, Choon-Man
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.415-420
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    • 2009
  • Selective Catalytic Reduction(SCR) has been used for the reduction of $NO_x$ in a steam supply boiler. Recently, the reduction of $NO_x$ becomes an important research field because of its negative effect on an environment. Shape optimization of circular poles installed in the chamber, which is located in upstream of a SCR, has been performed using response surface method and three-dimensional Navier-Stokes analysis to enhance gas flow uniformity. Three design parameters, diameter, arranging angle and stretching ratio of circular poles, are considered in the present study. Throughout the shape optimization of a circular pole, gas flow uniformity is successfully increased by decreasing local recirculation flow in a square duct chamber. Recirculation flow observed in the corner of the square duct can be reduced by proper installation of a guide vane or a blunt body. Detailed flow characteristics are also analyzed and discussed.

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Calculation of Developing Turbulent Flow in a Square Duct (정사각형 관내의 전개 중인 난류 유동 해석)

  • 신승주;박승오;김의택
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.170-177
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    • 1989
  • The non-linear k-.epsilon. model developed by Speziale was employed for the prediction of developing turbulent flow in a square duct. The numerical procedure incorporated a finite volume method using a strong conservation form of the partially-parabolized Navier-Stokes equation. Results of the calculation were compared with available experimental data on the mean velocity field and turbulent kinetic energy, and was found to be in favorable agreement.

Improvement Noise Attenuation Performance of the Active Noise Control System Using RCMAC (RCMAC를 이용한 능동소음 제어시스템의 소음저감 성능개선)

  • Han, S.I.;Yeo, D.Y.;Kim, S.H.;Lee, K.S.
    • Journal of Power System Engineering
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    • v.14 no.5
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    • pp.56-62
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    • 2010
  • In this paper, a recurrent cerebellar modulation articulation control (RCMAC) has been developed for improvement of noise attenuation performance in active noise control system. For the narrow band noise, a filter-x least mean square (FXLMS) method has bee frequently employed as an algorithm for active noise control (ANC) and has a partial satisfactory noise attenuation performance. However, noise attenuation performance of an ANC system with FXLMS method is poor for broad band noise and nonlinear path since it has linear filtering structure. Thus, an ANC system using RCMAC is proposed to improve this problem. Some simulations in duct system using harmonic motor noise and KTX cabin noise as a noise source were executed. It is shown that satisfactory noise attenuation performance can be obtained.

Pressure Drop Characteristics in a Coolant Passage With Turning Region and Rotation (냉각유로 내 곡관부 및 유로의 회전이 압력강하에 미치는 영향)

  • Kim, Kyung-Min;Cho, Hyung-Hee
    • The KSFM Journal of Fluid Machinery
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    • v.10 no.2 s.41
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    • pp.32-40
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    • 2007
  • The present study investigated local pressure drop in a rotating smooth square duct with turning region. The duct has a hydraulic diameter $(D_h)$ of 26.7mm and a divider wall of 6.0mm or $0.225D_h$. The distance between the tip of the divider and the outer wall of the duct is $1.0D_h$. The Reynolds number (Re) based on the hydraulic diameter is kept constant at 10,000, and the rotation number (Ro) is varied from 0.0 to 0.20. The pressure coefficient distribution $(C_p)$, the friction factor (f) and the thermal performance $({\eta})$ are presented on the leading, the trailing and the outer surfaces. It is found that the curvature of the $180^{\circ}-turn$ produces Dean vortices that cause the high pressure drop in the turning region. The duct rotation results in the pressure coefficient discrepancy between the leading and trailing surfaces. That is, the high pressure values appear on the trailing surface in the first-pass and on the leading and side surfaces in the second-pass. As the rotation number increases, the pressure discrepancy enlarges. In the fuming region, a pair of the Dean vortices in the stationary case transform into one large asymmetric vortex cell, and then the pressure drop characteristics also change.

An attenuation effect of noise according to the direction of secondary sound source in duct ANC system (Duct ANC 시스템에서 2차음원 방향별 소음감소효과)

  • Lee, Hyung-Seok;Lee, Eung-Suk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.11a
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    • pp.497-502
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    • 2008
  • In this paper, we studied on an attenuation effect of automobile exhaust noise according to the direction of secondary sound source in duct ANC system. Automobile exhaust noise was recorded at 800rpm. 3500rpm and 5000rpm of a diesel engine. Directions of loudspeaker(second sound source) can be exchanged to $30^{\circ}$, $90^{\circ}$ and $150^{\circ}$ against the primary noise flow by acrylic ducts to be made for experimentation. DSP board with TMS320C6416 chip of Texas Instrument Co used to control adaptive ANC system. This ANC system is based on the single-channel FxLMS algorithm. In experiment result, when the loud speaker direction was $150^{\circ}$, the attenuation effect showed largely. In case of $90^{\circ}$ duct, the noise was a little increased. In case of $30^{\circ}$ duct, the noise was a little increased or decreased according to the frequency range and the sound pressure(dB) of exhaust noise to comply with engine rpm.

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A Study on the Optimum Design of Air-Conditioning Duct with Multiple Diffusers (다수의 취출구를 갖는 A/C덕트의 최적설계에 관한 연구)

  • 김민호;이대훈
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.5
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    • pp.98-106
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    • 2002
  • The airflow characteristics of an air-conditioning duct with multiple diffusers were investigated through one-dimensional analysis, CFD simulation and experimental measurement. One-dimensional program based on Bernoulli's equation and minor loss equations was developed in order to evaluate the air distribution rate at each diffuser. In CFD simulation, three-dimensional flow characteristics inside air-conditioning duct were computed for incompressible viscous flow, adopting the RNG k-$\xi$turbulence model. Also, in an effort to equalize the discharge flow rate at each outlet, the optimization procedure has been performed to obtain the optimum diffuser area. In this process, square of difference between maximum discharge rate and minimum discharge rate is used as an object function. Diffuser area and discharge velocity are established as constraints. After optimization process, determined design variables are applied again in CFD simulation and experiment to validate the optimized result by one-dimensional program. Comparison with the experimental data of airflow rate distribution showed that the developed program seems to be acceptable and can be useful design tool for an automotive air-conditioning duct in an initial design stage.