• 제목/요약/키워드: Cascade effect

검색결과 262건 처리시간 0.028초

축류터빈 내부의 3차원 압축성 점성 유동특성에 관한 수치 시뮬레이션 (Numerical Simulation of Three-Dimensional Compressible Viscous Flow Characteristics in Axial-Flow Turbines)

  • 정희택;정향남
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2004년도 춘계 학술대회논문집
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    • pp.42-48
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    • 2004
  • Numerical simulation of viscous compressible flow in turbomachinery cascade involves many problems due to the complex geometry of blade but also flow phenomena. In the present study, numerical investigations have been performed to examine the three-dimensional flow characteristics inside the transonic linear turbine cascades using a commercial code, FLUENT. Multi-block H-type grids are applied to the high-turning turbine rotor blades and comparisons with the experimental data and the numerical results have been done. In addition, the effects of turbulence models on the prediction of the endwall flows are analyzed in the sense of the flow compressibility.

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가속되는 압축기 익렬의 비정상 성능해석 (Unsteady Performance Analysis of Accelerating Compressor Cascade)

  • 김명호;최정열;김귀순;이기수;김유일;임진식
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2001년도 춘계 학술대회논문집
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    • pp.121-126
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    • 2001
  • An accelerating flow field through a compressor cascade is studied numerically by unsteady computational simulation. The two-dimensional Navier-Stokes equations for compressible flow is used for the study of unsteady high incidence angle flow, with preconditioning scheme to cover the wide range of Mach number and $\kappa-\omega$ model for the turbulent viscous flow analysis. A DCA(double circular arc) compressor blade is accelerated artificially in this study to understand the unsteady effect by comparing the present results with the existing steady-state experimental and computational results. Also, the accelerating flow field during the starting phase of gas turbine is studied with actual experimental data for the understanding of flow field and performance characteristics at off-design condition.

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주 변압기실 화재시나리오에 적용한 미세물분무 노즐의 소화성능 (Performance of Fire Extinguishing of Water Mist Nozzle for Power Transformer Fire Scenario)

  • 이경덕
    • 한국안전학회지
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    • 제21권6호
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    • pp.46-54
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    • 2006
  • Fire extinguishing experiment was conducted with water mist nozzle in case of the pool fire, cascade fire and spray fire on flammable liquid of class B whether water mist system can be effective system for power transformer fire scenario. In the event of a pool fire, flow rate and time to extinguish was inclined to be increased according to the obstruction rate of ignition space. Furthermore, the performance of fire extinguishing depended upon the spraying angle of the nozzles. In case of cascade fire, the effect of extinguishment was began to show from a combustion pan filled with fuel and fuel flowing plate later on.

축류 회전차 팁 틈새에서의 유동특성 해석 (An Analysis of the Flow Characteristics in the Tip Clearance of Axial Flow Rotor)

  • 정재구;이명호
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권5호
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    • pp.735-745
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    • 2004
  • A linear cascade of NACA 65-1810 profiles are investigated for tip leakage flow characteristics. and calculation results are compared with experimental result. STAR-CD commercial code was used to solve the three dimensional incompressible Navier-Stokes equation that was adopted for steady flow and high Reynolds $\kappa$- $\varepsilon$turbulent model. Numerical calculation of a linear cascade is carried out to investigate effect of tip clearance on pitchwise variations of velocity Profiles. and static pressure distributions on the blade surface at spanwise positions. In case of evolution of tip vortex core location. tip vortex geometry and static pressure at the center of the tip vortex core compared with experimental results. Calculation results are agreed well with the experimental data, and validated. The static pressure losses by tip leakage flow at 2% tip clearance were more than those at 1% tip clearance.

CNTs Electric Field Enhancement of CIGS Solar Cells

  • 한성환
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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    • pp.67-67
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    • 2011
  • Compound semiconductor/CNTs composites have shown considerably improved efficiency improvement in photovoltaic devices, which is often attributed to two different factors. One is the formation of efficient electronic energy cascade structures. The other effect of CNTs on the performance of photovoltaic devices is the decrement of interfacial resistance. The interfacial resistances at n-type/ p-type materials and/or n-type materials/TCO electrode are reduced by an outstanding electrical property of CNTs. In addition to the effects of CNTs, we report the third reason for increment of efficiency in photovoltaic devices by CNT's well-known electrical field enhancement effects. The improved ${\beta}$ values in reverse-FE currents of CIGS electrode with SWNTs layers indicate the enhancement of electrical field in photovoltaic devices, which implies the acceleration of the electron transfer rate in the cell. Due to the formation of an efficient electronic energy cascade structure and the decrease of the interfacial resistance as well as the improvement of the electrical field in the photovoltaic devices, the power conversion efficiency of electrochemically deposited superstrate-type CIGS solar cells was increased 24.3% in the presence of SWNTs and showed 10.40% conversion efficiency.

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자유유동 난류강도가 터빈 동익 표면에서의 열(물질)전달 특성에 미치는 영향 (Free-Stream Turbulence Effect on the Heat (Mass) Transfer Characteristics on a Turbine Rotor Surface)

  • 이상우;박진재;권현구;박병규
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1442-1446
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    • 2004
  • The heat (mass) transfer characteristics on the blade surface of a first-stage turbine rotor cascade has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is employed for the measurements of the local heat (mass) transfer coefficient on the curved blade surface. The experiments are carried out for two free-stream turbulence intensities of 1.2% and 14.7%. The high free-stream turbulence results in more uniform distributions of heat load on the both pressure and suction surfaces and in an early boundary-layer separation on the suction surface. The heat (mass) transfer enhancement on the suction surface due to the endwall vortices is found to be relatively small under the high free-stream turbulence.

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박판형 고효율 터보홴의 공력학적 설계 (Aerodynamic Design of Slim and High-efficient Turbo-Fan)

  • 이명재;김남욱;박덕준;조인수;이승배
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회B
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    • pp.2600-2605
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    • 2008
  • Turbo-fans for a FFU unit should be aerodynamically designed to provide the FFU system with the given flow-rate at the lowest rotational-speed by considering the interaction effect with the FFU casing. In this study, slim and highly efficient turbo-fans are designed to satisfy the given performance at the specific speed by using the hybrid-stacking method of an inducer and a 2D-bladed turbo fan. The mean-line analysis, cascade theory, and CFD technique are all together applied to control the passage areas on the meridional plane from the inlet to the exit of the blade. Furthermore, the torque control algorithm is adopted to improve the performances within the constraints by the motor rpm-torque characteristics, and the resulting measured performances of mock-up fans are discussed.

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익단 누설 와류내의 레이놀즈 응력 분포 (Distribution of the Reynolds Stress Tensor inside Tip Leakage Vortex)

  • 이공희;박종일;백제현
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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    • pp.496-501
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    • 2003
  • Reynolds averaged Wavier-Stokes simulations based on the Reynolds stress model was performed to investigated the effect of inlet flow angle on the distributions of the Reynolds stress tensor inside tip leakage vortex of a linear compressor cascade. Two different inlet flow angles ${\beta}=29.3^{\circ}$(design condition) and $36.5^{\circ}$(off-design condition) were considered. Stress tensor analysis, which transforms the Reynolds stress into the principal direction, was applied to show an anisotropy of the normal stresses. Whereas the anisotropy was highest in the region where the tip leakage vortex collides the suction side of the blade and tip leakage flow enters between blade tip of the pressure side and the endwall, it had the lowest value at the center of tip leakage vortex. It was also found that the magnitude of maximum shear stress at design condition was greater than that of off-design condition.

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Co-60과 Cs-134의 연발감마선에 대한 방향 및 편극상관 측정 (Measurements of the Direction and Polarization Correlation for Cascade Gamma-rays of Co-60 and Cs-134)

  • Hyung-Ju Woo;Kie-Hyung Chung;Hae-Ill Bak
    • Nuclear Engineering and Technology
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    • 제14권2호
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    • pp.64-69
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    • 1982
  • 동시섬광분석기를 써서, 각도범위 90$^{\circ}$에서 180$^{\circ}$에 대하여, Co-60 및 Cs-134 감마선의 방향상관을 측정하였다. 그리고, 방향-편극상관의 측정에는 컴프턴산란효과를 응용한 감마선 편광분광기를 병용하였다. 이론적인 배경과 더불어 실험방법이 기술되었으며, 측정값이 이론적인 개산치와 일치함을 보이기위해 실험결과를 도식적으로 나타내었다.

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끝틈새가 선회각이 큰 터빈 동익 익렬 후류영역에서의 3차원유동 및 압력손실에 미치는 영향 (The Effect of Tip Clearance Height on the Three-Dimensional Flow and Aerodynamic Loss in the Wake Region of a High-Turning Turbine Rotor Cascade)

  • 권현구;박진재;이상우
    • 한국유체기계학회 논문집
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    • 제7권5호
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    • pp.36-42
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    • 2004
  • The effect of tip clearance height on the three-dimensional flow and aerodynamic loss in the wake region of a high-turning turbine rotor cascade has been investigated with a miniature cone-type five-hole probe. Distributions of velocity magnitude, secondary velocity vectors, and total-pressure loss coefficient are presented for three tip gap-to-span ratios of h/s = 0.0, 0.5 and 1.0 percent. The result shows that with the increment of h/s, tip leakage vortex tends to be intensified and aerodynamic loss due to the leakage vortex is increased as well. In the case of h/s = 1.0 percent, aerodynamic loss in the tip-leakage flow region is found dominant in comparison with that in the passage vortex region. With increasing h/s, mass-averaged secondary loss coefficient has a greater portion in the mass-averaged total-pressure loss coefficient.