• Title/Summary/Keyword: Leading Edge

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Cause of Cavitation Instabilities in Three Dimensional Inducer

  • Kang, Dong-Hyuk;Yonezawa, Koichi;Horiguchi, Hironori;Kawata, Yutaka;Tsujimoto, Yoshinobu
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.3
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    • pp.206-214
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    • 2009
  • Alternate blade cavitation, rotating cavitation and cavitation surge in rocket turbopump inducers were simulated by a three dimensional commercial CFD code. In order to clarify the cause of cavitation instabilities, the velocity disturbance caused by cavitation was obtained by subtracting the velocity vector under non-cavitating condition from that under cavitating condition. It was found that there exists a disturbance flow towards the trailing edge of the tip cavity. This flow has an axial flow component towards downstream which reduces the incidence angle to the next blade. It was found that all of the cavitation instabilities start to occur when this flow starts to interact with the leading edge of the next blade. The existence of the disturbance flow was validated by experiments.

High-Efficiency Design of Axial Flow Fan through Shape Optimization of Airfoil (익형의 형상최적화를 통한 고효율 축류송풍기 설계)

  • Lee, Ki-Sang;Kim, Kwang-Yong;Choi, Jae-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.11 no.2
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    • pp.46-54
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    • 2008
  • This study presents a numerical optimization to optimize an axial flow fan blade to increase the efficiency. The radial basis neural network is used as an optimization method with the numerical analysis by Reynolds-averaged Navier-Stokes equations using SST model as turbulence closure. Four design variables related to airfoil maximum camber, maximum camber location, leading edge radius and trailing edge radius, respectively, are selected, and efficiency is considered as objective function which is to be maximized. Thirty designs are evaluated to get the objective function values of each design used to train the neural network. Optimum shape shows the efficiency increased by 1.0%.

A Study on the Ultraprecision Cutting of Aluminium Alloy by the Diamond Tool (Diamond 공구에 의한 aluminium 합금의 초정밀 절삭가공에 관한 연구)

  • Yu, Ki-Hyun;Mun, Sang-Don;Yu, Jong-Sun;Kim, Tae-Young;Seo, Nam-Seob
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.1
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    • pp.78-83
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    • 1996
  • This paper presents the characteristics of surface roughness and cutting force in ultraprecision cutting of aluminium alloy using natural diamond tools whose edge radii are smaller than those of tools made of other materials. The feed rate and depth of engagement were set to be a micrometer order. After measuring the surface roughness of machined surface and cutting force for each cutting condition, the relations between the surface quality and its condition were investigated qualitatively. If the feed rate was under a certain limit, the machined surface quality was deteriorated unexpectedly. This is supposed to have happened due to vibration leading its condition to abnormal one. In a certain situation the machined surface roughness by a natural diamond tool was inferior to that made by a carbide tool whose cutting edge radius is larger. This is supposed to be caused by not normal machining but burnishing effect.

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Proof Test of a 750kW Wind Turbine Blade (750kW 로터 블레이드 인증시험)

  • Kim, Myoung-Jin;Sung, Dae-Young;Park, Byoung-Jun
    • 한국신재생에너지학회:학술대회논문집
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    • 2008.10a
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    • pp.328-331
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    • 2008
  • For the purpose of verifying the calculation, the rotor blade shall be subjected to test for the natural frequencies and the static loading within the scope of the assessment. This paper presents a full scale static test procedure of the rotor blade for certification by GL. This blade model is manes as KM24 designed for IEC type IA. The test and calculation values are all most similar. Also there is not founded any marks of cracks or buckling at the shell, and bonding area is T/E, L/E and shear web. Therefore, the test is successful and the rotor blade is satisfied the safety requirement at the maximum design load.

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Aeroelastic Stability Analysis of Composite Bearingless Rotor Blades in Hover (복합재 무베어링 로우터 블레이드의 정지 비행시 공력탄성학적 안정성 해석)

  • Lim In-Gyu;Choi Ji-Hoon;Lee In;Han Jae-Hung
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.04a
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    • pp.83-86
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    • 2004
  • The aeroelastic stability analysis of composite bearingless rotors is investigated using a large deflection beam theory in hover. The bearingless rotor configuration consists of a single flexbeam with a wrap-around type torque tube and the pitch links located at the leading edge and trailing edge of the torque tube root. For the analysis of composite bearingless rotors, flexbeam is assumed to be a rectangular section made of laminate. Two-dimensional quasi-steady strip theory and Loewy's aerodynamic theory with the lift deficiency function are used for unsteady aerodynamic computation. The finite element equations of motion for beams are obtained using Hamilton's principle. Numerical results of selected bearingless rotor configurations are obtained for the lay-up of laminae in the flexbeam and pitch links location.

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Influence of Flow Conditions on a Boundary Layer to the Near-Wake of a Flat Plat (평판 경계층 유동조건이 근접후류에 미치는 영향)

  • Kim, D.H.;Chang, J.W.
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1625-1630
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    • 2004
  • An experimental study was carried out to investigate influence of flow conditions on a boundary layer to the near-wake of a flat plate. The flow condition in the vicinity of trailing edge that is influenced by upstream condition history is an essential factor that determines the physical characteristics of a near-wake. Various tripping wires were used to change boundary layer flow condition of upstream at the freestream velocity of 6.0 m/sec. Measurements of the boundary layer and near-wake according to the change of upstream conditions were conducted by using both I-probe(55P14 for boundary layer) and X-probe(55P61 for wake). Normalized velocity profiles of the boundary layer were shown the flow types such as laminar boundary layer, transition, and turbulent boundary layer at 0.95C from the leading edge. The velocity and turbulence intensity profiles of the near-wake for the case of laminar boundary layer at the flat plate surface exhibited a defect and a double peak showing perfect symmetry, respectively.

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Experimental Study on a Rectangular Variable Intake for Space Planes

  • Kojima, T.;Taguchi, H.;Okai, K.;Futamura, H.;Maru, Y.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.649-656
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    • 2004
  • Hypersonic wind tunnel test of the rectangular variable geometry intake is performed. For realization of a Precooled turbojet engine, development of a hypersonic ramjet engine is planned. To investigate performance of the intake of the hypersonic ramjet engine, wind tunnel test is done with freestream Mach number of 5.1. The total pressure recovery was 18 % with 12.9 % of ramp bleed. Several reasons for low total pressure recovery are shown. Supersonic internal compression is not enough. Then, the throat Mach number is high (M2.61) and total pressure losses at the terminal shock is large. Supersonic flow at the throat and position of the terminal shock is sensitive to a difference of the second ramp's throat height and the third ramp's throat height. Flow separations at the second ramp's trailing edge and the third ramp's leading edge are seen those could result in the trigger of unstart. The seal mechanism between the ramps and the sidewalls is important.

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Numerical Analysis of a Tip Leakage Vortex in an Axial Flow Fan (축류홴 익단누설와류의 수치적 해석)

  • Jang, Choon-Man;Kim, Kwang-Yong
    • 유체기계공업학회:학술대회논문집
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    • 2003.12a
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    • pp.404-411
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    • 2003
  • Three-dimensional vortical flow and separated flow topology near the casing wall in an axial flow fan having two different tip clearances have been investigated by a Reynolds-averaged Wavier-Stokes (RANS) flow simulation. The simulation shows that the tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction. On the casing wall, a separation line is formed upstream of the leakage vortex center due to the interference between the leakage vortex and main flow. The reverse flow is observed between the separation line and the attachment line generated downstream of the trailing edge, and increased with enlarging tip clearance. The patterns of a leakage velocity vector including a leakage flow rate are also analyzed according to two tip clearances. It is noted that the understanding of the distribution of a limiting streamline on the casing wall is very important to grasp the characteristics of the vortical flow in the axial flow fan.

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On the Development Strategy of the Container Port coping with the Innovation Process of Logistics (로지스틱스의 진화에 대응한 항만의 발전 전략에 관하여(1))

  • 이철영;여기태;김현
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 1999.10a
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    • pp.43-57
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    • 1999
  • Recently, leading edge companies use the Supply Chain Management as a competitive weapon to secure and maintain customer loyalty. As a consequence, they are concentrating resources on the company's core business and employing strategic alliances with third-party providers to ensure the company provides its customers' desired logistics service levels at acceptable costs. Under this circumstances, this paper surveys the third party logistics as a loading edge logistics industry coping with the progress of the supply chain management. The status and the type of the TPL including the Forwarder are analyzed in the view point of global logistics. Also, the development strategy of third party logistics in the future is suggested.