• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.95-106
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• 2016

A method of optimization design for the blade profile of a centrifugal impeller by controlling velocity distribution is presented, and a plenum fan is successfully designed. This method is based on the inner flow calculation inside the centrifugal impeller, and is related to the distribution of relative velocity. The results show that after optimization, the boundary layer separation on the suction surface has been inhibited and the stability of plenum fan is improved. The flow at the impeller outlet is also studied, and the jet-wake pattern at the impeller outlet is improved obviously by optimization. The calculation result shows that the static pressure and static pressure efficiency can be increased by 15.4% and 21.4% respectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.428-433
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• 2000

The characteristics of unsteady heat transfer and boundary layer flow in the SSME turbine rotor passage are investigated with LRN $k-{\varepsilon}$ turbulence model. The unsteady flow and heat transfer in a rotor blade passage as a result of wake/blade interaction is modeled by the inviscid/boundary-layer flow approach. The relevant governing equations are discretized to a system of finite different equations by means of a BTBCS implicit method. These equations have been solved numerically, for the velocity and temperature fields using TDMA method. Heat flux on the blade surface and flow parameters in the rotor passage are calculated with wake interaction. Numerical results show that velocity, pressure, turbulent kinetic energy and heat flux on the blade surface are varied periodically by wake passing.

• 한국소음진동공학회논문집
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• 제14권6호
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• pp.486-494
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• 2004

This paper addresses the dynamic modeling and closed-loop eigenvibration analysis of composite rotating pretwisted fan blade modeled as non-uniform thin-walled beam with bi-convex cross-section fixed at the certain presetting angle and incorporating piezoelectric induced damping capabilities. The blade model incorporates non-classical features such as transverse shear, rotary inertia and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration of the blade are highlighted.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1696-1701
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• 2003

This paper deals with a vibration control analysis of a rotating composite blade, modeled as a tapered thinwalled beam induced by heat flux. The displayed results reveal that the thermally induced vibration yields a detrimental repercussions upon their dynamic responses. The blade consists of host graphite epoxy laminate with surface and spanwise distributed transversely isotropic (PZT-4) sensors and actuators. The controller is implemented via the negative velocity and displacement feedback control methodology, which prove to overcome the deleterious effect associated with the thermally induced vibration. The structure is modeled as a composite thin-walled beam incorporating a number of nonclassical features such as transverse shear, secondary warping, anisotropy of constituent materials, and rotary inertias.

• 대한조선학회논문집
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• 제28권2호
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• pp.69-76
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• 1991

포텐셜 유동에서 규정된 속도 분포에 대한 2차원 날개 단면을 설계하는 방법을 제시하며 날개 표면에는 보오텍스를 분포시켰다. 보오텍스 분포를 결정하는데 사용한 경계조건은 날개 표면에서 유체유동이 유선이라는 것이다. 최종 2차원 요구 단면을 얻기위하여 반복 계산법을 채택하였고 개발된 program으로 설계한 몇가지 수치해를 나타내었다.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1401-1417
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• 2004

Experimental and computational studies were performed to determine the effects of different blade designs on a flow pattern inside a double-spindle counter rotating mower deck. In the experimental study, two different blade models were tested by measuring air velocities using a forward-scatter LDV system. The velocity measurements were taken at several different azimuth and axial sections inside the deck. The measured velocity distributions clarified the air flow pattern caused by the rotating blades and demonstrated the effects of deck and blade designs. A high-speed video camera and a sound level meter were used for flow visualization and noise level measurement. In the computational works, two-dimensional blade shapes at several arbitrary radial sections have been selected for flow computations around the blade model. For three-dimensional computation applied a non-inertia coordinate system, a flow field around the entire three-dimensional blade shape is used to evaluate flow patterns in order to take radial flow interactions into account. The computational results were compared with the experimental results.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2183-2195
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• 2020

A mathematical model for the flowrate and rotation speed of RCP during idling was established. The numerical calculation method and dimensionless method were used to analyze the flow, head, torque and pressure and speed changes under idle conditions. Regularity, using the Q criterion vortex identification judgment method combined with surface flow spectrum morphology analysis to diagnose the vortex dynamic characteristics on RCP blade. On impeller blade, there is two oscillations in the pressure ratio on pressure surface in blade outlet region. The velocity on the suction surface is two times more oscillating than the inlet of blade, and there is an intersection with the velocity ratio curve on pressure surface. On blade of guide vane, the pressure ratio increases along the inlet to outlet direction, and the speed ratio decreases with the increase of idle time. There is a vortex that rotates counterclockwise on the suction surface, and the streamline on the suction surface of blade is subjected to the entrainment and blocking action of the vortex creates a large reverse flow in the main flow region. There are two vortices at the outlet of guide vane suction side and the vortices are in opposite directions.

• 한국해안·해양공학회논문집
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• 제31권5호
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• pp.314-319
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• 2019

초기 유속과 블레이드의 회전수에 따라 변화하는 쉬라우드 시스템 내 유속 변화와 블레이드의 효율 특성을 분석을 위해 수치해석 방법을 이용한 연구를 수행했다. 해석 조건으로 0.35 m/s에서 1.0 m/s까지 초기 유속 변화와 50 rpm부터 300 rpm까지 블레이드의 회전수를 변화시키며 기계적 효율을 추정했다. 유속 변화는 유입부 대비 중심부에서 모든 경우 약 1.8배 이상 증가하는 경향을 보였으며, 초기 유속 0.5 m/s 대비 0.75 m/s에서 유속 변화율이 감소했다. 또한 블레이드의 토크를 이용한 기계적 효율 역시 0.5 m/s의 경우 가장 높은 효율을 보였으며, 모든 경우 유사한 경향성을 보였다. 한편 최대 효율은 초기 유속 0.5 m/s인 경우 TSR 4.77에서 약 20.88%로 산정됐다. 본 연구에서 수행한 블레이드의 기계적 효율 분석은 수리모형실험에 필요한 기초적 자료를 제시할 수 있을 것으로 기대된다.

• 한국가시화정보학회지
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• 제18권2호
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• pp.59-65
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• 2020

Vertical axis wind energy systems including 3 and 4 blades are numerically investigated in a two-dimensional (2D) computational domain. The power coefficient (C_p) is adopted to measure the efficiency of the system and the effect of the rotating velocity on the power coefficient is analyzed for the two different systems. The rotating velocity varies from 30 rad/s to 90 rad/s, which corresponds to the tip speed ratio (T.S.R) of 0.5 to 1.5. The torque exerted on the blades is mainly determined by the aerodynamic force in the x-direction and maximized when the blade is positioned at around θ = 186°. The efficiency of the 4-blade system is higher than that of the 3-blade system within the tip speed ratio range between 0.5 and 0.67, besides where the 3-blade system shows a better performance. For the 3-blade system, the maximum efficiency is reached to 0.082 at the tip speed ratio of 1.083. The maximum efficiency of the 4-blade system is 0.071 at T.S.R. = 0.92. The velocity fields in the x-direction, pressure fields, and the vorticity magnitude are analyzed in detail for the optimal cases of the 3- and 4-blades systems, respectively.

• 한국산학기술학회논문지
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• 제19권12호
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• pp.54-61
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• 2018

자동차의 엔진에서 불완전 연소는 유해 배기가스 생성의 주요 원인이다. 따라서 본 연구에서는 자동차 엔진에서 불완전 연소를 방지하고 배출되는 배기가스의 양을 줄이기 위하여 흡기 매니폴드에 가스켓 블레이드를 적용하여 유입되는 공기의 유속 증가에 따른 배기가스의 변화를 해석과 실험을 통하여 고찰하였다. 먼저 3D 유동 해석 프로그램을 사용하여 가스켓 블레이드의 개수와 각도에 따른 유동 해석을 수행하였으며, 해석 결과 가스켓 블레이드를 적용한 흡기 매니폴드 출구에서 공기의 평균 유속은 블레이드 개수가 6개와 $30^{\circ}$각도에서 가장 좋게 나타났다. 해석 결과를 기반으로 무부하 엔진 시뮬레이션 시스템에서 가스켓 블레이드가 배기가스에 미치는 영향을 확인하기 위하여 실험을 진행하였으며 엔진 회전수가 2000 rpm에서 4000 rpm으로 증가함에 따라 배기가스인 HC, CO, NOx는 평균적으로 각각 23.4%, 16.5%, 3.8% 감소하였으며 배기가스의 배출량 감소 효과는 점점 줄어드는 것으로 나타났다.