• 한국항공우주학회지
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• 제31권8호
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• pp.99-106
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• 2003

본 논문에서는 액체추진로켓용 터보펌프내 초음속 충동형 터빈의 공력성능 향상을 위해 기하학적 설계변수를 수치적으로 연구하였다. 터빈의 기하학적 설계변수는 아랫면, 윗면 원호반경, 입사각, 익단두께로 설정, 적절한 구속조건을 도입하였고 목적함수로는 최대파워를 채택하였다. 목적함수를 얻기 위해 2-D Navier-Stokes 방정식과 Chien의 k-$\varepsilon$ 난류 모델링을 수치적으로 계산하였다. 초기모델에서 이형 중앙부에 흐름박리를 볼 수 있었으나 개선된 익형에서 흐름박리는 제거되었다. 본 연구를 통해 약 3.2 %의 축 파워가 증대되었다.

• 항공우주기술
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• 제12권2호
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• pp.180-185
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• 2013

본 연구에서는 공기역학적 성능을 고려하여 인간의 힘만으로 이륙할 수 있는 초경량 인간동력 항공기의 개념설계를 수행하였다. 이를 위해 조종사를 포함한 항공기 전체 무게를 결정한 이후 적절한 익형을 선정하여 주날개/보조날개를 설계하였다. 설계된 비행기의 형상을 기초로 3차원 전산해석을 하였으며, 이를 통해 양력/항력 등의 성능계수 및 항공기 무게 중심(CG)에 대한 계산을 수행하였다. 그 결과 비행기의 양력 및 추력이 양력 및 추력의 제한 조건을 만족하였다. 또한 비행기의 무게 중심(CG)이 주익의 공력 중심(AC)에 위치함으로써 26%의 정적 안정성이 보장되었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.652-655
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• 2008

Despite of the laminar-turbulent transition region co-exist with fully turbulence region around the leading edge of an airfoil, still lots of researchers apply to fully turbulence models to predict aerodynamic characteristics. It is well known that fully turbulent model such as standard k-${\varepsilon}$ model couldn't predict the complex stall and the separation behavior on an airfoil accurately, it usually leads to over prediction of the aerodynamic characteristics such as lift and drag forces. So, we apply correlation based transition model to predict aerodynamic performance of the NREL (National Renewable Energy Laboratory) Phase IV wind turbine. And also, compare the computed results from transition model with experimental measurement and fully turbulence results. Results are presented for a range of wind speed, for a NREL Phase IV wind turbine rotor. Low speed shaft torque, power, root bending moment, aerodynamic coefficients of 2D airfoil and several flow field figures results included in this study. As a result, the low speed shaft torque predicted by transitional turbulence model is very good agree with the experimental measurement in whole operating conditions but fully turbulent model(k-${\varepsilon}$) over predict the shaft torque after 7m/s. Root bending moment is also good agreement between the prediction and experiments for most of the operating conditions, especially with the transition model.

• 동력기계공학회지
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• 제9권3호
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• pp.33-38
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• 2005

The aerodynamic performance of a cross-flow fan is strongly influenced by the various design factors of a rear-guider and a stabilizer. The purpose of this paper is to investigate the effects of a rear-guider and a stabilizer on the aerodynamic performance of a cross-flow fan. The design factors considered in this paper are a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle, respectively. This experiment was carried out with a constant revolution number of 700 rpm in a cross-flow fan installed in the fan tester. The static pressure, flowrate, torque, and revolution number were measured in this paper. Also, the pressure coefficient and the efficiency were analysed according to the various assembly conditions using a stabilizer setup angle, a stabilizer clearance, and a rear-guider clearance in the indoor room air-conditioner.

• Advances in aircraft and spacecraft science
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• 제8권4호
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• pp.303-330
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• 2021

The paper discusses the effect of the winglets on the aerodynamic and aeroacoustic performance of Boeing 737-800 aircraft by numerical approach. For this purpose, computational fluid dynamics and fluent commercial software are used to solve the compressible flow governing equations. The RANS method and the K-ω SST turbulence model are selected to simulate the subsonic flow around the wing with acceptable accuracy and low computational cost. The main variables of steady flow around the simple and blended wing in constant atmospheric conditions are computed by numerical solution of governing equations. The solution of the acoustic field has also been accomplished by the broad-band acoustic source model. The results reveal that adding a blended winglet increases the pressure difference near the wingtip,which increases the lift force. Also, the blended winglet reduces the power and magnitude of vorticities around the wingtip, which reduces the wing's drag force. The effects of winglets on aerodynamic forces lead to a 3.8% increase in flight range and a 3.6% increase in the maximum payload of the aircraft. Also, the acoustic power level variables on the surfaces and fields around the wing have been investigated integrally and locally.

• 항공우주시스템공학회지
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• 제17권6호
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• pp.94-99
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• 2023

최근 신재생에너지는 주로 사용되는 화석연료의 부족과 환경문제로 풍력에너지와 태양에너지 자원으로 널리 사용되고 있다. 이런 상황에서 풍력에너지는 중요한 에너지원으로 떠오르고 있으며, 풍력 발전 시장은 전 세계적으로 급격한 성장을 보여주고 있다. 본 연구에서는 분리형 블레이드의 선행연구를 위해 일체형 블레이드 공력 설계로 고효율 풍력 터빈 블레이드를 설계를 수행하였다. 블레이드 에어포일은 NACA 4418로 적용하였고, 설계된 블레이드를 평가하기 위해 해석 결과와 비교하여 검증하였다.

• 한국유체기계학회 논문집
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• 제19권6호
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• pp.5-13
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• 2016

Three-dimensional unsteady numerical analysis has been performed to observe aerodynamic characteristics of a H-rotor. Generally, the structure of the H-rotor is simple but the aerodynamic characteristics are exceptionably complicated since the angle of attacks and incident velocities to a blade are considerably varied according to the azimuth angles and solidities. The blade in the upwind revolution between 0 to 180 degree obtains aerodynamic energy from the free stream but the blade in the downwind revolution between 180 to 360 degree does not. When the rotating speed increases, the blade in the downwind revolution accelerates the air around the blade like a fan and it consumes the energy and shows negative torque in the area. On the other hand, the direction of the free stream is bent because of the interaction between blade the free stream. Therefore, the operation point (highest power coefficient) appears at a lower tip-speed-ratio what it is expected.

• 한국추진공학회지
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• 제3권3호
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• pp.40-46
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• 1999

풍력발전용 회전날개의 공력성능과 시동특성은 정격출력 및 운용방법 등의 전체적인 시스템 성능을 결정짓는 중요한 요소이다. 따라서, 풍력발전용 회전날개를 설계한 경우 공력성능과 풍속 및 깃각에 따른 시동특성은 반드시 검토되어야 한다. 이를 위해 본 연구에서는 수평축 풍력발전용으로 개발된 회전날개의 공력성능을 해석하기 위한 프로그램을 개발하였으며, 타당성 검증을 위해 상용화 되어있는 회전날개의 공력성능해석을 수행한 결과 회사측에서 제시한 실험치와 잘 일치함을 확인하였다. 또한 개발된 공력 해석 프로그램을 바탕으로 시동특성 해석 프로그램을 개발하여 분석한 결과 우리나라와 같이 저풍속에서 운용되는 풍력발전기에는 가변깃각 제어방식이 유리함을 확인하였다.

• International Journal of Aeronautical and Space Sciences
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• 제17권2호
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• pp.157-166
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• 2016

Aerodynamic loads for a horizontal axis wind turbine of the National Renewable Energy Laboratory (NREL) Phase VI rotor in yawed condition were predicted by using the blade element momentum theorem. The classical blade element momentum theorem was complemented by several aerodynamic corrections and models including the Pitt and Peters' yaw correction, Buhl's wake correction, Prandtl's tip loss model, Du and Selig's three-dimensional (3-D) stall delay model, etc. Changes of the aerodynamic loads according to the azimuth angle acting on the span-wise location of the NREL Phase VI blade were compared with the experimental data with various yaw angles and inflow speeds. The computational flow chart for the classical blade element momentum theorem was adequately modified to accurately calculate the combined functions of additional corrections and models stated above. A successive under-relaxation technique was developed and applied to prevent possible failure during the iteration process. Changes of the angle of attack according to the azimuth angle at the specified radial location of the blade were also obtained. The proposed numerical procedure was verified, and the predicted data of aerodynamic loads for the NREL Phase VI rotor bears an extremely close resemblance to those of the experimental data.

• 한국태양에너지학회 논문집
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• 제33권1호
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• pp.40-47
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• 2013

An aerodynamic design tool was developed for small wind turbine blades based on the blade element momentum theory. The lift and drag coefficients of blades that are needed for aerodynamic blade design were obtained in real time from the Xfoil program developed at University of Illinois. While running, the developed tool automatically accesses the Xfoil program, runs it with proper aerodynamic and airfoil properties, and finally obtains lift and drag coefficients. The obtained aerodynamic coefficients are then used to find out optimal twist angles and chord lengths of the airfoils. The developed tool was used to design a wind turbine blade using low Reynolds number airfoils, SG6040 and SG6043 to have its maximum power coefficient at a specified tip speed ratio. The performance of the blade was verified by a commercial code well known for its prediction accuracies.