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최재호(J. H. Choi),이진수(J. S. Lee),조현준(H. J. Cho),이성준(S. J. Lee),전승배(S. B. Chen),차봉준(B. J. Cha) 한국유체기계학회 2008 유체기계 연구개발 발표회 논문집 Vol.2008 No.-
This paper presents an aerodynamic design, flow analysis and performance test of a transonic centrifugal compressor for APU applications. The compressor is made up of a centrifugal impeller, a wedge diffuser and a des wirier. The impeller and diffuser for this kind of application should be developed to meet air-bleeding requirement and shaft power extraction requirements, that is, very wide operational range. Aerodynamic design for this purpose is performed and three-dimensional numerical analysis with Reynolds-averaged Navier-Stokes solver is performed to analyze the flows in the impeller, diffuser and deswirler considering the impeller tip clearance. Test module and Jig facilities for the compressor stage performance test are developed. The overall compressor stage performances measured at the test Jig are compared with aerodynamic design results.
Rear-spoiler를 이용한 자동차의 항력감소에 관한 실험적 연구
최재호(J. H. Choi),이상준(S. J. Lee) 한국자동차공학회 1996 한국 자동차공학회논문집 Vol.4 No.3
The effect of rear-spoiler attached at rear end of automobile trunk on the aerodynamic charac-teristics of a MIRA reference car model was experimentally investigated. For different shapes and positions(G/H) of the rear-spoiler, the aerodynamic forces on the automobile were measured at various flow speed(Re?).The effect of rear-spoiler on the wake structure behind the automobile was also investigated using flow visualization and hot-wire anemometer. The rear-spoiler modifies the near wake structure and decreases aerodynamic drag and increases driving stability compared with those of the conventional automobile without rear-spoiler. From the experimental results, rear-spoiler of airfoil shape installed at the position of G/H=0.084 shows the best aerodynamic performance.<br/>
최재호(J.H.Choi),김광용(K.Y.Kim),지명석(M.S.Jie) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_1
A numerical optimization process using a three-dimensional Naveer-Stokes solver has been developed to design a low noise automotive cooling fan. The conjugate gradient method is used to look for the search direction and the golden section method is used for the one dimensional search. Three variables concerned to stagger angle and sweep angle are chosen as design variables. To satisfy the constraints. exterior penalty functions ars employed. The final shape has been obtained after fifth changes of shape function in the present optimization using the object function defined as a ratio of production rate of turbulent kinetic energy to pressure head.<br/>
직류전송을 위한 CIGRE benchmark 모델의 재구성
왕효진(H.J.Wang),최재호(J.H.Choi),김찬기(C.K.Kim) 전력전자학회 2003 전력전자학술대회 논문집 Vol.2003 No.7(1)
This paper makes more stronger than original model about sending station fault and saves total construction cost to replace established six-pulse bridge by each six thyristor for DC-transmission. Also, varying of controller for sending station has a robust characteristics for harmonics and unbalanced faults. This paper is verified by simulation using EMTDC program. Comparing with the results of original model, This paper is proved superiority.
초고속 플라이휠 에너지 저장시스템을 이용한 Off-line UPS 제작
정환명(H. M. Jeoung),최재호(J. H. Choi) 전력전자학회 2000 전력전자학술대회 논문집 Vol.2000 No.11
This paper presents a designing for the Off-line UPS using 5MB Flywheel Energy Storage System. This described flywheel energy storage system is designed to replace of the conventional EMB(Electro Mechanical Battery) system. To realize the high efficiency and to minimize the torque ripple, the waveform of the inverter output current is controlled to be sinusoidal. The actual performance of the Off-line UPS using flywheel energy storage system is described. The prototype device was manufactured. The experimental result has good characteristics at a time of power transition region and regeneration modes
전원전압의 불평형 및 왜곡에 강인한 3상 4선식 전력용 능동 필터의 설계
민준기(J.K. Min),최재호(J.H. Choi),김효성(H.S. Kim),김경환(K.H. Kim) 전력전자학회 2003 전력전자학술대회 논문집 Vol.2003 No.7(2)
Tins paper proposed a novel current control strategy on active power filters using p-q-r instantaneous power theory which can compensate the line current harmonics and the neutral line current in unbalanced and/or distorted source conditions m three-phase four-wire systems. The proposed current control method is based on a sinusoidal PWM for fully-digital implementation which was compared with a hysteresis PWM. Simulation results showed good performance of the proposed current control strategy on shunt type APFs<br/>
이진목(J.M.Lee),김홍균(H.G.Kim),최재호(J.H.Choi),이상훈(S.H.Lee) 전력전자학회 2003 전력전자학술대회 논문집 Vol.2003 No.7(1)
Need of power stability, reliability IS Increased, as using of sensitive, nonlinear load are increasing. Therefore, Power Quality Problems become the center of public Interest Many kinds of algorithms have been studied for monitoring of Power Quality Problems. Monitoring algorithms of using RMS, FT and the others are easy to applicate to system But, It IS not enough to monitor all of Power Quality problems Wavelet Transform is more proper to applicate. so, This paper presents measurement system using discrete wavelet transform