• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.495-499
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• 2009

본 논문에서는 상호역회전 풍력발전기와 New Yaw System 실증시험에 대하여 제시한다. 상호역회전 풍력발전기는 공기의 유동을 가진 운동에너지의 공기역학적(aerodynamic) 특성을 이용하여 동일한 바람방향에 대해 상호 반대방향으로 회전하는 Front Blade와 Rear Blade를, Generator의 Rotor와 Stator에 각각 결합 형성한 것으로, Generator와 Dual Blade의 회전력이 원심력이 아닌 구심력으로 변환되어 무게중심이 균형을 이루게 한다. 이렇게 변환된 구심력은 회전구동부분의 편마모 현상, 소음발생 현상 및 불균형 톨크 발생 현상 감소효과가 공히 구현되도록 하여 풍력발전기의 구조적 안정성 및 발전효율 증대효과를 얻을 수 있도록 한 기술이다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.108-111
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• 2004

Structural dynamic characteristics and aeroelastic stability of a small-scale bearingless rotor system have been investigated. A flexbeam is one of the most important component of bearingless hub system. It must have sufficient torsional flexibility as well as baseline stiffness in order to produce feathering motion. In the present paper, a cross-shaped composite flexbeam has been proposed for a guarantee of torsional flexibility and flapwise and lagwise bending stiffness. One dimensional elastic beam model was used for the construction of a structural model. Equivalent isotropic sectional stiffness was used in the blade model, and the flexbeam was regarded as anisotropic; which has ten independent stiffness quantities. CAMRAD II has been used for the analysis of structural dynamic characteristics of the bearingless rotor system. Rotational natural frequencies and aeroelastic stability at hovering have been investigated. Analysis result shows that the cross-shaped flexbeam has the rotational natural frequency tuning capacity.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.119-122
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• 2003

This report describes the procedure of detailed design and structural test for the composite flexure which is a part of the hingeless hub system. First, stacking sequence design for composite flexure was done, and structural analysis by using NASTRAN was made to verify structural stability and safety. Using FPS installed at KIMM, composite flexure was laid up and cured using a autoclave. Before rotor ground test, the basic structural tests such as a bench test, tensile strength test and shear strength test, for flexure, were accomplished. Through replacing existing metal hub part with new fabricated composite flexure, improvement of aeroelastic stability and weight reduction were achieved. This result will be applied to composite rotor system design fur helicopter.

• Journal of Aerospace System Engineering
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• v.1 no.1
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• pp.73-78
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• 2007

Self-noise from the rotor blade of the UH-1H Helicopter is obtained numerically by using the Brooks' empirical noise model. All of the five noise sources are compared with each other in frequency domain. From the calculated results the bluntness noise reveals dominant noise sources at small angel of attack, whereas the separation noise shows main noise term with gradually increasing angel of attack. From the results of two different tip Mach numbers with the change of angel of attack, the OASPLs at M = 0.8 show about 15dB larger than those at M = 0.4.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.514-519
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• 2003

The aircraft engine is usually supported by rolling element bearings and has a small damping rate, which is vol y sensitive to external force. The high-performance requirement of the rotors leads to complex assembly designs and are more flexible. Squeeze film dampers (SFDs) are introduced to provide damping while crossing the critical speeds and stability to the rotor s :stem. Hence, the focus of the present investigation is on the decision of an optimal size of the flexible rotor system supported by the squeeze film dampers to minimize the maximum transmitted load and unbalance response over a range operating speeds. The enhanced genetic algorithm (EGA), which was developed by authors, is used in the optimization process. This algorithm is based on the synthesis of a modified genetic algorithm and simplex method. The results show significant benefits in using EGA when compared with nonlinear programming (NLP).

• Journal of Ocean Engineering and Technology
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• v.1 no.2
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• pp.83-92
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• 1987

Inorder ot estimate the running life of turbine rotors, fatigue crack propagation low, da/dN = C(${\DELTA}K)^m$, proposed by paris et al. has been widely applied. In this study, fatigue crack propagation rates for 16 samples of 1% Cr-Mo-V rotor steel were measured and statistical characteristics of m and C values in above equation were reviewed. The results are summarized as follows. 1. C and m follow a log-normal distribution and normal distribution, respectively. And the relation of C and shows a strong negative correlation. 2. Fatigue crack propagation equation can be expressed as da/dN=$4.11{\times}10^{-4}({\Delta}K/153.8)^m$, introducing the ralationship C=$C_oK_o^{-m}$. In this case, contribution of $C_o$ distribution to the distribution of log C shows very small compared to degrees of contribution by m.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.50-62
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• 2011

In this paper, analytical techniques for performance characteristics analysis of wind power generator with outer permanent magnet rotor are proposed. Furthermore, the proposed analytical techniques are validated by performance experiments of the manufactured generator. In this part, characteristic equations of losses such as copper loss, core loss are derived. Using the derived loss characteristic equations, electrical parameters obtained in [15] and d-q axes method, constant load and constant speed characteristics of wind power generator are analyzed. And then, to analyze performance of wind power system according to wind speed, d-q analysis model considering wind turbine characteristics is proposed. Finally, the obtained performance characteristics results are validated in comparison with those by experiments.

• Proceedings of the KSME Conference
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• 2004.04a
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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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.27-31
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• 1999

This paper covers starting characteristics and design of wound motor induction rmtor can used to double excited induction mootor. They are employing in many electrical equiprrent system of industrial field The stator is satre as that of conventional induction motor. But rotor was rewind with new style, as result both of starting torque and operating efficiency could be high, But starting current could be small. Could obtain the satre result as that of conventional induction rmtor with external resistance on the rotor. The structure could be simple, system cost could be low and the maintanence free, Because of no slip rings, no brushes and no external resistance.stance.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.11
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• pp.742-748
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• 2000

This paper presents a numerical method to analyze the electromechanical-coupled field in the spindle motor of a computer hard drive and investigates dynamic response due to the electromechanical excitation, i.e. unbalanced magnetic force and centrifugal force for the rotational asymmetric motor. Magnetic field is calculated from Maxwells equation and voltage equation by introducing nonlinear time-dependent finite element analysis. Mechanical motion of rotor is calculated by solving Newton-Euler equation. Electromechanical excitation and dynamic response are characterized by analyzing the free response of a rotating rotor and Fourier analysis of the excitation force and resulting vibration of a rotor. It shows that centrifugal force produces the unbalanced magnetic force even in the rotational symmetric motor. It also shows that resonance produces quite considerable vibration even when the high excitation frequency with small amplitude matches with the natural frequency of the spindle motor.