• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.43-46
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• 2008

Quad-Rotor, which consists of four blades, performs a flight task by controling each rotation speed of the four blades. Quad-Rotor blade making no use of cyclic pitch or collective one is a type of fixed-wing as different from helicopter blade. Although, Quad-Rotor is simple and easy to control for those reasons, blade configuration of the fixed wing is one of the critical factors in determining the performance of Quad-Rotor. In the present study, coefficients for thrust and power of Quad-Rotor blade were derived from the data acquired by using 6-component balances. Firstly, Measurements for aerodynamic force were conducted at various pitch angles (i.e., from 0$^{\circ}$ to 90$^{\circ}$ with the interval of 10$^{\circ}$). The blade used in this experiment has aspect ratio of 6 and chord length of 35.5 mm. Secondly, assembled-blade, which was an integral blade but divided into many pieces, was used in order to test aerodynamic forces along twist angles. The curve of thrust coefficient along pitch angle indicates a parabola form. Stall which occurs during wind tunnel test to calculate lift coefficient of airfoil does not generate. When deciding the blade twist angle, structural stability of blade should be considered together with coefficients of thrust and power. Those aerodynamic force data based on experimental study will be provided as a firm basis for the design of brand-new Quad-Rotor blade.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권1호
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• pp.78-83
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• 2005

Currently in Japan, the use of the small wind turbine is an upward trend. There are already many well established small wind turbine generators in use and their various failures have been reported. The most commonly sighted failure is blade damage. Thus the research purpose was set to develop a simple failure diagnostic system, where an Acoustic Emission (AE) signal was produced from the failure part of a blade which was measured by AE sensor. The failure diagnostic technique was thoroughly examined. Concurrently, the damage part of the blade was imitated, the AE signal was measured, and a FFT(Fast Fourier Transform) analysis was carried out, and was compared with the output characteristic. When one sheet of a blade was damaged 40mm or more, the level was computed at which failure could be diagnosed.

• Ocean Systems Engineering
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• 제5권3호
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• pp.221-243
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• 2015

This paper compares simplified and finite element method (FEM) models for tower and blade in dynamic coupled analysis of floating wind turbine. A SPAR type wind turbine with catenary mooring lines is considered in numerical analysis. Floating body equation is derived using boundary element method (BEM) and convolution. Equations for mooring line, tower and blade are formulated with theories of catenary, elastic beam and aerodynamic rotating beam, respectively and FEM is applied in the formulation. By combining the equations, coupled solutions are calculated. Tower or blade may be assumed rigid or lumped body for simplicity in modeling. By comparing floating body motions, mooring line tensions and tower stresses with the simple model and original FEM model, the effect of including or neglecting elastic, rotating and aerodynamic behavior of tower and blade is discussed.

• 대한기계학회논문집B
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• 제21권7호
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• pp.911-918
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• 1997

The turbulent viscous wake flows behind a single airfoil, two-dimensional stationary blade row and three-dimensional rotating blade row were calculated, and the numerical results were compared with experimental ones. The numerical technique was based on the SIMPLE algorithm using three turbulent closure models, standard k-.epsilon. model(WFM), low Reynolds number k-.epsilon. model(LRN) and Reynolds stress model (RSM). In the case of a single airfoil, WFM, LRN and RSM presented fairly good velocity distributions in the wake compared with experimental data. In the case of the stationary blade row, LRN and RSM presented better results than WFM for wake velocity distribution, and especially LRN showed best results among these three turbulent models. In the case of the rotating blade row, WFM and LRN showed fairly good agreement with experimental data of the three-dimensional velocity component distributions in the range from hub to mid span region. LRN was also superior to WFM in accuracy of prediction for the wake velocity distribution as same with the cases of a airfoil and the stationary blade row.

• 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.

• 전기학회논문지
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• 제59권10호
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• pp.1862-1868
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• 2010

A corona motor, as one of a powerful cooling means of microelectronic devices, has been employed because of its very simple structure of no coils and no brushes. In this paper, the effect of polarity of applied voltage and the number of blade corona electrodes on the fundamental properties of rotation of the motor was investigated. The I-V and rotation characteristics of the blade corona electrode were significantly different from the different polarities of applied voltages and the blade corona electrode numbers, due to the different space charge effect resulted by the different migration mobility of the positive and negative ions generated near the blade corona electrode tip of the rotor of the motor. The rotation speed of the motor was influenced significantly by the polarity of corona discharge, the number of blades, and mass of rotor. At the same corona current, an effective rotation can be obtained with the positive corona caused by the lower ion mobility. On the other hand, the higher rotation speed can be obtained with the negative corona resulted from its higher corona current. The highest rotation speed and energy efficiency can be obtained with the rotor having 4 blades.

• International Journal of Fluid Machinery and Systems
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• 제4권4호
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• pp.396-409
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• 2011

Water turbines have been used in electricity generation for well over a century. Hydroelectricity now supplies 19% of world electricity. Many hydro power plants are operated with Pelton turbines, which is an impulse turbine. The main reasons for using impulse turbines are that they are very simple and relatively cheap. As the stream flow varies, water flow to the turbine can be easily controlled by changing the number of nozzles or by using adjustable nozzles. Scientific investigation and design of turbines saw rapid advancement during last century. Most of the research that had been done on turbines were focused on improving the performance with particular reference to turbine components such as shaft seals, speed increasers and bearings. There is not much information available on effects of blade friction on the performance of turbine. The main focus in this paper is to analyze the performance of Pelton turbine particularly with respect to their blade friction.

• 한국항공우주학회지
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• 제36권12호
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• pp.1139-1145
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• 2008

로터 블레이드의 구조변형을 포함한, 제자리 비행하는 로터 블레이드의 공력해석을 수행하였다. 와류포획능력을 향상시킨 전산유체 코드와 간단한 오일러-베르누이 보 모델에 기반을 둔 구조역학 방정식을 결합시켜 회전익 유동에 대한 연계 계산을 수행하였으며 계산결과 타당한 로터블레이드 구조변형 및 공력특성을 얻었다.

• 한국소음진동공학회논문집
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• 제15권4호
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• pp.429-436
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• 2005

터보기계에서 mistuning은 구조적, 기하학적인 측면에서의 blade와 blade 사이의 미소한 특성차이를 의미하며, blade의 제작과정이나 운전 중 발생하는 마모의 차이에 의해 발생한다고 알려져 있다. Blade사이에서 발생하는 이러한 미소한 차이가 강제 진동 시 아주 큰 국부진동을 야기 시킬 수 있다는 사실이 여러 논문들에 의해 확인되었다. 최근에는 조화패턴의 intentional mistuning 배열을 사용하여 제작 및 사용 중에 발생하는 unintentional mistuning에 의한 blade의 강제진동 응답을 줄일 수 있다는 연구가 발표되었다. 따라서 본 논문에서는 두 가지 형태의 blade(A와 B)를 사용하고, blade감쇠와 coupling 효과를 고려하여 bladed disk의 강제진동응답을 줄일 수 있는 intentional mistuning의 최적배열패턴을 인공지능 알고리즘의 하나인 유전알고리즘과 steepest descent법을 이용하여 구하고자 한다. 그리고 단순 bladed disk와 17-bladed로 된 산업체 로터의 수치예제를 통하여 intentional mistuning 된 bladed disk의 이점을 증명하려고 한다.

• International Journal of Aeronautical and Space Sciences
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• 제12권4호
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• pp.346-353
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• 2011

In this study, the structural performance tests, i.e., static tests and dynamic tests of the composite wind turbine blade, were carried out by using the embedded fiber Bragg grating (FBG) sensors. The composite wind turbine blade used in the test is the 1/23 scale of the 750 kW composite blade. In static tests, the deflections along the blade were evaluated. Evaluations were carried out with simple beam theory and quadratic fitting method by using the embedded FBG sensors to predict the structural behavior with respect to the load. The deflections were compared to those obtained from the laser displacement sensor and electric strain gauges. They showed good agreement. Modal tests were performed to investigate the dynamic characteristics using the embedded FBG sensors. The natural frequencies obtained from the FBG sensors corresponding to the nine mode shapes of the blade were compared to those from the laser Doppler vibrometer. They were found to be consistent with each other. Therefore, it is concluded that the embedded FBG sensors have a great capability for measuring the structural performances of the composite wind turbine blade when structural performance tests are carried out.