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미래 풍력발전산업의 집적지육성을 위한 녹산클러스터 발전방향
임희창,한규택,장광호,진성호,김용환,Lim, Hee-Chang,Han, Gyu-Taek,Jang, Gwang-Ho,Jin, Seong-Ho,Kim, Yong-Hwan 산업클러스터학회 2009 산업클러스터 Vol.3 No.1
현재 풍력에너지는 세계적으로 가장 급격하게 관심이 집중되고 있는 에너지원으로 평가되고 있다. 이러한 환경의 변화와 신재생에너지에의 집중된 관심은 보다 추진력을 얻으며 풍력발전관련 산업체들에 힘을 실어주고 있다. 부산의 녹산 풍력클러스터는 풍력발전기의 요소부품을 생산하는데 있어 주요한 기업체들이 몰려있으며, 과거 몇 년간 세계적인 관심에 편승하여 산업입지가 높아지고 있지만, 이에 반해 관심은 여전히 제한적이었다. 본 논문은 서구에서 이루어지고 있는 풍력발전산업에서 최근까지 이루어졌던 주관심 이슈에 대해 조사하고자 한다. 또한 녹산 풍력클러스터의 현황과 보다 효과적인 집적지를 구성하기 위한 향후 계획에 대한 제안을 하고자 한다.
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O-ring을 이용한 원주의 항력감소에 관한 실험적 연구
임희창,이상준,Lim, Hee-Chang,Lee, Sang-Joon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.8
The flow around a circular cylinder was controlled by attaching O-rings to reduce drag force acting on the cylinder. Four experimental models were tested in this study; one smooth cylinder of diameter D (D=60mm) and three cylinders fitted with O-rings of diameters d=0.0167 D, 0.05D and 0.067 D with pitches of PPD=2D, 1D, 0.5D and 0.25D. The drag force, mean velocity and turbulence Intensity profiles in the near wake behind the cylinders were measured for Reynolds numbers based on the cylinder diameter in the range of Re$_{D}$=7.8$\times$10$^3$~1.2$\times$10$^{5}$ . At Re$_{D}$=1.2$\times$10$^{5}$ , the cylinder fitted with O-rings of d=0.0167D in a pitch interval of 0.25D shows the maximum drag reduction of about 5.4%, compared that with the smooth cylinder. The drag reduction effect of O-rings of d=0.067D is not so high. For O-ring circulars, as the Reynolds number increases, the peak location of turbulence intensity shifts downstream and the peak magnitude is decreased. Flow field around the cylinders was visualized using a smoke-wire technique to see the flow structure qualitatively. The size of vortices and vortex formation region formed behind the O-ring cylinders are smaller, compared with the smooth cylinder.der.
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NACA0015 익형의 공력특성에 대한 수치해석적 연구
임희창,이수정,정의철 한국풍공학회 2012 한국풍공학회지 Vol.16 No.4
In this study, a numerical simulation is made to understand the effect of the angle of attack on a NACA airfoil, which will be used for a basic shape to apply for making the vertical axis Darius wind turbine. The near-wall y+ value which is less than 1 is known to be most desirable for a near-wall modeling. Therefore, this study is aiming to observe the variation and find the optimized value of y+. The Reynolds number used in this study was 360,000, where the chord length and the velocity were 0.12m and 43.8m/s, respectively. Generally, the lift coefficient of the airfoil tends to increase as the angle of attack increases and it decreases substantially at the stall angle and then it decreases. As expected, the lift coefficient increases rapidly from 0 to 10 degs and then after the sudden drop of the lift (i.e., the stall) at around 10 to 16 degs depending on the y+ value. In this paper, it seems to be reliable and appropriate to use y+ value close to 1. From the surface pressure distribution, the maximum and minimum peaks were obtained at the C/Cm 1.89, and these peaks move forward or backward as the angle of attack increases. 본 연구에서는, NACA 익형의 받음각의 변화에 따른 영향을 파악하기 위한 연구로서, 수직축 다리우스 풍력 발전기를 만들기 위한 기본적 형상을 이용하였다. 특히 수치해석에 있어 근접벽면 모델링에서 y+값이 1에 가까울수록 수치결과값이 정확해진다고 알려져 있다. 따라서 본 연구에서는, y+값의 변화를 통하여 최적의 y+값을 찾는 것을 목표로 하고 있다. 본 연구에서 사용한 레이놀즈 수는 360,000로 익형길이, 입구 유속은 각각 0.12m, 43.8m/s으로 설정하였다. 수치해석결과 익형의 양력계수는 받음각이 증가함에 따라 증가하는 경향을 보이며, 실속각 이후에 급격히 감소하는 것을 확인하였으며 양력계수는 받음각이 0° ∼ 10°까지 증가하였고 이후, y+값에 따라 다르지만 대략 10° ∼ 16°에서 급격히 떨어졌다. 본 논문에서 실험결과에 근거하여 수치해석에 y+값이 1에 가까운 것이 적절하다고 판단된다. 표면 압력 분포에서 최대값과 최소값 C/Cm은 1.89, 그리고 최대값의 변화는 받음각의 증가에 따라 앞쪽, 혹은 뒤쪽으로 이동되었다.
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Short-term observation of wind energy potentiality in the Wol-Ryong wind site
임희창 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11
Accurate analysis of the atmospheric wind profiles and climate characteristics in a certain area is a prerequisite for providing reliable information on a wind energy site. Two 2-D ultrasonic anemometers and one cup anemometer, arranged perpendicularly to the prevailing wind direction, were used to measure the atmospheric wind environment at a height of 4.5 m in the coastal region of Wol-Ryong, Jeju,South Korea. This study aims to estimate future wind resources with various estimation methods. The wind energy is theoretically estimated at 75 m, the hub height of 800 kW and 1500-kW-class wind turbines, at the Wol-Ryong site. Methods using three equations, a logarithmic profile, a modified logarithmic profile, and a power law, are applied for accurate prediction of the atmospheric wind profile. In addition, yearly wind power can be calculated by using the probability distribution from Weibull and Rayleigh profiles. It is found that the predicted wind speed is strongly affected by surface atmospheric conditions such as the friction velocity, atmospheric stability, and averaged roughness length. The Rayleigh profile gives more power generation than the Weibull distribution, especially under low–windspeed conditions. The logarithmic profile method seems to be the proper method for estimating the energy production at the Wol-Ryong site for neutral atmospheric conditions. On the other hand, the other two methods - the modified logarithmic profile method and the power law method - seem to be improper for neutral conditions.
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Wind flow around rectangular obstacles with aspect ratio
임희창 한국풍공학회 2009 Wind and Structures, An International Journal (WAS Vol.12 No.4
It has long been studied about the flow around bluff bodies, but the effect of aspect ratio on the sharp-edged bodies in thick turbulent boundary layers is still argued. The author investigates the flow characteristics around a series of rectangular bodies (40d × 80w × 80h, 80d × 80w × 80h and 160d × 80w × 80h in mm) placed in a deep turbulent boundary layer. The study is aiming to identify the extant Reynolds number independence of the rectangular bodies and furthermore understand the surface pressure distribution around the bodies such as the suction pressure in the leading edge, when the shape of bodies is changed, responsible for producing extreme suction pressures around the bluff bodies. The experiments are carried out at three different Reynolds numbers, based on the velocity U at the body height h, of 24,000, 46,000 and 67,000, and large enough that the mean boundary layer flow is effectively Reynolds number independent. The experiment includes wind tunnel work with the velocity and surface pressure measurements. The results show that the generation of the deep turbulent boundary layer in the wind tunnel and the surface pressure around the bodies were all independent of Reynolds number and the longitudinal length, but highly dependent of the transverse width.
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