• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.558-563
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• 2004

Experiments were performed to see the effect of radial tip clearance on a turbopump inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7. Hydraulic and cavitation tests were done for three cases of tip clearance ratio, that is, 0.026, 0.053, and 0.079. With increase in the tip clearance, inducer head and pressure on the inducer tip decreased. Attached cavitation and cavitation surge were found in the cavitation tests. In the attached cavitation one cell rotated at the same rotational speed as that of the inducer. Cavitation performance deteriorated with increase in the tip clearance. The level of casing vibration increased in the cavitation condition and the level was very high when the attached cavitation appeared.

• 한국유체기계학회 논문집
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• 제9권1호
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• pp.19-24
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• 2006

Experiments are carried out to investigate the effect of radial tip clearance on a turbopump inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7. Hydraulic and cavitation tests are performed for three cases of tip clearance ratio, that is, 0.026, 0.053, and 0.079. With increase in the tip clearance, inducer head and pressure on the inducer tip decrease. Attached cavitation and cavitation surge are observed in the cavitation tests. In the attached cavitation one cell rotates at the same rotational speed as that of the inducer. Cavitation performance deteriorates with increase in the tip clearance. The level of casing vibration increases in the cavitation condition and the level is very high when the attached cavitation appears.

• Wind and Structures
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• 제27권3호
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• pp.187-197
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• 2018

In this study, aerodynamic characteristics of a horizontal axis wind turbine (HAWT) were evaluated and discussed in terms of measured data in existing onshore wind farm. Five wind turbines (T1, T2, T3, T4 and T5) were selected, and hub-height wind speed, $U_D$, wind turbine power output, P and turbine rotational speed, ${\Omega}$ data measured from these turbines were used for evaluation. In order to obtain characteristics of axial flow induction factor, a, power coefficient, $C_p$, thrust force coefficient, $C_T$, thrust force, T and tangential flow induction factor, a', Blade Element Momentum (BEM) theory was used. According to the results obtained, during a year, probability density of turbines at a rotational speed of 16.1 rpm was determined as approximately 45%. Optimum tip speed ratio was calculated to be 7.12 for most efficient wind turbine. Maximum $C_p$ was found to be 30% corresponding to this tip speed ratio.

• 대한기계학회논문집B
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• 제30권3호
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• pp.278-286
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• 2006

Experiments were conducted to estimate the performance of drag force type vertical axis wind turbine with an opening-shutting rotor. It was operated by the difference in drag force generated on both sides of the blades. The rotational speed was measured by a tachometer in a wind tunnel and the tunnel wind speed was measured by using a pilot-static tube and a micro manometer. The performance test for a prototype was accomplished by calculating power, power coefficient, torque coefficient from the measurement of torque and rpm by a dynamometer controller. Various design parameters, such as the number of blades(B), blade aspect ratio(W/R), angle of blades$(\alpha)$ and drag coefficient acting on a blade, were considered for optimal conditions. At the experiment of miniature model, maximum efficiency was found at N=15, $\alpha=60^{\circ}$ and W/R=0.32. The measured test variables were power, torque, rotational speed, and wind speeds. The data presented are in the form of power and torque coefficients as a function of tip-speed ratio V/U. Maximum power was found in case of $\Omega=0.33$, when the power and torque coefficient were 0.14 and 0.37 respectively. Comparing model test with prototype test, similarity law by advance ratio for vertical axis wind turbine was confirmed.

• Structural Engineering and Mechanics
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• 제45권1호
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• pp.69-93
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• 2013

The present study deals with the dynamics of the flapwise (out-of-plane) vibrations of a rotating, internally damped (Kelvin-Voigt model) tapered Bernoulli-Euler beam carrying a heavy tip mass. The centroid of the tip mass is offset from the free end of the beam and is located along its extended axis. The equation of motion and the corresponding boundary conditions are derived via the Hamilton's Principle, leading to a differential eigenvalue problem. Afterwards, this eigenvalue problem is solved by using Frobenius Method of solution in power series. The resulting characteristic equation is then solved numerically. The numerical results are tabulated for a variety of nondimensional rotational speed, tip mass, tip mass offset, mass moment of inertia, internal damping parameter, hub radius and taper ratio. These are compared with the results of a conventional finite element modeling as well, and excellent agreement is obtained.

• 한국해양공학회지
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• 제30권2호
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• pp.125-133
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• 2016

In this paper, we propose a vertical axis water turbine with dual blades. A parametric study was conducted using numerical analyses. First, a two-dimensional finite-volume analysis with a commercial code was used to find the pitch angle of the main blade under different tip speed ratio conditions. Second, we developed a potential-based panel method to find the best configuration of the inner blades. Experimental tests were conducted at the circulating water channel of Chungnam National University. Various configurations of the dual blades were considered, and their performances were comparatively investigated. The results showed that the turbine with movable dual blades produces a constant torque and tip speed ratio at various flow rates.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1465-1469
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• 2009

Darrieus wind turbine blade is one of the vertical wind power system in which the lift of blade is used. In the calculation of wind power for the type of that, the multiple streamtubes method is known as an effective method. But it has big difference in the region of higher tip speed ratio because the incoming air velocity is used in the calculation of lift. The incoming air velocity is reduced from inlet to outlet continually by transferring energy to the wind blade. In this study, the air velocity on the blade, which is called blade velocity, is obtained with newly developed algorithm and used to determine the lift. And it is verified that applying blade velocity on the lift calculation cause the power prediction to improve dramatically in the region of higher tip speed ratio.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1750-1752
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• 2005

This paper presents a variable speed wind generation system where fuzzy logic controllers is used as efficiency optimizer. The fuzzy logic controller increments the machine flux by on-line search to improve the generator efficiency in case of light load. The speed of the induction generator is controlled according to the variation of the wind speed in order to produce the maximum output power The generator reference speed is adjusted according to the optimum tip-speed ratio. The complete control system has been developed by simulation study.

• 한국해양환경ㆍ에너지학회지
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• 제14권4호
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• pp.230-238
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• 2011

100 kW 용량의 조류발전용 수평축 터빈(HAT)임펠러의 성능에 대한 연구를 위하여 단면 및 날개 끝 형상을 변형시킨 지름700 mm의 모형 임펠러를 설계하고 부산대학교 예인수조에서 모형 시험을 수행하였다. 축척효과를 확인하기 위하여 각각의 임펠러에 대하여 회전수를 바꾸어 레이놀즈수 변화에 따른 특성을 살펴보았으며 날개끝속도비(TSR)별로 비교 검토 하였다. 본 연구에서 제안된 레이크 임펠러의 성능이 기존 임펠러 보다 우수함을 확인 하였으며 추후 실험시설을 보완하여 보다 큰 레이놀즈수에서 실험을 수행하고 계산과 비교할 예정이다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.117-121
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• 2008

슈라우드가 장착된 초음속 충동형 터빈의 팁간극에 따른 성능변화를 시험적으로 고찰하였다. 시험은 30톤급 터보펌프용 터빈을 이용하였으며 고압공기를 이용하여 다양한 압력비 및 회전수 범위에서 이루어졌다. 터빈의 효율민감도는 기준시험점에서 0.05의 매우 작은 값을 나타내었다. 터빈효율변화는 간극의 크기에 다라 비선형적으로 변화하였으며 고정된 압력비에서 효율민감도는 회전수의 세제곱에 비례하는 것으로 나타났다. 아울러 회전수에 무관하게 효율민감도는 기준시험 압력비에서 최소값을 보이는 것으로 나타났다.