• International Journal of Naval Architecture and Ocean Engineering
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• 제4권3호
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• pp.241-255
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• 2012

Three types of 100 kW-class tidal stream turbines are proposed and their performance is studied both numerically and experimentally. Following a wind turbine design procedure, a base blade is derived and two additional blades are newly designed focusing more on efficiency and cavitation. For the three designed turbines, a CFD is performed by using FLUENT. The calculations predict that the newly designed turbines perform better than the base turbine and the tip vortex can be reduced with additional efficiency increase by adopting a tip rake. The performance of the turbines is tested in a towing tank with 700 mm models. The scale problem is carefully investigated and the measurements are compared with the CFD results. All the prediction from the CFD is supported by the model experiment with some quantitative discrepancy. The maximum efficiencies are 0.49 (CFD) and 0.45 (experiment) at TSR 5.17 for the turbine with a tip rake.

• 대한기계학회논문집B
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• 제41권11호
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• pp.709-717
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• 2017

연구는 직렬 2단 Weis-Fogh형 수차모델을 제안하고, 이 수차모델의 유체역학적 특성을 개선 와법으로 수치계산한 것이다. 기본조건 및 각 날개의 움직임은 이전에 저자가 제안한 단단 수차모델에서와 같게 했다. 두 날개(NACA0010 airfoils) 및 양쪽 수로벽은 소스 및 볼텍스 판넬로 근사하였고, 자유볼텍스는 각 물체 표면 전체에서 도입하였다. 계산변수로는 앞날개와 뒷날개의 날개 축 사이의 거리 및 두 날개 운동의 위상차 즉 동위상과 역위상으로 했다. 각 경우에 대해 비정상 유동장 및 압력장 그리고 두 날개에 작용하는 힘의 계수 및 효율을 계산하였고, 이 수차모델의 유체역학적 특성을 논의하였다.

• 대한기계학회논문집A
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• 제38권3호
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• pp.269-274
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• 2014

본 논문에서는 사보니우스형 풍력터빈의 저소음 설계에 관한 연구를 수행하였다. 선행연구를 통해 BPF 보다 높은 주파수를 기본주파수로 가지며 발생하는 하모닉 성분의 순음소음이 사보니우스형 풍력터빈의 주요한 소음임을 밝혔고, 이러한 하모닉 성분의 소음은 와류에 의한 것임을 확인하였다. 본 연구에서는 이러한 선행연구결과를 바탕으로, 사보니우스형 풍력터빈의 저소음 설계를 위해 이탈되는 와류에 위상차를 유도할 수 있는 터빈 날개 끝단을 도입하였다. CFD 기법 및 음향상사법을 적용한 복합 전산공력음향학 기법을 적용하여 제안한 저소음 사보니우스형 풍력터빈의 방사 소음을 수치적으로 예측하였고, 기존의 형상과 비교를 통해 소음 저감 효과를 확인하였다.

• 대한기계학회논문집B
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• 제21권6호
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• pp.813-821
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• 1997

Three-dimensional turbulent incompressible flow through the tip clearance of a linear turbine rotor cascade with high turning angle has been analyzed numerically. As a preliminary study to predict the tip clearance loss realistically, a generalized k-.epsilon. model derived by RNG (renormalized group) method is used for the modeling of Reynolds stresses to account for the strain rate of turbulent flow. The effects of the tip clearance flow on the passage vortex, the total pressure loss are considered qualitatively. The existences of vena contract and tip clearance vortex have been confirmed and it has been shown that as the size of the tip clearance increases, the accumulated flow through the tip clearance and the total pressure loss downstream of the cascade increase.

• 대한기계학회논문집B
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• 제29권8호
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• pp.887-894
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• 2005

This paper describes effects of incidence angle on the wake turbulent flow of a high-turning turbine rotor blade. For three incidence angles of -5, 0 and 5 degrees, energy spectra as well as profiles of mean velocity magnitude and turbulence intensity at mid-span are reported in the wake. Vortex shedding fiequencies are obtained from the energy spectra. The result shows that as the incidence angle changes from -5 to 5 degrees, the suction-side wake tends to be widened and the deviation angle is increased. Strouhal numbers based on the shedding fiyequencies have a nearly constant value, regardless of the tested incidence angles.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.273-276
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• 2006

To generate electricity from wind energy, wind turbine generally has a rotor blade. Since this rotor blade is a kind of the rotating machinery, the wake from the rotor is very Important role in the side of the aerodynamic performances. Thus the study about wake is essential to analyze wind turbine aerodynamics. In this study wake characteristics are analyzed by hot-wire probe in the K.A.F.A(Korea Air Force Academy) wind tunnel. It is possible to analyze the wake characteristics by hot-wire probe from acquiring the velocity fluctuations at given positions in the flow. This velocity data are arranged by trigger signal at same azimuth of the blade in periodic manner of the rotor blade. From this various wake characteristics are found : radial and axial position of the tip vortex, vortex core characteristics in the flow etc.

• 한국유체기계학회 논문집
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• 제17권2호
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• pp.12-23
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• 2014

A parametric study on anti-vortex holes for turbine blade cooling was investigated numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations and shear stress transport turbulence model were used for analysis of anti-vortex film cooling. Validation of numerical results was carried out comparing with experimental data. The cooling performance of anti-vortex holes was assessed by two geometric variables, the ratio of diameters of holes and the lateral distances between the primary hole and anti-vortex hole at blowing ratios of 0.5 and 1.0. The results showed that the spatially-averaged film-cooling effectiveness increases as the ratio of the diameters increases and the distance between the primary hole and anti-vortex hole decreases.

• 한국항공우주학회지
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• 제37권4호
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• pp.336-343
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• 2009

터빈 익렬 내의 2차유동손실은 터빈 익렬에서 발생하는 전체 공기역학적 손실의 30~50% 차지한다. 따라서 터빈 효율 향상에 있어 개선해야 될 중요한 부분으로 인식되고 있다. 또한, 과거부터 2차유동에 의한 손실을 줄이기 위한 많은 연구들이 수행되어졌다. 본 논문에서는 2차유동손실을 일으키는 요인 중의 하나인 말굽와류의 강도를 감쇄시키기 위해 일반적인 날개 앞전에 판을 설치하였으며, 판의 설치 높이 및 길이 등의 형상변수에 따라 발생된 말굽와류의 특성에 대해 연구하였다. 연구를 위해 $FLUENT^{TM}$를 이용하였다. 그리고 기준 모델의 경우보다 전압력 손실 계수가 약 4.0% 향상되었다.

• 한국전산유체공학회지
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• 제7권3호
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• pp.9-16
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• 2002

Most of modem aerospace gas turbines must be operated at a gas temperature which is several hundreds of degrees higher than the melting temperatures of the materials used in their construction. Complicated cooling schemes need to be employed in the combustor walls and in the high pressure turbine stages. Internal passages are cast or machined into the hot sections of aero-gas turbine engines and air from the compressor is used for cooling. In many cases, the cooling system is engineered to utilize jets of high velocity air, which impinge on the internal surfaces of the components. They are categorized as 'Impinging Cooling Method' and 'Vortex Cooling Method'. Specially, research of new cooling system(Vortex Cooling Method) that overcomes inefficiency of film cooling and limitation of space. The focus of new cooling system that improves greatly cooling efficiency using less amount of cooling air on surface heat transfer elevation. Therefore, in this study, a numerical analysis has been peformed for characteristics of flow and heat transfer in the swirl chamber and compared with the flow measurements by LDV. Especially, for understanding high heat transfer efficiency in the vicinity of wall, we considered flow structure, vortex mechanism and heat transfer characteristics with variation of the Reynolds number.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.521-524
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• 2009

This study describes aerodynamic noise of high speed wind turbine system, which is invented as a new concept in order to reduce the torque of main shaft, for design parameters of the rotor blade. For parametric study of high speed rotor aerodynamic noise, Unsteady Vortex Lattice Method with Nonlinear Vortex Correction Method is used for analysis of wind turbine blade aerodynamic and Farassat1A and Semi-Empirical are used for low frequency noise and airfoil self noise. Parameters are chord length, twist and rotational speed for this parametric research. In the low frequency range, the change of noise is predicted the same level as each parameters varies. However, in case of broadband noise of blade, the change of rotational speed makes more variation of noise than other parameters. When the geometric angles of attack are fixed, as the rotational speed is increased by 5RPM, the noise level is increased by 4dB.