• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.444-447
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• 2009

The optimum design and the performance analysis software called POSEIDON for the HAWT (Horizontal Axis Wind Turbine) was developed by use of BEMT. The Prandtl's tip loss theory was adopted to consider the blade tip loss. The aerodynamic characteristics of NACA 63415 airfoils were predicted via X-FOIL and the post stall characteristics were estimated by the Viterna's equations. All the predicted aerodynamic characteristics are fairly well agreed with the Velux wind tunnel test results. The rated power of the testing rotor is 5kW at design conditions. The power, estimated by use of predicted lift and drag coefficient via X-FOIL becomes a little higher than experimental one.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.129-129
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• 2004

본 연구에서는 나노스케일 절삭가공(nanometric cutting process)시에 미세 팁과 가공표면사이에서 발생하는 현상들에 대하여 분자동역학적 시뮬레이션을 통하여 살펴보았다 본 연구의 목적은 실험적으로는 파악하기 어려운 극미세 가공에서 발생하는 나노트라이볼로지적 현상을 이해하고, 이를 토대로 기계적 가공에 기반하여 개발된 '기계-화학적 나노리소그래피(Mechano-Chemical Scanning Probe Lithography)' 공정을 개선, 발전시키는데 있다. 기계-화학적 나노리소그래피 기술은 극초박막의 리지스트(resist)를 미세탐침을 이용하여 기계적 가공으로 제거하고 이로인해 표면으로 드러난 모재부분을 화학적 에칭에 의해 추가로 가공하여 원하는 패턴형상을 얻어내는 기술이다.(중략)

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.561-564
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• 2011

다양한 공학/산업적 측면에서 동적 취성 파괴 현상은 매우 중요하다. 취성 균열은 다른 균열 전파에 비해 그 전파 속도가 매우 빠르고 전파 범위가 넓기 때문에 대규모의 파괴 현상을 일으킨다. 동적 전파 중인 취성 균열 거동을 모델화하기 위해 오랜 기간 동안 많은 연구가 진행되었지만, 여전히 많은 부분들이 해석되지 못한 채 남아있다. 특히 균열 생성 및 전파를 위해 인위적인 조건들을 도입해야 하는 것은 기존 방법론들이 가지는 공통적인 문제점이다. 본 연구는 peridynamics를 동적 분기 균열 문제 해석에 도입한다. Peridynamics는 전통적인 연속체 이론에 기반한 수치해석 모델화 기법으로 균열과 같은 비연속성이 있는 문제의 모델화에 강점이 있으며, 인위적인 조건 없이 매우 간단한 방법으로 파괴 현상을 해석할 수 있다. 본 연구에서는 peridynamics 모델이 실험적으로 관측된 분기균열 형상과 균열 전파 속도를 매우 잘 예측해 낼 수 있음을 보인다. 또한 균열팁 주변에 높은 응력이 발생할 때 나타나는 연쇄 분기 현상도 해석할 수 있다. 이와 같은 연구를 통해 응력파가 균열 전파 속도를 변화시키고 전파 방향에도 영향을 주는 것을 알 수 있었다. 수치해석 결과도 또한 실험 결과들과 잘 부합함을 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.356-362
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• 2007

The optimum design and the performance analysis software called POSEIDON for the HAWT (Horizontal Axis Wind Turbine) was developed by use of BEMT. The Prandtl's tip loss theory was adopted to consider the blade tip loss. The aerodynamic characteristics of NACA 63-415 airfoils were predicted via X-FOIL and the post stall characteristics were estimated by the Viterna's equations. All the predicted aerodynamic characteristics are fairly well agreed with the Velux wind tunnel test results. The rated power of the testing rotor is 1 kW at design conditions. The power, estimated by use of predicted lift and drag coefficient via X-FOIL becomes a little higher than experimental one.

• Proceeding of EDISON Challenge
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• 2016.11a
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• pp.15-18
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• 2016

본 연구는 조류발전 터빈의 블레이드 형상 최적화 해석 시스템 개발에 대한 사전연구의 일환으로 EDISON CFD의 프로펠러 단독성능 S/W와 SNUFOAM ShipMesh Advanced 자동격자생성기를 이용하여 조류발전 터빈 주위 유동장에 대한 수치해석을 수행하였다. TSR 조건 변화에 따라 수치해석을 수행하고 이에 대한 power, total coefficient를 동일한 조건에서 수행된 실험결과와 비교 검증하여 해석자의 신뢰도를 확인하였다. 또한, 블레이드 전체를 모델링한 full body 해석과 하나의 블레이드만을 모델링한 single body 해석 결과를 비교하여 경제적이면서 정도 높은 터빈 성능해석 프로세스를 제안하였다. 조류발전 터빈의 TSR 조건 변화에 따라 낮은 TSR 조건에서는 국부적 와동발생에 의해 $C_P$가 감소하는 것을 확인하였고 설계 TSR에서 가장 좋은 효율을 보임을 확인하였다. 이를 통해 suction side의 압력 분포, 팁 와동의 강도 등 성능개선을 위한 주요한 설계변수를 식별하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.11
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• pp.1127-1133
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• 2012

A finned-tube-type evaporator module has been proposed for a 2 t/h-class water-tube-type industrial boiler with multiple burners. The geometry of the fins was changed at each module to equalize the evaporation. The modules were designed by considering the energy balance at each row rather than by following a conventional bulk design procedure. The designed module was built into a 2 t/h-class water-tube-type boiler, and its performance was tested. A numerical simulation was also conducted to evaluate the two- or three-dimensional effects of factors such as the inlet conditions. The numerical simulation also included the conjugate heat transfer problem to predict the fin tip temperature. The heat transfer coefficient with fins is lower than that obtained from the empirical correlation of a bare tube. The fin tip temperature from CFD is higher than that from the analytical solution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.161-169
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• 2017

The present study investigated the effect of the rib arrangement and a guide vane for enhancing internal cooling of the blade. Two types of rib arrangements were used in the first and second passage in parallel. Aspect ratio of the channel was 5 and a fixed Reynolds number based on hydraulic diameter was 10,000. The attack angle of rib was $60^{\circ}$, rib pitch-to-height ratio (p/e) was 10, and the rib height-to-hydraulic-diameter ratio ($e/D_h$) was 0.075. The effect of an interaction between Dean vortices and the secondary vortices from the first passage was observed. Overall, the attack angle of rib in the first passage was dominant factor to heat transfer and flow patterns in turning region. Also, the channel with a guide vane showed enhanced heat transfer at the tip surface with reducing flow separation and recirculation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.20-25
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• 2005

The thickness, loading, and broadband noise generated from the trailing edge of the UH-1H main rotor are numerically compared each other. The Kocureck and Tangler's prescribed wake model is adopted to represent the wake geometry during the hovering motion. Three tip Mach numbers of $M_{T}$ = 0.2, 0.4, and 0.8, are selected to analyze the effects of different tip Mach numbers. At $M_{T}$ = 0.8, in considering the A-weighting and audible frequency band, the random noise is smaller than the tonal noises such as the thickness and the loading noise which have the low frequency characteristics. Especially most of the random noise frequency spread on the ultrasound region. On the other hand, below $M_{T}$ = 0.4, the band of random noise moves to the audible frequency region, and the random noise becomes larger than the tonal noise. It turns out that the random noise analysis of the rotor should be necessary at low speed operating condition.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1222-1230
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• 2022

The rotor blade is an important component of a tidal stream turbine and is affected by a large thrust force and load due to the high density of seawater. Therefore, the performance must be secured through the geometrical and structural design of the blade and the blade structural safety to which the composite material is applied. In this study, a 1 MW class large turbine blade was designed using the blade element momentum (BEM) theory. GFRP is a fiber-reinforced plastic used for turbine blade materials. A sandwich structure was applied with CFRP to lay-up the blade cross-section. In addition, to evaluate structural safety according to flow variations, static load analysis within the linear elasticity range was performed using the fluid-structure interactive (FSI) method. Structural safety was evaluated by analyzing tip deflection, strain, and failure index of the blade due to bending moment. As a result, Model-B was able to reduce blade tip deflection and weight. In addition, safety could be secured by indicating that the failure index, inverse reserve factor (IRF), was 1 or less in all load ranges excluding 3.0*Vr of Model-A. In the future, structural safety will be evaluated by applying various failure theories and redesigning the laminated pattern as well as the change of blade material.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.1007-1013
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• 2013

This study aims to analyze the aerodynamics when the geometry of the turbine rotor is modified. The turbine used in this study is a small engine used in the APU of a helicopter. It is difficult to improve the performance of small engines owing to the structural weakness of the blade tip. Therefore, the improvement of the hub geometry is investigated in many ways. The working fluid of a turbine is a high-temperature and high-pressure gas. The heat transfer rate of the turbine surface should be considered to avoid the destruction of blade owing to the heat load. The SST turbulence model gives an excellent prediction of the aerodynamic behavior and heat transfer characteristics when the numerical simulations are compared with the experimental results. In conclusion, the aerodynamic efficiency is improved when a bulbous design is applied to the leading edge near the hub. The endwall loss is reduced by 15%.