• 한국해양공학회지
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• 제19권6호통권67호
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• pp.1-7
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• 2005

This paper deals with the design and aerodynamic analysis of a special-type impulse turbine, with an end plate for wave energy conversion. Numerical analysis was performed using a CFD code, FLUENT. The main idea of the proposed end plate was to minimize the adverse effect of tip clearance of turbine blade, and was borrowed from ducted propeller, with so-called penetrating end plate for special purpose marine vehicles. Results show that efficiency increases up to $5\%$, depending on the flow coefficient; a higher flow coefficient yields increased efficiency. Decrease of input coefficient CAwith an end plate is the main reason for higher efficiency. Performance of end plate at various design parameters, as well as flow conditions, was investigated; the advantages and disadvantages of the presentimpulse turbine were also discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1033-1038
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• 2003

A wind turbine obtains its power input by converting the force of the wind into a torque (turning force) acting on the rotor blades. The amount of energy which the wind transfers to the rotor depends on the density of the air, the rotor area, and the wind speed. Because it has long term operating life and very complex load condition, the fatigue strength of each component must be considered. In this paper, we calculated the load condition by wind using a combined blade elemental theory and a FEM based analytical approach was use to evaluate the fatigue strength of a Hub of wind turbine. The effect of tensile mean stress was taken into account by the modified Goodman diagram. Using this approaches, we evaluated the fatigue strength of hub and main shaft and improved the design.

• 대한조선학회논문집
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• 제30권1호
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• pp.20-29
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• 1993

본 논문에서는 선체-프로펠러-주기관 사이의 상호 작용을 해석함으로써, 선박의 추진 계통을 최적화하는 방안을 제시하였다. 프로펠러의 직경과 전개 면적비를 체계적으로 변화시켜 가면서, 캐비테이션을 고려하여, 주어진 선속에서의 최적의 회전수-소요 마력의 조합을 선정한다. 그리고, 이에 대응하는 주기관 후보를 찾아내어, 각 후보의 연료 소비율을 비교함으로써, 연료 소비율이 최소가 되는 주기관을 결정하고, 동시에 프로펠러의 주요 요목을 결정하는 프로그램의 개발과정을 설명하였다.

• 한국소음진동공학회논문집
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• 제22권4호
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• pp.352-357
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• 2012

The ground resonance instability of a helicopter with bearingless main rotor hub were investigated. The ground resonance instability is caused by an interaction between the blade lag motion and hub inplane motion. This instability occurs when the helicopter is on the ground and is important for soft-inplane rotors where the rotating lag mode frequency is less than the rotor rotational speed. For the analysis, the bearingless rotor was composed of blades, flexbeam, torque tube, damper, shear restrainer, and pitch links. The fuselage was modeled as a mass-damper-spring system having natural frequencies in roll and pitch motions. The rotor-fuselage coupling equations are derived in non-rotating frame to consider the rotor and fuselage equations in the same frame. The ground resonance instabilities for three cases where are without lead-lag damper and fuselage damping, with lead-lag damper and without fuselage damping, and finally with lead-lag damper and fuselage damping. There is no ground resonance instability in the only rotor-fuselage configuration with lead-lag damper and fuselage damping.

• Korean Journal of Acupuncture
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• 제18권1호
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• pp.165-170
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• 2001

전북 진안지역에서 재배된 백하수오 2년생 생근을 공시재료로 이용하여 백하수오의 적정 기계박피 조건을 구명하고자 박피날은 돌기형 고무, 플라스틱 패드, 마름모형 철제날과 솔브러시를 공시하고 연마재로서 인조석, 모래, 잔자갈을 이용하여 박피시험을 수행한 결과를 요약하면 다음과 같다. 1. 손박피의 경우 철제칼을 이용하여 1kg을 박피하는 시간이 36분으로 가장 적게 걸렸고 기계박피는 통일 무게 처리에 2분이 소요되는 것으로 나타났으며 명도의 경우 손박피가 기계박피에 비해 다소 높게 나타나는 경향이었다. 2. 백하수오 기계박피시 박피날과 연마재 처리조건에서 수율은 마름모형 철제날에 모래을 처리한 조합에서 89.9%로 가장 낮게 나타났으며 박피율은 마름모형 철제날에 잔자갈을 처리 한 조합에서 71.3%로 가장 높게 나타났다. 3. 백하수오의 박피후 품질결정에 중요한 요소중의 하나인 명도의 경우 마름모형 철제날에 잔자갈을 연마재로 사용한 조합에서 61.90.으로 가장 높게 나타났다. 4. 백하수오 기계박피시 적정 회전속도를 구명하기 위한 조건에서는 박피 회전속도가 빨라 칠수록 수율은 낮은 경향을 나타냈으며 박피율의 경우 회전속도 30r.p.m.에서 66.8%로 가장 높게 나타났으며 명도 또한 57.16으로 나타나 백하수오 기계박피시 적정 회전속도는 30r.p.m.으로 처 리 하는 것이 타당하다고 분석 되었다.

• 환경생물
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• 제37권4호
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• pp.707-718
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• 2019

최근 양식기법이 보급되어 어가의 양식이 활발해진 감태(Ecklonia cava Kjellman)는 향후 다양한 품종개발이 예상되고, 이들의 구분을 위한 신품종 심사기준(특성조사요령) 작성과 기초자료가 되는 자연 개체군의 변이 폭과 지역적 형태 변이에 관한 연구 필요성은 더욱 커지고 있다. 본 연구는 감태 양식 개체군과 국내 연안 16개소에서 채집한 자연개체군의 형태를 비교하고, 주요 형태 형질의 특성과 변이 폭을 규명하고자 하였다. 감태의 품종 구분에 적합한 형질은 1차엽과 2차엽, 줄기에 대한 주요 형태와 특징에 관한 14개 측정 형질과 4개 비율 형질, 총 18개 특성을 선정하였다. 군집 분석에서 전체 19개 개체군 중, 자연개체군인 장길(E4), 소록(S7)은 동일 지역 개체군들과 유의한 차이를 보였고, 동해와 남해의 나머지 자연 개체군은 양식 2년생인 수유(Q6, Q8, Q10)를 포함한 2개 집단으로 구분되었고, 제주의 3개 개체군은 별도의 집단을 이루어 지역적으로 구분되었다. 주성분 분석에서도 군집 분석에서 집단을 이룬 동해와 남해 개체군을 중심으로 양식 개체군은 중앙에 모여 나타났고, 장길(E4), 소록(S7)과 제주 개체군들은 주성분 1 (PC1)과 주성분 2 (PC2)에 연관된 2차엽 지수, 줄기의 길이와 직경, 줄기 길이/1차엽 길이, 1차엽 길이와 너비, 2차엽 수, 2차엽 길이와 너비의 형질에 의해 각 축에 따라 구분되어 나타났다. 이상의 결과로 본 연구에서 조사한 18개 형질은 각 해역에서 유의한 차이를 보이는 개체군 구분을 위한 기준으로 유용성이 확인되었으며, 감태의 각 지역 개체군은 향후 신품종 개발 후보 종으로 가능성이 클 것으로 기대되었다.

• 한국해양공학회지
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• 제20권1호
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• pp.20-25
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• 2006

This paper deals with the design and aerodynamic analysis of a so-called 'ring-type' impulse turbine for wave energy conversion. Numerical analysis was performed using the CFD cock, FLUENT. The main idea of the proposed turbine rotor was to minimize the adverse effect of tip clearance of the turbine blade; the design was borrowed from a ducted propeller with connected ring tip for special purpose marine vehicles. Results show that the efficiency increases up to $10\%$, depending on flaw coefficient, with the higher flaw coefficient yielding better efficiency. Decrease of input coefficient CA was the main reason for higher efficiency. Performance of ring-type rotor at various design parameters, as well as flaw conditions, was investigated, and the advantages and the disadvantages of the present impulse turbine were also discussed.

• 한국소음진동공학회논문집
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• 제18권4호
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• pp.465-472
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• 2008

An automotive windshield wiper system is modeled mainly for vibration analysis purpose. The model is composed of solid links, ideal joints, imperfect joints to simulate unavoidable manufacturing defects and bushings having stiffness, contact between a wiper blade and a wind screen glass, friction, a spring and an actuator. Main stream of wiper dynamics analysis has been obtaining a closed form of system of equations using Newton's or Lagrange's formula and doing a numerical simulation study to understand and predict the behavior of it. However, the modeling process is complex since a wiper system is of multibody and a contact problem occurs. When imperfection, such as dead zone of a joint and stiffness of a rubber bushing, should be included, the added complexity makes the modeling difficult. Since the imperfection is understood as main cause of problematic vibration, the dynamics model of a wiper system aiming vibration analysis should include such unavoidable manufacturing defects in the model. An open form of dynamic model of a automotive windshield wiper system with imperfect joints using a commercial software is obtained and a simulation analyssis is conducted for vibration reduction study.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.82-87
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• 2007

A cleaner has trouble with too much noise and power consumption. To solve these problems, the investigation for motors, which are the main component of vacuum cleaner, is required. However, it is difficult to analyze the flow by the experimental means because of the high speed of the fan rotation ranging from 30,000 rpm to 50,000 rpm. Moreover it takes much time to perform the numerical simulation for the flow. In this research, it is aimed to analyse the flow through the centrifugal fan which is believed to be a main noise source, by the computational method. The efficiency of the centrifugal fan is affected by friction loss, shock loss and so on. Those losses depend on factors like the velocity of impeller, blade shape and etc. Accordingly, the influence of the shape of impeller on the flow is investigated in this study. The computational analysis was done by changing impeller shapes. The flow around the centrifugal fan is simulated by applying the moving mesh. To verify the validity of the computation results, the air flow rate and the pressure field to the cleaner is compared with the experimental data. All simulations are performed by using commercial code SC/Tetra. The calculated results show good agreement with the experimental ones qualitatively and it is believed to be promising to use computational simulation in the improvement of the vacuum cleaner performance.

• 대한기계학회논문집B
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• 제21권8호
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• pp.996-1008
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• 1997

This paper describes a methodology and results for the analysis of a small steam injected gas turbine cogeneration system. A performance analysis program for the gas turbine engine is utilized with modifications required for the model of steam injection and the heat recovery steam generator (HRSG). The object of simulation is a simple cycle gas turbine engine under development which adopts a centrifugal compressor. The analysis is based on the off-design operation of the gas turbine and the compressor performance map is utilized. Analyses are carried out with the injection ratio as the main parameter. The effect of steam injection on the power and efficiency of gas turbine and cogeneration capacity is investigated. Also presented is the variation in the main operating parameters inside the HRSG. Remarkable reduction in NOx generation by steam injection is confirmed. In addition, it is observed that for the 100% power operation the temperature of the cooled first nozzle blade decreases by 100.deg. C at full steam injection, which seems to have a favorable effect on the engine life time.