• 한국자동차공학회논문집
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• 제22권7호
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• pp.1-7
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• 2014

A variable displacement vane pump is possible to improve the fuel economy by varying the pump capacity with a vane mechanism according to the engine operating speed range and reducing its driving torque. In general the experimental evaluation of the vane pump for the transmission has been performed mainly not with the vehicle or dynamometer test rig but with component test rig due to the implementation and safety problems. In this paper, in order to evaluate the performance of the developed vane pump as well as the compatibility with other rotary and hydraulic components of the target transmission, the transmission dynamometer based test rig is implemented where the developed pump is built into it and then the variable pump capacity and effect of power reduction are investigated experimentally.

• 대한교통학회지
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• 제24권7호
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• pp.115-128
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• 2006

도로용량편람(2004)에 제시된 합류부 분석 방법론은 수요가 용량을 초과할 경우 정체가 발생한다는 가정을 전제로 하고 있다. 그러나 많은 경우, 본선과 연결로 수요의 합이 용량을 초과하지 않은 상태에서도 합류부에서는 정체가 발생하고 있는 실정이며, 현재의 분석방법으로는 본선 및 연결로가 정체발생과 관련하여 어떠한 영향을 끼치는지에 대한 분석이 어려운 실정이다. 본 연구에서는 합류부 본선 및 연결로 수요교통량의 조합에 따라 발생할 수 있는 합류부 교통상태를 추정할 수 있는 모형을 개발하였다. 본 연구에서 제시하는 모형의 가장 큰 특징은 가변용량 개념의 도입인데 즉, 합류부 본선 및 연결로 수요교통량의 조합에 따라 정체되지 않고 통과될 수 있는 최대통과가능교통량 및 정체발생시의 최대통과교통량 산정에 있다. 이를 통해 합류부의 교통상태가 정체될 것인지, 또한 정체시 최대통과교통량 및 정체규모는 얼마가 될 것인지 추정할 수 있었다. 한편, 현재 사용하고 있는 합류부 서비스수준 평가기법은 실제 교통상황을 반영하지 못함으로 인해 고속도로 현장에서는 정체상황이 발생되고 있으나 수요가 용량을 초과하지 않았다는 이유로 정상교통류 상태로 평가하는 단점을 지니고 있다. 따라서 본 연구에서는 보다 현실적인 합류부 서비스수준 평가기법을 제시하기 위해 본 연구에서 개발한 합류부 분석방법론을 토대로 새로운 합류부 서비스수준 구분 기준을 제시하였다.

• 한국전산유체공학회지
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• 제16권3호
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• pp.75-81
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• 2011

The turbo blowers having large power capacity are generally composed of the variable inlet guide vane, the impeller and the variable diffuser. In the present study, the effect of the stagger angles on the aerodynamic performances has been investigated by CFD methods. The design specifications of the reference model having 400kW power were given as 7.43kg/s of mass flow rate, 1.66 of pressure ratio with 12000rpm of impeller rotating speed. As the first simulation parameter, the diffuser vane angle was varied in the range of ${\pm}$20 degree from the initial-design point. The inlet guide vane angles, as the second one, was changed in the range of ${\pm}$40 degree from the initial-design point. The commercial Navier-Stokes solver, ANSYS-CFX, was applied to solve the three-dimensional unsteady flow fields inside the turbo blower. Through the numerical results, the desirable setting angles were proposed to fit the best performance to the variation of the operating conditions.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 하계학술발표대회 논문집
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• pp.183-183
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• 2007

• 국제초고층학회논문집
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• 제2권4호
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• pp.315-321
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• 2013

This building is a first-class super-high office building. This article briefly introduces energy-saving technique and measures adopted in HVAC system, such as cooling and heat sources, water and air system etc.

• Current Photovoltaic Research
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• 제2권4호
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• pp.147-151
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• 2014

A boron doping process using a boron tri-bromide ($BBr_3$) as a boron source was applied to form a $p^+$ emitter layer on an n-type mono-crystalline CZ substrate. Nitrogen ($N_2$) gas as an additive of the diffusion process was varied in order to study the variations in sheet resistance and the uniformity of doped layer. The flow rate of $N_2$ gas flow was changed in the range 3 slm~10 slm. The sheet resistance uniformity however was found to be variable with the variation of the $N_2$ flow rate. The optimal flow rate for $N_2$ gas was found to be 4 slm, resulting in a sheet resistance value of $50{\Omega}/sq$ and having a uniformity of less than 10%. The process temperature was also varied in order to study its influence on the sheet resistance and minority carrier lifetimes. A higher lifetime value of $1727.72{\mu}s$ was achieved for the emitter having $51.74{\Omega}/sq$ sheet resistances. The thickness of the boron rich layer (BRL) was found to increase with the increase in the process temperature and a decrease in the sheet resistance was observed with the increase in the process temperature. Furthermore, a passivated emitter solar cell (PESC) type solar cell structure comprised of a boron doped emitter and phosphorus doped back surface field (BSF) having Ni/Cu contacts yielding 15.32% efficiency is fabricated.

• 한국주조공학회지
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• 제32권6호
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• pp.276-283
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• 2012

This study presents the results on the changes of crucible thermal conductivity and inflow of Ar, and constructed the mathematical model about heat transfer into furnace. As process variables, simulation model was designated thermal conductivity of crucible to $0.5W{\cdot}m^{-1}{\cdot}K^{-1}$, $1W{\cdot}m^{-1}{\cdot}K^{-1}$, $2W{\cdot}m^{-1}{\cdot}K^{-1}$, $4W{\cdot}m^{-1}{\cdot}K^{-1}$, and inflow rate of Ar to 15 L/min, 30 L/min, 60 L/min. Initial condition and boundary condition were set respectively in two terms of process. Each initial conditions were set up by the preceding simulation of heat and fluid flow. The primary goal is the application of unidirectional growth of Si ingot using the result. In the result of the change of heat conductivity of crucible, the higher thermal conductivity of crucible shows the shorter solidification time and the bigger temperature difference. And the flow patterns are changed with the inflow rate of Ar. Finally, we found that the lower crucible's thermal conductivity, the better crucible is at polycrystalline Si ingot growth. But in case of Ar inflow, it is hard to say about good condition. This data will be evaluated as useful reference used in allied study or process variable control of production facilities.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.244-254
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• 2002

To enhance the acceleration performance and fuel consumption rate of a vehicle, the torque converter is modified or newly-developed with reliable analysis model. Up to recently, the one dimensional performance model has been used for the analysis and design of torque converter. The model is described with constant parameters based on the concept of mean flow path. When it is used in practice, some experiential correction factors are needed to minimize tole estimated error. These factors have poor physical meaning and cannot be applied confidently to the other specification of torque converter. In this study, the detail dynamic model of torque converter is presented to establish the physical meaning of correction factors. To verify the validity of model, performance test was carried out with various input speed and oil temperature. The effect of oil temperature on the performance is analysed, and it is applied to the dynamic model. And, to obtain the internal flow pattern of torque converter, CFD(Computational Fluid Dyanmics) analysis is carried out on three-dimensional turbulent flow. Correction factors are determined from the internal flow pattern, and their variation is presented with the speed ratio of torque converter. Finally, the sensitivity of correction factors to the speed ratio is studied for the case of changing capacity factor with maintaining torque ratio.

• 에너지공학
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• 제14권3호
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• pp.194-202
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• 2005

본 연구는 다양한 수직 액막형 흡수기에서 열 및 물질전달 과정에 따른 흡수 특성 예측을 이론 및 실험적으로 수행하였다. 열 및 물질전달 향상은 해석적으로 조사되었으며, 흡수 성능에 대한 유동 형태, 삽입기구 및 주름에 의한 형상 변수의 영향 등을 조사하였다. 특히, 최대 흡수 성능에 대한 동적 변수(수용액 유량, 유동형태)와 흡수기 형상(ID=22.8mm, L=1150m)의 최적값을 수치 해석적으로 예측하였다 수치 해석 및 실험에서 최대 흡수 성능은 삽입기구(스프링)에 의한 파동 유동에서 나타났다.

• 태양에너지
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• 제9권2호
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• pp.42-50
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• 1989

The Buoyant Jets were analysed experimentally changing flow rate (0.0291/s, 0.0371/s, 0.0451/s), ratio of nozzle tip area to throat area (aspect ratio ${\beta}$=0.4, 1.0, 1.9), and also the temperature difference (${\Delta}T=Ti-T{\infty}$) between the temperature of the inflow water into the storage tank ($1m{\times}1m{\times}3m$) and the mean temperature of the water in the storage tank were changed as $25^{\circ}C,\;35^{\circ}C$ and $45^{\circ}C$. The more aspect ratio decreased, the more the trajectories of Buoyant Jets center-line were decreased and not the more the trajectories of Buoyant Jets centerline were influenced by the increment of the difference of the temperature. The more aspect ratio decreased, the more the half widths and dilution ratio of Buoyant Jets were increased and not the more the half widths and dilution ratio of Buoyant Jets were influenced by the increment of the difference of the temperature. Fr number is the factor that can predict the flow pattern over the whole flow field. And yet for the consideration the near field of Buoyant Jets flow pattern is dominated by magnitude of momentum and buoyancy force.