• 한국유체기계학회 논문집
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• 제17권5호
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• pp.19-26
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• 2014

The cross flow turbine attracts more and more attention for its relatively wide operating range and simple structure. In this study, a novel type of micro cross flow turbine is developed for application to a step in an irrigational channel. The head of the turbine is only H=4.3m and the turbine inlet channel is open ducted type, which has barely been studied. The efficiency of the turbine with inlet open duct channel is relatively low. Therefore, a guide nozzle on the turbine inlet is attached to improve the performance of the turbine. The guide nozzle shapes are investigated to find the best shape for the turbine. The guide nozzle plays an important role on directing flow at the runner entry, and it also decreases the negative torque loss by reducing the pressure difference in Region 1. There is 12.5% of efficiency improvement by attaching a well shaped guide nozzle on the turbine inlet.

• 한국전산구조공학회논문집
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• 제28권1호
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• pp.71-78
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• 2015

LNG 선박에서 발생하는 슬로싱 충격하중은 다상유동 및 기체의 압축효과에 따라 CCS에서 발생하는 압력과 구조응답에 큰 영향을 미칠 수 있다. 본 연구에서는 슬로싱 운동 시 LNG의 유동에 의해 발생하는 슬로싱 충격을 시뮬레이션하기 위해서 다상유동을 적용한 수치해석 모델을 제시하였으며, 그 결과를 실험과 비교하여 타당성을 검토하였다. 또한 효율적인 구조 응답 계산을 위해 분사모델을 이용한 유체구조 연성해석 방법에 대해서 검토하고 멤브레인형 Mark III 화물창의 강도평가에 적용하여 LNG 화물창의 강도평가를 위한 가능성을 검토하였다.

• Nuclear Engineering and Technology
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• 제40권2호
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• pp.133-138
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• 2008

The use of Supercritical Fluids(SCF) has been proposed for numerous power cycle designs as part of the Generation IV advanced reactor designs, and can provide for higher thermal efficiency. One particular area of interest involves the behavior of SCF during a blowdown or depressurization process. Currently, no data are available in the open literature at supercritical conditions to characterize this phenomenon. A preliminary computational analysis, using a homogeneous equilibrium model when a second phase appears in the process, has shown the complexity of behavior that can occur. Depending on the initial thermodynamic state of the SCF, critical flow phenomena can be characterized in three different ways; the flow can remain in single phase(high temperature), a second phase can appear through vaporization(high pressure low temperature) or condensation(high pressure, intermediate temperature). An experimental facility has been built at the University of Wisconsin to study SCF depressurization through several diameter breaks. The preliminary results obtained show that the experimental data can be predicted with good agreement by the model for all the different initial conditions.

• 한국기계가공학회지
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• 제8권2호
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• pp.53-59
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• 2009

The analysis of injection molding process by CAE is widely used in development of plastic products. That comes from the fact that CAE analysis can reduce trial and error based on optimized design. On this study, by use of MOLDFLOW, the causes of product defects were found and solved by trade-off study. CAE analysis includes Flow-Cool-Warpage Analyses and finally a new mold-die design with better product quality was suggested. On injection molding of round-shaped plastic fan, new mold-die system with 4-tunnel gates located on the edge of a fan disc shows better quality rather than pin-point gate located on the center of a disc. That was effective in terms of flow mark removal and flatness improvement of the product.

• 대한기계학회논문집B
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• 제33권4호
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• pp.242-247
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• 2009

AILU type preconditioners for a two-dimensional combined P2P1 finite element formulation of the interaction of rigid cylinder with incompressible fluid flow have been devised and tested by solving fluid-structure interaction (FSI) problems. The FSI code simulating the interaction of a rigid cylinder with an unsteady flow is based on P2P1 mixed finite element formulation coupled with combined formulation. Four different preconditioners were devised for the two-dimensional combined P2P1 finite element formulation extending the idea of Nam et al., which was proposed for the preconditioning of a P2P1 mixed finite element formulation of the incompressible Navier-Stokes equations. It was found that PC-III or PC-IV among them perform well with respect to computational memory and convergence rate for some bench-mark problems.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.597-600
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• 2008

Preconditioners for a two-dimensional combined finite element formulation have been devised and tested for fluid-structure interaction (FSI) problems. The FSI code simulating the interaction of a elastic body with an unsteady flow is based on P2P1 finite element combined formulation. It has been shown that two preconditioners among them perform well with respect to computational memory and convergence for a bench-mark problem. Based on the verification of the preconditioners for the two-dimensional combined formulation, four preconditioners are proposed for the problem of an elastic body interacting with a flow.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.251-251
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• 2000

Tangjin Power Plant is modern Korean standard plant which is made up Once Through Super Critical Boiler, Turbin, Generator and Flue Gas Desulfarization System. INFI-90 system fur control of the 500 MW Korean standard super critical once through boiler Mark-V for Turbine, EX-2000 fer Generator, WDPF for FGD were installed in Tangiin thermal power plant. There were two BFPTs, BFPM, 25% control valve, 35% control valve to control boiler feed water flow. It is very difficult to tune the Separator Tank level control system and change the mode from Wet to Dry. This paper focuses on test results and modification control logic for feed water control system in Tangjin power plant.

• Bulletin of the Korean Chemical Society
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• 제19권8호
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• pp.868-874
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• 1998

An equivalent retention has been experimentally observed in thermal field-flow fractionation (ThFFF) for different polymer-solvent systems. It is shown that iso-retention between two sets of polymer-solvent systems can be obtained by adjusting the temperature difference (ΔT) according to the difference in the ratio of ordinary diffusion coefficient to thermal diffusion coefficient. This method uses a compensation of field strength (ΔT) in ThFFF at a fixed condition of cold wall temperature. It is applied for the calculation of molecular weight of polymers based on a calibration run of different standards obtained at an adjusted AT. The polymer standards used in this study are polystyrene (PS), polymethylmethacrylate (PMMA), and polytetrahydrofuran (PTHF). Three carrier solvents, tetrahydrofuran (THF), methylethylketone (MEK) and ethylacetate (ETAc) were employed. Though the accuracy in the calculation of molecular weight is dependent on the difference in the slope of log λ vs. log M which is related to Mark-Houwink constant a, it shows reasonable agreement within about 6% of relative error in molecular weight calculation for the polymer-solvent systems having similar a value.

• 한국유체기계학회 논문집
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• 제17권4호
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• pp.30-39
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• 2014

The cross flow turbine is economical because of its simple structure. For remote rural region, there are needs for a more simple structure and very low head cross flow turbines. However, in this kind of locations, the water from upstream always flows into the turbine with some other materials such as sand and pebble. These materials will be damage to the runner blade and shorten the turbine lifespan. Therefore, there is a need to develop a new type of cross flow turbine for the remote rural region where there is availability of abundant resources. The new design of the cross flow turbine has an inlet open duct, without guide vane and nozzle to simplify the structure. However, the turbine with inlet open duct and very low head shows relatively low efficiency. Therefore, the purpose of this study is to optimize the shape of the turbine inlet to improve the efficiency, and investigate the internal flow of a very low head cross flow turbine. There are two steps to optimize the turbine inlet shape. Firstly, by changing the turbine open angle along with changing the turbine inlet open duct bottom line (IODBL) location to investigate the internal flow. Secondly, keeping the turbine IODBL location at the maximum efficiency achieved at the first step, and changing the turbine IODBL angle to improve the performance. The result shows that there is a 7.4% of efficiency improvement by optimizing turbine IODBL location (open angle), and there is 0.3% of efficiency improvement by optimizing the turbine IODBL angle.

• 한국환경과학회지
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• 제20권1호
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• pp.107-118
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• 2011

While the assessment of mean flow field is very important to characterize the hydrodynamic aspect of the flow regime in river, the conventional methodologies have required very time-consuming efforts and cost to obtain the mean flow field. The paper provides an efficient technique to quickly assess mean flow field by developing and applying spatial averaging method utilizing repeatedly surveyed acoustic Doppler current profiler(ADCP)'s cross-sectional measurements. ADCP has been widely used in measuring the detailed velocity and discharge in the last two decades. In order to validate the proposed spatial averaging method, the averaged velocity filed using the spatial averaging was compared with the bench-mark data computed by the time-averaging of the consistent fix-point ADCP measurement, which has been known as a valid but a bit inefficient way to obtain mean velocity field. The comparison showed a good agreement between two methods, which indicates that the spatial averaging method is able to be used as a surrogate way to assess the mean flow field. Bed shear stress distribution, which is a derived hydrodynamic quantity from the mean velocity field, was additionally computed by using both spatial and time-averaging methods, and they were compared each other so as to validate the spatial averaging method. This comparison also gave a good agreement. Therefore, such comparisons proved the validity of the spatial averaging to quickly assess mean flow field. The mean velocity field and its derived riverine quantities can be actively used for characterizing the flow dynamics as well as potentially applicable for validating numerical simulations.