• Transactions of the Korean hydrogen and new energy society
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• v.10 no.2
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• pp.107-118
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• 1999

A 5-kW MCFC stack with $3,000cm^2$ electrode area was tested to investigate cell performance and operation characteristics. The stack performance was evaluated based on electrical output and I-V change. The stack showed high cell performance (7.6 kW) than the design performance and operated for more than 5,760 hours, but a significant temperature gradient inside the stack was observed. A 3-dimensional mathematical model for molten carbonate fuel cell (MCFC) was developed for the purpose of simulation of stack performance during the operation. The model was solved using PHOENICS, a computational fluid dynamics (CFD) code. The simulation result demonstrated a close prediction of the temperature gradient and stack performance.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.172-174
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• 2018

기존선형과 저항을 최소화하는 최적선형에 대한 에너지효율 성능을 평가하는 것이다. 설계 흘수와 설계 선속을 고려하여 대상선박의 선수부 형상을 검토하였다. 실제 운항 상태에서 대상선박의 저항성능을 평가하였다. 상용 전산유체역학(CFD) 코드와 수조 모형시험 자료는 유효마력 평가를 위해 사용되었다. 실제 운항 상태를 고려하여 최소저항을 가지는 최적선형을 제시하였다. 기존선형과 최적선형에 대하여 3가지 선속에서 유효마력을 추정하였다. 최적선형의 저항성능은 기존선형과 비교하여 볼 때 설계속도(12노트)에서 약 6% 향상된 결과를 보여 주었다. 준추진효율 계수(ETAD, ${\eta}D$)는 모형시험 자료를 활용하였다. 에너지 효율 성능은 년간 운항일수, 벙커C유 가격, 1일 연료사용량 그리고 연료소비계수를 바탕으로 작성되었다.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.70-80
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• 2016

The comparison of two commercial codes(FLUENT and STAR-CCM+) and an open-source code(OpenFOAM) are carried out for the aerodynamic analysis of flight vehicles at low speeds. Tailless blended-wing-body UCAV, main wing and propeller of HALE UAV(EAV-3) are chosen as geometries for the investigation. Using the same mesh, incompressible flow simulations are carried out and the results from three different codes are compared. In the linear region, the maximum difference of lift and drag coefficients of UCAV are found to be less than 2% and 5 counts, respectively and shows good agreement with wind tunnel test data. In a stall region, however, the reliability of RANS simulation is found to become poor and the uncertainty according to code also increases. The effect of turbulence models and meshes generated from different tools are also examined. The transition model yields better results in terms of drag which are much closer to the test data. The pitching moment is confirmed to be sensitive to the existence and the location of transition. For the case of EAV-3 wing, the difference of results with ${\kappa}-{\omega}$ SST model is increased when Reynolds number becomes low. The results for the propeller show good agreement within 1% difference of thrust. The reliability and uncertainty of three codes is found to be reasonable for the purpose of engineering use. However, the physical validity and reliability of results seem to be carefully examined when ${\kappa}-{\omega}$ SST model is used for aerodynamic simulation at low speeds or low Reynolds number conditions.

• Journal of Energy Engineering
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• v.12 no.4
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• pp.320-327
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• 2003

A CFD (Computational fluid Dynamics) research is conducted for the investigation of the fuel alteration of MBTU (medium-Btu) gas in IGCC gas turbine combustor. The computational analysis method of the gas turbine combustor is constructed by incorporating MBTU gas reaction and fuel NOx models into commercial CFD code. With the use of the present analysis method, comparisons are made on the flow velocity, the chemical species and the temperature distributions, and on the flame shape and behavior of gas turbine combustor firing natural gas and MBTU gases (coal gas, heavy residue oil gas). Furthermore, the NOx formation characteristics and the turbine matching condition of the combustor are analyzed. Based on the computed analysis results, the present study provides the directions for the redesign and the design modification of IGCC gas turbine combustor firing MBTU gas as alternative fuel.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.3
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• pp.255-267
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• 2008

Using the commercial CFD code FLOW-$3D^{(R)}$ which has an implicit General Moving Object (GMO) method, the ship-induced wave has been simulated. In the implicit GMO method of the FLOW-$3D^{(R)}$, a rigid body's motion which is either user-prescribed (prescribed motion) or dynamically coupled to fluid flow (coupled motion) can be computed with six degrees of freedom (DOF). The simulated horizontal wave patterns are agree with the wave patterns represented by depth Froude number. The model has been well-simulated to generate the depth-dependent wave transformation in comparison of uniform depth case to complicated depth case. Additionally, it shows that ship-induced waves have been reasonably generated by two ships passing each other and by a ship moving in a curve. Therefore, it is suggested that the FLOW-$3D^{(R)}$ model calibrated with observed data should provide more accurate prediction for the ship-induced wave in a certain fairway or harbor.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.96-101
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• 2011

In this study, we have established the design techniques, with which we can design and evaluate performance of blades on a horizontal axis current turbine, by application of blade element momentum theory considering the blade tip's loss model, and finally developed the domestic software(MCT-blade V2.0). We have designed and evaluated performance of blades for the 2MW class by using of the software, and confirmed its calculation results from BEMT by comparing those results from commercial code of ANSYS FLUENT. In a state of rated velocity 2.5m/s, the mechanical power from BEMT is calculated as 2,121kW, which is considered to satisfy the electrical power, but the value from CFD is calculated as 1,901kW, which is considered a little deficient for the target output.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.432-438
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• 2017

The primary objective of the current work was to develop a standardized retrofit hull form capable of saving energy based on existing vessels. The bow shape of existing vessels was investigated, giving consideration to design draft and speed. Resistance performances were assessed for existing vessels according to operating conditions. Commercial CFD codes and model test materials were used for assessment of effective power. Three retrofit hull forms with minimum resistance were selected given real operating conditions. These vessels were named after customized ready-made hull forms to enable ship owners to make easier choices. The effective power of each vessel was estimated under real operating conditions. Subjects were operated with the lowest draft, and performance for retrofit No. 3 showed an 11-16% improvement in effective power at low speed ranges of 16-18 knots compared to existing vessels. When operated with a middle draft, performance for retrofit No. 3 showed a 6-11% improvement in effective power at low speed ranges compared to existing vessels. When operated with the highest draft, performance for all vessels showed little difference in effective power.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2006.05a
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• pp.164-169
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• 2006

본 연구는 가정용 가스 보일러의 배기가스 유동특성을 전산유체역학을 이용하여 정밀 분석하고 CO 검지 장치의 최적화 설계를 결정하는 것을 목적으로, CFD 상용코드 FLUENT 6.2를 이용하였다. 배기가스 포집위치에서 가스 유속의 균일성과 CO농도 검출기에서의 속도가 주요 성능 인자이며 포집기의 위치, 포집구멍의 크기 및 배기가스의 유량을 주요 변수로 선택하였다. 포집기의 위치는 배기부의 상부와 하부인 두가지의 경우이고 두 경우의 배관 높이 차이는 10 mm이다. 포집구멍의 직경 변화는 3 mm, 4 mm 및 5 mm인 세가지 경우이다. 마지막 변수인 배기가스의 유입속도는 20,000 kcal/hr용량의 k사 가스 보일러가 공기비 1.1일 경우에 정상 연소시 0.5 m/s임을 알았고 저부하와 고부하일 경우를 고려해서 0.3 m/s, 0.5 m/s 및 0.7 m/s의 세가지 경우를 변수로 결정하여 총 18가지 형태의 대상을 전산유체 역학을 통해서 분석하였다. 궁극적인 목표였던 배기가스의 균일성은 한가지 경우를 제외 하고는 만족할만한 결과를 얻었기 때문에 CO검지 장치가 위치할 곳에서의 속도 및 포집구멍의 크기가 CO농도 검출기 유속의 주요 인자라 할 수 있다. 결론적으로 포집구멍의 크기가 5 mm인 6가지 경우 중에서 두가지 경우는 검지장치의 유효속도를 초과하였고 포집구멍의 크기가 3 mm인 경우는 검지장치의 유입 속도가 상대적으로 작으므로 포집구멍의 크기는 4 mm가 적합한 것으로 판단하였다.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.28-35
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• 2003

A numerical analysis of electrochemical reaction and dynamics of the fluid flow in the channels of a DMFC separator was carried out by using a commercial Computational Fluid Dynamics(CFD) code fluent(ver.6.0). From the simulation work, many valuable informations were obtained in terms of distributions of velocity, pressure, temperature, concentration and current density over the flow field. And it was possible to optimize the flow field structure by using the simulation results. The simulation work using the Cm code was found very helpful in analysing the phenomena occurring in the fuel cell and optimizing the structures of electrodes and flow field.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.9-14
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• 2009

A numerical investigation was performed based on the Reynolds-Averaged Navier-Stokes(RANS) equations for the two-dimensional unsteady flow around a vertical axis turbine(VAT) with three or four blades. VAT is one of the promising devices for tidal current energy conversion. The geometry of the turbine blade was $NACA65_3$-018 airfoil, for which CFD analysis using Fluent was carried out at several angles of attack and the results were compared with the corresponding experimental data for validation and calibration. Then CFD simulations were carried out for the whole vertical axis turbine with a two-dimensional setup. The CFD simulation demonstrated the usefulness of the method to study the typical unsteady flows around VATs and the results showed that the optimum turbine efficiency could be achieved for carefully selected combinations of the number of blade and Tip-Speed Ratio(TSR).