• 대한기계학회논문집B
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• 제41권10호
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• pp.667-673
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• 2017

공개소스 전산유체 해석 라이브러리인 OpenFOAM을 이용하여 음극 지지체형 고체산화물 연료전지의 온도균일성에 관한 연구를 수행하였다. 3가지 유형의 유동흐름(병행류, 대향류, 직교류)에 대하여 수치해석이 이루어졌다. 다공성 물질내에서의 기체의 흐름은 유효확산계수를 이용하여 계산하였고 분리판의 리브 영향도 고려하였다. 전기화학반응의 계산을 위하여 실험식으로부터 얻은 집중내부저항 모델이 사용되었다. 수치해석 결과 대향류가 가장 균일한 온도분포를 나타내었다.

• 신재생에너지
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• 제8권3호
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• pp.6-13
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• 2012

This paper describes unsteady internal flow characteristics of a cathode air blower, used for the 1 kW fuel cell system. The cathode air blower considered in the present study is a diaphragm type blower. To analyze the flow field inside the diaphragm cavity, compressible unsteady numerical simulation is performed. Moving mesh system is applied to the numerical analysis for describing the volume change of the diaphragm cavity in time. Throughout a numerical simulation by modeling the inlet and outlet valves in a diaphragm cavity, unsteady nature of an internal flow is successfully analyzed. Variations of mass flow rate, force and pressure on the lower moving plate of a diaphragm cavity are evaluated in time. The computed mass flow rate at the same pressure and rotating frequency of a motor has a maximum of 5 percent error with the experimental data. It is found that flow pattern at the suction process is more complex compared to that at the discharge process. Unsteady nature of internal flow in the cathode air blower is analyzed in detail.

• 전기화학회지
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• 제11권1호
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• pp.51-58
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• 2008

고분자 전해질 연료전지의 성능향상을 위한 방법으로 유동채널의 형상을 변경한 많은 연구가 진행되어 왔으나 동일한 유동채널 형상에서 유동방향 변경에 따른 연구는 많이 진행되지 못하였다. 본 연구에서는 동일한 반응면적과 동일한 유동채널의 고분자 전해질 연료전지의 수소와 산소의 유동방향을 Co-flow에서 Counter-flow로 변경될 경우의 연료전지의 성능변화를 분석하기 위하여 연료극과 공기극이 포함된 3차원 수치해석모델을 개발하였다. 개발된 수치해석모델을 활용하여 Co-flow와 Counter-flow의 유동채널 내부의 압력손실, 반응물질의 농도분포, 고분자 전해질 막을 통한 Water Transport, 고분자 전해질 막의 이온전도도 및 I-V 성능곡선을 비교하였다. 그 결과 반응물질의 농도분포, Water Transport, 고분자 전해질 막의 이온전도도가 우수한 Counter-flow 유동조건에서의 성능이 Co-flow 유동조건에 비하여 더욱 우수하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1184-1189
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• 1990

In order to investigate liquid fuel filming over the intake manifold wall, an electrode-type probe has been developed by lines of authors and this probe was employed in a single cylinder two and four-stroke cycle engine and in a four cylinder four-stroke engine operated by neat methanol fuel. The performance of the probe was dependent upon several parameters including the liquid fuel layer thickness, temperature, additive in the fuel, and electric power source (i.e., AC and voltage level) and was independent of other variables such as direction of liquid flow with respect to the probe arrangement. Several new findings from this study may be in order. The flow velocity of the fuel layer in the intake manifold of engine was about (if the air velocity in the steady state operation, the layer thickness of liquid fuel varied in both the circumferential and longitydinal directions. In the transient operation of the engine, the temporal variation of fuel thickness was determined, which clearly suggests that there was difference between fuel/air ratio in the intake manifold and that in the cylinder. The variation was greatly affected by the engine speed, fuel/air ratio and throttle opening. And the variation was also very significant from cylinder to cylinder and it was particularly strong different engine speeds and throttle opening.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.472-477
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• 2003

This study was performed to investigate the behavior of vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The images of vapor phases were measured in the motoring engine using exciplex fluorescence method. The conventional engine was modified as GDI engine with swirl flow. Fuel was injected into atmospheric nitrogen to prevent quenching phenomenon by oxygen. Injection pressure is 5.1MPa. Two dimensional spray fluorescence image of vapor phases was acquired to analyze spray behavior and fuel distribution inside of cylinder. Three injection timings were set at BTDC $180^{\circ}$, $60^{\circ}$and $60^{\circ}$. With a fuel injection timing of BTDC $60^{\circ}$, fuel-rich mixture was concentrated in near the cavity center. With a fuel injection timing of BTDC $60^{\circ}$, fuel-rich mixture level in the center region was highest in the S-type during the late compression stroke. With a fuel injection timing of BTDC $180^{\circ}$, fuel was not affected in a piston cavity and generally distributed as homogeneous mixture.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.251-253
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• 2017

Prefilming air blast 연료노즐의 다상유동 해석을 수행하였다. 연료가 미립화되는 과정을 관찰하였으며 liquid film의 두께와 속도를 계산하였다. Slot에서 분사된 연료는 prefilmer surface에서 얇은 액막을 형성한 후 연료노즐 lip에서 액적으로 분열되었다. 또한 계산된 liquid film의 두께와 속도를 경계조건으로 하여 반응유동장 해석을 수행하였다. 분사된 액적은 venturi throat를 지나면서 기화되었고 연료노즐 하류에 반응영역이 형성되어 안정적으로 보염이 이루어졌다.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1153-1163
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• 2002

A transient analysis on temperatures of fuel and oil in hydraulic and lubrication systems in an aircraft was studied using the finite difference method. Numerical calculation was performed by an explicit method with modified Dufort-Frankel scheme. Among various missions, air superiority mission was considered as a mission model with 20% hot day ambient condition in subsonic region. The ambience of the aircraft was assumed as turbulent flow. Convective heat transfer coefficient were used in calculating heat transfer between the aircraft surface and the ambience. For an aircraft on the ground, an empirical equation represented as a function of free-stream air velocity was used. And the heat transfer coefficient for flat plate turbulent flow suggested by Eckert was employed for in-flight phases. The governing equations used in this analysis are the mass and energy conservation equations on fuel and oils. Here, analysis of fuel and oil temperature in the engine was not carried out. As a result of this analysis, the ground operation phase has shown the highest temperature and the largest rate of temperature increase among overall mission phases. Also, it is shown that fuel flow rate through fuel/oil heat exchanger plays an important role in temperature change of fuel and oil. This analysis could be an important part of studies to ensure thermal stability of the aircraft and can be applicable to thermal design of the aircraft fuel system.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1556-1568
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• 2021

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect stress conditions, mechanical behaviors and thermal-hydraulic performance of the fuel assembly. This paper is the Part II work of a two-part study devoted to analyzing the complex unique mechanical deformation and thermal-hydraulic characteristics for the typical plate-type fuel assembly under irradiation effect, which is on the basis of developed and verified numerical thermal-fluid-structure coupling methodology under irradiation in Part I of this work. The mechanical deformation, thermal-hydraulic performance and Mises stress have been analyzed for the typical plate-type fuel assembly consisting of support plates under non-uniform irradiation. It was interesting to observe that: the plate-type fuel assembly including the fuel plates and support plates tended to bend towards the location with maximum fission rate; the hot spots in the fuel foil appeared at the location with maximum thickness increment; the maximum Mises stress of fuel foil was located at the adjacent location with the maximum plate thickness increment et al.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.319-321
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• 2012

The flammability limit and the flame instability of nitrogen-diluted LPG fuel was experimentally studied on a co-flow flame configuration. The combustion reaction of nitrogen-diluted hydrocarbon with air could be interpreted as the equivalent reaction of pure fuel with nitrogen-diluted air. Nitrogen-diluted LPG with nitrogen up to 90 % of nitrogen mole fraction in fuel, which is close to the flammability limit, could form a co-flow flame. Various parameters such as laminar or turbulent flame, the existence of diffusion flame with pure fuel, air temperature could affect the limit of flame formation.

• 한국연소학회지
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• 제9권3호
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• pp.1-9
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• 2004

This study is aimed to characterize the combustion behavior of solid fuel in the various types of the combustors: stoker, rotary kiln and fluidized bed type combustors. Three different types of reduced-scale combustors are introduced, and temperatures and flue gas compositions are measured for various fuel sizes, water contents, initial temperature, and air flow rates. In case of the rotary kiln combustor, effects of rotating speed of the combustor are also investigated. Mean carbon conversion time (MCCT) and flame propagation rate (FPR) are used for the quantitative analysis. It is revealed that the reaction rates of the fuel are significantly influenced by the fuel characteristics, type of the combustors and air flow rate. Major design parameters for each type of the combustors are summarized through the reduced-scaled model analysis.