• 한국수소및신에너지학회논문집
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• 제29권6호
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• pp.587-595
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• 2018

Recently, research is being conducted to use a fuel cell as a power source of unmanned aircraft. However, safety standards about applying fuel cells to unmanned aircraft are insufficient. In this paper, to improve the safety of the fuel cells for unmanned aircraft is experimentally studied. For this reason, standards for safety of fuel cells were analyzed. And influence of vibration among the evaluation items related to the safety of the fuel cell for unmanned aircraft was discussed. In order to, at constant intervals, vibration was applied to the fuel cell, then the performance was measured, the measurement items were gas tightness, polarization curve, frequency response analysis (FRA). A total of 220 hours was experimented at 20 hour intervals. the result of vibration test, gas leakage rate was a maximum of -0.04826 kPa/min and Polarization curve reached a maximum of 1.0103 times of the initial value, the charge transfer resistance reached a maximum of 1.0104 times of the initial value. This research indicate that performance of fuel cell is affected by vibration and this study is expected to contribute to the safety of fuel cell for unmanned aircraft.

• 한국환경과학회지
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• 제15권6호
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• pp.601-606
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• 2006

The coal gasification fuel is important to replace petroleum fuel. Also they have many benefits for reducing the air pollution. Measurements on the combustion characteristics of synthetic gas from coal gasification have been conducted as compared with LPG in constant volume combustion chamber. The fuel is low caloric synthetic gas containing carbon monoxide 30%, hydrogen 20%, carbon dioxide 5%, and nitrogen 45%. To elucidate the combustion characteristics of the coal gasification fuel, the combustion pressures, combustion durations, and pollutants(NOx, $CO_2$, CO) are measured with equivalence ratios($\phi$), and initial pressures of fuel-air mixture in constant volume chamber. In the case of the coal gasification fuel, maximum combustion pressure and NOx concentration are lower rather than LPG fuel. However CO and $CO_2$ emission concentration are similar to that of LPG fuel.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.743-748
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• 2022

The initial operation stability of hydrogen-fueled, solid oxide fuel cell with Ni thin-film anode fabricated by direct current sputtering was evaluated in terms of electrochemical properties such as peak power density, open circuit voltage, overpotential, and alternating current impedance at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.592-597
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• 1996

The KALIMER core, of which nuclear design is largely governed by inherent safety and reactivity control issues, is fueled with metallic fuel, and the initial core will be loaded with 20% enriched Uranium metal fuel. KALIMER safety design objectives include the accommodation of unprotected, ATWS events without operator action, and without the support of active shutdown, shutdown heat removal, or any automatic system without damage to the plant and without jeopardizing public safety. The transient analysis of the core designs has been focused on severe events to assess the margins in the design, and ATWS events are the most severe events that must be accommodated by the KALIMER design. The ATWS performance has been evaluated for the preliminary initial core design of KALIMER with a particular emphasis on the inherent negative reactivity feedback effects, including the Doppler, sodium density, fuel axial expansion, core radial expansion, and control rod driveline expansion. Results show that the Uranium metal core design meets the temperature limits with margin.

• 대한기계학회논문집B
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• 제27권11호
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• pp.1595-1603
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• 2003

Droplet combustion at high ambient pressures is studied numerically by formulating one dimensional combustion model in the mixture of n-heptane fuel and air. The ambient pressure is supercritical conditions. The modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties to account for the real gas effect on fluid p-v-T properties in high pressure conditions. Non-ideal thermodynamic and transport property at near critical and supercritical conditions are also considered. Several parametric studies are performed by changing ambient pressure and initial droplet diameter. Droplet lifetime decreased with increasing pressure. Surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• 대한기계학회논문집B
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• 제33권5호
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• pp.373-380
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• 2009

The evaporation process of multi-component fuel is different from one of a single component, because the properties of each component affects among the components. In actual engine, the spatial distribution of fuel vapor concentration dominates auto-ignition and initial combustion, and depends on the volatility and diffusivity of each component fuel contained in the multi-component fuel. Then, this study proposes a simplified numerical scheme for analysis of evaporation process of multi-component fuel sprays. Evaporation process is calculated by KIVA-II code based on the simple two-phases region that is approximated by modified saturated liquid-vapor line, which was obtained by connecting the 50% distillation temperature for each component under several pressure fields. Consequently, it can be quantitatively simulated that vapor of low boiling fuel component mostly exists around nozzle and spray tip region, the high boiling duel component, on the other hand, mostly appears near the spray tip.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.135-147
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• 2020

A methodology for evaluation of mechanical and thermal effects of localized non-axisymmetric oxidation in zircaloy claddings on LWR fuel reliability is proposed. To this end, the basic capabilities of the FALCON fuel behaviour code are used. Examples of methodology application to adjustment of selected operational limits for modern BWR fuel rods, to capture effects of the excess local oxidation, are presented. Specifically, the limiting rod internal pressure for the onset of cladding lift-off is reduced, depending on initial excess oxidation spot sizes. Also, the power limits for Anticipated Operational Occurrences are adjusted, to preclude fuel melting and cladding failure due to PCMI and PCI-SCC in the affected fuel rods.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1096-1108
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• 2016

Metal fuel is being developed for the prototype generation-IV sodium-cooled fast reactor (PGSFR) to be built by 2028. U-Zr fuel is a driver for the initial core of the PGSFR, and U-transuranics (TRU)-Zr fuel will gradually replace U-Zr fuel through its qualification in the PGSFR. Based on the vast worldwide experiences of U-Zr fuel, work on U-Zr fuel is focused on fuel design, fabrication of fuel components, and fuel verification tests. U-TRU-Zr fuel uses TRU recovered through pyroelectrochemical processing of spent PWR (pressurized water reactor) fuels, which contains highly radioactive minor actinides and chemically active lanthanide or rare earth elements as carryover impurities. An advanced fuel slug casting system, which can prevent vaporization of volatile elements through a control of the atmospheric pressure of the casting chamber and also deal with chemically active lanthanide elements using protective coatings in the casting crucible, was developed. Fuel cladding of the ferritic-martensitic steel FC92, which has higher mechanical strength at a high temperature than conventional HT9 cladding, was developed and fabricated, and is being irradiated in the fast reactor.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2880-2886
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• 2020

A small leak occurring on the surface of a fuel rod due to damage exposes UO₂ to a steam atmosphere. During this time, fission gas trapped inside the fuel rod leaks out, and the gas leakage can be increased due to UO₂ oxidation. Numerous studies have focused on the steam oxidation and its thermodynamic calculation in UO₂. However, the thermodynamic calculation of the UO₂ oxidation in a pressurized water reactor (PWR) environment has not been studied extensively. Moreover, the kinetics of the oxidation of UO₂ pellet also has not been investigated. Therefore, in this study, the thermodynamics of UO₂ oxidation under steam injection due to a damaged fuel rod in a PWR environment is studied. In addition, the diminishing radius of the UO₂ pellet with time in the PWR environment was calculated through an experiment simulating the initial time of steam injection at the puncture.

• International Journal of Automotive Technology
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• 제7권5호
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• pp.519-526
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• 2006

For investigating the effect of fuel stratification on flame propagation, initial flame development and propagation were visualized under different axially stratified states in a port injection SI engine. Stratification was controlled by the combination of the port swirl ratio and injection timing. Experiments were performed in an optical single cylinder engine modified from a production engine and images were captured through the quartz window mounted in the piston by an intensified CCD camera. Firstly in this paper, the characteristics under no port-generated swirl condition, i.e. normal conventional case was studied. Under various stratified conditions, flame images were captured at the pre-set crank angles. These were averaged and processed to characterize the flames propagation. The flame stability was estimated by the weighted average of flame area and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance, and mean absolute deviation of propagating direction. Results show that stratification state according to injection timing do not affect on the direction of flame propagation. The flame development and the initial flame stability are strongly dependent on the stratified conditions and the initial flame stability is closely related to the engine stability and lean misfire limit.