• Proceedings of the KSME Conference
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• 2001.06d
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• pp.708-714
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• 2001

Although LP gas has lots of advantages, there has been limitation in application for automotive engine due to the several disadvantages, such as power decrease, complex fuel supply unit, and back fire etc. However LP gas direct injection engine has possibility to solve the problems above mentioned. LEM(Light Extinction Method) was employed for analysis of spacial and temporal distribution of LP gas which is directly injected into combustion chamber under various pressure and temperature conditions. The results from CVC(Constant Volume Chamber) were compared to those of RICEM(Rapid Induction, Compression and Expansion Machine) which simulate early- and late injection of direct injection engine. LPG fuel spray is affected by temperature and pressure in evaporation characteristics but it is more benefit to direct injection engine in every way such as, fuel distribution, evaporating speed and well wetting reduction.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1572-1582
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• 2003

Hybrid rocket combustion has a manifestation of stable response to the perturbations compared to solid propellant combustion. Recently, it has revealed that the low frequency combustion instability about 10 Hz was occurred mainly due to thermal inertia of solid fuel. In this paper, the combustion response function was theoretically derived by use of ZN (Zeldovich-Novozhilov) method. The result with HTPB/LOX combination showed a quite good agreement in response function with previous works and could predict the low frequency oscillations with a peak around 10 Hz which was observed experimentally. Also, it was found that the amplification region in the frequency domain is independent of the regression rate exponent n but showed the dependence of activation energy. Moreover, the response function has shown that the hybrid combustion system was stable due to negative heat release of solid fuel for vaporization, even though the addition of energetic ingredients such as AP and Al could lead to increase heat release at the fuel surface.

• Nuclear Engineering and Technology
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• v.12 no.4
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• pp.255-266
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• 1980

The dynamics of a typical PWR fuel rod are investigated. Mathematical models of the support grid and fuel rod were derived and verified experimentally. The finite element model and SAP V computer program were used to calculate the natural frequencies and mode shapes. A singlespan beam model is also given for predicting the fundamental mode dynamics of prototype fuel rods. The results agree quite well with the finite-element model results.

• International Journal of Safety
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• v.3 no.1
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• pp.20-26
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• 2004

The system considered in this model consists of a single, semi- transparent, diesel fuel droplet, which is immobile in the heating area and surrounded by a quiescent air. A uniform external radiation field surrounds the droplet. Results from mathematical simulation suggest that because of the higher surface temperature, the external radiative heating of the droplet can promote an earlier ignition of the fuel vapour/air mixture. The radiative heating of the droplet increases the mass transfer from the droplet to the surrounding gas-phase, thus, decreasing the heterogeneity of the fuel droplet/air system.

• Environmental Engineering Research
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• v.13 no.4
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• pp.192-196
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• 2008

The generation of high purity hydrogen from reformed hydrocarbon fuels, or syngas, is essential for efficient operation of the fuel cell (PEMFC, Polymer Electrolyte Membrane Fuel Cell). Usually, major components of reformed gas are $H_2$, CO, $CO_2$ and $H_2O$. Especially a major component, CO poisons the electrode of fuel cells. The water gas shifter (WGS) that shifts CO to $CO_2$ and simultaneously produces $H_2$, was developed to a two stage catalytic conversion process involving a high temperature shifter (HTS) and a low temperature shifter (LTS). Also, experiments were carried out to reduce the carbon monoxide up to $3{\sim}4%$ in the HTS and lower than 5,000 ppm via the LTS.

• Journal of the Korean Ceramic Society
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• v.33 no.6
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• pp.631-636
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• 1996

The powder characteristics of UO2 via AUC prepared by precipitation from a UN with AC soiution produced from nuclear fuel powder conversion plant and that of the existing facility were compared. Mean particle size of AUC powder was decreased and agglomerates were much occured in case of using the AC solution that that of the gases but other properties such as particle size distribution and shape of particle are thought to be similarly. In compaction of UO2 powder the breaking pressur of agglomerated UO2 powder and the sintered density of final UO2 pellet from AC solution were measured 1.45$\times$108 N/m2 and 10.52 g/cc, These values could be used in nuclear fuel powder fabrication process.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.4
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• pp.569-579
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• 1994

A 5.9kW phosphoric acid fuel cell(PAFC) power generation system that consists of a reformer, a stack, heat exchangers, an automatic data acquisition and control system was designed, fabricated and analyzed. This system which was firstly fabricated in Korea has been operated for 140 hours with an electricity generation of 684kWh. The PAFC generate electricity in the range of 38-52V and 50-160A and has a typical I-V characteristics of a fuel cell. Using the reformed fuel, the system performance is decreased in some degree due to CO content, compared to using the simulated fuel. At steady state operation condition, the total efficency of this system was 45.2%.

• Nuclear Engineering and Technology
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• v.45 no.4
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• pp.505-512
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• 2013

Three types of zirconium base alloy were evaluated to study how their work hardening behavior is affected by alloy composition. Repeated-tensile tests (5% elongation at each test) were performed at room temperature at a strain rate of $1.7{\times}10^{-3}s^{-1}$ for the alloys, which were initially controlled for their microstructure and texture. After considering the yield strength and work hardening exponent (n) variations, it was found that the work hardening behavior of the zirconium base alloys was affected more by the Nb content than the Sn content. The facture mode during the repeated tensile test was followed by the slip deformation of the zirconium structure from the texture and microstructural analysis.

• Advances in aircraft and spacecraft science
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• v.9 no.1
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• pp.17-37
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• 2022

This paper discusses an improved unmanned aerial vehicle, UAV, configuration characterized by telescopic booms to optimize the flight mechanics and fuel consumption of the aircraft at various loading/flight conditions.The starting point consists of a full-composite smaller UAV which was derived by a general aviation ultralight motorized aircraft ULM. The present design, named ToBoFlex, extends the two-booms configuration to a three tons aircraft. To adapt the design to needs relevant to different applications, new solutions were proposed in aerodynamic fields and materials and structural areas. Different structural solutions were reported. To optimize aircraft endurance, the innovative concept of Telescopic Tail Boom was considered along with two different tails architecture. A new structural configuration of the fuselage was proposed. Further consideration of hydrogen fuel cell electric propulsion is now being studied in collaboration between the Polytechnic of Turin and Prince Mohammad Bin Fahd University which could be the starting point of future investigations.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.256-263
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• 2010

A Crofer 22 APU mesh coated with a conductive ceramic material was developed as an alternative cathode current collector to Ag-based materials for solid oxide fuel cells. $(La_{0.80}Sr_{0.20})_{0.98}MnO_3$ (LSM) layer was deposited onto the Crofer mesh using a spray-coating technique, in an attempt to mitigate the degradation of electrical properties due to surface oxidation at high temperatures. The oxidation experiments at $800^{\circ}C$ in air indicated that the areaspecific resistance (ASR) of the LSM-coated Crofer mesh was strongly dependent on the wire diameter and the contact morphology between mesh and cell. In addition, the post-heat-treatment in $H_2/N_2$ resulted in a reduced thickness of Cr-containing oxide scales at the interface between Crofer mesh and LSM layer, leading to a decreased ASR.