• 한국가스학회지
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• 제15권2호
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• pp.9-14
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• 2011

CNG 저장용기 재료인 SA-372 강에 대해 수소취화 영향을 조사하기 위한 시험을 수행하였으며 대기조건과 불활성 가스인 아르곤 그리고 CNG, HCNG 및 수소가스에 대해 35 MPa로 가압된 가스분위기에서 인장시험이 이루어 졌다. 또한 인장시험 속도는 4*10^-4 /s와 4*10^-5/s로 각각 설정하였다. 분위기 가스를 고압으로 유지한 상태에서 시험하기 위해 가압형 오토크레이버가 장착된 인장시험기를 사용하였다. 시험 결과 불활성 가스와 CNG 분위기에서는 대기조건의 인장강도, 연신률 및 단면수축률과 거의 유사한 특성을 보였으며 인장속도의 변화에 대해서도 큰 차이가 없는 것으로 나타났다. 그러나 30% 수소가 혼합된 수소혼합가스와 100% 수소 조건에서 인장강도는 큰 차이를 나타나지 않았지만 연신율과 단면 수축률에서는 눈에 띄는 변화가 있었다. 이로부터 수소가스의 취화효과는 수소가 포함된 조건에서 확인할 수 있었으며 수소농도가 높을수록 연신율과 단면수축률 변화가 크게 나타났다. 또한 인장 속도가 느릴수록 수소취화가 더 많이 나타나는 것으로 확인되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.179-179
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• 2016

A radio-frequency (RF) Inductively Coupled Plasma (ICP) torch system was used for boron-nitride nano-tube (BNNT) synthesis. Because of electrodeless plasma generation, no electrode pollution and effective heating transfer during nano-material synthesis can be realized. For stable plasma generation, argon and nitrogen gases were injected with 60 kW grid power in the difference pressure from 200 Torr to 630 Torr. Varying hydrogen gas flow rate from 0 to 20 slpm, the electrical and optical plasma properties were investigated. Through the spectroscopic analysis of atomic argon line, hydrogen line and nitrogen molecular band, we investigated the plasma electron excitation temperature, gas temperature and electron density. Based on the plasma characterization, we performed the synthesis of BNNT by inserting 0.5~1 um hexagonal-boron nitride (h-BN) powder into the plasma. We analysis the structure characterization of BNNT by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy), also grasp the ingredient of BNNT by EELS (Electron Energy Loss Spectroscopy) and Raman spectroscopy. We treated bundles of BNNT with the atmospheric pressure plasma, so that we grow the surface morphology in the water attachment of BNNT. We reduce the advancing contact angle to purity bundles of BNNT.

• 한국가스학회지
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• 제18권1호
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• pp.25-30
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• 2014

수소와 압축천연가스의 혼합연료 HCNG의 가스공급 및 충전을 위해 혼합장치 제작 및 충전실험을 수행하였다. 비율제어방식 개념으로 수소와 압축천연가스는 30 : 70의 비율로 혼합된다. HCNG 충전방법으로는 탱크의 압력을 이용하여 충전할 수 있는 FULL충전, 일정량을 충전할 수 있는 정량충전 방식이 있다. Full충전과 정량충전 결과 모두 혼합비율 30 : 70에 오차 제한범위인 수소$30{\pm}2%$ 조건을 만족시켰다. 탱크에 충전된 HCNG의 조성을 Gas Chromatography로 분석한 결과도 오차제한범위를 만족시켜 충전탱크에서도 30 : 70의 비율을 확인하였다.

• 에너지공학
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• 제26권4호
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• pp.7-13
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• 2017

환경문제가 생존문제로까지 부각되면서 대기환경 개선을 위해 친환경에너지에 대한 관심이 높아져 그에 따른 환경 친화적 연료인 수소, LPG, CNG에 대한 수요가 점차 증가하고 있는 추세이다. 특히, 대부분의 연료를 수입에 의존하고 있는 우리나라의 경우 높은 생산량과 에너지 자립적 측면에서 유리한 위치에 있는 수소 에너지의 개발에 투자를 아끼지 않고 있는 상황이다. 하지만 매년 증가하고 있는 수요만큼 작은 누출사고부터 대형 화재 폭발사고까지 충전소사고 또한 다양하게 발생하고 있기 때문에 그에 대한 연구가 필요하다. 따라서 본 연구에서는 국내 외 충전소에서 발생하는 수소, LPG, CNG의 사고 사례들을 비교 분석하였고 위험성평가를 위한 다양한 프로그램을 사용해 가스누출에 의한 피해거리를 예측하고 위험거리를 평가하였다.

• 천문학회보
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• 제43권2호
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• pp.55.1-55.1
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• 2018

Theoretical models of reionization require that approximately 10% of the Lyman Continumm (LyC) photons escape from their host dark matter haloes and re-ionize neutral hydrogen in the Universe. However, observations of Lyman break galaxies (LBGs) at z~3 report much lower escape fractions of $f_{esc}{\sim}1%$. In an attempt to understand the discrepancy, we perform radiation-hydrodynamics simulations of isolated disk galaxies using RAMSES-RT with high resolution (maximum ~ 9 pc). We find that $f_{esc}$ is ~6% on average for the reference run ($Z=0.1Z{\odot}$), whereas the fraction decreases to ~1% in the case of metal-rich disk ($Z=1Z{\odot}$). This happens because dense metal-poor gas clumps are disrupted early due to strong Lya pressure and supernova explosions, while star particles are trapped for a longer period of time in the metal-rich environments. We also find that $f_{esc}$ is still significant (~4%) even when the amount of metal-poor gas is increased by a factor of 5. Our preliminary results suggest that the low escape fractions in LBGs may be better explained by (locally) metal-enriched gas near young stars than high gas fractions in galaxies.

• Journal of Magnetics
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• 제8권3호
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• pp.124-127
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• 2003

HDDR (hydrogenation, disproportionation, desorption, recombination) and mechanical milling processes have been applied to the $SmCo_{5}$ alloy in an attempt to produce a highly coercive powder. The $SmCo_{5}$ alloy had very high structural stability under the hydrogen atmosphere and the 1:5 phase was only partially disproportionated under up to 10 kgf/$\textrm{cm}^2$ hydrogen gas. The partially disproportionated material was recombined not into 1:5 phase after the HDDR, but rather into multi-phase mixture consisting of 1:5, 2:17, 2:7 and 1:7 phases. The $SmCo_{5}$ alloy HDDR-treated with hydrogen up to 10 kgf/$\textrm{cm}^2$ had poor coercivity. For a useful HDDR to prepare a high coercivity $SmCo_{5}$ alloy powder, much higher hydrogen pressure well exceeding 10 kgf/$\textrm{cm}^2$ would be required. The $SmCo_{5}$ alloy lump was amorphized by an intensive mechanical milling, and it was crystallised ultra-finely by a subsequent optimum annealing. The optimally annealed material had very high coercivity, and it was found that the mechanical milling followed by an annealing was an effective way of producing highly coercive $SmCo_{5}$ alloy powder.

• International Journal of Automotive Technology
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• 제2권2호
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• pp.39-45
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• 2001

Hydrogen is seen as one of the important energy vectors of the next century. Hydrogen as a renewable energy source, provides the potential for a sustainable development particularly in the transportation sector. Hydrogen driven vehicles reduce both local as well as global emissions. The laboratory of transporttechnology (University of Gent) converted a GM/Crusader V-8 engine for hydrogen use. Once the engine is optimised, it will be built in a low-floor midsize hydrogen city bus for public demonstration. For a complete control of the combustion process and to increase the resistance to backfire (explosion of the air-fuel mixture in the inlet manifold), a sequential timed multipoint injection of hydrogen and an electronic management system is chosen. The results as a function of the engine parameters (ignition timing. injection timing and duration, injection pressure) we given. Special focus is given to topics related to the use of hydrogen as a fuel: ignition characteristics (importance of electrode distance), quality of the lubricating oil (crankcase gases with high contents of hydrogen), oxygen sensors (very lean operating conditions), noise reduction (configuration and length of inlet pipes). The advantages and disadvantages of a power regulation only by the air to fuel ratio (as for diesel engines) against a throttle regulation (normal gasoline or gas regulation) are examined. Finally the goals of the development of the engine are reached: power output of 90 kW, torque of 300 Nm, extremely low emission levels and backfire-safe operation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.383-386
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• 2007

This paper describes the design and integration of the wind- fuel cell hybrid system. The hybrid system components included a wind turbine, an electrolyzer (for generation of H2), a PEMFC (Proton Exchange Membrane Fuel Cell), storage system and BOP (Balance of Plant) system. The energy input is entirely provided by a wind turbine. A DC-DC converter controls the power input to the electrolyzer, which produces hydrogen and oxygen form water. The hydrogen used the fuel for the PEMFC. The hydrogen is compressed and stored in high pressure tank by hydrogen gas booster system.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.507-510
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• 2008

Characteristics of an autothermal reformer at various operating parameters have been studied in this paper. Numerical method has been used, and simulation model has been developed for the analysis. Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction are assumed as dominant chemical reactions in the autothermal reformer. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Veolcity(GHSV). SR reaction rate decreases with low inlet temperature. If OCR is increased, $H_2$ yield is increased but optimal point is suggested. WGS reaction is activated with high SCR. When GHSV is increased, reforming efficiency is increased but pressure drop may decrease the system efficiency.

• 한국재료학회지
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• 제27권9호
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• pp.466-470
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• 2017

With the matters of climate change, energy security and resource depletion, a growing pressure exists to search for replacements for fossil fuels. Among various sustainable energy sources, hydrogen is thought of as a clean energy, and thus efficient hydrogen storage is a major issue. In order to realize efficient and safe hydrogen storage, various porous materials are being explored as solid-states materials for hydrogen storage. For those purposes, it is a prerequisite to characterize a material's textural properties to evaluate its hydrogen storage performance. In general, the textural properties of porous materials are analyzed by the Brunauer-Emmett-Teller (BET) measurement using nitrogen gas as a probe molecule. However, nitrogen BET analysis is sometimes not suitable for materials possessing small pores and surfaces with high curvatures like MOFs because the nitrogen molecule may sometimes be too large to reach the entire porous framework, resulting in an erroneous value. Hence, a smaller probe molecule for BET measurements (such as hydrogen) may be required. In this study, we describe a cost-effective novel cryostat for BET measurement that can reach temperatures below the liquefaction of hydrogen gas. Temperature and cold volume of the cryostat are corrected, and all measurements are validated using a commercial device. In this way, direct observation of the hydrogen adsorption properties is possible, which can translate directly into the determination of textural properties.