• Clean Technology
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• v.15 no.4
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• pp.258-264
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• 2009

Thermodynamic measurements were performed to show the possibility of recovering $CO_2$ from fuel gas (the mixture of $CO_2$ and $H_2$) by forming gas hydrates with water where water was dispersed in the pores of silica gel particles having nominal 100 nm of pore diameter. The hydrate-phase equilibria for the ternary $CO_2+H_2$+water in pores were measured and $CO_2$ concentrations in vapor and hydrate phase were determined under the hydrate-vapor two phase region at constant 274.15 K. It was shown that the inhibition effect appeared due to silica gel pores, and the corresponding equilibrium dissociation pressures became higher than those of bulk water hydrates at a specific temperature. In addition, direct measurement of $CO_2$ content in the hydrate phase showed that the retrieved gas from the dissociation of hydrate contained more than 95 mol% of $CO_2$ when 42 mol% of $CO_2$ and balanced Hz mixture was applied. Compared with data obtained in case of bulk water hydrates, which showed just 83 mol% of $CO_2$ where 2-stage hydrate slurry reactor was intended to utilize this property, the hydrate formation in porous silica gel has enhanced the feasibility of $CO_2$ separation process. Hydrate formation as not for slurry but solid particle makes it possible to used fixed bed reactor, and can be a merit of well-understood technologies in the industrial field.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1686-1691
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• 2004

The effect of recirculated exhaust gas on performance and exhaust emissions with FGR rate are investigated by using a natural circulation, pressurized draft and water tube boiler with FGR system operating at several boiler loads and over fire air(OFA) damper openings. The purpose of this study is to apply the FGR system to a power plant boiler for reducing $NO_{x}$ emissions. To activate the combustion, the suction damper of two stage combustion system installed in the upper side of wind box is opened by handling the lever between $0^{\circ}$ and $90^{\circ}$ , and the OFA with 0 to 20% into the flame is supplied, as the combustion air supplied to burner is reduced. It is found that the fuel consumption rate divided by evaporation rate does not show an obvious tendency to increase or decrease with rising the FOR rate, and $NO_{x}$ emissions are decreased, at the same OF A damper opening, as FOR rates are elevated and boiler loads are dropped.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.4
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• pp.740-746
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• 2009

Two step serial load induction superheater has been proposed using resonance type induction heat method in this paper. Heat method is a type of flowing the electron induction and current to special alloy heater in body from external heat coil with non-contact method. Inverter was a full bridge serial load resonance type and inductor was used as load in LC resonance design to maximize the efficiency. The developed system is a new heat exchanging method combined with electromagnetic induction heater and fluid movement, ana very accurate to control of heating the gas, liquid and evaporated mass, so on without combustion process.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.40.2-40.2
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• 2011

초경합금은 경도가 높은 재료를 말하며 일반적으로는 탄화텅스텐(WC)계 재료를 말한다. 국내 현재 초경합금 동향은 반도체 산업, 내마모성 공구, 절삭공구, 금형 등 많은 분야에 사용되어지고 있다. 또한 최근 들어 FSW (Friction Stir Welding, FSW)기술이 발전함에 따라 접합기술개발이 다양화되면서 FSW Tool의 고성능의 초경 재료가 요구되어지며 장수명의 Tool개발이 되어야 한다. 국내에서는 초경 합금 재료로 사용되어지고 있는 텅스텐 카바이드(WC)와 코발트(Co)를 이용하여 많은 연구가 진행되었다. 본 실험에서는 텅스텐 카바이드와 코발트 및 몰르브덴 카바이드를 혼합하여 소결체를 제조하였다. 실험에 사용된 텅스텐 카바이드는 높은 경도를 가지고 강한 취성을 나타내며, 소결에 어려운 단점이 있다. 이러한 단점을 코발트와 몰리브덴 카바이드를 첨가하여 소결온도를 낮춰주는 역할과 액상 소결시 텅스텐카바이드 입자사이에 침투하여 액상소결에 의한 치밀화가 가능하게 해주며 인성이 향상되어 고인성 재료를 만들 수 있었다. 본 실험에서는 합성과 치밀화가 동시에 진행되는 SPS (Spark Plasma Sintering:SPS) 장비를 이용하여 실험을 진행하였다. 이 방법은 방전플라즈마 소결 공법으로, 기존의 연소법과 열간 가압기술(Hot-press, HIP)을 결합한 방식으로 단 시간, 단일공정으로 치밀한 소결체를 얻을 수 있는 장점이 있다. 본 연구에서는 $WC-5Mo_2C$-5wt%Co 소결체 제조를 위해 원소 분말을 Horizontal ball milling 혼합하였다. 균일하게 혼합된 분말을 흑연다이에 충진하여 펄스전류와 기계적 압력을 동시에 가하여 $WC-5Mo_2C-5Co$ 복합재료를 제조하고 소결체의 밀도, 순도, 상변태, 미세조직 등을 분석 및 평가하였다. SPS공정 조건은 고진공하에서 $1,200^{\circ}C$-60MPa, 펄스비 12:1 조건으로 수행하였으며, 얻어진 $WC-5Mo_2C-5Co$ 소결체의 상대 밀도는 98%이상 이였다. 또한, 결정립 크기는 약 400 nm였으며, 경도는 $2,453kg/mm^2$를 나타내었다.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.602-608
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• 2014

Hydrogen energy, a field of low-carbon substitute energy, can be produced by fossile fuel reforming and electrolysis of water etc. We developed 1kW class flat type reformer for PEM Fuel Cells. The PEMFC is highly sensitive to carbon monoxide because CO has detrimental effects on the performance of the fuel cell. Thus, reformed gas supplied to Fuel cell system, which maintained CO concentration below 10ppm. After applying optimum drive condition, reformed gas was measured with gas chromatography and could find out about each experimental condition of $H_2$ and CO concentration. As a results, The 1kW class plate type hydrogen generation system's optimum condition is A/F ratio ${\alpha}=1.3$, STR temperature 1023K, S/C ratio 3, and $PrOx1{\cdot}2$ 30cc/min. It turns out that installation of PrOx 2 stage is more efficient for reducing CO concentration.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.928-935
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• 2010

A bag filter system was partially burnt down during a trial run of waste wood incineration boiler. This brought about unburned hydrocarbon which caused a rapid deactivation of low temperature SCR catalyst set up in two stage after the bag filter. The deactivated catalyst was investigated in order to trace the origin by several characterization methods such as XRD, EDX, BET, TGA, SEM. The deactivated catalyst was regenerated by different methods such as acid washing, water washing in ultrasonication, and calcination treatment under air condition. It is found the calcination treatment under air condition at $450^{\circ}C$ for 2 hours to be the best regeneration method. The catalytic activity was measured in the form of 2 cm ${\times}$ 2 cm ${\times}$ 10 cm (catalyst weight 10 g) honeycomb type. A deNOx efficiency of the regenerated catalyst showed 100% at $180^{\circ}C$ which is the same level of fresh one.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.45-51
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• 2012

This work was investigated 2-stage injection strategy on combustion and emissions in a direct injection compression-ignition engine fueled with DME. Single cylinder engine was equipped with common rail. Injection pressure was 700bar, dSOI between the main injection and the pilot injection was varied. Diesel was used as compared fuel of DME in all cases. The results was shown that maximum pressure was higher than all cases and its amount of DME and diesel was similar. Regardless the pilot injection, the main fuel injection timing was same. The heat release rate of the main injection for diesel was high while that of pilot injection for DME was high. The THC was very low regardless of the fuel type and injection strategy. In the single injection, NOx was increased to retard of main injection timing regardless of the fuel type. NOx emissions was decreased with the retardation of the main injection timing regardless of the fuel type in the case of 2-stage injection strategy.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.97-102
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• 2013

A prestudy on expendable turbine engine for high-speed vehicle was conducted. After two possible mission profiles were established to decide the engine requirements, design point analysis was performed with the values of design parameter which were obtained from similar class engines, references, etc. The results showed that specific net thrust and specific fuel consumption with turbine inlet temperature of 3,600 R are 2,599.4 ft/s and 1.483 lb/(lb*h) respectively at the flight condition of sea level, Mach 1.2. It was also found that major design parameters for determining maximum net thrust were turbine inlet temperature for low supersonic and transonic flight speed and compressor exit temperature for high supersonic flight speed from the results of performance analysis on the two possible mission profiles. In addition, simple turbojet engine with an axial compressor, a straight annular combustor, an one stage axial turbine and a fixed throat area converge-diverge exhaust nozzle was proposed as the configuration of simple low cost lightweight turbine engine.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.376-377
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• 2011

최근 Mg, Mg-Al합금, Al은 전자제품의 케이스, 차량의 휠 등의 신소재로서 활용성이 높아 사회적 수요가 급격히 늘고 있다. 이러한 수요 증가와 함께 관련 사업장에서는 취급 과정에서 폭발사고 위험성이 높아지고 있는데, 2010년도에는 국내 사업장에서 금속 분진에 의한 폭발사고가 4건이 발생하여 인명 및 재산피해가 발생하였다. Mg-Al합금의 폭발사고로 사망 1명과 부상 2명이 발생하였으며, Al분진의 폭발사고는 3건이 발생하여 사망 2명과 부상 3명의 인명피해로 이어졌다. 사고조사를 통하여 사업장에서의 금속분진에 대한 위험인식이 매우 낮은 것이 유사 사고가 반복되고 있는 가장 큰 이유로 알려지고 있는데, 이는 금속분진에 대한 부족한 안전기술정보와 밀접한 관련이 있다. 본 연구에서는 Mg, Mg-Al합금, Al등을 취급하는 관련 사업장에서 폭발사고 예방대책을 위하여 활용할 수 있는 폭발특성에 관한 안전기술정보 제공을 목적으로 하고 있다. 보다 구체적으로는 사고 다발 금속분진에 대한 위험성 이해에 도움을 될 수 있도록 동일 입경분포 조건에서의 위험성을 정량적으로 평가하였으며, 이를 위하여 각 금속분진의 동일 입경 조건에서 최대폭발압력, 폭발하한계 등의 폭발위험성 데이터를 실험적으로 조사 하였다. 조사한 시료는 평균입경 200 mesh의 Al, Mg, Mg-Al(60:40 wt%)로서 입도분석기(Beckman Coulter LSI 3320)를 사용하여 측정한 결과 평균입경은 약 $155{\mu}m$로 나타났다. Al분진의 농도변화에 따른 폭발압력을 조사한 결과, 최대폭발압력(Pmax)은 7.9 bar였으며 최대폭발압력상승속도 (dt/dP)max는 농도 $1500[g/m^3]$에서 322 [bar/s]로 최대가 되었으며 폭발 하한계(LEL)는 $70[g/m^3]$가 얻어졌다. 반면에 순수한 Mg의 LEL은 $30[g/m^3]$였으며 Pmax는 6.4 bar, (dP/dt)max는 100 [bar/s]가 얻어졌다. 이러한 결과로부터 LEL이 낮은 Mg는 Al보다 연소성이 큰 것으로 나타났으며, Al은 화염을 유지하는데 필요한 최저 열분해 가스농도를 확보하는데 Mg보다도 고농도의 분진이 필요함을 알 수 있었다. 또한 Mg-Al(60:40 wt%)의 LEL은 $50g/m^3$이었으며 Pmax는 9.4 bar, (dP/dt)max는 472 [bar/s]가 얻어졌다. 이러한 결과로부터 Mg-Al(60:40 wt%)합금의 연소성을 살펴보면 착화하기 쉬운 정도는 Mg와 Al의 성분비에 의해 변화하지만 Mg와 Al의 중간 정도로 나타나는 반면, Pmax는 Mg 또는 Al의 단독 물질 성분보다도 매우 큰 것을 알 수 있었다. 본 연구를 통하여 단일 성분의 Mg와 Al보다도 Mg와 Al이 일정 비율로 구성된 Mg-Al합금의 경우가 화재폭발 위험성이 증가한다는 사실을 알 수 있었으며, 이와 같은 폭발위험특성 자료를 활용하여 분진의 보관, 취급, 폐기 등의 지속적 관리가 필요하며 사업장 특성에 적합한 안전대책을 통한 사고예방대책이 요구된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.28-37
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• 2004

A two-dimensional direct numerical simulation was performed to investigate the evolution and vortical structure of a single vortex in reacting and non-reacting jet flow fields. A predictor-corrector-type numerical scheme with a low Mach number approximation was used, and a two-step global reaction mechanism was adopted as the combustion model. Through the comparisons of single vortex behaviors in reacting and non-reacting jet flow fields, it was found that the evolution characteristics and vortical structure of the single vortex were significantly influenced by a outer vortex that was generated from the buoyance effect as well as the chemical heat release. Furthermore, it was also identified that the differences of the vortical structure in reacting and non-reacting jet flow fields were mainly attributed to the thermal expansion, Baroclinic torque and buoyance effect.