• 한국안전학회지
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• 제18권4호
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• pp.71-77
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• 2003

To inject fresh air into a fire room, Positive Pressure Ventilation (PPV) can be used and the blower of PPV increases inside pressure of the room. It makes high flow rate of products of combustion, smoke and heat from the structure, and it is very helpful to fireman on the fire extinguishing work. The flame moves to the direction of airflow and the temperature of flame can be decreased rapidly. In this experiment, a water mist system is applied to PPV to increase the effectiveness, and various effective factors are studied. n-Heptane and pine wood stick were used as fuel. Temperatures at the above and behind the combustion pan were strongly reduced by the water mist system and by the convective cooling with airflow. The smoke density was also decreased by PPV with water mist system and it can be explained by the absorption of smoke particles on the water mist droplet and by the strong exhausting effects of mobile fan.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.9-10
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• 2013

This study reports the results of an experimental investigation of emission and temperatures from the syngas-air premixed flame with a various mixture composition in the region of large equivalence ratios. The effects of hydrogen contents and equivalence ratios on the flame velocity, which reported before, and emission of syngas fuel are examined. In this study, representative syngas mixture compositions ($H_2:CO$) such as $H_2:CO=10:90$, 25:75, 50:50 and 75:25 and equivalence ratios from 0.5 to 5.0 have been conducted. The emissions of syngas fuel were measured by the high precision analyzer with enclosure configuration and the adiabatic temperatures are calculated by used Chemkin basis. The NOx emission level is coincided relatively well with the adiabatic temperature distributions in lean mixture conditions, but for rich mixture conditions NOx level was also increased again even though the adiabatic temperature decreases. Such an increasing characteristics in rich mixture conditions is coincided well with the tendency that rather the flue gas temperature increases.

• 한국항공우주학회지
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• 제36권1호
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• pp.62-71
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• 2008

액체로켓엔진에서 발생하는 고주파 연소불안정을제어하기 위하여 인젝터의 길이 변화를 줄 수 있는 다중 스월 인젝터의 감쇠효과를 분석하였다. 음향흡수자로서 인젝터의 효과를 분석하기 위하여 인젝터는 1/4 파장 공명기로 해석하였고, 상온에서 감쇠 효과의 적합성을 검증하였다. 인젝터 내부에 형성되는 air core의 부피가 감쇠 효과에 직접적인 영향을 주므로 이를 모사한 다수의 튜브로 실험을 하였다. 실험을 통해 각 모드의 배(anti-node point)에 장착된 인젝터의 수의 증가로 감쇠 효과가 커지는 것을 확인하였다. 또한 1L, 1T, 1L1T 모드에 동조된 인젝터들을 동시에 각 모드의 배에 장착했을 경우, 각 모드에서 단일 모드에 튜닝된 인젝터들을 장착하였을 경우와 거의 같은 감쇠 효과를 얻을 수 있었다.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.114-120
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• 2006

The basic effects of hydrogen addition for engine performance and emission were investigated in single cylinder research engine. Seven commercial injectors were tested to choose a suitable injector for hydrogen injection prior to its engine implementation. The hydrogen fuel leakage and flow rate were evaluated for each injector and KN3-1(Keihin, CO.) showed the best performance for hydrogen fuel. At the higher excess air ratio(${\lambda}=1.7$, 2.0), the better combustion stability was found with hydrogen addition even though its effect was small at lower excess air ratio (${\lambda}=1.0$, 1.3). Stable operation of the engine was even guaranteed at ${\lambda}=2.0$, if the amount of hydrogen gas was near 15% of total energy. In the lean region, ${\lambda}>1.3$, thermal efficiency was improved slightly while it was not clearly observed at ${\lambda}=1.0$, 1.3. It is considered that, in some cases, high temperature environment due to hydrogen combustion caused further heat loss to surroundings. Except for ${\lambda}=1.0$, with larger amount of hydrogen addition, CO was reduced drastically but it was emitted more at the leaner region. Nitric oxides(NOx) was increased a little more with hydrogen addition at ${\lambda}=1.0$, 1.3. However, at ${\lambda}>1.3$ its relative amount of emission was low. In addition, the amount of NOx was continuously decreased with hydrogen addition, but, at ${\lambda}=2.0$ the amount of NOx was lowered to 1/100 of that of ${\lambda}=1.0$. THC emission was significantly increased as air/fuel ratio was raised to leaner region due to misfire and partial burn.

• 한국분무공학회지
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• 제24권1호
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• pp.35-42
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• 2019

Syngas is widely produced by incomplete combustion of coal, water vapor, and air (oxygen) in a high-temperature/high-pressure gasifier through a coal-gasification process for power generation. In this study, a simulation syngas which was mainly composed of $H_2$, CO, $CO_2$, and $N_2$ was fueled with diesel. A modified single cylinder compression ignition (CI) engine is equipped with intake port syngas supply system and mechanical diesel direct injection system for dual fuel combustion. Combustion and emission characteristics of the engine were investigated by applying various syngas composition ratios and compression ratios. Diesel fuel injection timing was optimized to increase indicated thermal efficiency (ITE) at the engine speed 1,800 rpm and part load net indicated mean effective pressure ($IMEP_{net}$) 2 to 5 bar. ITE of the engine increased with the $H_2$ concentration, compression ratio and engine load. With 45% of $H_2$ concentration, compression ratio 17.1 and $IMEP_{net}$ 5 bar, ITE of 41.5% was achieved, which is equivalent to that of only diesel fuel operation.

• Journal of Advanced Marine Engineering and Technology
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• 제36권2호
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• pp.244-249
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• 2012

최근 화석연료 사용으로 인한 에너지 위기와 환경오염 문제가 사회적 문제점으로 떠오르고 있어 친환경 에너지 개발에 대한 연구가 활발히 진행되고 있다. PEMFC는 기본적으로 수증기 개질반응을 통해 고순도 수소를 얻고 있지만 운전 시 기동시간이 길고 빠른 기동을 필요로 하는 곳에는 문제가 있다. 따라서 본 연구실에서는 1KW급 평판형 STR 반응기에 적용할 연소기의 고효율 및 균일가열을 목표로 세라믹 허니컴을 적용하는 가능성을 알아본다. 한편, 축열체의 열량 보존시간에 대한 실험결과는 마일드연소기 개발에서 공기의 고온화를 위한 기초자료로 활용하고자 한다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.13-19
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• 2003

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthen. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, it is well known that HCCI engines increased HC and CO. Thus, the investigation of combustion characteristics which consists cool and hot flames for HCCI engines were needed to obtain the optimal combustion condition. In this study, combustion characteristics for direct inject type HCCI engine such as quantity of cool flame and hot flame, ignition timing and ignition delay were investigated to clarify the effects of these parameters on performance. The results revealed that diesel combustion showed the two-stage ignition of cool flame and hot flame, the rate of cool flame increase and hot flame decrease with increasing intake air temperature. On the other hand, the gasoline combustion is the single-stage ignition and ignition timing is near the TDC. In addition mixed fuel combustion showed different phenomenon, which depends on the ratio of gasoline component. Ignition timing of mixed fuel is retarded near the TDC and the ignition delay is increased according to ratio of gasoline.

• Nuclear Engineering and Technology
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• 제51권7호
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• pp.1749-1757
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• 2019

Predicting lower flammability limits (LFL) of hydrogen has become an ever-important task for safety of nuclear industry. While numerous experimental studies have been conducted, LFL results applicable for the harsh environment are still lack of information. Our aim is to develop a calculated non-adiabatic flame temperature (CNAFT) model to better predict LFL of hydrogen mixtures in nuclear power plant. The developed model is unique for incorporating radiative heat loss during flame propagation using the CNAFT coefficient derived through previous studies of flame propagation. Our new model is more consistent with the experimental results for various mixtures compared to the previous model, which relied on calculated adiabatic flame temperature (CAFT) to predict the LFL without any consideration of heat loss. Limitation of the previous model could be explained clearly based on the CNAFT coefficient magnitude. The prediction accuracy for hydrogen mixtures at elevated initial temperatures and high helium content was improved substantially. The model reliability was confirmed for $H_2-air$ mixtures up to $300^{\circ}C$ and $H_2-air-He$ mixtures up to 50 vol % helium concentration. Therefore, the CNAFT model developed based on radiation heat loss is expected as the practical method for predicting LFL in hydrogen risk analysis.

• Advances in materials Research
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• 제8권1호
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• pp.11-24
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• 2019

This paper presents a review study for energy-efficient gas turbines (GTs) with cycles which contributes significantly towards sustainable usage. Nonetheless, these progressive engines, operative at turbine inlet temperatures as high as $1600^{\circ}C$, require the employment of highly creep resistant materials for use in hotter section components of gas turbines like combustion chamber and blades. However, the gas turbine obtain its driving power by utilizing the energy of treated gases and air which is at piercing temperature and pushing by expanding through the several rings of steady and vibratory blades. Since the turbine blades works at very high temperature and pressure, high stress concentration are observed on the blades. With the increasing demand of service, to provide adequate efficiency and power within the optimized level, turbine blades are to be made of those materials which can withstand high thermal and working load condition for longer cycle time. This paper depicts the recent developments in the field of implementing the best suited materials for the GTs, selection of proper Thermal Barrier Coating (TBC), fracture analysis and experiments on failed or used turbine blades and several other designing and operating factors which are effecting the blade life and efficiency. It is revealed that Nickel based Superalloys were promising, Cast Iron with Zirconium and Pt-Al coatings are used as best TBC material, material defects are the foremost and prominent reason for blade failure.

• 한국항공우주학회지
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• 제47권9호
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• pp.629-641
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• 2019

고온, 고압의 연소가스에 의해 유입되는 많은 열을 효과적으로 차단하여 고체 로켓 노즐의 공력형상을 최대한 유지하면서 구조물의 온도 상승을 일정수준 이하로 제한하기 위해 연소가스와 접하는 위치에 내삭마성이 우수한 C/C 복합재 등의 내열재를, 그 배면에는 열확산계수가 낮은 단열재를 적용한다. 내산화성이 우수한 SiC/SiC 복합재는 가스터빈 엔진에 적용되고 있으며, 경량화와 내열성 향상으로 인해 엔진 성능 증가에 기여하고 있다. 극초음속으로 비행하는 스크램제트는 흡입 공기 온도가 매우 높아서 흡열 연료를 냉각제로 사용하는 C/SiC 구조물 개발 연구가 수행되고 있다. 본 논문에서는 고체 로켓 노즐, 가스터빈 엔진 및 램제트/스크램제트 추진기관에 사용되는 다양한 내열 복합재의 특성, 적용사례 및 개발 동향을 고찰하였다.