• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.163-167
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• 2008

In this study, the 1/35 reduced-scale model experiment were conducted to investigate designed ventilation effect on the smoke movement at rescue station fire in railway tunnel. A model tunnel with 2 mm thick, 10 m long, 0.19 m high and 0.26 m was made by using Froude number scaling law. The cross-passages installing escape door at the center were connected between incident tunnel and rescue tunnel. The n-heptane pool fires with heat release rate 698.97W were used as fire source. The fire source was located at the center and portal of incident tunnel as worst case. A operating ventilation system extracted smoke amount of 0.015 cms(cubic meters per second). The smoke temperature and CO gas concentration in cross-passage were measured to verify designed ventilation system. The result showed that, at center fire case without ventilation, smoke did not propagate to rescues station. In portal fire case, smoke spreaded to rescues station without ventilation. But smoke did not propagated to rescues station with designed ventilation.

• 대한기계학회논문집
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• 제16권9호
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• pp.1736-1743
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• 1992

본 연구에서는 기화기부착 4행정 4기통 전기점화기관을 사용하여 흡기관내 액 막흐름에 의한 연료의 불균일화가 기관의 연소특성과 배기특성에 미치는 영향을 규명 하는데 궁극적인 목적을 두고 우선, 연소특성을 해석하기 위하여 비교적 고가인 연소 해석 시스템을 개발하는데 1차적인 목적으로 하였으며, 시험제작한 연소해석 시스템으 로 액막흐름의 가시화 및 배기가스 농도측정과 지압선도 해석을 행하여 구조적으로 대 칭인 1번과 4번 실린더의 연소특성과 배기특성을 비교 검토하였다.

• 한국통신학회논문지
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• 제35권11A호
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• pp.1091-1096
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• 2010

Stiction in microelectromechanical systems (MEMS) has been a major failure mechanism. Especially, in RF MEMS switches, moving parts often suffered in-use and release related stiction problems. Some materials and methods have been used to prevent this problem. Diamond-like carbon (DLC) has not only been used as a protective material owing to its good mechanical properties but also has been used as a hydrophobic material. Its properties could be controlled by post annealing treatment in various conditions. We synthesized DLC films using a radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. Then, the change of the hydrophobic property of the films was investigated undervarious annealing temperatures in nitrogen and in oxygen ambient. The films, that were annealed above $700^{\circ}C$ in nitrogen ambient, showed a high contact angle of water (> $90^{\circ}$) even though their mechanical property was sacrificed to some degree. The structural variation and the changes of the hydrophobic and mechanical properties of the DLC films were analyzed by Raman spectrum, contact angle measurement, surface profiler, and a nanoindentation test.

• 대한기계학회논문집B
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• 제26권1호
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• pp.74-81
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• 2002

Combustion phenomena in a sub-millimeter scale combustor have been investigated. To evaluate scale effect on flame propagation characteristics, a cylindrical combustion chamber with variable depth was built in-house. The combustor was charged with premixed gas of hydrogen and air and ignited electronically. A piezo electric pressure transducer recorded transient pressure after the ignition. Measurements were made at different test conditions specified with chamber depth and initial pressure as parameters. Visual observation was made through a quartz glass window on top side of the combustion chamber using high speed digital video camera. From the pressure data, available work was estimated and compared with energy input required for stable ignition. The preliminary results suggested that the net thermal energy release is sufficient to generate power and enables a combustor of the size in the present study to be used as the energy source of a micro power devices .

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2011년도 춘계학술논문발표회 논문집
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• pp.325-329
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• 2011

오늘날 대부분의 화재조사의 기본 원칙은 숫자를 찾는 데 목적이 있고, 화재의 중요한 양상을 묘사할 수 있는 물리학적으로 정확한 경험식과 하나의 모델로 바꾸는 데 가치를 두고 있다. 화재는 일반적으로 화재 초기에 발생하는 열이 상호작용 과정에 의해 성장하며, 이 간단한 과정이 화재 성장률을 결정하며, 그 예측을 어렵게 한다. 그러므로 화재성장에서 대부분의 모델은 경험으로부터 정해지게 되는데, 그 모델은 매우 제한적이다. 콘칼로리미터는 특별히 노출된 부분에서 중요한 재료 특성의 변화 수치를 얻을 수 있으며, 측정기준은 발화, 질량손실률, 열 발생률, 연기 발생률, 가스 분석 등이며, 이 모든 측정은 테스트의 시작에서 끝날 때까지 실행되며, 이는 발화 전, 발화 후를 모두 포함한다. 국내외 콘칼로리미터의 연구를 비교, 분석하여 화재안전 데이터베이스 구축에 활용되는 콘 칼로리미터의 중요성 평가를 본 연구의 목적으로 한다.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.40-46
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• 2001

An experimental investigation is proceeded to study on the relationship between spark ignition characteristics and the performances of an S. I. engine. The ignition parameters examined in this study are the ignition energy and discharging duration. The combustion pressure and exhaust gas are measured during the experiment. From the measured data of cylinder pressure, the heat release rate, the mass fraction burned, and the COV of IMEP are calculated. The dwell time and the injection time are varied. A single cylinder engine and a 30kW dynamometer are employed. Four different kinds of ignition systems are assembled, and one commercial ignition system is adopted. The experimental results show that the ignition energy is increased as the dwell time extended until the ignition energy is saturated. The higher ignition energy is effective in achieving the laster burning velocity and less producing HC emission. However, when the amount of ignition energy is similar, while the discharge duration becomes longer, the burning velocity is reduced but the engine operation becomes stable in terms of the COV of IMEP.

• 신재생에너지
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• 제3권2호
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• pp.60-67
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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), hydrogen storage tank 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. Hydrogen may be produced and stored in high pressure tank by hydrogen gas booster system. Wind conditions are changing with time of day, season and year. So, wind power is a variable energy source. The main purpose with these WT-FC hybrid system is to store hydrogen by electrolysis of water when wind conditions are good and release the stored hydrog en to supply the fuelcell when wind is low.

• 한국항공우주학회지
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• 제33권8호
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• pp.75-83
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• 2005

확대형 채널 내의 정상 천음속 희박 예혼합 연소에 대해 점근해석을 이용하여 연구하였다. 이 모델은 근음속의 유동 속도와 일직선 채널로부터 벗어난 작은 형상변화 그리고 1단 1차 Arrhenius 화학 반응율에 의한 적은 열 방출 사이에서 일어나는 비선형 상호작용에 대하여 탐구하였다. 반응유체 유동은 연소 가스의 질량 분율을 계산하는 상미분 방정식과 연계된 비균질 천음속 미교란 방정식(TSD)을 사용하여 묘사하였다. 또한 점근해석으로부터 반응유체 유동 문제를 지배하는 상사 파라미터들을 유도하였다. 수치 결과들은 대류와 화학반응 그리고 형상효과 사이에 일어나는 복잡한 비선형 상호작용과 유동에 미치는 이것의 영향 등이 잘 나타나 있다.

• 한국자동차공학회논문집
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• 제18권4호
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• pp.132-139
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• 2010

This paper describes an investigation of the performance and emission characteristics of a commercial cylinder direct injection diesel engine operating on natural gas with pilot diesel ignition. Engine tests for variations in the pilot injection timing were performed at an engine speed of 1500 rpm. This study showed that the performance of the dual-fuel diesel engine increased as the engine load increased and as the pilot diesel injection timing angle advanced. The peaks of cylinder pressure, pressure rise rate, and heat release rate all increased while the fuel ignition timing advanced with the pilot injection timing. The engine operation was stable, and the least smoke was produced at a pilot injection timing of $12^{\circ}$ before top dead center. NOx emissions were only exhausted under high-load conditions, and they increased as the pilot injection timing angle advanced.

• 에너지공학
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• 제26권4호
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• pp.74-83
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• 2017

Coal-fired power plants supply roughly 50 percent of the nation's electricity but produce a disproportionate share of electric utility-related air pollution. Coal combustion technology can facilitate volume reduction of up to 90%, with the inorganic contaminants being captured in furnace bottom ash and fly ash residues. These disposal coal ash residues are however governed by the potential release of constituent contaminants into the environment. Accelerated carbonation process has been shown to have a potential for improving the chemical stability and leaching behavior of bottom ash residues. The aim of this work was to quantify the volume of $CO_2$ that could be sequestrated with a view to reducing greenhouse gas emissions and stabilize the contaminated heavy metals from bottom ash samples. In this study, we used PC boiler bottom ash, Kanvera reactor (KR) slag and calcined waste lime for measuring chemical analysis and heavy metals leaching tests were performed and also the formation of calcite resulting from accelerated carbonation process was investigated by thermo gravimetric and differential thermal analysis (TG/DTA).