• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1246-1257
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• 2004

The objective of this paper is to characterize dynamic pressure traces measured at self-excited combustion instabilities occurring in two combustion systems of different hardware. One system is a model lean premixed gas turbine combustor and the other a fullscale bipropellant liquid rocket thrust chamber. It is commonly observed in both systems that low frequency waves at around 300㎐ are first excited at the onset of combustion instabilities and after a short duration, the instability mode becomes coupled to the resonant acoustic modes of the combustion chamber, the first longitudinal mode for the lean premixed combustor and the first tangential mode for the rocket thrust chamber. Low frequency waves seem to get excited at first since flame shows the higher heat release response on the lower frequency perturbations with the smaller phase differences between heat release and pressure fluctuations. Nonlinear time series analysis of pressure traces reveals that even stable combustion might have chaotic behavior with the positive maximum Lyapunov exponent. Also, pressure fluctuations under combustion instabilities reach a limit cycle or quasi-periodic oscillations at the very similar run conditions, which manifest that a self-excited high frequency instability has strong nonlinear characteristics.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.86-96
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• 2007

A direct-injection stratified-charge(DISC) engine has been considered as a promising alternative in spite of high unburned hydrocarbon emission levels during light load operation. In this paper investigation is made to characterize formation and combustion processes of stratified mixture charge in a simple constant volume combustion chamber. Both experimental and numerical analyses are performed for fluid and combustion characteristics with 3 different induction types for rich, homogeneous and lean mixture conditions. The commercial code FIRE is applied to the turbulent combustion process in terms of measured and calculated pressure traces and calculated distributions of mean temperature, OH radical and reaction rate. It turns out that the highest combustion rate occurs for the rich state condition at the spark ignition location due to existence of stoichiometric mixture and timing.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2009년도 춘계학술대회
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• pp.1-6
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• 2009

국보 1호인 숭례문 화재는 화재조사자뿐만 아니라 국민들에게 크나큰 아픔을 안겨 주었다. 이 연구의 목적은 현장조사를 통하여 목조 문화재 화재 시 생성되는 연소패턴과 목재 마루바닥에 인화성물질을 살포 후 착화하였을 때 나타나는 촉진제에 의한 연소 흔적 등을 확인하는데 있다. 또한 이 연구결과는 유사한 화재 발생 시 화재조사요원에게 정확한 화재 원인을 감식할 수 있는 자료가 될 것이다.

• 한국화재조사학회논문지
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• 제11권1호
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• pp.74-82
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• 2008

국보 1호인 숭례문 화재는 화재조사자뿐만 아니라 국민들에게 크나큰 아픔을 안겨 주었다. 이 연구의 목적은 현장조사를 통하여 목조 문화재 화재 시 생성되는 연소패턴과 목재 마루바닥에 인화성 물질을 살포 후 착화하였을 때 나타나는 촉진제에 의한 연소 흔적 등을 확인하는데 있다. 또한 이 연구결과는 유사한 화재 발생 시 화재조사요원에게 정확한 화재 원인을 감식할 수 있는 자료가 될 것이다.

• 한국연소학회지
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• 제18권1호
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• pp.7-12
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• 2013

A quasidimensional program is developed for a four stroke cycle homogeneous GDI (Gasoline Direct Injection) engine. It includes models for spray, burning rate and chemistry to predict knock and emissions. With early injection a homogeneous GDI engine goes through spark ignited, turbulent premixed combustion as in PFI (Port Fuel Injection) engines. The cylinder charge is divided into unburned and burned zone with the latter divided into multiple zones of equal mass to resolve temperature stratification. Validation is performed against measured pressure traces, NOx and CO emissions at different load and RPM conditions. Comparison is made between an empirical knock model and predictions by the chemistry model in this work.

• International Journal of Automotive Technology
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• 제6권6호
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• pp.571-577
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• 2005

Combustion of turbulent sprays in a direct injection diesel engine is modeled by the conditional moment closure (CMC) model. The CMC routines are combined with the KIVA code to provide conditional flame structures to determine mean state variables, instead of mean reaction rates. An independent transport equation is solved for each flame group with equal mass of sequentially evaporating fuel vapor. CMC calculation begins as the fuel mass for each flame group begins to evaporate with corresponding initialization conditions. Comparison is made with measured pressure traces for four operating conditions at different rpm's and injection conditions. Results show that the CMC model with multiple flame histories can successfully be applied to ignition and mixing-controlled combustion phases of a diesel engine.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.107-109
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• 2012

A quasidimensional model is developed with the surrogate mechanism of isooctane and n-heptane to predict knock and emissions of a homogeneous GDI engine. It is composed of unburned and burned zone with the latter divided into multiple zones of equal mass to resolve temperature stratification. Validation is performed against measured pressure traces, NOx and CO emissions at different load and rpm conditions. Comparison is made between the empirical knock model and predictions by the chemistry model in this work.

• 한국분말재료학회지
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• 제11권4호
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• pp.308-313
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• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

• 한국화재소방학회논문지
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• 제27권6호
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• pp.89-96
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• 2013

본 연구의 목적은 연소 실험을 통하여 에어컨 실내기의 화염확산에 관한 형상을 관찰하여 화재원인 및 발화지점을 확인하기 위함이다. 본 실험은 화염이 주변으로부터 에어컨 상단에 옮겨 붙는다는 것을 가정하여 실내기 상단을 n-햅탄을 적신 천으로 착화시켰으며, 동일한 조건으로 2회의 반복실험을 하였다. 착화 후 559 s와 734 s 사이에 실내기와 연결된 냉매관이 파열되면서 내부에 충입되어 있던 냉매와 함께 윤활유가 커다란 폭음을 내며 고온 고압의 화염이 급격히 분출되었으며 연소 잔류물을 확인한 결과, 증발기 일부와 모터, 금속함 등을 제외한 대부분은 소실되었다. 에어컨 자체에서 발화되었을 경우와 외부 화염에 의해 소훼되었을 경우 배선의 합선흔적 위치는 유사하였다. 따라서 연소 잔류물의 형상만으로 발화원인과 지점을 특정 짖는 것은 불확실하다는 것을 확인하였다.

• 한국안전학회지
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• 제26권4호
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• pp.111-119
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• 2011

This study was designed to provide basic data applicable to fire investigation through consideration of combustion products and propose vulnerability of combustibles through analysis of $CO_2$ emission. In order to achieve these research objectives, characteristics of combustion products such as smoke release rate of each part(raw leaves, branches and barks), $CO_2$ emission and ash production were considered targeting on 6 oak species(Quercus variabilis Blume, Quercus aliena Blume, Quercus serrata, Quercus mongolica Fisch, Quercus dentata Sapling and Quercus acutissima) using cone calorimeter and smoke density tester. As a result, it was found that raw leaves release smoke more relatively than branches and barks, when they burn, and that Quercus variabilis Blume has the highest smoke density. Also, Quercus acutissima released CO and $CO_2$ which are respectively, 6.67 times and 1.43 times more than Quercus variabilis Blume with low $CO_2$ emission. In addition, branches released CO and $CO_2$ more relatively. There was a big difference in ash production among raw leaves(3.1 g), branches(10.5 g) and barks(16.43 g). It was identified that Quercus serrata produces ashes which are nearly 9.95 times more than Quercus variabilis Blume. It demonstrates that Quercus serrata contains relatively higher minerals and that Quercus variabilis Blume can leave lots of traces like stain and carbonization, as it releases smoke a lot and it's difficult to predict visibility, when a forest fire breaks out in its community area. It is also considered that smoke particles containing oil in the air leave strain on the surface of a tree, and that CO and $CO_2$ emission increases, when crown fire to burn branches breaks out.