• 한국자동차공학회논문집
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• 제13권2호
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• pp.170-177
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• 2005

The fuel-lean premixed flame has been considered one of the most efficient ways to reduce $NO_X$ emission during a combustion process. However, it is difficult to achieve stable fuel-lean premixed flames over the wide range of equivalence ratios: therefore, the application of fuel-lean flames to a practical combustion system is rather limited. In this study, the stability characteristics of fuel-lean flames stabilized by fuel-rich flames are investigated experimentally using a slot burner as a part of the basic research for practical application such as lean burn engines. Spontaneous emission of radical species were examined to understand the stability mechanisms of rich-lean premixed flames. The presence of fuel-rich flames could significantly lower the lean limit of fuel-lean flames. The stability of a fuel-lean flame is enhanced with the increase of fuel flow rate in a fuel-rich flame; how ever, it is not sensitive to the equivalence ratio of fuel-rich flames in the range of 1.2-2.4. The mechanisms of stable rich-lean premixed flames could be understood based on the characteristics of triple flame.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.19-24
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• 2002

Recent studies of a triple flame suggested that the presence of triple point (triple line in this planar configuration) could explain the mechanisms of stable fuel-lean premixed flames with equivalence ratio lower than the flammability limit. In the present study, for better understanding of the stability mechanisms of fuel rich-lean premixed flames, the fuel-rich flames were replaced with hot coils that will provide heat flux into the fuel-lean flames. It is found that the fuel-lean premixed flames could be stabilized without any triple point (triple line): however, the equivalence ratio limit for stable fuel-lean flame in this case is higher than that of the present work with the presence of fuel-rich flames. These results demonstrate that heat flux coming from fuel-rich flames should be considered in order to properly understand the roll of a triple flame for stable fuel rich-lean flames.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.233-234
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• 2014

Lean-rich combustion system was composed both fuel-lean and fuel-rich flame at once. Each of fuel-lean and fuel-rich combustion types to reduce Thermal $NO_x$ and obtain flame stability. This study was confirmed a stability of flame through variation of flame shape that EGR was applied and compared the emission characteristics of EGR lean-rich combustion system to normal premixed combustion system at real condition to review a utility of the system. As a result, emission index of $NO_x$ and CO generated from EGR lean-rich combustion system at global equivalence ratio is 0.85 just half level($NO_x$ 0.31 g/kg, CO 0.08g/kg) compared to the amount generated from normal premixed combustion system at equivalence ratio is 0.78.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
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• pp.97-103
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• 2001

The characteristics of flame stability have been studied experimentally using a slot burner. The blowout conditions of a fuel-lean premixed laminar flame, which is located in the middle of fuel-rich premixed laminar flames, are identified for propane, ethylene, and methane flames. The fuel-rich flames could stabilize the fuel-lean flame for the equivalence ratio as low as 0.2. The laminar flame speed along with the heat release rate is likely to be the important factor in stabilizing a fuel-lean flame. The increase of heat release rate on a fuel-rich flame lowers the equivalence ratio limit for the stable fuel-lean flames. The stability of fuel-lean flames, however, was not sensitive to the equivalence ratio of a fuel-rich flame.

• 한국추진공학회지
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• 제26권1호
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• pp.12-19
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• 2022

덕티드 로켓의 가스발생기에 사용되는 추진제는 연료과농 추진제로서, 일반적인 고체 로켓 추진제에 비하여 과량의 금속연료와 소량의 산화제를 포함한다. 본 논문에서는 연료과농 추진제를 제조하기 위하여 보론 분말과 MgAl(Magnesium-Aluminium Alloy)를 적용하였다. 이 금속연료를 적용한 추진제의 특성을 분석하였고, 이를 통하여 최적의 조성을 연구하였다. 추진제의 연소생성물 분석을 통하여 보론 비드가 아닌 미립의 보론 분말로도 가스발생기용 연료과농 추진제가 가능함을 확인하였다.

• 한국추진공학회지
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• 제18권5호
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• pp.12-18
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• 2014

공기흡입형 추진기관의 가스발생기에 사용하기 위한 연료과농(Fuel-rich) 고체 추진제의 특성에 대한 연구를 수행하였다. 일반적인 고체 추진제는 평균 60%이상의 산화제를 포함하는 데, 연료과농 고체 추진제를 개발히기 위해 산화제 함량을 30%내외로 낮추고 매우 높은 부피당 열량을 가지는 비정질 붕소를 입자화(Bead)하여 금속연료 함량을 증가시켜 고체 추진제의 제조 공정성 및 연소속도 특성을 확인하였다. 과립화붕소의 입도가 작을수록 추진제 제조 공정에서 초기 점도가 높아지고, 입도가 클수록 연소속도 및 압력지수가 증가하는 것을 확인할 수 있었다.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.9-17
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• 2001

This paper is the second of 3 companion papers which investigate axial stratification process. In-cylinder fuel behavior has been investigated in the port injected Sl engine by visualizing for the purpose of understanding stratification. Planar laser light sheet from an Nd:YAG laser has been illuminated through the transparent quartz cylinder of the single cylinder optical engine and the Mie scattered light has been captured through the quartz window in the piston head with an ICCD camera. Fuel has been replaced with an air-ethanol mixture to utilize atomized fuel spray fur the visualization purposes. This results have been compared with steady flow concentration measurement. For low/medium swirl port, the early injection makes such a fuel distribution state that is upper-rich, middle-lean and lower-rich along the combustion chamber and cylinder by tumbling motion. On the other hand, the late injection induces upper-rich, middle-lean and lower-rich state due to the short fuel penetration.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.299-308
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• 2003

This paper provides a review of the status and of the perspectives of advanced catalytic combustion for ultra clean combustion of gas turbines and for industrial combustors. The development of catalytic materials and their combustion techniques for gas turbines are briefly reported. The fuel-rich approaches to catalytic combustion are mentioned for a new technology of thermal- and fuel-NOx control. The fuel-rich catalytic combustion are also applicable to the combustor of ceramic gas turbine, and to the combustion of biomess and municipal waste sludge. Some extended technologies of combustion synthesis are introduced for the synthesis of carbon nanotube and of Perovskite combustion catalysts

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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• pp.104-109
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• 2006

Improvements in internal combustion engine and aftertreatment technologies are needed to meet future environmental quality goals. Plasmatron fuel converters provide a rapid response, compact means to transform a wide range of hydrocarbon fuels (including gasoline, natural gas and diesel fuel) into hydrogen-rich gas. Hydrogen-rich gas can be used as an additive to provide NOx reductions of more than 80% in diesel engine vehicles by enabling very lean operation or heavy exhaust engine recirculation. For diesel engines, use of compact plasmatron reformers to produce hydrogen-rich gas for the regeneration of NOx absorber/absorbers and particulate traps for diesel engine exhaust after-treatment could provide significant advantages. Recent tests of conversion of diesel fuel to hydrogen-rich gas using a low current plasmatron fuel converter with non-equilibrium plasma features are described.

• Nuclear Engineering and Technology
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• 제43권2호
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• pp.159-166
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• 2011

Si-rich-layer-coated U-7 wt%Mo plates were prepared in order to evaluate the diffusion barrier performance of the Si-rich layer in U-Mo vs. Al interdiffusion. Pure Si powder was used for coating the U-Mo plates by annealing at $900^{\circ}C$ for 1 h under vacuum of approximately 1 Pa. Si-rich layers containing more than 60 at% of Si were formed on U-7 wt%Mo plates. Diffusion couple tests were conducted in a muffle furnace at $560-600^{\circ}C$ under vacuum using Si-rich-layer-coated U-Mo plates and pure Al plates. Diffusion couple tests using uncoated U-Mo plates and Al-(0, 2 or 5 wt%)Si plates were also conducted for comparison. Si-rich-layer coatings were more effective in suppressing the interaction during diffusion couple tests between coated U-Mo plate and Al, when compared with U-Mo vs. Al-Si diffusion couples, since only small amounts of Al in the coating could be found after the diffusion couple tests. Si-rich-layer-coated U-7wt%Mo particles were also prepared using the same technique for U-7 wt%Mo plates to observe the microsturctures of the coated particles.