• 한국연소학회지
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• 제18권4호
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• pp.37-43
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• 2013

The effects of preferential diffusion of hydrogen in interacting counterflow $H_2$-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range $30-5917s^{-1}$, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, $H_2$ and $N_2$ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of $H_2$ and CO as a function of the strain rate. The main oxidation route for CO is $CO+O_2{\rightarrow}CO_2+O$, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely $CO+OH{\rightarrow}CO_2+H$, can be significant, provided that hydrogen from the $H_2$-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the $H_2$-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean $H_2$-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich $H_2$-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

• 한국가스학회지
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• 제12권2호
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• pp.77-84
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• 2008

제트상사성 이론에 의해 잘 이해되어온 층류부상화염의 부상화염 거동에 대해 연료 노즐 직경 변화 효과를 통한 부력효과의 중요성을 밝히기 위한 실험적 연구를 수행하였다. 부력 효과를 평가하기 위해 연료노즐 직경을 $0.1{\sim}6\;mm$ 정도의 크기까지 변화시켰고, 헬륨을 희석제로 프로판과 메탄 화염을 순수 연료로부터 희석하면서 부상 거동을 체계적으로 관찰하였다. 부상화염 거동 설명을 위해 중요 물리 변수인 희석율로 표현되는 연료강도, 화염 스트레치, 화염 곡률 효과로 부상 거동을 체계적으로 설명하기 위해 척도 법칙(scaling law)을 통한 중요 물리 변수를 실험 변수로 유도하였다. 노즐 직경이 큰 경우와 연료 희석율이 큰 경우에 대해서는 부력 효과가 중요하다는 것을 실험 결과로부터 입증하였다. 또한, Chen 등의 결과에 따라 0.5

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.109-112
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• 2015

This article describes a cellular instability and laminar burning velocity of simulated synthetic natural gas(SNG) including 3% hydrogen. In this study, experimental apparatus is employed using cylindrical bomb combustor, and investigation is carried out with high speed camera and Schlieren system. The cellular instability is caused by the buoyancy, hydrodynamic instability. Unstretched burning velocity can be determined by extrapolated stretch rate of zero point from measured results. These results were also compared with numerical calculation by Chemkin package with GRI 3.0, USC-II, WANG, C3 Fuel mechanism. As an experimental conditions, equivalence ratios was adjusted from 0.8 to 1.3. From results of this work, the one was found that the cellular instability has occurred by effect of thermal expansion rate and flame thickness. As the other results, unstretched laminar burning velocity was best coincided with GRI 3.0 mechanism.

• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1358-1365
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• 2005

Flue gas recirculation (FGR) is widely adopted to control NO emission in combustion systems. Recirculated flue gas decreases flame temperature and reaction rate, resulting in the decrease in thermal NO production. Recently, it has been demonstrated that the recirculated flue gas in fuel stream, that is, the fuel induced recirculation (FIR), could enhance much improved reduction in NO per unit mass of recirculated gas, as compared to conventional FGR in air. In the present study, the effect of dilution methods in air and fuel sides on NO reduction has been investigated numerically by using $N_2$ and $CO_2$ as diluent gases to simulate flue gases. Counterflow diffusion flames were studied in conjunction with the laminar flamelet model of turbulent flames. Results showed that $CO_2$ dilution was more effective in NO reduction because of large temperature drop due to the larger specific heat of $CO_2$ compared to $N_2$. Fuel dilution was more effective in reducing NO emission than air dilution when the same recirculation ratio of dilution gas was used by the increase in the nozzle exit velocity, thereby the stretch rate, with dilution gas added to fuel side.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.453-456
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• 2011

합성가스를 이용한 충돌제트 버너에서 신장된 예혼합 화염의 열전달 특성에 관한 실험적 연구를 수행하였다. 본 연구에서는 석탄을 가스화하는 과정에서 추출되는 수소와 일산화탄소를 혼합한 합성가스를 연료로 사용하였다. 정체점에서의 열유속은 전체 신장율이 증가함에 따라 증가하다 다시 감소하는 것이 관찰되었다. 또한 정체점에서의 열유속이 노즐로부터 충돌판까지 거리가 증가함에 따라 증가하는 것을 확인하였다. 본 연구는 석탄에서 발생하는 부생가스의 주성분인 수소와 일산화탄소를 실용화하는 연구 중 기초 연구이다.