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관 내부 메탄-공기 분류 비예혼합 화염의 부상 특성 기초 연구
김고태(Go Tae Kim),김남일(Nam Il Kim) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.4
비예혼합 화염의 부상 조건은 연소기의 운전 조건을 한정하는 매우 중요한 변수이다. 동축류 층류 비예혼합 화염의 경우 점성계수와 물질 확산 계수의 비로 정의되는 슈미트 수가 1 보다 큰 조건에서 안정적인 부상화염이 존재하고 그 반대의 경우 부상이 불가능한 것으로 알려져 있다. 본 연구에서는 동축 관내에서의 화염의 부상 특성에 대해 슈미트 수가 1 보다 큰 프로판과 슈미트 수가 1 보다 작은 메탄 비예혼합 화염의 부상 안정화를 실험적으로 비교하였다. 그 결과, 제한된 공간에서는 슈미트 수가 1 보다 작은 조건에서도 안정적인 부상화염이 존재할 수 있음을 확인하였다. 그 원인 규명을 위해 간단한 비반응 유동장에 대한 수치해석을 수행하였다. 결론적으로 개방공간에서와는 달리 관내 조건에서는 유한한 크기의 화염 공간으로 인해 인접한 상류에서 유동 재편이 물질확산에 비해 선택적으로 재편됨으로써 새로운 안정화 기구가 형성될 수 있음을 확인하였다. 이러한 결과는 제한된 공간내에 화염이 형성되는 일반적인 연소기의 화염안정화 설명에 중요한 단서를 제공한다. Flame lift-off conditions determine the operating conditions of burners. It is known that a flame can be lifted when the Schmidt number (Sc), which is the ratio of the dynamic viscosity to the mass diffusivity, is greater than unity. In this study, the flame lift-off characteristics of non-premixed flames of propane (Sc > 1) and methane (Sc < 1) in a coaxial outer air tube were experimentally compared. The experimental results indicated that stable lifted flames could be obtained even when Sc < 1 in a confined air tube. On the basis of the results of a simple numerical analysis, it was confirmed that a new flame stabilization mechanism exists in the tube. A velocity field is preferentially developed upstream of the flame, and it results in a new stabilization condition. This result can be very useful in explaining the stabilization of the flames of ordinary burners in which a flame is produced in a confined space.
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반밀폐 연소공간 내 동축관 형상에 따른 DME-공기 확산화염의 안정화 특성
김고태(Go Tae Kim),김남일(Nam Il Kim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.11
The effects of configuration of fuel and air tubes on the flame stabilization were experimentally investigated in half-closed combustors. Flame behaviors and stabilities of methane, propane, and DME flames were compared by changing tube diameters and the locations of the fuel and air tubes. It was found that flammability limits are significantly affected by the outlet boundary condition, which disturbs compositions of burned and unburned mixtures near the flame base. And it was found that there exist critical inner tube heights, over which flame stability is determined only by the fuel flow rate. Conclusively, flame stabilization is governed by the flame propagation velocity in an ordinary mixing flow and the non-uniform mixture concentration in the combustion space which is affected by flow recirculation and the combustor configuration. The compositions of NOX and CO were compared to know basic characteristics of methane, propane, and DME flames.
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평면화염 및 동심형 확장 채널 연소기를 이용한 연소속도 측정 방법 비교
김고태(Go Tae Kim),김남일(Nam Il Kim) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.40
Currently, demands for alternative energies have been increasing in step with fossil fuel depletion and climate change. With the increasing usage of coal-based syngases and biomass, in situ measuring of laminar burning velocities of various combustible fuels is essential in practical fields. This study experimentally investigated a new measuring method using an annular diverging channel. Burning velocities of methane, propane and DME were measured and the results were compared with that of a flat flame burner. The increase of the cross-sectional area of the annular diverging channel in the flow direction helps hydrodynamic flame stabilization, and the burning velocity can be assessed directly from the flame location. Consequently, the estimated burning velocities using the annular diverging channel were well agreed to those evaluated using a flat flame burner, and all results were also showed good agreement with the results from other literatures.
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산화 알루미나 입자 첨가에 따른 동축류 예혼합 연소기의 연소 특성 기초연구
박승일(Seung Il Park),김고태(Go Tae Kim),김남일(Nam Il Kim) 한국연소학회 2011 한국연소학회지 Vol.16 No.1
Thermal spray technology has been used in many industrial application. Especially, thermal spray coating have been employed with the purposes of achieving better resistances in abrasion, heat and corrosion. In the previous studies on the thermal spray coating, thermal spray characteristics from the perspective of combustion engineering have not been investigated sufficiently, while the material characteristics of the coated substrates have been investigated widely. In this study, the effect of spray particles on the flame behavior was experimentally investigated. The amount of the injected particles was measured using the light scattering method and the temperature of the particles was estimated using a two-color method. Various flame-spray interactions were observed and it was found that the high temperature zone near the flame is elongated by particles density. Based on these results, the applicability of the light scattering method and the two-color method was discussed.
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산화 알루미늄 입자 첨가에 따른 동축류 메탄-공기 예혼합 화염의 거동 특성
박승일(Seung Il Park),김고태(Go Tae Kim),김남일(Nam Il Kim) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.41
Recently, mechanical element of better resistance in abrasion, heat and corrosion have been required in industry. Thus, the technology of the thermal spray coating has been employed. However, previous studieds on the thermal spray coating has been focused on the material characteristics of the coated substrates. On the contrary, researches on the flame itself have not been sufficient. Thus, studies about theraml spray mechnism in terms of combustion engineering have also been necessary. In this study, the pheonmena of the thermal spray flame and the interaction between flames and alumina particles is focused. Temperature distribution was measured and a light scattering method was studied to measure particle amount near the flame. As a result, high temperature zone of the flame was found to be elongated by particles and the method to estimate actual particle density near the flame was discussed. This study is expected to help understand fundamental performance of an actual spray coating phenomenon through a continuous study.
ScienceON
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