• 대한기계학회논문집B
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• 제36권2호
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• pp.181-188
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• 2012

대향류확산화염의 화염소화에 있어서 에지화염 역할에 관한 실험적 연구가 진행되었다. 속도비, 버너직경, 그리고 버너간격을 변화시키며 수행된 실험에서 전체신장률에 따른 화염소화 임계질소몰분율의 그래프는 c-커브 형태로 나타났다. 고신장률화염에서는 화염소화 임계질소몰분율의 그래프가 하나의 곡선으로 일치하였으며, 화염이 일차원의 응답특성을 갖는 것을 확인하였다. 화염 소화는 바깥 에지화염이 반경방향으로의 진동 후에 화염 중심으로 수축하며 소화하는 영역, 진동 없이 화염중심으로 수축하며 소화하는 영역, 그리고 바깥 에지부분의 수축과 진동 없이 화염중심에 화염 구멍이 생기며 소화하는 영역으로 세 가지 모드로 나타났다. 화염 표면온도 측정과 에너지 방정식의 각항을 수치해석 한 결과를 토대로 에지화염부분에서의 반경방향 전도 열손실이 에지화염의 불안정을 야기한다는 것과 전도를 통한 열 공급뿐만 아니라 대류를 통한 열 공급도 바깥 에지화염의 안정화에 기여한다는 것을 보였다. 그리고 반경방향의 전도열손실이 수축하며 소화하는 메커니즘의 지배적인 역할을 함을 보였다.

• 한국연소학회지
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• 제10권2호
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• pp.1-8
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• 2005

Incomplete combustion due to quenching in a narrow confinement has been a major problem for realization of a reliable micro combustion device. In most micro combustors, effects of flows are absent in the quenching because the flow is laminar and no severe stretch is present. In such circumstance, quenching is caused either by heat loss or by removal of active radicals to the wall surface of the confinement. An experimental investigation was carried out to investigate the relative significance of these two causes of quenching of a premixed flame. A premixed jet burner with a rectangular cross section at the exit was built. At the burner exit, the flame stands between two walls with adjustable distance. The gap between the two walls at which quenching occurs was measured at different wall surface conditions. The results were analyzed to estimate the relative significance of heat loss to the wall and the removal of radicals at the surface. The measurements indicated that the quenching distance was independent of the wall surface characteristics such as oxygen vacancy, grain boundary, or impurities at low temperature. At high temperature, however, the surface characteristics strongly affect the quenching distance, implying that radical removal at the wall plays a significant role in the quenching process.

• 한국연소학회지
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• 제1권2호
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• pp.31-39
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• 1996

This study was carried out to delvelop the burner for condensing gas boiler which can save energy by utilizing latent heat of combustion gas. A perforated can-type burner adopting premixed flame was chosen to reduce NOx emission and to simplify the manufacturing process. Basic experiments using unit cell combustor have been conducted to obtain data about the design parameters of perforated burner surface which can make stable flame for a wide operating conditions. Can-type burners designed on the basis of above data shows that flames are stable and also CO and NOx emission are low for a wide operating range.

• Journal of Mechanical Science and Technology
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• 제14권3호
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• pp.298-305
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• 2000

The functionally graded material (FGM) is the new concept for a heat resisting material. FGM consists of ceramics on one side and metal on the other. A composition and microstructure of an intermediate layer change continuously from ceramics to metal at the micron level. This study is carried out to analyze the thermal shock characteristics of functionally graded PSZ/ metal composites. Heat-resistant property was evaluated by gas burner heating test using $C_2H_2/O_2$ combustion flame. The ceramic surface was heated with burner flame and the bottom surface cooled with water flow. Also, the composition profile and the thickness of the graded layer were varied to study the thermo mechanical response. Furthermore, this study carried out the thermal stress analysis to investigate the thermal characteristics by the finite element method. Acoustic emission (AE) monitoring was performed to detect the microfracture process in a thermal shock test.

• 대한기계학회논문집B
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• 제32권7호
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• pp.504-512
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• 2008

The characteristics of nonpremixed oxy-fuel flame in a multi-jet burner were experimentally and numerically investigated. The overall flow rate of fuel and oxygen was fixed, and the oxygen feeding ratio (OFR) was varied by 0.25, 0.5, and 0.75. The results of numerical simulation were compared with the measured results which are temperature profile and direct flame observation. The probability density function (PDF) model was applied accounting to the description between turbulence and chemistry, and standard ${\kappa}-{\varepsilon}$ model was used for turbulent flow field. Equilibrium assumption is very reasonable due to fast chemistry of the oxy-fuel combustion. Thus, the equilibrium calculation based on Gibbs free energy minimization was guaranteed to generate the solution of the oxy-fuel combustion. The result was obtained by numerical simulation. The predicted radial temperature profiles were in good agreement with the measured results. The flame length was shorten and was intensified with the decrease of OFR because the mixture of fuel and oxidizer are fast mixed and burnt. The maximum temperature became lower as the OFR increased, as a consequence of large flame surface area.

• 한국연소학회지
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• 제16권4호
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• pp.31-37
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• 2011

This paper presents both experimental and numerical investigation of the combustion characteristics of stretched premixed lift-off flames using synthetic gas($H_2$/CO) in an impinging burner. We used "Spin code" for numerical analysis. An ICCD camera was employed to measure flame location and flame thickness. The impinging surface temperature was affected by local strain rate K, equivalence ratio, and composition ratio of fuel. In spite of the difference of boundary conditions in experimental and numerical results, the tendencies of surface temperatures were agreed. From result of this work, we also found that flame location and flame thickness directly related to surface temperature are greatly affected by local strain rate K.

• 한국연소학회지
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• 제17권4호
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• pp.5-10
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• 2012

The reformer system is a chemical device that drives the conversion of hydrocarbon to hydrogen rich gas under high temperature environment($600-1,000^{\circ}C$). Generally, NG(Natural Gas) or AOG(Anode Off Gas) is used as fuel of fuel cell reformer combustion system. The experimental study to analyze the combustion characteristics of a premixed ceramic burner used for 0.5-1.0 kW fuel cell reformer was performed. Ceramic burner experiments using NG and AOG were carried out to investigate the flame stability characteristics by heating capacity, equivalence ratio and different fuels respectively. The results show that surface flames can be classified into green, red, blue and lift-off flames as the equivalence ratio of methane-air mixture decreases. And the stable flames can be established using NG and AOG as reformer fuel in the perforated ceramic burner. In particular, the blue flame is found to be stable at a lean equivalence ratio under different mixture conditions of NG and AOG for the 0.5 to 1.0 kW fuel cell system power range. NOx emission is under 60 ppm between 0.70 to 0.78 of equivalence ratio and CO emission is under 50 ppm between 0.70 to 0.84 of equivalence ratio.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.493-502
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• 2012

Syngas laminar burning velocity measurements were carried out at atmospheric pressure and ambient temperature using the Bunsen flame configuration with nozzle burner as a fundamental study on flame stability of syngas fuel. Representative syngas mixture compositions ($H_2$:CO) such as 25:75%, 50:50% and 75:25% and equivalence ratios from 0.5 to 1.4 have been conducted. Average laminar burning velocities have been determined by the stabilized nozzle burner flames using the angle method, radical surface area method and compared with the data obtained from the other literatures. And the results of each experimental methodologies in the various composition ratios and equivalence ratios were coincided with the result of numerical simulation. Especially, it was confirmed that there was necessary to choice a more accurate measurement methodology even the same static flame method for the various composition ratios of syngas fuel including hydrogen. Also, it was reconfirmed that the laminar burning velocities gradually increased with the increasing of hydrogen content in a fuel mixture.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.79-81
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• 2012

Flame stabilization conditions and combustion noise characteristics induced by premixed flames in sudden expansion channels were experimentally investigated. Nozzle size and channel scale were varied continuously, and variation of flame behaviors was examined. Combustion noise was observed at specific configurational conditions, and their mechanism was investigated. This study will help understand premixed flame instability at the burner surface.

• 에너지공학
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• 제19권3호
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• pp.163-170
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• 2010

소결버너를 이용한 표면점화는 제철공정에서 철광석의 소결을 위한 중요한 공정 중 하나이다. 본 연구에서는 듀얼 타입 소결 버너의 연소 특성을 분석하기 위하여 실험실적 규모의 실험과 전산 해석을 수행하였다. 라디칼 측정을 통해 연소특성을 파악하였으며, 열전대를 이용한 실험과 전산 해석 결과를 검증하였다. 검증된 전산 해석 모델을 바탕으로 싱글타입 소결 버너와 듀얼 타입 소결버너의 연소를 비교하였으며, 노즐 간격과 각도가 연소에 미치는 영향을 분석하기 위하여 3가지 노즐 간격 및 4개의 노즐 각도에 대한 전산해석을 수행하였다. 듀얼 타입이 싱글 타입 소결 버너보다 넓고 균일한 화염 폭을 형성함을 확인하였으며, 45도 비대칭 노즐 간격이 소결 베드 표면 점화를 위한 최적의 화염 폭을 형성함을 확인할 수 있었다.