• 대한기계학회논문집
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• 제17권1호
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• pp.153-161
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• 1993

본 연구에서는 각 운전모드별 열특성을 전체적으로 고려하여 양질의 MHD발전 용 작동플라즈마를 얻기 위하여 필요한 효과적인 방책에 관하여 집중적으로 고찰하고 자 한다.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.113-120
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• 2013

A steam reformer is a chemical reactor to produce high purity hydrogen from fossil fuel. In the steam reformer, since endothermic steam reforming is heated by exothermic combustion of fossil fuel, the heat transfer between two reaction zones dominates conversion of fossil fuel to hydrogen. Steam Reforming is complex chemical reaction, mass and heat transfer due to the exothermic methane/air combustion reaction and the endothermic steam reforming reaction. Typically, a steam reformer employs burner to supply appropriate heat for endothermic steam reforming reaction which reduces system efficiency. In this study, the heat of steam reforming reaction is provided by anode-off gas combustion of stationary fuel cell. This paper presents a optimization of heat transfer effect and average temperature of cross-section using two-dimensional models of a coaxial cylindrical reactor, and analysis three-dimensional models of a coaxial cylindrical steam reformer with chemical reaction. Numerical analysis needs to dominant chemical reaction that are assumed as a Steam Reforming (SR) reaction, a Water-Gas Shift (WGS) reaction, and a Direct Steam Reforming(DSR) reaction. The major parameters of analysis are temperature, fuel conversion and heat flux in the coaxial reactor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.49-53
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• 2001

A conventional flame type gas combustion major portion of heat is transferred to the body by convection due to small radiant ability of the gas flame. Increasing the radiation component of heat flux in the combustion zone allows to augment the efficiency of gas utilization. Such effect can be reached by using radiative gas burner applied to metal mesh combustion. Basically the gas radiant burner consists of metallic mesh of high heat resisting steels. In terms of this regards, we have made the burner consisted of metal mesh and measured the radiative flame stability of natural gas/air mixture on the metal mesh burner. The pressure loss through the metal mesh is defined by pressure-velocity slope. The more increased the pressure-velocity slope of the metal mesh is, the wider the stable zone of radiave flame on the metal mesh burner is. And the augmentation of mixture flowrate through the metal mesh make narrow the permissible range of equivalence ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제32권7호
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• pp.1019-1029
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• 2008

In this study, visual investigation of sprays and flames has been performed and soot formation in Diesel and GTL fuels has been compared in a specially designed Rapid Charging Combustion Vessel (RCCV) under various ambient gas $O_2$ concentrations and two injection pressures. It has been concluded that soot in the mixing-controlled combustion of Diesel and GTL fuels has similar tendency to be formed in the leading portion of the jet boundaries. Auto-ignition delay for GTL fuel is shorter than that for diesel fuel. The temporal and special variation of soot concentration in the diesel flame jets at various $O_2$ concentrations was correlated with the heat release rate. Soot concentration appears in the regions when diffusion combustion starts, and its concentration reaches maximum at the peak of heat release curve and then decreases due to oxidation. Visualization by shadowgraph method showed that soot decreases with lower $O_2$ concentration, and higher injection pressure.

• 한국연소학회지
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• 제12권4호
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• pp.14-21
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• 2007

In order to enhance combustion efficiency, oxygen-enriched combustion is used by increasing the oxygen ratio in the oxidizer. However, since the flame temperature increases, NOx formation in the furnace seriously increases for low oxygen enrichment ratio. In this case, reburning is a useful technology for reducing nitric oxide. In this research, experimental studies have been conducted to evaluate the hybrid effects of reburning/selective non-catalytic reaction (SNCR) and reburning/air staging on NOx formation and also to examine heat transfer characteristics in various oxygen-enriched LPG flames. Experiments were performed in flames stabilized by a co-flow swirl burner, which were mounted at the bottom of the furnace. Tests were conducted using LPG gas as main fuel and also as reburn fuel. The paper reported data on flue gas emissions, temperature distribution in furnace and various heat fluxes at the wall for a wide range of experimental conditions. Overall temperature in the furnace, heat fluxes to the wall and NOx generation were observed to increase by low level oxygen-enriched combustion, but due to its hybrid effects of reburning, SNCR and Air staging, NOx concentration in the exhaust have decreased considerably.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.853-858
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• 2001

The knowledge of flame structure is essential for control of combustion instability phenomena. Some results of an experimental study on mechanism of naturally occurring combustion oscillations with a single dominant frequency are presented. Tests were conducted in a laboratory-scale dump combustor at atmospheric pressure. Sound level meter was used to track the pressure wave inside the combustor. The observed instability was a longitudinal mode with a frequency of $\sim341.8Hz$. Instability map was obtained at the condition of inlet temperature of $360^{\circ}C$, mean velocities of $8.5\sim10.8m/s$ and well premixed mixture. It showed that combustion instability was susceptible to occur in the lean conditions. In this study, unstable flame was observed from stoichiometric to 0.7 in overall equivalence ratio. At selected unstable conditions, phase-resolved OH chemiluminescence images were captured to investigate flame structure with various mean velocities. As mean velocity is increased, the flame grows and global heat release was changed. Due to these effects, combustion instability can be maintained at more lean air-fuel ratio. Also, these results give an insight to the controlling mechanism for an increasing heat release at maximum pressure.

• 한국화재소방학회논문지
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• 제27권3호
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• pp.47-51
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• 2013

폭발한계는 가연성물질의 화재 및 폭발위험성을 결정하는데 주요한 특성치 가운데 하나이다. 많은 유기산류는 연소열과 폭발한계, 화학양론계수와 폭발한계가 상관관계가 있음을 보여주고 있다. 본 연구에서, 유기산류의 폭발하한계와 상한계에 대해 연소열과 화학양론계수를 이용하여 예측하였다. 제시된 예측식에 의한 예측값은 문헌값과 적은 오차범위에서 일치하였다. 제시된 방법론을 사용하여 다른 유기산류의 폭발한계 예측이 가능해졌다.

• 한국연소학회지
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• 제19권1호
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• pp.29-38
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• 2014

This paper described an experimental investigations of combustion instability mode in a lean premixed dual swirl combustor for micro-gasturbine system. When such the instability occurs, a strong coupling between pressure oscillations and unsteady heat release excites a self-sustained acoustic wave which results in a loud, annoyed sound and may also lead a structural damage to the combustion chamber. The detailed period of flame behavior and heat release in combustion instability mode have been examined with high speed OH and CH-PLIF system and $CH^*$ chemiluminescence measurement, flame tomography with operated at 10 kHz and 6 kHz each. Experiment results suggest that unstable flame behavior has a specific frequency with 200 Hz and this frequency is accords with about 1/2 sub-harmonic of combustor resonance frequency, not fundamental frequency. This is very interesting phenomenon that have not reported yet from other previous works. Therefore, when a thermo-acoustic instability with Rayleigh criterion occurs, the fact that the period of heat release and flame behavior are different each other was proposed for the first time through this work.

• Korean Chemical Engineering Research
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• 제50권6호
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• pp.1049-1055
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• 2012

화염 없이 연소가 일어나고 원적외선 복사열을 활용할 수 있는 매트 촉매버너를 제작하여 연소실험과 전열특성 분석을 수행하였다. 매트 촉매버너를 이용한 예혼합 연소실험에서 연소열의 9~17% 정도가 현열로 배출되었으며, 연소조건에 따라 차이를 보였다. 촉매버너와 시료 사이 거리증가에 따라 복사강도가 적어졌는데, 매트 촉매버너 아래에서 거리에 따라 변하는 복사에너지 흡수면적을 계산할 수 있는 수식을 유도하였다. 이 식을 멜라민 건조실험 결과와 비교하여 상관성이 있음을 보였다. 매트 촉매버너를 이용하여 멜라민, wood chip, 농산 pallet 등에 대한 건조실험을 수행하고, 이들의 건조속도로부터 에너지 이용효율을 계산하였다. 매트 촉매버너를 이용한 건조에서 최대 에너지 이용효율은 wood chip 건조에서 79% 정도까지 얻을 수 있었다.

• 한국화재소방학회논문지
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• 제33권3호
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• pp.29-36
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• 2019

다층·다성분 난연성 케이블의 화재시뮬레이션에서 요구되는 연소물성이 콘 칼로리미터를 통해 측정되었다. 난연성 케이블의 주요 재질에 따른 CO 및 Soot yields 그리고 연소열이 검토되었다. 케이블의 난연성능이 우수한 TFR-8(고난연성 PCV 및 XLPE 첨가), TFR-CVV-SB(고난연성 PCV 및 일반 PVC로 구성) 및 VCTF가 각각 대상으로 고려되었다. 주요 결과로서, 난연성케이블인 TFR-8과 TFR-CVV-SB는 입사 복사열유속이 25 kW/㎡에서 50 kW/㎡으로 증가됨에 따라 CO yield(y_CO) 는 각각 23% 와 16% 증가한다. 반면에 VCTF의 CO yield는 복사 열유속의 변화에 큰 영향을 받지 않는다. 마지막으로 Soot yield 및 연소열은 시스의 재질(난연성능)이 강화될수록 복사 열유속에 의한 차이가 증가됨이 확인되었다. 따라서 다양한 열유속이 공존하는 화재환경에서 난연성 케이블의 연소물성의 적용에는 상당한 주의가 요구된다.