• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2001년도 제22회 KOSCI SYMPOSIUM 논문집
• /
• pp.31-45
• /
• 2001

The effect of adding carbon dioxide to methane-air flame was investigated experimentally. Measurements included extinction limits, flame temperature and photographic investigation of flame. A diffusion flame was stabilized between counterflowing streams of methane diluted with carbon dioxide and air diluted with carbon dioxide. Extinction limits and temperature for such flames were measured over a wide parametric range and were compared with those for other flames that fuel or oxidant was diluted with nitrogen or argon. The experimental results indicate that extinction phenomena can be explained by thermal effect and as an amount of carbon dioxide in fuel or oxidant increases, greatly as compared with other flames flame-temperature falls and flame-thickness is reduced.

• 대한기계학회논문집B
• /
• 제20권2호
• /
• pp.605-615
• /
• 1996

Laminar flows in which mixing and chemical reactions take place between parallel streams of reactive species are studied numerically. The governing equations for laminar flows are from two-dimensional compressible boundary-layer equations. The chemistry is a finite rate single step irreversible reaction with Arrhenius kinetics. Ignition, premixed flame, and diffusion flame regimes are found to exist in the laminar reacting mixing layer at high activation energy. At high Mach numbers, ignition occurs earlier due to the higher temperatures in the unburnt gas. In diffusion regimes, property variations affect the laminar profiles considerably and need to be included when there are large temperature differences. The maximum temperature of a laminar reacting mixing layer is almost linear with the adiabatic flame temperature at low heat release, but only weakly at high heat release.

• 한국연소학회지
• /
• 제8권3호
• /
• pp.1-7
• /
• 2003

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by the improvement of burning rate and by the high temperature flame. Flame figures, OH radical intensities, temperature distributions and emission concentrations were measured according to oxygen enriched concentration and swirl number in a turbulent diffusion flat flame. It appeared that flame figure became flat and NO concentration decreased with increase of swirl number, and that the flame temperature increased high with increase of oxygen enriched concentration. In particular, it was most significant between oxygen concentration $40{\sim}60%$.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
• /
• pp.51-56
• /
• 2001

An experiment using preheated air in the coaxial diffusion flame burner was carried out in order to decrease NOx emission and improve the thermal efficiency. Preheated air combustion generally produces high NOx emissions but it was known very well to reduce NOx emission by diluting the combustion air with inert gas in preheated air combustion. In our study, $N_2$ gas was used for diluent and propane was utilized for fuel. We set the combustion air temperature on 300K, 500K, 700K, 900K and dilution level from 21% to 10% in terms of oxygen concentration. NOx emission increased along increment of combustion air temperature and decreased along increment of dilution level(lowering of oxygen concentration in combustion air). Flame-off limit with dilution level enhanced, flame length became longer and the location of maximum flame temperature became lower with increasing of combustion air temperature.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
• /
• pp.231-240
• /
• 1999

The temperature distribution in double-concentric diffusion flames have been investigated experimentally by rapid insertion technique. Using a fine thermocouple and rapid insertion mechanism, the temperature has been measured before soot particles attach the thermocouple junction which can affect the temperature signal by changing the radiation heat loss. For double-concentric diffusion flames, the temperature at the axis is higher than that of normal coflow diffusion flames because of the inverse diffusion flame at the center of the flame. However, it is almost same at the periphery on which the inverse flame does not have an effect.

• 한국연소학회지
• /
• 제7권2호
• /
• pp.1-6
• /
• 2002

Characteristics of laminar lifted flames of propane highly-diluted with nitrogen have been investigated at various temperatures of coflow air. At various fuel mole fractions, the base of laminar lifted flames has the structure of tribrachial (or triple) flame. The liftoff heights are correlated well with the stoichiometric laminar burning velocity considering initial temperature at a given coflow velocity. It shows that lifted flames are stabilized on the basis of the balance mechanism between local flow velocity and the propagation speed of tribrachial flame, regardless of the temperature of coflow and fuel mole fraction. Lifted flames exist for a jet velocity even smaller than the stoichiometric laminar burning velocity, and liftoff velocity increases more rapidly than stoichiometric laminar burning velocity as coflow temperature increases. These can be attributed to the buoyancy effect due to the density difference.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2007년도 제29회 추계학술대회논문집
• /
• pp.377-380
• /
• 2007

스월 난류연소기에서의 혼합기 유입온도와 스월세기에 따른 연소불안정 발생 메커니즘 알아보기 위하여 Large Eddy Simulation을 수행하였다. 스월각 45도 경우 연료공기 혼합기의 온도를 600K에서 660K으로 증가시켰을 경우 화염분기(Bifurcation)현상이 관찰되었고, 스월 강도가 변할 경우 온도와 관계없이 화염분기가 일어나거나 그렇지 않음을 확인하였다. 벽면근처의 혼합가스 유동속도와 화염속도간의 상관관계는 화염분기현상의 발생에 주요한 인자임을 확인하였다.

• 대한기계학회논문집B
• /
• 제24권12호
• /
• pp.1608-1614
• /
• 2000

For the purpose of obtaining fundamental data which is needed to develope combustion system of LPG engine, we made constant volume chamber and analyzed flame propagation characteristics under different intial temperature, initial pressure and equivalence ratio which affect combustion of LPG. We investigated flame propagation speed of each fuel using laser deflection method and compared with the investigated flame propagation speed of each fuel using laser deflection method and compared with the results of image processing of flame. As a result, the maximum flame propagation speed was found at equivalence ratio 1.0 and 1.1 for LPG and gasoline, respectively. In the lean region, we can see that flame propagation speed of LPG surpasses that of gasoline. On the contrary, flame propagation speed of gasoline surpasses LPG in the rich region. As initial temperature and initial pressure were higher, flame propagation speed was faster. And, as equivalence ratio was larger and initial temperature was higher, combustion duration was shorter and maximum combustion pressure was higher.

• 한국위성정보통신학회논문지
• /
• 제9권2호
• /
• pp.33-37
• /
• 2014

본 논문은 컬러 영상에서 화염의 후보 영역을 검출하기 위해 화염의 온도 분포 특성을 이용하여 화염의 영역을 분할한다. 기존 화염 검출 알고리즘에서는 단순히 화염의 색상을 황색에서 적색사이를 화염 후보 영역으로 검출하여 많은 오검출을 포함한다. 하지만 실제 화재에서 화염은 백색에서 적색사이의 색상을 보이고 있고, 화염의 영역 위치에서 따라 서로 다른 색상을 보인다. 본 논문에서는 화염의 온도 분포에 따른 색상을 분리하여 오검출 요소를 최소화한다. 제안하는 방법은 화염의 온도 분포 특성을 표현할 수 있는 색상 모델을 찾고, 색상 모델의 값을 비선형 양자화 단계로 나누어 히스토그램으로 분석하여 화염 후보 영역을 결정한다. 제안된 방법은 기존의 수 작업한 결과와 비교하면 정합도가 71.8%가 되고, 비화염 화소의 비율은 기존의 방법 중 최대 비화염 화소 수와 비교하면 약 27배 개선된 성능을 확인하였다.

• 한국연소학회지
• /
• 제21권4호
• /
• pp.6-15
• /
• 2016

The oxygen fuel MILD (Moderate or Intense Low-oxygen Dilution) combustion has been considered as one of the promising combustion technology for flame stability, high thermal efficiency, low emissions and improved productivity. In this paper, the effect of oxygen and fuel injection condition on formation of MILD combustion was analyzed using lab scale oxygen fuel MILD combustion furnace. The results show that the flame mode was changed from a diffusion flame mode to a split flame mode via a MILD combustion flame mode with increasing the oxygen flow rate. A high degree of temperature uniformity was achieved using optimized combination of fuel and oxygen injection configuration without the need for external oxygen preheating. In particular, the MILD combustion flame was found to be very stable and constant flame temperature region at 7 KW heating rate and oxygen flow rate 75-80 l/min.