• 대한기계학회논문집B
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• 제23권6호
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• pp.788-794
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• 1999

The swirl flame is mostly used to stabilize the flame on the burner nozzle in the industrial combustor. In the case of the weak swirl flame(S<0.4), the recirculation zone could not be formed, but in the strong swirl(S>0.6) flame, it could be formed in the center of the swirl flame. In this study, the measurement and analysis of emission species, temperature, radicals of premixed swirl flame in the combustor were performed to understand the NO formation and emission characteristics of the swirl flame of natural gas. The result of NO emission in the swirl flame is that the amount of NO emission in the strong swirl flame decreased about 60% compared with that of the weak swirl flame. The main region of NO formation of the weak swirl flame is positioned in the down stream(z=100~200mm) of the flame, but that of the strong swirl flame is positioned in the up stream(z=40mm) where the recirculation zone seems to be formed. It is supposed that the increase of flame surface and the formation of inversed flame cause the reduction of the high temperature region on the production of NO in the strong swirl flame. The result of NO-temperature relation revealed that the factor of NO formation is not only temperature but also another parameters in the weak swirl flame, but in the strong swirl flame, NO is proportional to the temperature of higher than 1200K.

• 대한기계학회논문집B
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• 제29권9호
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• pp.1013-1021
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• 2005

In this work, $TiO_2$ nanoparticles were synthesized using a N2-diluted hydrogen coflow diffusion flame. The effects of flame temperature on the crystalline structure and the size of formed nanoparticles were investigated. The maximum centerline temperature of the flame ranged from 1,920K for $H_2-only$ flame to 863k for $81\%\;N_2-diluted$ flame. The morphology and the crystal structure of $TiO_2$ nanoparticles were analyzed by a TEM and a XRD, respectively. The particle size distribution was also measured by using a scanning mobility particle size. (SMPS). The mean particle diameter was calculated from the TEM images depended on the flame temperature, having minimum at about 1,look. Based on the SMPS measurements, the mean particle diameter of $TiO_2$ nanoparticles at flame temperatures > 1,300K was smaller than that at flame temperatures < 1,300K. From the XRD analysis, it was evident that the anatase fraction increased with decreasing the flame temperature. The portion of anatase phase in $TiO_2$ nanoparticles might be greater than $80\%$ when the flame temperature was lower than 1,000K.

• 대한기계학회논문집B
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• 제28권11호
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• pp.1417-1423
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• 2004

The thickness of laminar flame and preheat zone was computed from equation with burning velocity and the temperature profile, which is obtained by using premix code of Chemkin program for ethanol-air mixture. The computations were carried out under the unburned gas pressure 0.5bar-30bar and temperature of 300k-700K at 1.0. A difference flame thickness showed between temperature profile and equation with burning velocity. The ratio of flame thickness derived from the equation was about 45∼65% of the temperature profile, and the thickness of preheat zone was about 67.1% of the flame thickness. The flame thickness was decreased by increasing the pressure and temperature, but the effect of pressure is more significant than the effect of temperature on the flame thickness. The flame thickness was predicted by using the following equation. X(mm) = $X_{st}$ (T/300)$^{-0}$.65/(P)$^{-0}$.68/ (0.5bar$\leq$P$\leq$30bar, 300K$\leq$T$\leq$700K)K)

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
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• pp.104-110
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• 2001

Characteristics of lifted flame for highly diluted propane with nitrogen in high temperature coflowing air have been experimentally investigated, and the stabilization mechanism of lifted flame in high temperature air coflow have been proposed. As the coflow temperature increases, the liftoff height of flame decreased due to the increase of stoichiometry laminar burning velocity. At same coflow temperature, the difference of liftoff height between the fuel mole fractions has been disappeared by scaling the liftoff velocity with stoichiometry laminar burning velocity. It has been found that lifted flame can be stabilized for even smaller fuel velocity than stoichiometry laminar burning velocity. This can be attributed to buoyancy effect and the liftoff velocity characteristics for coflow temperature support it.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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• pp.122-127
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• 2006

The objective of this research is to determine generally applicable design principles for the development of Rapid mix burner. Details operating RMB(Rapid mix burner) is designed that thermal NOx and prompt NOx formation be reduced through control of low peak flame temperature, and nearly uniform flame temperature by rapid mixing at the ignition point. Results from RMB(Rapid mix burner) achieving lower than 43 ppm NOx emissions and nearly flame temperature uniform

• 한국가스학회지
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• 제14권3호
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• pp.8-13
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• 2010

최근 석유에너지의 대체에너지로 수소에 대해 사회적인 관심이 높아짐에 따라, 수소의 연소특성에 관한 연구가 많이 진행되고 있다. 하지만, 수소화염의 온도는 고온이며, 전파속도가 빠르며, 수소화염은 가시광을 거의 방출하지 않기 때문에 화염의 특성을 파악하는 것이 쉽지 않다. 본 연구에서는 직경12.7, 25.4, 50.8 ${\mu}m$인 3종류의 극세선 열전대를 이용하여 화염의 도달시간 및 온도를 동시에 측정하였다. 이론혼합농도에서의 화염도달시간을 검출한 결과, 빠른 수소화염의 전파속도를 정밀히 측정할 수 있음이 확인되었다. 또한, 열전대의 시정수를 고려함으로써, 화염온도를 추측하는 것이 가능함을 확인했다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.140-149
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• 2006

Characteristics of a laminar diffusion flame placed near wall in microgravity have been numerically analyzed in a two-dimension. The fuel for the flame is $C_2H_4$. The flame is initiated by imposing a high temperature ignition source. The flow field, temperature field, and flame shape in microgravity diffusion flame are detailed. Especially, effects of surrounding air velocity and fuel injection velocity on the microgravity diffusion flame have been discussed accounting for standoff distance. And, the effect of curvature rate has been also studied. The results showed that velocities in a diffusion flame were overshoot because of volumetric expansion and distribution of temperature showed regularity by free-buoyancy This means that the diffusion flame in microgravity is very stable, while the flame in normal gravity is not regular and unstable due to buoyancy. Standoff distance decreases with increase in surrounding air velocity and with decrease in fuel injection velocity. With increasing curvature rate, the position of reaction rate moves away the wall.

• 대한기계학회논문집B
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• 제27권5호
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• pp.561-568
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• 2003

An experiment using high preheated air in a turbulent non-premixed flame was performed to investigate the effects of high preheated air on the combustion characteristics. Combustion using high preheated and diluted air with flue gas is a new technology which enables NO emission to be reduced. In this study, Na was used as diluent and propane as fuel. Combustion characteristics, especially the distributions of the flame temperature, NO concentration and OH radical intensity were examined under the condition of 300 K, 600 K, 1000 K in terms of the combustion air temperature, and also under the condition of the dilution level from 21% to 13% in terms of oxygen concentration. As the preheated air temperature increased, it appeared that the flame length became shorter, maximum flame temperature increased, the reaction region moved to upstream, and NO concentration increased, but the flame temperature's fluctuation was reduced. In opposite, it was shown with decrement of oxygen concentration at the maximum temperature that both maximum value and the gradient of the flame temperature decreased, and NO emission also decreased considerably, but its fluctuation became larger, being inclined to be unstable.

• 대한기계학회논문집B
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• 제28권3호
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• pp.281-288
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• 2004

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by improving the burning rate and by increasing the flame temperature. Flame figures, OH radical intensities, temperature distributions and emissions concentration were examined according to oxygen enriched concentration(OEC) in a turbulent diffusion flat flame. As long as the oxygen enriched concentration was increased, the length and volume of the flat flame was decreased while OH radical intensity was raised and the flame temperature was increased. However, RMS of the fluctuating temperature was decreased, and more homogeneous temperature field was formed. Thermal NO also was increased with increase of oxygen enriched concentration, but CO was decreased due to the increase of chemical reaction rate.

• 한국분무공학회지
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• 제7권2호
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• pp.1-6
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• 2002

It is necessary to develope a high frequency diode laser sensor system based on the absorption spectroscopy for the measurement of temperature of the spray flame. DFB diode laser operating near $2.0{\mu}m$ was used to scan over selected $H_2O$ transitions near $1.9{\mu}m\;and\;2.2{\mu}m$, respectively. The measurement sensitivity at wide range of sweep frequency was evaluated using multi-pass cell containing $CO_2$ gas. This diode laser absorption sensor with high temporal resolution up to 10kHz was applied to measure the gas temperature in the spray flame region of liquid-gas 2-phase counter flow flame. The successful demonstration of time series temperature measurement in the spray flame gives us motivation of trying to establish non-intrusive temperature measurement method in the practical spray flame.