• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.42-50
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• 2001

An experimental study has been carried on high-preheated temperature air combustion. Because the flames with high-preheated temperature air combustion were much more stable and homogeneous(both temporally and spatially) as compared to the room-temperature combustion air. The global flame feature showed range of flame colors (yellow, blue, blurish-green) over the range of conditions. Low level of NOx along with low level of CO have been obtained under high-preheated air combustion conditions. The thermal and chemical behavior of high-preheated air combustion flames depends on preheated temperature and oxygen concentration air.

• Journal of the Korean Society of Combustion
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• v.7 no.3
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• pp.1-8
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• 2002

An experimental study has been carried on high-preheated temperature air combustion. The flames with high-preheated temperature air combustion turned out to be both temporally and spatially much more stable and homogeneous than these with room-temperature combustion air. The global flame feature showed a range of flame colors (yellow, blue, blurish-green) according to the flame conditions. A low level of NOx along with low level of CO has been obtained under high-preheated air combustion conditions. The thermal and chemical behavior of high-preheated air combustion flames depends on the preheated temperature and the oxygen concentration of air.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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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.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.112-117
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• 2001

An experiment using high preheated and swirled air in the coaxial diffusion flame burner was carried out in order to decrease NOx emission and improve the thermal efficiency. $N_2$ gas was used for diluent and propane was utilized for fuel. Combustion using high preheated air has two remarkable characteristics ; (1) low NOx emission with increasing dilution level, (2) high thermal efficiency in the furnace. Also, swirled air can mix fuel and oxidizer well in condition of diffusion flme and maintain the stable combustion. The color of flame changes from yellow to blue green according to increasing the dilution level of mixture gas. NO emission decreased with increasing dilution level and the swirl number.

• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.51-56
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• 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.

• Journal of the Korean Society of Combustion
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• v.8 no.1
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• pp.17-24
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• 2003

The conventional regenerative system has a high thermal efficiency as well as energy saving using the high preheated combustion air. in spite of these advantages, it can not avoid high nitric oxide emissions. Recently, flameless combustion has received much attention to solve these problems. In this research, numerical analysis is performed for flow-combustion phenomena in the self regenerative burner. In this analysis we used Fluent 6.0 code. the that is developed for commercial use, Methane gas is used as a fuel and two-step reaction model for methane and Zeldovich mechanism for NO generation are used. the velocity of the preheated combustion air is used as a parameter and we analyze the characteristics of flow-field, temperature distributions and NO emissions. Due to the increased recirculation rate, the maximum temperature of flame is significantly increased and NOx emissions is reduced.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.97-104
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• 2002

The conventional regenerative system has a high thermal efficiency as well as energy saving using the high preheated combustion air. in spite of these advantages, it can not avoid high nitric oxide emissions. Recently, flameless combustion has received much attention to solve these problems. In this research, numerical analysis is performed for flow-combustion phenomena in the self regenerative burner. In this analysis we used Fluent 6.0 code. the that is developed for commercial use, Methane gas is used as a fuel and two-step reaction model for methane and Zeldovich mechanism for NO generation are used. the velocity of the preheated combustion air is used as a parameter and we analyze the characteristics of flow-field, temperature distributions and NO emissions. Due to the increased recirculation rate, the maximum temperature of flame is significantly increased and NOx emissions is reduced

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.65-70
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• 2001

OH radical and NOx have been measured in a methane-air partially premixed flame using PLIF technique to define preheated air combustion characteristics. The temperature of mixture is determined by 300K, 400K, 600K and 800K below the auto-ignition temperature respectively. Flame height increases as equivalence ratio increased. As initial enthalpy is supplied, the radius of flame was increased and much amount of yellow flame in rich equivalence ratio was observed. This is due to the faster burning velocity. Also initial oxidization begins earlier as the initial temperature of mixture increased. It means that height of premixed flame front decreased. This phenomenon can be observed OH PLIF image. The qualitative analysis of OH concentration in the PLIF image shows that overall OH concentration increases with equivalence ratio and the initial temperature of mixture increased. At the preheating temperature goes up, axial gradient of OH concentration is less steep than that of lower temperature condition. This may identify that combustion reacts continuously, so preheated air combustion can evade the local heating and make high temperature indiscriminately in the overall reaction zone.

• Journal of the Korean Society of Combustion
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• v.3 no.1
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• pp.49-57
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• 1998

High temperature preheated and diluted air combustion has been developed as the technology to realize higher thermal efficiency. In this type of combustion, there are many interesting phenomena which cannot be observed in room temperature air combustion. The characteristics of the combustion, investigated using a 3500 kcal/h LPG fired test facility, are described. The flame is demonstrated to have a blue and green in color and has a large volume. As the preheated air temperature increased up to $1000\;^{\circ}C$, the NOx emission incrased exponentially over a few hundred ppm with 11% $O_2$ correction. But, it drastically reducedabout 20ppm when the air was diluted from 21% $O_2$ to 5% $O_2$.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.95-103
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• 1999

Experimental study on combustion characteristics of a regenerative combustor has performed. High-temperature air combustion in the regenerative combustor is obtained through heat recovery from exhaust gas flow by porous ceramic materials and through alternation of air flow direction through the combustor. Temperature field, CO and NOx emission with respect to the frequency of alternation are measured. It is found that at initial stage of the alternation, temperature of inlet section of main combustion chamber is increased sharply since both high temperature air preheated by the ceramics and prompt fuel injection results in rapid combustion. Following this initial stage, combustion temperature is reduced as the preheated air temperature is reduced. However peak temperature in the chamber and exhaust gas temperature are decreased as the alternation period is reduced, increased temperature of ceramic is observed. CO and NOx emission with respect to the alternation period is also examined. It is found that there exists a range of optimum alternating period for CO and NOx emission characteristics.