• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1669-1678
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• 1990

The annular and coaxial swirl flows between which LPG is supplied was selected to study the swirling flames in double co-swirl flows. The objective of this study is to research into the effects of double co-swirl flow conditions on the stability limit, the reverse flow boundary, and the time mean temperature distributions of the swirling flames. The increase of swirl intensity of axial flow makes the stability limit decrease, but the annular swirl flow (SM>0.5) makes stability and swirl intensity of axial flow increase, And the existence of axial swirl flow makes flame intensive and small in size, and this may be applicable to the design of high power compact combustor.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.178-185
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• 2005

The synergistic effect of ethylene/propane mixture on soot formation is studied experimentally using a concentric co-flow diffusion burner, which provides the stratified fuel mixture. The soot volume fraction, soot particle diameter, number density and PAH concentrations are measured with various fuel supply configurations and compared to the homogeneously mixed case. When propane is supplied through the inner nozzle, an increase of soot formation is observed. However, when propane is supplied through the outer nozzle, a decrease is observed. The reaction path of PAH's formed from the pyrolysis process of propane is likely to be responsible to the observed differences. When propane is supplied through the outer nozzle, PAH's are formed in the relatively near oxidation region and exposed to the oxidization environment; on the other hand, when propane is supplied through the inner nozzle, PAH's are not likely to be oxidized and thus get involved in soot formation process. The synergistic effect in ethylene/propane diffusion flames is found to be affected not only by the com position of the mixture but also by the way of mixing.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.6
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• pp.553-560
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• 2010

The characteristics of syngas-oxyfuel combustion has been investigated experimentally in the present study. Experimental measurements were conducted to aid a fundamental design of a syngas-oxyfuel combustor with a double coaxial burner configuration. To examine the effects of different syngas fuels on combustion characteristics, various fuel types are utilized such as commercial coal gases (Texaco, Shell), COG (cokes oven gas), and $CH_4$ as a main component of natural gas. $CO_2$ was added to the four fuel types as a diluent gas to reduce the flame temperature. The flame images and emission characteristics of NOx and CO were examined for various equivalence ratio and $CO_2$ dilution ratio. The results show that CO emission was rapidly increased as equivalence ratio approached the stoichiometry condition by reducing the amount of oxygen. As the $CO_2$ dilution increased, CO emission increased while NOx emission decreased due to reduced flame temperature. When the syngas-oxyfuel combustor is operated with 20~40% of $CO_2$ dilution ratio, the CO and NOx emission levels were kept below 50 ppm and 25 ppm, respectively, with a high concentration of $CO_2$ over 95 vol.% in exhaust gases.

• Fire Science and Engineering
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• v.24 no.6
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• pp.170-175
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• 2010

The effect of carbon dioxide addition on soot formation was investigated in jet diffusion flames in coflow. Flame temperature were measured with R-type thermocouple and the boundary temperature between blue and yellow flame was confirmed. Light-extinction method was introduced for the relative soot density (1-I/$I_0$) in the in-flame region. He-Ne laser with wave length at 632.8 nm was used for the light source, and the signal attenuated by absorption and scattering was detected directly. Oxidizer velocity effect on soot formation was studied to know that the thermal influence for soot formation. The results showed that the temperature of both blue and yellow flame were decreased according to the dilution of carbon dioxide but boundary temperature was nearly constant. The relative soot density was lower when carbon dioxide was added in oxidizer stream and oxidizer velocity increased. These were caused by the reduction of flame temperature and shorter residence time for soot growth. Also carbon dioxide addition enhanced the instability of jet flames like flickering, so the flame length was a little longer than pure ethylene/air flame.

• Journal of the Korean Society of Combustion
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• v.3 no.1
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• pp.11-19
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• 1998

The influence of oxidant addition on soot formation is investigated experimentally with ethylene, propane and mixture fuel co-flow diffusion flames. Oxidant addition into fuel shows the increase of integrated soot volume fractions for ethylene, ethylene/ethane and ethylene/methane mixture flames. However, the increase of integrated soot volume fraction with oxidant addition was not significant for propane and ethylene/propane mixture flames. This discrepancy is explained with $C_2\;and\;C_3$ chemistry at the early stage of soot formation process. The oxidant addition increases the concentration of $C_3H_3$ in the soot formation region, and therefore, enhances soot formation process. A new soot formation rate model that includes both dilution effect and chemical effect of oxygen is suggested to interpret the increase of integrated soot volume fractions with oxidant addition into ethylene. Also, the role of adiabatic flame temperature for the chemical effect of oxygen addition into fuel was reviewed. The influence of oxidant or diluent addition into fuel on soot formation process are the fuel dilution effect, the adiabatic flame temperature altering effect and/or the chemical effect of oxygen. Their relative importance could change with fuel structure and adiabatic flame temperature.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.185-191
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• 2002

The influence of N2 addition on soot formation, flame temperature and NOx emissions is investigated experimentally with methane fuel co-flow diffusion flames. The motivation of the present investigation is the differences in NOx reduction reported between fuel-side and oxidizer-side introduction of N2. To determine the influence of dilution alone, fuel was diluted with nitrogen while keeping the adiabatic flame temperature fixed by changing the temperature of the reactants. And to see the thermal effect only, air was supplied at different temperature without N2 addition. N2 addition into fuel side suppressed the soot formation than the case of oxidizer-side, while flame temperature enhanced the soot formation almost linearly. These results reveals the relative influences of the thermal, concentration effects of N2 additives on soot formation In accordance with experimental study, numerical simulation using CHEMKIN code was carried out to compare the temperature results with those acquired by CARS measurement, and we could find that there is good agreement between those results. Emission test revealed that NOx emissions were affected by not only flame temperature but also N2 addition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1464-1469
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• 2000

The effects of SiCl$_4$addition on flame structures have been studied in flame hydrolysis deposition (FHD) processes using Coherent anti-Stokes Raman spectroscopy (CARS) and planar laser induced fluorescence (PLIF) to measure temperatures and OH concentrations, respectively. The results demonstrate that even a small amount of SiCl$_4$ addition can change thermal and chemical structures of H$_2$/O$_2$ diffusion flames. When SiCl$_4$ is added to a flame temperature decreases in non-reacting zone due to the increases in both specific heat and density of the gas mixture, while flame temperature increase in particle formation zone due to the heat release through hydrolysis and oxidation reactions of SiCl$_4$. It is also found that OH concentration decreases dramatically in particle formation zone where temperatures increase. This can be attributed to consumption of oxidative species and generation of HCl during silica formation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.481-488
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• 2013

Nitric oxide ($NO_x$) formation characteristics in non-premixed diffusion flames of methane fuels have been investigated experimentally and numerically by adding 10% ammonia to the fuel stream, according to the variation of the oxygen ratio in the oxidizer with oxygen/carbon dioxide and oxygen/nitrogen mixtures. In an experiment of coflow jet flames, in the case of an oxidizer with oxygen/carbon dioxide, the $NO_x$ emission increased slightly as the oxygen ratio increased. On the other hand, in case of an oxygen/nitrogen oxidizer, the $NO_x$ emission was the maximum at an oxygen ratio of 0.7, and it exhibited non-monotonic behavior according to the oxygen ratio. Consequently, the $NO_x$ emission in the condition of oxyfuel combustion was overestimated as compared to that in the condition of conventional air combustion. To elucidate the characteristics of $NO_x$ formation for various oxidizer compositions, 1D and 2D numerical simulations have been conducted by adopting one kinetic mechanism. The result of 2D simulation for an oxidizer with oxygen/nitrogen well predicted the trend of experimentally measured $NO_x$ emissions.