• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.275-280
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• 2005

At previous study, nitrogen oxide emission was decreased with decreasing pressure index. This tendency was explained by the flame oscillation with changing combustor pressure. In this study, the characteristics of flame oscillation with changing combustor pressure were investigated. It can be found that flame length is extended and flame width is narrowed by decreasing combustor pressure. It can be observed that pilot flame and the surrounding air converge on the inner flame in the $P^{\ast}{\geqq}1$ conditions and that surrounding air and flow pattern was widely dispersed in the $P^{\ast}<1$ conditions. In the respect of average flame length, low fluctuation was shown in the $P^{\ast}<1$ conditions. On the other hands, large fluctuation was shown in the $P^{\ast}<1$ conditions. Flame oscillation are observed from $P^{\ast}=$ 0.98 in the condition of $P^{\ast}<1$ and the amplitude of flame oscillation becomes larger when $P^{\ast}$ is lowered. These results demonstrate that low NOx phenomenon was caused by flame oscillation with changing combustor pressure.

• Journal of the Korean Society of Combustion
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• v.10 no.2
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• pp.35-41
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• 2005

Behaviors of lean premixed flame of propane/air and methane/air flame anchored by a pilot flame in a tube were investigated experimentally varying the mean velocity from 10 to 140 cm/s and the equivalence ratio from 0.45 to 0.8. Behaviors of both flames are divided into five regions of stable, flash-back, tail-out, flickering and vibrating. General characteristics of each region and Le number effect are investigated. Two main instabilities, flickering and vibration, are both unstable but the instability mechanism, the frequency and the amplitude of pressure fluctuation are different. In the edge of the vibrating region, pressure fluctuation repeats generation and extinction. Repeated growth and decrease of the amplitude of pressure fluctuation are explained by Rayleigh#s index.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1257-1264
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• 2011

This paper presents 3D simulation by STAR-CCM+ for lean premixed combustion in a stationary gas turbine combustor with separate pilot and main nozzles. The constant for the source term in the flame area density transport equation was modified to account for a low global equivalence ratio and validated against measurement data. A Partially-premixed Coherent Flame Model(PCFM) involves propagation of a laminar premixed flame with the predicted flame surface density and equilibrium assumption in the burned gas with spatial inhomogeneity. The conditions for cooling by radiation and convection are considered for accurate determination of the heat flux on the wall. A parametric study is of the pilot-fuel-to-total-fuel-ratio is carried out. A chemical reactor network (CRN) was constructed on the basis of the 3D simulation results and compared against measurements of NOx.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.70-79
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• 2013

The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine (MGT) were numerically investigated. Location of pilot burner, swirl angle and direction were varied as main parameters with the identical thermal load. As a result, the variations in location of pilot nozzle, swirl angle and direction resulted in the significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus the flame stability and emission performance might be significantly changed. With the comparison of experimental results, the case of swirl angle $45^{\circ}$ and co-swirl flow including optimum location of pilot burner were chosen in terms of the flame stability and emissions for the development of hybrid/dual swirl jet combustor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.389-394
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• 2004

An experimental study on the NOx formation of LNG flame in fuel staged combustor has been studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is a act as a pilot flame for the secondary combustion stage combustion zone, where most of fuel bums. Experiments were performed on a semi-industrial scale (thermal input 0.233 MW) in a laboratory furnace and Liquefied Natural Gas(LNG) was used as a primary and secondary fuels. This study included parametric study to identify the optimum operating conditions which are primary/secondary fuel ratio, and primary/secondary air ratio for reducing NOx emission with two types of nozzle. The test demonstrated that NOx emission can be reduced by >70% in accordance with operating conditions.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.161-166
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• 2001

An Experimental study on the NOx formation of LNG flame in fuel staged combustor has been studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is act as a pilot flame for the secondary combustion stage combustion zone, where most of fuel burns. Experiments were performed on a semi-industrial scale (thermal input 0.233 MW) in a laboratory furnace and Liquefied Natural Gas(LNG) was used as primary and secondary fuels. The study included parametric study to identify the optimum operating conditions which are primary/secondary fuel ratio, and primary/secondary air ratio for reducing NOx emission with two types of nozzle. The test demonstrated that NOx emission can be reduced by >70% in accordance with operating conditions.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.11
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• pp.1119-1123
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• 2006

The flame image processing and analysis system has been investigated for the optimal pulverized coal firing of thermal power plant, especially for lower nitrogen oxide generation and more safe operation. We aimed at gaining the relationship between burner flame image information and emissions of nitrogen oxide and unburned carbon in furnace utilizing the flame image processing methods, by which we quantitatively determine the condition of combustion on the individual humors. Its feasibility test was undertaken with a pilot furnace for coal firing, through which the system was observed to be effective for the monitoring of the combustion condition of pulverized coal firing boilers.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.201-207
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• 1999

The combustion characteristics for the low NOx 50 kW-class gas turbine combustor have been experimentally investigated. In order to achieve the premixing and the lean burn combustion, the geometries of the primary zone including premixed chamber were modified from conventional combustor. The centerline profiles of CO and NO concentration, and temperature were measured for the premixed combustors with or without dilution holes in the liner. The effects of the pilot fuel injection rate and air dilution on flame stabilization and pollutant (CO, NO) emission are discussed in detail.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.26-31
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• 2006

Flickering behaviors of lean premixed flame of propane/air and methane/air flame anchored by a pilot flame in a tube were investigated. Unsteady behaviors of the flame were monitored by a high speed ICCD camera and the flickering frequency was defined as the number of flame curvatures passing a fixed spatial point in a second. Unlike previous studies in which flames are in open condition so that the flickering mechanism is an unstable interaction of hot buoyant products with the ambient air, flames in this study are surrounded by a tube which means they are not open to ambient air, so that there is no interaction between hot buoyant products and ambient air. Despite the fact, there exists flickering phenomena and the flickering frequency ranges from 10 Hz to 50 Hz which is wider compared to previous studies. We relate the flickering mechanism to flame-generated vorticity and analytic solution for locally approximated flow is used. As a result, the relationship between flickering wavelength and dimensionless vorticity is acquired and the cause of higher range of flickering frequency is explained.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.60-66
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• 2004

Increased energy costs have placed demands for improved combustion efficiency, high equipment availability, low maintenance and safe operation. Simultaneously low NOx modification, installed due to stricter environmental legislations, require very careful combustion management. The flame diagnostics system has been developed specially to meet these requirements. We aimed at gaining the relationship between burner flame image and emissions such as NOx and unburned carbon in furnace by utilizing the image processing method. For the first step of development, its possibility test was undertaken with bench furnace. The test proceeded to the second step with pilot furnace, the system was observed to be effective for evaluating the combustion conditions.