• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.99-105
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• 2004

The effects of pressure on combustion characteristics of the conical flameholder were investigated experimentally in the pressure range from 0.11 ㎫ to 0.40 ㎫. The result shows that the total equivalence ratio of lean limit becomes lower as the combustor inlet pressure rises and NOx emission is proportional to the pressure to the 0.5th power.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.233-235
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• 2015

This study is to investigate the combustion instability of the variation of combustion chamber length in dual swirl gas turbine model combustor. When equivalence ratio was fixed at 1.1, as the length of the combustion chamber increases the value of the frequency decreased in 7kW while the value of the frequency was constant in 4kW. The analysis of flame behaviors by high speed camera was conducted to identify such trend.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.273-274
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• 2015

Fuel flexibility remains a critical issue related the development of low emission lean premixed combustion system and the combustion adjustment technique. To cover the this work scope with our own technology, KEPCO had focused on operational technology related to GT combustion control. The main purpose of this paper is summary of the research works on fuel flexibility in KRPCO Research Institute recently. Furthermore, the specifications of test facility and research work in the future in KEPRI were also explained briefly for expected collaborative research team in Korea.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.174-180
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• 2017

Recently, the world faces the environmental problem such as air pollution due to harmful gas discharged from car and abnormal climate due to the green-house gases increased by the discharge of $CO_2$. Compressed Natural Gas (CNG), one of alternative for this problem, is less harmful, compared to the existing fossil fuel, as gaseous fuel, and less carbon in fuel ingredients and carbon dioxide generation rate relatively favorable more than the existing fuel. However, CNG fuel has the weakness of slow flame propagation speed and difficult fast burn. On the other hand, hydrogen does not include carbon in fuel ingredients, and does not discharge harmful gas such as CO and HC. Moreover, it has strength of quick burning velocity and ignition is possible with small ignition energy source and it's has wide Lean Flammability Limit. If using this hydrogen with CNG fuel, the characteristics of output and discharge gas is improved by the mixer's burning velocity improved, and, at the same time, is possible to have stable lean combustion with the reduction of $CO_2$ expected. Therefore, this research tries to identify the characteristics of engine and emission gas when mixing CNG fuel and hydrogen in each portion and burning them in spark igniting engine, and grasp the lean combustion limit and emission gas characteristics according and use it as the basic data of hydrogen-CNG premixed engine.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.46-53
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• 2017

This paper deals with an acoustic model for a lean premixed gas turbine combustor composed of three stages: premixing chamber, nozzle and flame tube. Our model is given as an acoustic transfer function whose input is a heat release rate perturbation and output is a velocity perturbation at a flame location. We have shown that the resonance frequencies are functions of three round-trip frequencies of acoustic wave in each stage, and area ratios between stages. By analyzing poles of the acoustic transfer function, we could characterize resonant frequencies and their dependency on various system parameters of a combustor. It was found that our analytic findings match with existing numerical and experimental results in literature.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.1-9
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• 2008

In the first part of the paper, Computational Fluid Dynamics analysis of the combusting flow within a high-swirl lean premixed gas turbine combustor and over the $1^{st}$ row nozzle guide vanes is presented. In this analysis, the focus of the investigation is the fluid dynamics at the combustor/turbine interface and its impact on the turbine. The predictions show the existence of a highly-rotating vortex core in the combustor, which is in strong interaction with the turbine nozzle guide vanes. This has been observed to be in agreement with the temperature indicated by thermal paint observations. The results suggest that swirling flow vortex core transition phenomena play a very important role in gas turbine combustors with modern lean-premixed dry low emissions technology. As the predictability of vortex core transition phenomena has not yet been investigated sufficiently, a fundamental validation study has been initiated, with the aim of validating the predictive capability of currently-available modelling procedures for turbulent swirling flows near the sub/supercritical vortex core transition. In the second part of the paper, results are presented which analyse such transitional turbulent swirling flows in two different laboratory water test rigs. It has been observed that turbulent swirling flows of interest are dominated by low-frequency transient motion of coherent structures, which cannot be adequately simulated within the framework of steady-state RANS turbulence modelling approaches. It has been found that useful results can be obtained only by modelling strategies which resolve the three-dimensional, transient motion of coherent structures, and do not assume a scalar turbulent viscosity at all scales. These models include RSM based URANS procedures as well as LES and DES approaches.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.6
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• pp.98-106
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• 2011

This paper reviews the state-of-the-art thermoacoustic(TA) modeling techniques and research trend to predict major parameters determining combustion instabilities in lean premixed gas turbine combustors. Linear TA modeling results give us an information on eigenfrequencies and initial growth rate of the instabilities. For the prediction, linear relation equation between acoustic waves and heat release oscillations should be derived in the determined system. Key information for this analysis is to determine the heat release fluctuations in the combustor, which is typically obtained by using n-${\tau}$ function from flame transfer function measurements and/or predictions. Great advancement in the linear TA modeling has been made over a couple of decades, and some successful prediction results have been reported in actual gas turbine combustors. However nonlinear TA model developments which are required to analyze nonlinear system behaviors such as limit cycle saturation and transition phenomena are still limited in a very simple system. In order to fully understand combustion instabilities in a complicated real system, nonlinear flame dynamics and acoustic wave interaction with nonlinear system boundary conditions should be explained from the nonlinear TA model developments.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1368-1375
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• 2004

Measurements of OH chemiluminescence in an atmospheric pressure, laboratory-scale dump combustor at equivalence ratios ranging from 0.63 to 0.89 were reported. The signal from the first electronically excited state of OH to ground state was detected through a band-pass filter with an ICCD. The objectives of this study are two: One is to see the effects of equivalence ratio on global heat release rate and local Rayleigh index distribution. To get the local Rayleigh index distribution, the line-of-sight images were inverted by tomographic method, such as Abel do-convolution. Another aim is to investigate the validity of using OH chemiluminescence acquired with an ICCD as a qualitative measure of local heat release. For constant inlet velocity and temperature, the overall intensities of OH emission acquired at different equivalence ratio showed periodic and higher value at high equivalence ratio. OH intensity averaged over one period of pressure increased exponentially with equivalence ratio. Local Rayleigh index distribution clearly showed the region of amplifying or damping the combustion instability as equivalence ratio increased. It could provide an information/insights on active control such as secondary fuel injection. Finally, local heat release rate derived from reconstructed OH images were presented fur typical locations.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2181-2185
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• 2008

Fuel processing systems which convert HC fuel into $H_2$ rich gas (such as stream reforming, partial oxidation, auto-thermal reforming) need high temperature environment($600-1000^{\circ}C$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1-5kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural & anode off gas as reformer fuel. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.1
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• pp.75-84
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• 2007

The effects of hydrogen enrichment to methane on NOx formation have been investigated with swirl stabilized pre-mixed hydrogen enriched methane flame in a laboratory-scale pre-mixed combustor(nominally of 5,000 kcal/hr). The hydrogen enriched methane fuel and air were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame stability was examined for different amount of hydrogen addition to the methane fuel, different combustion air flow rates and swirl strengths by comparing equivalence ratio at the lean flame limit. The hydrogen addition effects and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using gas analyzers, and OH chemiluminescence techniques to provide information about species concentration of emission gases and flowfield. The results of NOx and CO emissions were compared with a diffusion flame type combustor. The results show that the lean stability limit depends on the amount of hydrogen addition and the swirl intensity. The lean stability limit is extended by hydrogen addition, and is reduced for higher swirl intensity at lower equivalence ratio. The addition of hydrogen increases the NOx emission, however, this effect can be reduced by increasing either the excess air or swirl intensity. The NOx emission of hydrogen enriched methane premixed flame was lower than the corresponding diffusion flame under the fuel lean condition.