• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.32-40
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• 2012

For predicting eigenfrequency and initial growth rate of combustion instabilities in lean premixed gas turbine combustor, linear thermoacoustic analysis model was developed in the current paper. A model combustor was selected for the model validation, which has well-defined inlet and outlet conditions and a relatively simple geometry, compared to the combustor in the previous works. Analytical linear equations for thermoacoustic waves were derived for a given combustion system. It was found that the prediction results showed a good agreement with the measurements, even though there was underestimation for instability frequencies. This underestimation was more obvious for a longer flame (i.e. wider temperature distribution) than for a shorter flame.

• Journal of ILASS-Korea
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• v.20 no.3
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• pp.135-140
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• 2015

Flame transfer function is used to determine the relationship between flow fluctuations and heat release perturbations in a lean premixed gas turbine combustor. The characteristics of flame transfer function are known to depend greatly on flame geometries in addition to other various flow conditions. However, it is not easy to experimentally measure the flame transfer function under various actual combustor operating conditions in terms of time and cost. The current research tries to model the flame transfer function using CFD(Computational Fluid Dynamics). From the results, it is shown that the calculated steady flame geometry can be exactly captured with consideration of the wall heat transfer and radiations. Also, unsteady analysis results show the close characteristics of the flame transfer function to the measured one in both gain and phase.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.430-432
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• 2011

An experimental study of the flame response in a turbulent premixed combustor has been conducted in order to investigate mechanisms for combustion instabilities in lean premixed gas turbine combustor. A lab-scale combustor and mixing section system were fabricated to measure the flame transfer function. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function as a function of the modulation frequency and operating conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.75-83
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• 2005

A steady transonic dilute premixed combustion in a diverging channel is investigated by using asymptotic analysis. This model explores the nonlinear interactions between the near-sonic speed of the flow, the small changes in geometry from a straight channel, and the small heat release due to the one-step first-order Arrhenius chemical reaction. The reactive flow is described by a nonhomogeneous transonic small-disturbance (TSD) equation coupled with an ordinary differential equation for the calculation of the reactant mass fraction in the combustible gas. Also the asymptotic analysis reveals the similarity parameters that govern the reacting flow problem. The results show the complicated nonlinear interaction between the convection, reaction, and geometry effects and its effect on the flow behavior.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.9
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• pp.773-779
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• 2014

A qualitative and quantitative analysis on flame dynamics is required to model combustion instability characteristics in gas turbine lean premixed combustors. The current paper shows the flame transfer function modeling results using CFD(Computational Fluid Dynamics) techniques for the flame dynamics study. It is generally known that flame shapes determine the basic characteristics of the flame transfer function. The comparisons of the modeled flame shapes with the measured ones were made using the optimized heat transfer conditions. Modeling results of the flame transfer function show the close behaviors to the measured data with a reasonable accuracy if the flame geometry can be exactly captured.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.46-52
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• 2009

In this study the predictions of NOx in methane-air lean premixed combustion in PSR were carried out with GRI 3.0 methane-air combustion mechanism and Zeldovich, nitrous oxide, prompt, and NNH NO formation mechanism by using CHEMKIN code. The results are compared to the JSR experimental data of Rutar for the validation of the model. This study concerns about the importance of the chemical pathways. The chemical pathway most likely to form the NO in methane-air lean-premixed combustion was investigated. The results obtained with the 4 different NO mechanisms for residence time(0.5-1.6ms) and pressure(3, 4.7, 6.5 atm) are compared and discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.35-40
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• 2011

An experimental study of the flame response in a turbulent premixed combustor has been conducted in order to investigate mechanisms for combustion instabilities in a lean premixed gas turbine combustor. A lab-scale combustor and mixing section system were fabricated to measure the flame transfer function. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results show that the flame transfer functions are greatly dependent on the modulation frequency as well as operating conditions such as equivalence ratio. Flame dynamics can be generalized as a function of Strouhal number which is a ratio of flame length to modulation wave length.

• Journal of Energy Engineering
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• v.13 no.2
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• pp.144-151
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• 2004

Stabilization and reduction of combustion noise and NOx emission from dry low NOx combustor of GE MS7001F gas turbine were achieved. Dry low NOx gas turbines that adopt the lean premixed combustion technology frequently generate the flame instability and high NOx emissions if not adequately tuned. Dynamic pressure oscillation during the combustion mode transfer increased as ambient temperature decreased with frequency of 80㎐ and magnitude of 4-9 psi. Effects of both combustor tuning for uniform fuel flow with burner nozzles and fuel pre-filling into transfer fuel valves on stabilisation of the dry low NOx combustor were very significant. Dynamic pressure oscillation during the combustion mode change was decreased up to 2.5 psi. Also, NOx emission from GE7F DLN-1 combustor can be maintained as low as 35-43ppm (15% O$_2$) in base load operation of 150 MW.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.19-26
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• 2004

A prior fundamental study was executed using a constant volume chamber to improve the burning properties of lean pre-mixture by the injection of active radicals generated in the sub-chamber. In consequence, RI method shows remarkable progress in the aspects of burning velocity and combustible lean limit compared with SI method. In this study, the necessary additional works have been performed to be based on the former results. We changed parameters as the initial temperature and the initial pressure of mixture. And the effects of residual gas at issue in a real engine were investigated. As a result, the effects of initial temperature were significant, but on the other hand, those of initial pressure were slight. The correlation of passage hole number between overall passage hole area was grasped. And the more detailed analysis is required on residual gas.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1166-1171
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• 2004

The combustion instability acts as a serious obstacle for the lean premixed combustion of gas turbine and even causes the fatal damage to the combustor and whole system. In this experiment, the pressure fluctuation is highly related to the stabilizing position of flame and fuel injection location. The fuel injection location is connected with the convection time of the fresh mixture, which is important time scale to refresh the mixtures near the flame stabilization location. The flame is extremely unstable when the alternative stabilization occurs and bulk mode frequency (${\sim}10Hz$) of pressure fluctuation is observed in this condition. It was found that the convection time scale of the fresh reactant coincided with the time scale of the bulk mode fluctuation. Hence this phenomenon results from the local equivalence ratio change caused by the pressure fluctuation induced by thermo-acoustic effects.