• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.54-60
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• 2017

In order to identify the characteristics of the flame transfer function gain, cold-flow transfer function was introduced, which is the part of the combustion instability research. Nitrogen and carbon dioxide was used to obtain the cold-flow transfer function and input/output variables was measured by hot wire anemometry. Density and fluid flow rate affect the cold-flow transfer function gain and peak frequency. In addition, acoustic resonance frequency affects the peak frequency of gain in the fuel feeding line.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.4
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• pp.63-72
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• 2003

The combustion characteristics of the KSR-III engine were investigated numerically from the viewpoint of performance and combustion field. For numerical analysis of KSR-III engine with hub-and-spoke baffle, 3-D calculation was performed about $30^{\cire}$ section and the prediction of performance was in a good agreement with hot-firing test result. As a result of baffle installed, the performance of KSR-III engine was reduced in comparison with no baffle case and local high temperature region appeared on injector plate, combustion wall and baffle wall, This calculation was used practically as basic data for designing injector plate with film cooling holes and predicting the performance of KSR-III final flight test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.93-101
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• 2004

A method to calculate stability limits is investigated to predict the characteristics of high-frequency combustion instability in liquid-propellant rocket engine. It is based on the theory of linear stability analysis proposed in previous works and useful to predict combustion stability at the beginning stage of engine development. The system of equations governing reactive flow in combustor has the simplified and linearized forms. The overall equation expressing stability limits is adopted. The procedures to evaluate quantitatively each term included in the equation are proposed. The thermo-chemical properties and flow variables required in the evaluation can be obtained from calculation of thermodynamic equilibrium, CFD results, and experimental test data. Based on the existent data, stability limits are calculated with actual rocket engine (KSR-III rocket engine). The present calculations show the reasonable stability limits in a quantitative manner and the stability characteristics of the engine are discussed. The prediction from linear stability analysis could be serve as the first approximation to the true prediction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.8
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• pp.632-638
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• 2013

This paper describes on the flame stability and combustion instability of coal derived synthetic gas especially for gases of Buggenum IGCC in Netherlands and Taean IGCC in Korea. These combustion characteristics were observed by conducting ambient-pressure elevated-temperature combustion tests in GE7EA model combustor when varying heat input and nitrogen dilution ratio. Flame stability map is plotted according to the flame structure by dividing all regimes into six, and only regime I and II are identified to be stable. Both syngases of Taean and Buggenum with nitrogen integration corresponds to regime II in which syngas burnt stably and flame coupled with outer recirculation flow. Stable regime of Buggenum is larger than that of Taean when considering only $H_2$/CO ratio due to higher content of hydrogen. However, when considering nitrogen dilution, syngas of Taean is burnt more stably than that of Buggenum since more nitrogen in Buggenum has negative effect on the stability of flame.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.6
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• pp.62-73
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• 2022

This research proposes a method to control combustion instability in a gas turbine combustor having an annular combustor form and compares the effect of flow symmetric braking through nozzle arrangement and the corresponding change in equivalent ratio. To this end, the symmetry breaking effect was confirmed through mode analysis of FFT, Time signal, and phase trajectory. In addition, the unstable area and the stable area were identified through mode analysis, and this was shown on the contour map. The present research shows that instability occurs when the equivalent ratio and the arrangement of the nozzles are symmetry or when the nozzles are continuously arranged, but if the arrangement and equivalent ratio are not symmetry, the combustion instability decreases dramatically even if the difference in the equivalent ratio is small.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.27-35
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• 2004

In this paper a method for finding solution of acoustic, vortex and entropy wave-equations in a cylindrical tube with variable section area was suggested under the consideration of that the high frequency instability in a rocket engine combustion chamber is an acoustic phenomena, which is coupled with combustion reaction, and that a combustion chamber and exhaust nozzle are usually shaped cylindrically. As a consequence of that some method, which enable the quantitative analysis of the influence of entropy and vortex waves to acoustic wave, was suggested.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.303-308
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• 2006

This paper describes numerical efforts to investigate combustion characteristics of HyShot scramjet engine. The corresponding altitude, angle of attack, and equivalence ratio are 28 km, $0^{\circ}$, and 0.426 respectively. $H_2$ and OH mass fraction show that the upstream recirculation zone of injector has flame-holding effects and main combustion begins at 15 cm downstream from cowl. Two-dimensional simulation reasonably predicts combustor inner pressure and also reveals periodic combustion characteristics of HyShot scramjet engine.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.95-101
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• 2004

Dynamic behavior of diffusive-thermal instability in diluted $CH_4/O_2$ diffusion flames is numerically investigated by adopting detailed chemistry and transport. Counterflow diffusion flame is adopted as a model flamelet. Particular attention is focused on the pulsating-instability regime, which arises for Lewis numbers greater than unity, and the instability occurs at high strain rate near extinction condition in this flame configuration. Once a steady flame structure is obtained for a prescribed value of initial strain rate. transient solution of the flame is calculated after a finite amount of strain-rate perturbation is imposed Oil the steady flame. Transient evolution of the flame depends on the initial strain rate and the amount of perturbed strain rate. Basically, the dynamic behaviors can be classified into two types, namely non-oscillatory decaying solution and diverging solution leading to extinction. The peculiar oscillatory solution. which has been found in the previous study adopting one-step chemistry and constant Lewis numbers, is not observed in this study, which is attributed to both convective flow and preferential diffusion effects.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.4
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• pp.25-32
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• 2020

A numerical study on combustion instabilities in a model combustor was conducted with various momentum flux ratios. Five ratios are calculated based on an actual operating condition of rocket engine. As momentum flux ratio increases, the spreading angle on the injector outlet decreases. And, as increase of axial momentum flux, pressure fluctuation decreases inside the combustor. By using dynamic mode decomposition method, the acoustic modes inside the combustor are identified. Combustion stabilities are analyzed by comparing the damping coefficient of the 2^nd longitudinal mode.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.240-246
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• 2005

A series of combustion tests of a 30-tonf-class full scale liquid rocket thrust chamber under development has been carried out to verify its design. The test results revealed decent performance in the aspects of efficiency. The combustion stability is one of the most important parameters of liquid rocket engine in addition to the efficiency. Assessment tests of combustion stability must be accomplished to confirm the possibility of combustion instability due to spontaneous or external disturbances. The combustion stability rating tests of the full scale thrust chamber with temporary baffles made of stainless steel were carried out utilizing pulse guns to estimate combustion stability characteristics. The tests results show highly stable combustion stability characteristics. The outcome acquired from the present experimental study will be used to design an actively cooled baffle that can survive for the life time operation of the thrust chamber.