• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.47-53
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• 2017

One of the most common causes of failure of space launch vehicles is combustion instability. Combustion instability is a phenomenon that the pressure perturbation inside the combustion chamber is greatly amplified due to the interaction of the pressure perturbation inside the combustion chamber and the heat release perturbation. When this phenomenon becomes worse, an engine failure or launch vehicle crash occurs. In order to predict and avoid such combustion instability, understanding of the phenomenon is indispensable, and numerical, theoretical, and experimental approaches to combustion instability have been carried out worldwidely.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.83-87
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• 2009

Ramjet engine is weak for low frequency combustion instability because of their long air flow passage. A model combustor which has fuel injector and V-gutter shaped flame holder was designed and fabricated in order to simulate a combustion mechanism of ramjet engine, and it could demonstrate combustion instability which might occur in ramjet combustor. The frequency of the instability was very similar to that of acoustic resonance frequency of combustor, and it proved that a typical combustion instability by thermo-acoustic coupling occurred.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.63-77
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• 2008

This paper described the general concept of combustion instability and its mechanism in gas turbine engines. The approaching method to study this phenomenon was introduced including the up-to-date research activity in tile world. Combustion instability is one of critical problems, still now, affecting engine performance, durability and operation. In addition it is known that this problem is caused by coupling between fuel or air flow fluctuation and heat release rate in gas turbine engines, which is related with NOx reduction strategies. Therefore, in order to understand the current status of combustion instability we reviewed the combustion instability phenomenon in gas turbine engines.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.445-449
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• 2005

The mixed acoustic-convective mode combustion instability and the possibility of combustion control using a loudspeaker to these instabilities were studied. By changing inlet velocity, combustor length and equivalence ratio, the dynamic pressure signals and the flame structures were simultaneously taken. The results showed that as the combustor length increased and the inlet velocity decreased, the instability frequency decreased and the maximum power spectral densities of the dynamic pressures generally decreased. The instability frequency could be affected by an equivalence ratio over the operating conditions. From the data of close-loop control, as the loudspeaker may work out-of-phase with the natural instability, the optimum time-delay controller was confirmed to be able to reduce the vortex shedding from the mixed acoustic-convective mode combustion instability.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.54-58
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• 2017

A combustion instability has been one of the most serious problems in the development of combustion devices including rocket engine and gas turbine. In particular, a high-frequency combustion instability generated by resonant coupling between combustion phenomena and acoustic oscillations within thrust chamber causes severe damage to the hardware. Because it is accompanied by high amplitude pressure oscillations and excessive heat flux to the chamber wall. Therefore, combustion instability is one of the difficult problems that must be resolved in developing liquid rocket engine. This paper describes the cases of combustion instability encounted during the development of thrust chamber for KSR-III and KSLV-II.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.1
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• pp.71-84
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• 2007

The review of the liquid propellant rocket engine is presented. The combustion instabilities which were discovered on solid and liquid propellant rocket engines in 1930, have occurred on propulsion devices, such as gas turbine, ramjet, scramjet and rocket, and thus a study on the combustion instability became necessary. However, this problem has not been solved yet. Therefore, we investigated causes and mechanisms of the combustion instability and surveyed the efforts of solving combustion instability in various countries for developing stable liquid propellant rocket engines.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.28-36
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• 2018

A study was conducted to apply open-loop control to the combustion instability in a dump combustor using gaseous hydrocarbon fuels. Control power and frequency were varied by employing a loudspeaker under combustion conditions with similar characteristic chemistry times of the fuels. In the case of open-loop control where the frequency was identical to the combustion instability frequency, the open-loop control power affected the control performance. Results obtained from conducted open-loop control tests, where the frequency was different from the combustion instability frequency, show that setting the open-loop control frequency similar to the combustion instability frequency is effective.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.896-904
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• 2017

Lean premixed combustion was successful in meeting current NOx emission regulations. However, these often leads to combustion instability. This phenomena results from the feedback relationship between heat release perturbations and acoustic pressure oscillations in the combustor. Researches on the combustion instability in an annular combustor have recently received great attention due to the enhanced NOx requirement in aero-engines. In this study, the thermoacoustic network model has been developed in order to calculate the acoustics for longitudinal as well as circumferential modes in the annular combustor. The combustion model in the network model is calculated by flame transfer function(FTF). Numerical and analytical results are compared to an measurement data.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.24-33
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• 2021

Numerical study is conducted to analyze combustion instability in the partially premixed combustor. The simulations are performed according to fuel conditions, and Large Eddy Simulation(LES) model and PaSR combustion model are implemented in the solver. Comparison with the experimental result is conducted to confirm the validity of simulation, and quantitative and qualitative agreement is confirmed. The flame characteristics in the combustor are subsequently investigated, and the association with the occurrence of combustion instability is clarified. According to the simulation results, the flame length varies greatly depending on the fuel conditions. When the flame length becomes sufficiently long, flame-vortex interactions occurred around the wall sections, which works as the main cause of combustion instability.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.187-199
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• 2011

The main objective of this study was investigation of natural gas flames in a lean premixed swirl-stabilized dump combustor with an attention focused on the effect of the various fuel-air mixing section geometry on the combustion instability characteristics. The multi-channel dynamic pressure transducers were located on the combustor and inlet mixing section region to observe combustion pressure oscillation and difference phase at each dynamic pressure measurement results. Dynamic pressures were also measured to investigate characteristics of combustion at the same time. The combustor and mixing section length was varied in order to have different acoustic resonance characteristics from 800 to 1800 mm in combustor and 470, 550, 870 mm in mixing section. We observed two dominant instability frequencies in this study. Lower frequencies were obtained at lower equivalence ratio region and it was associated with a fundamental longitudinal mode of combustor length. Higher frequencies were observed in higher equivalence ratio conditions. It was related to secondary longitudinal mode of coupled with the combustor and mixing section. In this instability characteristics, pressure oscillation of mixing section part was larger than pressure oscillation of combustor. As a result, combustion instability was strongly affected by acoustic characteristics of combustor and mixing section geometry.