• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.79-87
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• 2003

Application of combustion stabilization devices such as baffle and acoustic cavity to liquid propellant rocket engine is investigated to suppress high-frequency combustion instability, i.e., acoustic instability. First, these damping devices are designed based on linear damping theory. As a principal design parameter， damping factor is considered and calculated numerically in the chambers with/without these devices. Next, the unbaffled chambers with/without acoustic cavities are tested experimentally for several operating conditions. The unbaffled chamber shows the peculiar stability characteristics depending on the operating condition and it is found to have small dynamic stability margin. As a result, the acoustic cavity with the present design has little stabilization effect in this specific chamber. Finally， stability rating tests are conducted with the baffled chamber, where evident combustion stabilization is observed, which indicates sufficient damping effect.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.73-77
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• 2003

Stability rating of KSR-III rocket engine is conducted based on stability rating tests in the course of development of KSR-III rocket engine. Rocket engine is approved to have combustion stabilization ability when it can suppress the external perturbation or pressure oscillation with finite amplitude and recover the original stable combustion. Rocket engine in flight nay be perturbed with unexpectedly large amplitude and thus a designer should not only assure combustion stabilization ability of the engine but also quantify the stabilization capacity. For this, several quantitative parameters and their evaluation are introduced. To verify dynamic stability of KSR-III rocket engine, five stability rating tests have been conducted. Based on these test results, such parameters are quantified and thereby, the stabilization capacity of KSR-III rocket engine is evaluated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.95-101
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• 2004

Stability rating of KSR-III rocket engine is conducted based on stability rating tests in the course of development of KSR-III rocket engine. Rocket engine is approved to have combustion stabilization ability when it can suppress the external perturbation or pressure oscillation with finite amplitude and recover the original stable combustion. Rocket engine in flight may be perturbed by unexpectedly large-amplitude pressure oscillation and thus a designer should not only assure combustion stabilization ability of the engine but also quantify the stabilization capacity. For this, principal quantitative parameters and their evaluation are introduced. To verify dynamic stability of KSR-III rocket engine, six stability rating tests have been conducted. Based on these test results, such parameters are quantified and thereby, the stabilization capacity of KSR-III rocket engine is evaluated.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.51-60
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• 1997

축대칭 곡면벽 제트 버너를 제작하여 화염의 안정화 특성을 실험적으로 연구하였다. 축대칭 곡면벽 제트 유동은 난류 강도의 증가와 더불어 버너 선단 부근에 재순환 영역을 형성하여 화염의 안정화를 촉진시킴으로서 기존의 튜브 버너에 비하여 화염의 안정화 특성이 향상되었다. 시간적으로 화염의 위치가 변동하는 난류 화염에서 화염의 안정화 특성과 밀접한 관계가 있는 OH 라디칼과 온도를 PLIF와 CARS를 각각 적용하여 측정하였다. 고유속으로 연소시키는 경우에 버너 선단에 형성된 재순환 영역에 OH 라디칼이 상당량 분포하고 있었으며 통계적으로 고온을 유지하였다. 이는 버너 선단에 형성되는 재순환 영역에 고온의 기연 가스가 점화원 역할을 하여 화학 반응이 활발하게 일어나고 있음을 의미한다. 이러한 결과로부터 고속의 출구유속에서 화염 안정화 특성은 재순환 영역에 의하여 영향을 받고 있음을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.815-823
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• 2011

Combustion phenomena in porous media combustors are widely used in industrial fields for the combustion of lowgrade fuels and the regeneration of combustion heat. However, studies of combustion phenomena in porous media have been limited, because these phenomena are difficult to observe, and the configurations of porous media are complex. We propose a simple model combustor: a multi-channel combustor that consists of many layers of combustion channels made of quartz plates. We conducted an experimental observation of the flames in the multi-channel combustor and obtained experimental results for the flame stabilization limits. Flames formulated in the multi-channel combustor showed variation in the spatial distribution depending on the heat transfer between neighboring channels. A simple analytical model was developed and the variation in the flammability limits of the multi-channel combustor was discussed. This study will enhance our understanding of flame behavior in a porous-media combustor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.889-902
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• 2020

In this study, a numerical analysis was performed to confirm the formation of supersonic flow and the stabilization time satisfying the design condition in a Direct-connect supersonic combustor. The process was examined in which the high-pressure gas of vitiation air heater propagates downstream to the supersonic combustor and forms a supersonic flow field. It was confirmed through the analysis of pressure and temperature that the supersonic flow field satisfies the design points of Mach number 2.0 and 1,000 K, and requires a minimum of 4.0 ms for stabilization. These results indicate that the time required for the supersonic flow field stabilization should be taken into account when testing for the supersonic combustion experiment.

• Journal of the KSME
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• v.56 no.9
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• pp.54-57
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• 2016

로켓연소기는 수백 개의 분사기로 구성된 연소실에서 연소반응이 발생하게 된다. 이때 구조적인 특성으로 난류유동, 밀도, 온도 등의 변화가 매우 불균일한 3차원적인 분포를 가지게 된다. 이러한 불균일한 분포에 의해 발생되는 압력의 시간변화가 연소기의 고유진동수와 일치될 경우 공진이 발생하게 되어 폭발이 발생하게 된다. 이러한 현상을 연소불안정이라 하고 이글에서는 관련된 연구의 동향을 소개하고자 한다.

• 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.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4
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• pp.105-112
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• 1996

A linear acoustic analysis for baffled rocket combustion chambers has been developed. This study provides the comprehensive theoretical background for the baffle as one of the stabilizing devices in a liquid rocket propulsion system. Several specific effects of baffles are presented as mechanisms by which baffles eliminate instability. Included are longitudinalization of transverse waves inside baffle compartments, severe restriction of velocity fluctuations near the injector face, and decreased normal mode frequency of the chamber.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.70-71
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• 2002

연소실의 세장비(aspect ratio)가 작으면서 추진제의 고 충전을 이용한 단시간 연소 모타는 유도탄의 사출 모타 용으로 사용될 수 있다. 사출 모타는 일반적으로 모타 무게에 대한 제약 조건이 까다롭지 않기 때문에 무게 경량화에 대한 부담은 줄어들지만, 모타의 부피가 커지면 유도탄 발사 장치의 부피가 커지기 때문에 공간적인 측면에서 가능한 작게 하는 것이 시스템 전체의 효율을 증대시킬 수 있다. 또한 사출 모타의 연소 시간이 짧기 때문에(1초 이내) 추진제의 웹 두께가 작으므로 연소실의 주어진 공간에서 추진제를 많이 채우기 위한 방법으로 원통 튜브형 그레인을 여러 개의 다발로 사용하는 방법이 효과적이다. 이러한 관점에서 사출 모타용으로 다발 원통 튜브형 그레인을 설계/제작/연소시험을 하였더니 작은 저주파(약 10Hz)의 연소 불안정 현상이 발생하였다. (그림1). 이러한 주파수 대역은 일반적으로 잘 알려진 연소 불안정 모드 (longitudinal, tangential, and radial mode)와는 다른 아주 특이한 현상이다. 이러한 현상의 주 원인은 연소실 내 압력의 비평형에 의한 현상이라 판단되어 다음과 같은 연구를 수행하였다. 1) 그레인 튜브간의 압력 평형을 원활하게 하기 위하여 그레인에 구멍(홀)을 뚫어서 연소 안정화에 미치는 영향에 대한 연구(그림2), 2) 그레인에 홀을 뚫지 않고 격자와 격자간의 공간을 이용하여 그레인 간에 발생된 저주파의 압력 진동을 산란/소멸 시키는 연소 안정화 연구(그림3).