• 제목/요약/키워드: Combustion oscillation

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A Study on Positive Use of Unsteady Combustion (비정상연소의 적극적 이용법에 관한 연구)

  • Yang, Young-Joon;Lee, Chi-Woo;Kim, Bong-Hwan;Akamatsu, Fumiteru
    • Journal of the Korean Society of Combustion
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    • v.10 no.4
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    • pp.1-9
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    • 2005
  • The usefulness of unsteady combustion was experimentally investigated using confined premixed flames stabilized by a rearward-facing step. For this purpose, apparatus of forced pulsating mixture supply, which could be modulated its amplitude and frequency, was designed. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations and furthermore it exhibits desirable performance, from a practical point of view, such as high load combustion and reduction of pollutant emission like nitric oxide.

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A cause analysis of Noise & Vibration of Gas Heater (가스히터의 소음 진동 원인 분석)

  • Koh, Jae-Pil;You, Hyun-Seok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.911-915
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    • 2006
  • 가스히터의 연소로부터 발생하는 소음 및 진동의 주원인은 연소소음(combustion roar)과 연소진동음(combustion oscillation)이다. 연소음의 특징은 음압이 넓은 주파수대에 걸쳐 비교적 일정하게 분포하고 있다. 본 논문에서 언급하고 있는 가스히터 초기 조건에서 볼 수 있는 상황으로 소음레벨이 낮고 진동 문제도 발생하지 않는다. 반면 연소진동음은 연소실내 기체의 고유진동수에 대하여 버너계가 Positive Feedback을 일으켜 공진할 때 발생되는 소음 및 진동이다. 연소진동의 발생 원인은 앞서 지적한 바와 같이, 연소할 때의 연소 진동수와 연소실의 구조적 고유진동수가 일치하면 큰 진동 및 소음을 발생시킨다. 따라서 소음 및 진동을 해결 할 수 있는 방법은 두 개의 고유진동수가 일치하지 않도록 하는 방법을 강구하여야 한다. 첫 번째 방법으로는 버너에서 연료와 공기량의 비율을 변화 시켜 진동수를 변화 시키거나, 연료와 공기의 통로길이, 연소실내에서의 연료와 공기의 혼합속도를 변화 시키는 방법이 있다. 두 번째 방법으로, 연소실의 고유진동수를 변화 시키는 방법으로 연소실의 길이나 덕트의 길이를 변경시켜 고유진동수의 주파수를 변경시키는 방법이다. 본 논문에서는 연소실의 조건을 변경하여 공명을 회피하는 방법을 채택하였고, 좋은 결과를 얻을 수 있었다.

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Stability Rating of KSR-III Rocket Engine (KSR-III 로켓엔진의 연소 안정성 평가)

  • Sohn, Chae-Hoon;Kim, Young-Mog
    • 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.

Combustion Stability Rating Test under Low Pressure Condition of a 75-tonf-class LRE Thrust Chamber (75톤급 액체로켓엔진 연소기의 저압 조건에서 수행된 연소안정성 시험)

  • Lee, Kwang-Jin;Kang, Dong-Hyuk;Kim, Mun-Ki;Ahn, Kyu-Bok;Han, Yeoung-Min;Choi, Hwan-Seok
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.5
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    • pp.92-100
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    • 2010
  • Combustion stability rating tests of 75-tonf-class thrust chamber for technology demonstration were carried out at a low pressure. Two kinds of mixing heads were used in this study. One of them has injectors of 631 and the other has injectors of 721. Mixing head with injectors of 631 showed a self-oscillation instability at the chamber pressure of 30 bar. Mixing head with injectors of 721 showed that a high frequency combustion stability was maintained under the same pressure and the same mass flow rate. But mixing head with injectors of 721 generated a self-oscillation instability at the chamber pressure of 20 bar and it was found that stability boundary region was changed due to the configuration of a mixing head from these results.

Visualization of Combustion by Using Laser Diagnostic Techniques (레이저 진단기법을 이용한 연소 가시화 기술)

  • Chung S. H.;Won S. H.
    • Journal of the Korean Society of Visualization
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    • v.2 no.1
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    • pp.52-56
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    • 2004
  • Several visualization techniques of laser diagnostics are presented for combustion phenomena, including Mie scattering for flow, Rayleigh and Raman scattering spectroscopy for major species, laser-induced fluorescence for minor species, and laser-induced incandescence for soot. These techniques have been applied to understand the various combustion phenomena more clearly, including buoyancy-dominant flow system, diffusion flam oscillation, laminar and turbulent lifted flames, flame propagation along a vortex ring, and soot zone characteristics. The usefulness of laser diagnostics on a better understanding of physical mechanism is demonstrated.

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Unsteady Analysis for Combustion Characteristics of PRF75 Fuel under HCCI Conditions (균일예혼합 압축착화 조건에서 PRF75 연료의 비정상 연소특성 해석)

  • Oh, Tae Kyun;Lee, Su Ryong
    • Journal of the Korean Society of Combustion
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    • v.18 no.4
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    • pp.21-28
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    • 2013
  • HCCI engines have mainly focused on achieving low temperature combustion in order to obtain higher efficiency and lower emission. One of practical difficulties in HCCI combustion is to control the start of combustion and subsequent combustion phasing. The choice of primary reference fuels in HCCI strategy is one of various promising solutions to make HCCI combustion ignition-controlled. The behavior of ignition delay to the frequency variation of sinusoidal velocity oscillation is computationally investigated under HCCI conditions of PRF75 using a reduced chemistry in a counterflow configuration. The second-stage ignition is more delayed as the higher frequency is imposed on nozzle velocity fluctuation whereas the first-stage ignition is not much influenced.

Study on Combustion Noise of Unsteady Flow (맥동류의 연소소음 연구)

  • Yang, Young Joon;Do, Seung Ju
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.10a
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    • pp.355-357
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    • 2014
  • The usefulness of unsteady combustion was experimentally investigated using confined premixed flames stabilized by a rearward-facing step. For this purpose, apparatus of forced pulsating mixture supply, which could be modulated its amplitude and frequency, was designed. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations and furthermore it exhibits desirable performance, from a practical point of view, such as high load combustion and reduction of pollutant emission like nitric oxide.

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Combustion Stability Test of LRE Thrust Chamber using Artificial Perturbation Method (강제교란 방법을 이용한 액체로켓엔진 연소기의 연소안정성 시험)

  • Lee, Kwang-Jin;Seo, Seong-Hyeon;Han, Yeoung-Min;Choi, Hwan-Seok;Ko, Young-Sung
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.3
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    • pp.52-60
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    • 2010
  • Combustion stability tests of 30 $ton_f$-class LRE thrust chamber with double swirl coaxial injector were carried out in domestic ground combustion test facility by means of artificial perturbation method. In these tests, thrust chambers with varying design factors like recess number of injector, baffle length, types of film cooling and chamber diameter were used and test results showed that these design factors are closely related with high frequency combustion stability. By using the oscillation decrement instead of the decay time in the combustion stability analysis of artificially perturbed LRE thrust chamber, it was confirmed that increment of damping factor results in the improvement of high frequency combustion stability of LRE thrust chamber.

Observation of flame oscillation with changing combustor pressure (연소실 압력변동에 따른 화염 진동현상의 관찰)

  • Kim, Jong-Ryul;Choi, Gyung-Min;Kim, Duck-Jool
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.275-280
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    • 2005
  • At previous study, nitrogen oxide emission was decreased with decreasing pressure index. This tendency was explained by the flame oscillation with changing combustor pressure. In this study, the characteristics of flame oscillation with changing combustor pressure were investigated. It can be found that flame length is extended and flame width is narrowed by decreasing combustor pressure. It can be observed that pilot flame and the surrounding air converge on the inner flame in the $P^{\ast}{\geqq}1$ conditions and that surrounding air and flow pattern was widely dispersed in the $P^{\ast}<1$ conditions. In the respect of average flame length, low fluctuation was shown in the $P^{\ast}<1$ conditions. On the other hands, large fluctuation was shown in the $P^{\ast}<1$ conditions. Flame oscillation are observed from $P^{\ast}=$ 0.98 in the condition of $P^{\ast}<1$ and the amplitude of flame oscillation becomes larger when $P^{\ast}$ is lowered. These results demonstrate that low NOx phenomenon was caused by flame oscillation with changing combustor pressure.

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