• 제목/요약/키워드: Thermo-acoustic Instability

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이산형 열-음향 모델을 이용한 부하 변동시 가스터빈 연소 불안정 특성 (Combustion Instability of Gas Turbine with Segmented Dynamic Thermo-Acoustic Model under Load Follow-Up)

  • 정지웅;한재영;정진희;유상석
    • 한국수소및신에너지학회논문집
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    • 제29권5호
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    • pp.538-548
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    • 2018
  • The thermo-acoustic instability in the combustion process of a gas turbine is caused by the interaction of the heat release mechanism and the pressure perturbation. These acoustic vibrations cause fatigue failure of the combustor and decrease the combustion efficiency. This study is to develop a segmented dynamic thermo-acoustic model to understand combustion instability of gas turbine. Therefore, this study required a dynamic analysis rather than static analysis, and developed a segmented model that can analyze the performance of the system over time using the Matlab/Simulink. The developed model can confirm the thermo-acoustic combustion instability and exhaust gas concentration in the combustion chamber according to the equivalent ratio change, and confirm the thermo-acoustic combustion instability for the inlet temperature and the load changes. As a result, segmented dynamic thermo-acoustic model has been developed to analyze combustion instability under the operating condition.

A CFD Study on Thermo-Acoustic Instability of Methane/Air Flames in Gas Turbine Combustor

  • Sohn, Chae-Hoon;Cho, Han-Chang
    • Journal of Mechanical Science and Technology
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    • 제19권9호
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    • pp.1811-1820
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    • 2005
  • Thermo-acoustic instability of methane/ air flames in an industrial gas-turbine combustor is numerically investigated adopting CFD analysis. The combustor has 37 EV burners through which methane and air are mixed and then injected into the chamber. First, steady fuel! air mixing and flow characteristics established by the burner are investigated by numerical analysis with single burner. And then, based on information on the flow data, the burners are modeled numerically via equivalent swirlers, which facilitates the numerical analysis with the whole combustion system including the chamber and numerous burners. Finally, reactive flow fields within the chamber are investigated numerically by unsteady analysis and thereby, spontaneous instability is simulated. Based on the numerical results, scaling analysis is conducted to find out the instability mechanism in the combustor and the passive control method to suppress the instability is proposed and verified numerically.

Rijke Tube를 이용한 열환경에서의 음향공 감쇠 특성연구 (A Study on Damping Characteristic under the Thermo-acoustic Condition using the Rijke Tube)

  • 김근철;전준수;김중일;고영성;김홍집
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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    • pp.47-50
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    • 2011
  • 본 연구에서는 열/음향 불안정성 환경 모사를 위하여 수평형의 Rijke tube를 설계/제작하였고, 이를 이용하여 구현하고자 하는 주파수대의 열구배를 갖는 공진현상이 발생됨을 확인하였다. Rijke tube를 이용해 열 음향 불안정 환경을 조성한 후, 음향공을 장착하여 얻어진 감쇠특성을 상온실험 자료와 비교/분석하여 열 음향 불안정 환경에서의 음향공 감쇠특성을 확인하였다. 열/유동 환경하에서의 감쇠 시간이 상온 환경에 비해 약 40% 증가함을 확인하였으며, 이로부터 음향공 설계시 열/유동 환경이 고려되어야 함을 확인하였다.

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헬름홀츠 솔버 기반의 3차원 열음향해석을 통한 발전용 단일 캔 연소기에서의 공진 모드 분석 (Resonance Mode Anlaysis in a Single Can-type Combustor through 3D Thermo-acoustic Analysis based on Helmholtz Solver)

  • 정준우;김대식
    • 한국분무공학회지
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    • 제29권1호
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    • pp.23-31
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    • 2024
  • This study conducted a 3D thermo-acoustic analysis based on the helmholtz solver to analyze the major resonance modes causing combustion instability in a single-can combustor. The experimental investigations were carried out on a test rig designed by the Korea Institute of Machinery & Materials (KIMM) under various conditions of hydrogen co-firing and fuel staging. Through these experiments, two primary unstable frequencies were identified. To determine the resonance modes of these frequencies, a 3D thermo-acoustic analysis was conducted using temperature information from the test rig. The results confirmed that the unstable frequencies observed in the experiments were all longitudinal modes. Additionally, the mode shapes identified in the analysis facilitated a simplification of the exit geometry for the low-order network model, confirming that this did not significantly affect the fundamental resonance modes.

Rijke tube를 이용한 열유동 환경하에서의 음향공 감쇠 특성 연구 (Research on Damping Characteristics of a Helmholtz Resonator using a Rijke Tube)

  • 김근철;전준수;김재호;고영성;김홍집;김영문
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2011년도 제37회 추계학술대회논문집
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    • pp.873-876
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    • 2011
  • 본 연구에서는 열적 구배를 갖는 열음향 진동 환경에 Helmholtz resonator를 적용하여 연소 불안정 연구를 수행하고자 하였다. 열음향 불안정 환경은 DC power supplier를 이용한 전기적 방법으로 정량적인 열량을 공급하고 blower를 이용하여 유량을 제어하는, 특정한 공진 주파수를 갖는 수평형 Rijke tube로 구현하였다. 열음향 불환경 환경 하에서 얻어진 Helmholtz resonator 의 감쇠특성을 상온 실험 자료와 비교/분석하여 열음향 불안정 환경에서의 Helmholtz resonator의 감쇠특성을 확인하기 위한 예비 연구를 수행하였다.

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분기관을 가진 연소 챔버 내 압력변동 특성에 관한 실험적 연구 (Experimental Study on the Characteristics of Pressure Fluctuation in the Combustion Chamber with Branch Tube)

  • 박장희;이대근;신현동
    • 대한기계학회논문집B
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    • 제33권7호
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    • pp.552-558
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    • 2009
  • An experimental study using the combustor with branch tube was conducted in order to model the industry combustor with FGR (flue gas recirculation) system and to study a thermo-acoustic instability generated by a branch tube. The branch tube is a structure used to modify a system geometry and then to change its pressure field, and the thermo-acoustic instability, usually occurs in a confined geometry, can result in serious problems on industrial combustors. Thus understanding of the instability created by modifying geometry of combustor is necessary to design and operate combustor with FGR system. Pressure fluctuation in the combustion chamber was observed according to diameter and length of branch and it was compared with the solution of 1-D wave equation. It was found that branch tube affects the pressure field in the combustion chamber, and the pressure fluctuation in the combustion chamber was reduced to almost zero when phase difference between an incipient wave in the combustion chamber and a reflected wave in the branch tube is $\pi$ at the branch point. Also, the reduction of pressure fluctuation is irrespective of the installed height of branch tube if it is below $h^*=0.9$ in the close-open tube and open-open tube.

열-음향에 의한 난류희박 예혼합연소의 불안정성에 관한 실험적 연구 (An experimental study on the instability of lean premixed turbulent combustion induced by thermo-acoustics)

  • 홍정구;이민철;신현동
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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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.

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초음속 공기흡입식 엔진 연소기의 연소불안정 발생 및 분석 (Occurance and Analysis of Combustion Instability in Supersonic Airbreathing Engine)

  • 황용석;이종근;최호진;길현용;변종렬;윤현걸;임진식
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2009년도 춘계학술대회 논문집
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    • pp.83-87
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    • 2009
  • 램제트 엔진은 다른 공기흡입식 엔진에 비해 상대적으로 매우 긴 유로를 지니고 있음으로 인해 저주파 연소불안정에 취약한 단점을 지니고 있다. 본 연구에서는 램제트 엔진에서 발생하는 연소 현상과 동일한 메카니즘을 모사할 수 있는 연료분사장치 및 V-gutter 형태의 화염안정화장치를 장착한 소형 연소기를 설계/제작하여, 램제트 연소기에서 발생할 수 있는 연소불안정 현상을 시현하였다. 이 연소기에서 발생한 연소불안정은 연소시스템의 음향학적인 공진 주파수와 유사하게 나타남을 확인하였으며, 이를 통해 thermo-acoustic coupling에 의한 전형적인 연소 불안정이 발생하였음을 확인할 수 있었다.

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파일롯 화엄에 의해 고정된 관내 예혼합 화염의 진동 특성 (Vibration Characteristics of Lean Premixed Flame Anchored by a Hydrogen Pilot Flame in a Tube)

  • 곽영태;오광철;신현동
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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    • pp.42-48
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    • 2004
  • Lean laminar premixed propane and methane flames which were anchored by a hydrogen-pilot flame in a tube were investigated experimentally. The flame shapes were observed by varying mean velocity from 10cm/s to 140cm/s and equivalence ratio from 0.45 to 0.8. In this study, behaviors of flames are divided into five regions such as tail-out, flash-back, flickering, stable and vibrating flames with respect to the mean velocity and the equivalence ratio. Although the flames are unstable in both the flickering and the vibrating region, they have different characteristics such as the frequency, sound generation and creation process of flame curvature. The flickering region exists near the flammability limit and the flame flickers in a frequency of about 10Hz. When flame front is bended, the propane flame front is straightened and the methane flame front is bended more by thermo-diffusive instability. In the vibrating region, the flame vibrates emitting audible sound in a frequency of about 100Hz. In the boundary of vibrating region, the vibration of flame changes between two modes such as single frequency vibration and dual frequency vibration. Increase and decrease of vibration in each mode are determined by thermo-acoustic instability.

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Thermo-Acoustic Instability in the Horizontal Rijke Tube

  • Song Woo-Seog;Lee Seung-Bae;Shin Dong-Shin;Na Yang
    • Journal of Mechanical Science and Technology
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    • 제20권6호
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    • pp.905-913
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    • 2006
  • The instability curve of a Rijke tube system was obtained accurately by following different paths of heat power and flow-rate for three regions and by defining its locus from the criterion based on the measured sound pressure levels. The unstable limits in the region of flow-rate lower than that at the minimal power are compared with previous data. To observe the effect of turbulence on the unstable limits, inflow turbulence was introduced by placing a bundle of circular cylinders upstream of the heating part ($50). The large-amplitude inflow fluctuation may delay the transition of the chamber acoustic mode to the unstable Bone even at a sufficient power.