• 제목/요약/키워드: Unsteady Flames

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층류화염편 모델을 이용한 난류 비예혼합 화염장 해석 (Flamelet Modeling of Thrbulent Nonpremixed Flames)

  • 김용모
    • 한국연소학회지
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    • 제5권2호
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    • pp.1-8
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    • 2000
  • The flamelet concept has been widely applied to numerically simulate complex phenomena occurred in nonpremixed turbulent flames last two decades, and recently broadened successfully the applicable capabilities to various combustion problems from simple laboratory flames to gas turbine engine, diesel spray combustion and partially premixed flames. The paper is focused on brief review of recently noticeable work related to flamelet modeling, which includes Lagrangian flamelet approach, RIF concept as well as steady flamelet approach. The limitation of steady flamelet assumption, the effect of transient behavior of flamelets, and the effect of spray vaporization on PDF model have been discussed.

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Large Eddy Simulation of Turbulent Combustion Flow Based on 2-scaler flamelet approach

  • Oshima, Nobuyuki;Tominaga, Takuji
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2006년도 추계 학술대회논문집
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    • pp.18-21
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    • 2006
  • This paper investigates LES of turbulent combustion flow based on 2-scalar flamelet approach, where a G-equation and a conserved scalar equation simulate a propagation of premixed flame and a diffusion combustion process, respectively. The turbulent SGS modeling on these flamelet combustion approach is also researched. These LES models are applied to an industrial flows in a full scale gasturbine combustor with premixed and non-premixed flames. The numerical results predict the characteristics of experiment temperature profiles. Unsteady features of complex flames in combustor are also visualized.

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Combustion Instability Modeling for a Lean Premixed Gas Turbine Combustor using Flame Transfer Function Approach

  • Kim, Daesik;Cha, Dong-Jin
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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    • pp.53-54
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    • 2012
  • In an IGCC plant, one of the most important issues on fuel flexibility in the lean premixed combustor is combustion instabilities. They are characterized by large amplitude pressure oscillations which are caused by unsteady heat release from the flames. The relationship between the unsteady heat release and flow oscillation can be qualitatively and quantitatively explained by flame transfer function. This paper introduces combustion instability modeling methods based on the flame transfer function approach.

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비정상연소의 특성과 연소진동 평가 (Evaluation on Characteristics of Unsteady Combustion and Combustion Oscillation)

  • 양영준
    • 한국기계가공학회지
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    • 제10권5호
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    • pp.125-130
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    • 2011
  • The characteristics of unsteady combustion were experimentally investigated using confined premixed flames stabilized by a rearward-facing step. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations and it has usually desirable performance such as high load combustion and low pollutant emission. It is known that combustion oscillation is occurred if Rayleigh's criterion is satisfied. The pressure fluctuation and OH-emission fluctuation were measured using pressure transducer and OH optical fiber respectively and then cross-corelation and phase difference were calculated to apply Rayleigh's criterion.

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

  • 양영준;도승주
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2014년도 추계학술대회 논문집
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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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비정상연소의 적극적 이용법에 관한 연구 (A Study on Positive Use of Unsteady Combustion)

  • 양영준;이치우;김봉환;아카마쓰 후미테루
    • 한국연소학회지
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    • 제10권4호
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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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질소희석된 메탄 동축류 제트에서 화염 부상 메커니즘에 관한 연구 (Mechanism of Lifted Flames in Coflow Jet with Diluted Methane)

  • 홍기정;원상희;김준홍;정석호
    • 한국연소학회:학술대회논문집
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    • 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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    • pp.177-184
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    • 2003
  • Stabilization mechanism of lifted flame in the near field of coflow jets has been investigated experimentally and numerically for methane fuel diluted with nitrogen. Lifted flames were observed only in the near field of coflow jets until blowout occurred in the normal gravity condition. To elucidate the stabilization mechanism for the stationary lifted flames in the near field of coflow jets for the diluted methane having the Schmidt number smaller than unity, the behaviors of the stationary lifted flame in microgravity and unsteady propagation phenomena were investigated numerically at various conditions of jet velocity. It has been founded that the buoyancy plays an important role for flame stabilization of lifted flame in normal gravity and the stabilization mechanism is due to the significant variation of the propagation speed of lifted flame edge compared to the local flow velocity at the edge.

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비정상 층류화염편 모델을 이용한 비예혼합 난류화염 해석 (Unsteady Flamelet Modeling of Turbulent Nonpremixed Flames)

  • 김성구;강성모;김용모
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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    • pp.133-141
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    • 2000
  • The present study is focused on modeling the transient behavior of the local flame structure which is especially important for slow reaction processes, such as NOx formation in the radiating flame field. The recently developed unsteady flamelet model has been applied to analyze a steady, turbulent jet flame. Numerical results are compared with experimental data and numerical results of the conventional steady flamelet model. The numerical result reveals that the unsteady flamelet model correctly predicts the nonequilibrium effect upsteam and the subsequent decay of the superequilibrium radical concentrations the further downstream.

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비정상 층류화염편 모델을 이용한 비예혼합 난류화염 해석 (Unsteady Flamelet Modeling of Turbulent Nonpremixed Flames)

  • 김성구;강성모;서보선;김용모
    • 한국분무공학회지
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    • 제6권3호
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    • pp.8-16
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    • 2001
  • The present study is focused on modeling the transient behavior of the local flame structure which is especially important for slow reaction processes, such as NOx formation in the radiating flame field. The unsteady flamelet model recently developed has been applied to analyze a steady, turbulent jet flame. Numerical results are compared with experimental data and numerical results of the conventional steady flamelet model. The numerical result reveals that the unsteady flamelet model correctly predicts the nonequilibrium effect upsteam and the subsequent decay of the superequilibrium radical concentrations further downstream.

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와동과 상호작용하는 대향류 비예혼합화염의 비정상 응답특성 (Unsteady Response of Counterflow Nonpremixed Flames Interacting with a Votex)

  • 오창보;박정;이창언
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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    • pp.52-60
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    • 2002
  • A two-dimensional direct numerical simulation is performed to investigate the flame structure of $CH_4/N_2-Air$ counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed reaction mechanism are adopted in this calculation. To quantify the strain on flame induced by a vortex, a scalar dissipation rate (SDR) is introduced. Results show that the fuel and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex is extinguished at much larger SDR than steady flame. It is also found that air-side vortex extinguishes a flame more rapidly than fuel-side vortex. The unsteady effect induced by flame-vortex interaction does not lead to a transient OH overshoot of the maximum steady concentration observed in experiment, while $HO_2$ radical increases more than the maximum steady concentration with increasing SDR. In addition, it is seen that NO and $NO_2$ are not sensitive to the unsteady variation of SDR.

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