• 제목/요약/키워드: Turbulent Diffusion Flame

검색결과 122건 처리시간 0.037초

질소로 희석된 LPG 연료의 가연한계와 화염 안정성 (Flammability Limit and Flame Instability of Nitrogen-Diluted LPG Fuel)

  • 안태국;남연우;이경우;이원남
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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    • pp.319-321
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    • 2012
  • The flammability limit and the flame instability of nitrogen-diluted LPG fuel was experimentally studied on a co-flow flame configuration. The combustion reaction of nitrogen-diluted hydrocarbon with air could be interpreted as the equivalent reaction of pure fuel with nitrogen-diluted air. Nitrogen-diluted LPG with nitrogen up to 90 % of nitrogen mole fraction in fuel, which is close to the flammability limit, could form a co-flow flame. Various parameters such as laminar or turbulent flame, the existence of diffusion flame with pure fuel, air temperature could affect the limit of flame formation.

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초음속 확산화염 내의 혼합과 재순환 영역에 대한 충격파의 영향 (Effects of Shock Waves on the Mixing and the Recirculation Zone of Supersonic Diffusion Flames)

  • 김지호;허환일;최정열;윤영빈;정인석
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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    • pp.123-129
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    • 1998
  • A numerical study has been conducted to investigate the effect of shock waves on the mixing and the recirculation zone of a hydrogen jet diffusion flame in a supersonic combustor. The general trends are compared with the experimental results obtained from the supersonic combustor at the University of Michigan. For the numerical simulation of supersonic diffusion flames, multi-species Navier-Stokes equations and detailed chemistry reaction equations of $H_2$-Air are considered. The $K-{\omega}/k-{\varepsilon}$ blended two equation turbulent model is used. Roe's FDS method and MUSCL method are used for convection fluxes in governing equations. Numerical results show that when slender wedges are mounted at the combustor wall the mixing and the combustion are enhanced and the size of recirculation zone is increased . The flame shape of supersonic flames is different in the flame-tip; it is not closed but open. The flame shape is shown to be greatly affected by shock waves.

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Numerical Modeling for Combustion and Soot Formation Processes in Turbulent Diffusion Flames

  • Kim, Hoo-Joong;Kim, Yong-Mo
    • Journal of Mechanical Science and Technology
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    • 제16권1호
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    • pp.116-124
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    • 2002
  • In order to investigate the soot formation and oxidation processes, we employed the two variable approach and its source terms representing soot nucleation, coagulation, surface growth and oxidation. For the simulation of the taxi-symmetric turbulent reacting flows, the pressure-velocity coupling is handled by the pressure based finite volume method. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical models used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reacting flow field.

원통형 보염기 후류에 형성되는 확산화염의 연소특성에 관한 연구 (A Study on the Combustion Characteristics of Diffusion Flame Formed in the Wake of Cylindrical Bluff Body)

  • 안진근;임덕재;노태선;송규근
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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    • pp.23-30
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    • 1998
  • The stabilization characteristics of diffusion flame formed in the wake of a cylindrical flame holder were investigated. Distribution of turbulence intensity, concentration distribution of combustion gas, and ion currents were measured. The turbulence intensity in the wake of cylindrical- game holder is increased with increase of diameter or blockage ratio of grid. If the auxiliary fuel is injected into recirculation zone, the concentration of $C_3H_8$ is high, but the concentration of $CO_2$ is low at the boundary of recirculation zone. The region with highest average value of ion currents in the middle of flame is moved to the upstream side by the turbulent components of main stream. The flame mass with partially active reaction is moved fast for uniform flow and turbulence generator G3, but the flame mass with relatively slow reaction is moved slowly for turbulence generator G1.

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상세 및 축소 반응 메커니즘을 이용한 희석된 수소-공기 확산화염의 소염과 음향파 응답 특성에 관한 수치해석 (Numerical study on extinction and acoustic response of diluted hydrogen-air diffusion flames with detailed and reduced chemistry)

  • 손채훈;정석호
    • 대한기계학회논문집B
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    • 제21권11호
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    • pp.1527-1537
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    • 1997
  • Extinction characteristics and acoustic response of hydrogen-air diffusion flames at various pressures are numerically studied by employing counterflow diffusion flame as a model flamelet in turbulent flames in combustion chambers. The numerical results show that extinction strain rate increases linearly with pressure and then decreases, and increases again at high pressures. Thus, flames are classified into three pressure regimes. Such nonmonotonic behavior is caused by the change in chemical kinetic behavior as pressure rises. The investigation of acoustic-pressure response in each regime, for better understanding of combustion instability, shows different characteristics depending on pressure. At low pressures, pressure-rise causes the increase in flame temperature and chain branching/recombination reaction rates, resulting in increased heat release. Therefore, amplification in pressure oscillation is predicted. Similar phenomena are predicted at high pressures. At moderate pressures, weak amplification is predicted since flame temperature and chain branching reaction rate decreases as pressure rises. This acoustic response can be predicted properly only with detailed chemistry or proper reduced chemistry.

SI 기관에서 초기 화염의 생성 및 성장에 대한 모델링 (A Modeling of Flame Initiation and Its Development in SI Engines)

  • 송정훈;선우명호
    • 대한기계학회논문집B
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    • 제23권2호
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    • pp.288-298
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    • 1999
  • In spark ignited engines, the electrical spark not only sets the time for the onset of combustion but also is able to greatly influence the character of the initial flame growth and the subsequent combustion, and thereby can influence engine performance. The relative importance of the ignition energy is particularly high under lean or high residual gas or exhaust gas recirculation (EGR). In this study, a modeling of flame Initiation and its development is proposed. Submodels consist in representing of cylinder pressure and temperature, heat transfer to cylinder wall, and flame kernel heat transfer to ambient air and to spark plug electrodes. The breakdown process and the subsequent electrical power input initially control the kernel growth while intermediate growth is mainly dominated by diffusion or conduction. Then, the flame propagates by the chemical energy, and laminar and turbulent flame velocity.

수송 확률밀도함수모델을 이용한 비예혼합 난류화염장 해석 (Transported PDF Model for Turbulent Nonpremixed Flames)

  • 이정원;석준호;김용모
    • 한국연소학회지
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    • 제14권2호
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    • pp.32-41
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    • 2009
  • The transported probability density function model combined with the consistent finite volume (FV) method has been applied to simulate the turbulent bluff-body reacting flows. To realistically account for the non-isotropic turbulence effects on the turbulent bluff-body reacting flows, the present PDF transport approach is based on the joint velocity- turbulent frequency-composition PDF formulation. The evolution of the fluctuating velocity of a particle is modeled by a simplified Langevin equation and the particle turbulence frequency is represented by the modified Jayesh - Pope model. Effects of molecular diffusion are represented by the interaction by exchange with the mean (IEM) mixing model. To validate this hybrid FV/PDF transport model, the numerical results are compared with experimental data for the turbulent bluff-body reacting flows.

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산소부화공기가 동축 비예혼합 제트의 연소특성에 미치는 영향 (I) - 화염의 부상과 안정성 (Effect of Oxygen Enriched Air on the Combustion Characteristics in a Coaxial Non-Premixed Jet ( I ) - Lift-off and Flame Stability -)

  • 곽지현;전충환;장영준
    • 대한기계학회논문집B
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    • 제28권2호
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    • pp.160-166
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    • 2004
  • Combustion using oxygen enriched air is known as a technology which can increase flame stability as well as thermal efficiency due to improving the burning rate. Lift-off, blowout limit and flame length were examined as a function of jet velocity, coflow velocity and OEC(Oxygen Enriched Concentration). Blowout limit of the flame below OEC 25% decreased with increase of coflow velocity, but the limit above OEC 25% increased inversely. Lift-off height decreased with increase of OEC. In particular, lift-off hardly occurred in the condition above OEC 40%. Flame length of the flames above OEC 40% was increased until the blowout occurred. Great flame stability was obtained since lift-off and blowout limit significantly increased with increase of OEC.

산소부화와 선회수에 따른 평면화염버너의 로 내 연소특성 (Combustion characteristics inside the furnace with a flat flame burner by oxygen enriched and swirled air)

  • 곽지현;전충환;장영준
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.177-184
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    • 2001
  • Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by the improvement of burning rate and high temperature flame. But information about it is not so enough yet. Flame figure, temperature distribution and emission concentration were measured with oxygen enriched concentration and swirl number in a turbulent diffusion flame to investigate the combustion characteristics. The results showed that flame figure became different as long as oxygen enriched concentration varied and that concentration of NO increased suddenly around $O_2$ 60%.

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산소부화공기를 이용한 동축 제트화염의 부상과 연소 안정성 (Lift-off and Flame Stability of a Coaxial Non-Premixed Jet Using Oxygen Enriched Air)

  • 곽지현;전충환;장영준
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 추계학술대회
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    • pp.326-331
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    • 2003
  • Combustion using oxygen enriched air is known as a technology which can increase flame stability as well as thermal efficiency due to improvement of the burning rate. Lift-off, blowout limit and flame length were examined as a function of jet velocity, coflow velocity and OEC(Oxygen Enriched Concentration). Blowout limit of the flame below OEC 25% decreased with coflow velocity, but the limit above OEC 25% increased inversely. Lift-off height decreased with increase of OEC. Especially lift-off hardly occurred in the condition above OEC 40%. Flame length of the flames above OEC 40% was increased until the blowout occurred. Flame stability became improved since lift-off and blowout limit increased much with increase of OEC.

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