• Title/Summary/Keyword: 스트레치 화염

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A Study of the Effect of Flame Stretch of Flame Speed (화염 스트레치가 화염전파속도에 미치는 영향에 관한 연구)

  • 정석호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.2
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    • pp.250-258
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    • 1985
  • 비균열 접선속도장에 기인한 화염스트레치 인자와 확산선호도가 예혼합화염의 전파속도에 미치는 영향을 연소가스와 예혼합기의 대향류 유동장을 모델로 하여 접합 전개 방법을 이용하여 일반 인 Lewis수 및 기체팽창을 고려하여 해석하였다. 이 결과 스트레치가 작은 경우에는 확산선호 도에 따라 화염특성이 급격히 변화하는데 이는 곡률을 가진 자유전파화염의 특성과 동일하며 스트레치가 큰 경우에는 확산선호도에 관계없이 화염전파속도는 감소하는 특성을 보여주었다. 또한, 화염스트레치의 실험적 측정 및 이론적 해석에 있어서의 정의 및 화염스트레치의 영향에 관한 현상적 설명에 대하여 재검토하였다.

Phenomenological Derivation of the Effects of Flame Stretch and Preferential Diffusion on Premixed Flame (화염스트레치와 확산선호도가 예혼합화염에 미치는 영향에 관한 현상적 고찰)

  • 정석호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.5
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    • pp.655-662
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    • 1985
  • 화염스트레치와 확산선호도가 예혼합화염에 미치는 영향을 몇가지 모델에 대해 현상적으로 고 찰하였다. 즉, 정상상태의 구형화염, 구형으로 전파되는 화염, 균일유동장내의 곡면화염, 일차원 평면화염, 그리고 확대유동장내에서 스트레치된 평면화염등을 고찰하였으며, 이 해석의 결과는 화염면의 면적 변화율로 정의된 화염스트레치의 제인자들 즉, 비균일 접선속도장과 전파화염의 곡률에 의한 영향들이 공통적 특성을 나타냄을 보여주고 있다. 화염스트레치와 확산선호도가 화염전파속도에 미치는 복합효과는 세가지로 나타나는데 이는 화염온도의 변화에 따른 화학반 응강도의 변동, 열 및 물질확산의 강도차이, 그리고 대류 및 확산전달의 방향의 상이함에 기인 한다.

On the Extinction Characteristics of the Interacting Lean-Lean Premixed Flames (상호작용을 하는 희박-희박 예혼합화염의 소화특성에 관한 연구)

  • 정석호;김종수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.2
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    • pp.232-240
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    • 1986
  • Extinction characteristics of the two interacting premixed flames are analyzed for the effects of flame stretch and preferential diffusion using large activation energy asymptotic analysis by adopting counterflow system as a model problem. Results show that the flammable limit of the thermally interacting premixed flames is extended compared to the single flame, and the extinction mechanism is classified into weak and strong interactions. As the lewis number of the deficient species increases, the region of strong interaction diminishes which can explain the different characteristics of the extinction boundaries of the lean (rich) methane/air and butane/air flames. The influence of the flame stretch to the interaction boundaries is also studied.

An Experimental Study on Heat Transfer Characteristics of Synthetic Gas($H_2/CO$)Air Premixed Flames in an Impinging Jet Burner - Part 1 : Stretched Lift-off Flames (충돌제트 버너에서 합성가스($H_2/CO$) 공기 예혼합 화염의 열전달 특성에 관한 실험적 연구 - Part 1 : 스트레치된 부상 화염)

  • Kang, Ki-Joong;Jo, Joon-Ik;Lee, Kee-Man
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.453-456
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    • 2011
  • An experimental investigation of the heat transfer characteristics of stretched premixed flames using Synthetic gas has been performed. Hydrogen and carbon mon-oxide which could be extracted from coal gasification process are the main fuel of synthetic-gas. Heat flux at the stagnation point was increased as global strainrate was increased, then the heat flux was decreased when a global strainrate reached a sudden point. Heat flux at the stagnation point is also affected by nozzle to impingement distance. Heat flux was increased as nozzle to impingement place distance was increased. This study is a foundation study of practical use of secondary gases from coals.

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Effects of propane substitution for safety improvement of hydrogen-air flame (수소-공기 화염의 안전성 향상을 위한 프로판 첨가 효과)

  • Kwon, Oh-Chae
    • Transactions of the Korean hydrogen and new energy society
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    • v.15 no.1
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    • pp.12-22
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    • 2004
  • In order to evaluate the potential of partial hydrocarbon substitution to improve the safety of hydrogen use in general and the performance of internal combustion engines in particular, the outward propagation and development of surface cellular instability of spark-ignited spherical premixed flames of mixtures of hydrogen, hydrocarbon, and air were experimentally studied at NTP (normal temperature and pressure) condition in a constant-pressure combustion chamber. With propane being the substituent, the laminar burning velocities, the Markstein lengths, and the propensity of cell formation were experimentally determined, while the laminar burning velocities and the associated flame thicknesses were computed using a recent kinetic mechanism. Results show substantial reduction of laminar burning velocities with propane substitution, and support the potential of propane as a suppressant of both diffusional-thermal and hydrodynamic cellular instabilities in hydrogen-air flames.

Calculation of Stretched Laminar Diffusion Flame Using the Coherent Flame Sheet Model (코히어런트 화염면 모델을 이용한 스트레치 층류 확산 화염의 수치 계산)

  • 정진은;진영욱
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.1
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    • pp.17-22
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    • 2000
  • The transient process simplified by the 1-D stretched laminar flame formed at the fuel-oxidizer interface was investigated using the coherent flame sheet model. Under the combustion environment of high temperatures and pressures the results show that the time required to reach the steady state was relatively short compared to the reverse of strain rate. Hence the employment of the tabulation of precalculated steady-flame results in the calculation of turbulent diffusion flames using the coherent flame sheet model is concluded valid, Also upstream temperatures were found to have only a minor effect on the nondimensional flame temperature and nondimensional fuel even through the letter is sensitive to pressure changes.

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A Numerical Study on the Lean-Rich Interaction of Methane/Air Flames (희박-과농 메탄 화염의 상호작용에 관한 수치해석적 연구)

  • Lee, Seung-Dong;Jeong, Seok-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.1
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    • pp.377-383
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    • 1996
  • Interaction of flames in a lean-rich concentration field is studied numerically adopting a counterflow as a model problem. Detailed kinetic mechanism is adopted in analyzing the structure of various type of flames which can be found in lean-rich interaction. Flow field is simplified to quasi one-dimensional by using boundary layer approximation and similarity formulation. Triple flames are identified and its structure shows that a diffusion flame is located in the middle of two premixed flames. Such a diffusion flame is formed by $H_2$ and CO generated from the rich premixed flame and $O_2$ leaked from the lean premixed flame. The flame position can be identified either from the hydrogen production rate or the heat release rate. Transition from single diffusion flame to triple flame is observed as degree of premixing is increased.

Experimental Study on the Effect of Velocity gradient on Propagation speed of Ttribrachial flame in Laminar Coflow Jets (삼지화염의 전파속도에 대한 속도구배의 영향에 관한 실험적 연구)

  • Kim, M.K.;Won, S.H.;Chung, S.H.;Fujita, O.
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.221-228
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    • 2005
  • The tribrachial flame in laminar coflow jet has been investigated experimentally with unsteady propagating condition. In this experiment, we found that the tribrachial point has an angle of flame surface because the location of tribrachial point is not on the base point of flame but on the inclined surface of flame. This angle of Flame surface at tribrachial point are increasing when the flame is approaching to the nozzle exit. With considering this angle of flame surface, the radial velocity gradient can affect flame propagation speed by increasing flow-stretch effect. The propagation speed of tribrachial flame was calculated with including above stretch effect. The speed decreases with increasing velocity gradient due to the increment of stretch effect.

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A Study on The Flame Propagation Velocity of Laminar Lifted Flame with Flame Curvatur e and Scalar Dissipation Rate (화염 곡률과 스칼라 소산율에 따른 층류부상화염의 화염전파속도에 관한 연구)

  • Kim, Kyung-Ho;Kim, Tae-Kwon;Park, Jeong;Ha, Ji-Soo
    • Journal of the Korean Institute of Gas
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    • v.15 no.2
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    • pp.47-56
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    • 2011
  • Flame propagation velocity is the one ofmainmechanismof the stabilization of triple flame. To quantify the triple flame propagation velocity, Bilger presents the triple flame propagation velocity depending on the mixture fraction gradient, based on the laminar jet flow theory. However, in spite of these many analyses, there was not presented any relation of these variables, triple flame propagation velocity, radius of flame curvature and scalar dissipation rate indirectly. In the present research, we have checked the results of numerical simulation with experiment and numerical analysis and verified the flame propagation velocity with a scalar dissipation rate proposed by Bilger through the numerical simulation. Also we have clarified that flame propagation velocity was depended on the radius of flame curvature and scalar dissipation rate.

Effects of Fuel Nozzle Diameter in the Behavior of Laminar Lifted Flame (노즐 직경 변화가 층류부상화염 거동에 미치는 영향)

  • Kim, Tae-Kwon;Um, Hyen-Soo;Kim, Kyung-Ho;Ha, Ji-Soo;Park, Jeong
    • Journal of the Korean Institute of Gas
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    • v.12 no.2
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    • pp.77-84
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    • 2008
  • Experimental study was conducted to clarify the importance of buoyancy effects in laminar lifted flames which have been well understood by cold jet similarity theory. To evaluate buoyancy effects, lifted flame behaviors were systematically observed in methane and propane lifted flames diluted with He as changing the fuel nozzle diameter from 0.1 to 6 mm. Important physical parameters such as fuel strength, flame stretch and flame curvature, which were derived through simple physical scaling laws, were estimated. It is experimentally proven that buoyancy effects are important in relatively large fuel nozzle diameter and large fuel dilution with He. The results of Chen et al., which displayed the existence of stably lifted flames for 0.5

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