• Title/Summary/Keyword: 전체화염신장율

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Edge-flame Instability in A Low Strain-rate Counterflow Diffusion Flame (저신장율 대향류확산화염에서 에지화염 진동불안정성)

  • Park, June-Sung;Kim, Hyun-Pyo;Park, Jeong;Kim, Song-Cho;Kim, Jeong-Soo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.11a
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    • pp.295-298
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    • 2006
  • Experiments in methane-air low strain rate counterflow diffusion flames diluted with nitrogen have been conducted to study the behavior of flame extinction and edge flame oscillation in which lateral conduction heat loss in addition to radiative heat loss could be remarkable at low global strain rates. Onset conditions of edge flame oscillation and flame oscillation modes are also provided with global strain rate. It is seen that flame length is closely relevant to lateral heat loss, and this affects flame extinction and edge flame oscillation. Edge flame oscillations in low strain rate flames are categorized into three: a growing oscillation mode, a decaying oscillation mode, and a harmonic oscillation mode. The regime of flame oscillation is also provided at low strain rate flames.

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Oscillatory Instabilities of Edge Flames in Solid Rocket Combustion (고체연료로켓에서 에지화염의 맥동 불안정성)

  • Kim Kang-Tae;Park Jun-Sung;Park Jeong;Kim Jeong-Soo;Keel Sang-In;Cho Han-Chang
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.05a
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    • pp.275-278
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    • 2006
  • Systematic experiments in $CH_4/Air$ counterflow diffusion flames diluted with He have been undertaken to study the oscillatory instability in which lateral heat loss could be remarkable at low global strain rate. The oscillatory instability arises for Lewis numbers greater than unity and occurs near extinction condition. The dynamic behaviors of extinction in this configuration can be classified into three modes; growing, harmonic and decaying oscillation mode near extinction. As the global strain rate decreases, the amplitude of the oscillation becomes larger. This is caused by the increase of lateral heat loss which ran be confirmed by the reduction of lateral flame size. Oscillatory edge flame instabilities at low global strain rate are shown to be closely associated with not only Lewis number but also heat loss (radiation and lateral heat loss).

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A Study on Transition of Flame Extinction at Low Strain Rate Counterflow Flames (저신장율 대향류화염에서 화염소화에 있어서 천이에 대한 연구)

  • Park, Dae-Geun;Park, Jeong;Kim, Jeong-Soo;Bae, Dae-Suk
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.197-201
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    • 2009
  • Experiments were conducted to study the transition of shrinking flame disk to flame hole in counterflow diffusion flames. The studies of transition are well described by varying burner diameters, global strain rate and velocity ratio. It is experimentally verified that radial conduction heat loss is affected at even high strain rate flames for appropriately small burner diameters. It is also shown that flame extinction modes are grouped into three and particularly, hole or stripe is observed in sufficiently high strain rate flames. There exists critical radius according to burner diameter which divide flame extinction modes into three parts.

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A Study on Flame Extinction and Edge Flame Oscillation in Counterflow Diffusion Flame (대향류확산화염에서 화염소화와 에지화염진동에 관한 연구)

  • Park, Dae-Geun;Yun, Jin-Han;Park, Jeong;Keel, Sang-In
    • Journal of the Korean Society of Propulsion Engineers
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    • v.13 no.2
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    • pp.64-76
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    • 2009
  • Experimental and numerical studies are conducted on the characteristics of flame extinction and edge flame oscillation in counterflow diffusion flames. The characteristics of flame extinction and edge flame oscillation are well described varying burner diameter, separation distance between two burners, global strain rate, and velocity ratio. It is verified numerically and experimentally that radial conduction heat loss significantly contributes to flame extinction and edge flame oscillation at low strain rate flames in zero- and micro-gravity. It is also shown that for appropriately small burner diameters flame extinction modes are grouped into four and these are significantly attributed to excessive radial conduction heat loss. The edge flame oscillation can be characterized well by one curve with Strouhal number and Peclet number.

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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Oscillatory Instability of Low Strain Rate Edge Flame (저신장율 에지 화염의 진동 불안정성)

  • Kim Kang-Tae;Park June-Sung;Kim Jeong-Soo;Oh Chang-Bo;Keel Sang-In;Park Jeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.4 s.247
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    • pp.343-349
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    • 2006
  • Systematic experiments in $CH_4/Air$ counterflow diffusion flames diluted with He have been undertaken to study the oscillatory instability in which lateral flame size was less than burner nozzle diameter and thus lateral heat loss could be remarkable at low global strain rate. The oscillatory instability arises for Lewis numbers greater than unity and occurs near extinction condition. The oscillation is the direct outcome from the advancing and retreating edge flame. The dynamic behaviors of extinction in this configuration can be classified into three modes; growing, harmonic and decaying oscillation mode near extinction. As the global strain rate decreases, the amplitude of the oscillation becomes larger. This is caused by the increase of lateral heat loss which can be confirmed by the reduction of lateral flame size. Oscillatory edge flame instabilities at low global strain rate are shown to be closely associated with not only Lewis number but also heat loss (radiation and lateral heat loss).

Effects of Heat Losses on Edge-flame Instabilities in Low Strain Rate Counterflow Diffusion Flames (저신장율 대향류확산화염에서 에지화염 불안정성에 관한 열손실 효과)

  • Park June-Sung;Hwang Dong-Jin;Kim Jeong-Soo;Keel Sang-In;Kim Tae-Kwon;Park Jeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.10 s.253
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    • pp.996-1002
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    • 2006
  • Experiments in methane-air low strain rate counterflow diffusion flames diluted with nitrogen have been conducted to study the behavior of flame extinction and edge flame oscillation in which flame length is less than the burner diameter and thus lateral conduction heat loss in addition to radiative heat loss could be remarkable at low global strain rates. Critical mole fraction at flame extinction is examined with velocity ratio and global strain rate. Onset conditions of edge flame oscillation and flame oscillation modes are also provided with global strain rate and added nitrogen mole fraction to fuel stream (fuel Lewis number). It is seen that flame length is closely relevant to lateral heat loss, and this affects flame extinction and edge flame oscillation considerably. Edge flame oscillations in low strain rate flames are experimentally described well and are categorized into three: a growing oscillation mode, a decaying oscillation mode, and a harmonic oscillation mode. The regime of flame oscillation is also provided at low strain rate flames. Important contribution of lateral heat loss even to edge flame oscillation is clarified

Effects of Counterflow Burner Diameter on the Characteristics of Flame Extinction in C-curve (C-곡선상의 화염 소화 특성에 있어서 대향류 버너직경 효과)

  • Park, Dae-Geun;Park, Jeong;Yun, Jin-Han;Kee, Sang-In
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.7
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    • pp.535-540
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    • 2009
  • Experiments are conducted to elucidate effects of counterflow burner diameter on flame extinction behaviors in C-curve. Present experimental results with burner diameters of 18, 26, and 50 mm in normal-gravity are compared with the numerical result of Oppdif code as well as the previous experimental results in micro-gravity. The turning point migrates to a higher global strain rate as burner diameter decreases. It is shown that the C-curve with the burner diameter of 50mm is best-fitted to the numerical result of Oppdif code and the previous micro-gravity results also excurse to the numerical result. This suggests that the precise C-curve can be obtained only with an appreciably large burner. The main reason why these differences appear is shown to be attributed to the transition of shrinking flame disk to flame hole due to strong effects of radial conduction heat loss, which is the typical extinction characteristics of low strain rate flames with a finite burner diameter in a counterflow diffusion flame.