• Title/Summary/Keyword: Flashback

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The Effects of Nozzle Shapes and Pressures on Boundary Layer Flashback of Hydrogen-Air Combustor (수소 전소용 연소 노즐 형상과 연소실 압력이 경계층 역화에 미치는 영향)

  • WON JUNE LEE;JEONGJAE HWANG;HAN SEOK KIM;KYUNGWOOK MIN;MIN KUK KIM
    • Transactions of the Korean hydrogen and new energy society
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    • v.33 no.6
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    • pp.776-785
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    • 2022
  • Hydrogen combustion in modern gas-turbine engine is the cutting edge technology as carbon-free energy conversion system. Flashback of hydrogen flame, however, is inevitable and critical specially for premixed hydrogen combustion. Therefore, this experimental investigation is conducted to understand flashback phenomenon in premixed hydrogen combustion. In order to investigate flashback characteristics in premixed hydrogen (H2)/air flame, we focus on pressure conditions and nozzle shapes. In general, quenching distance reduces as pressure of combustion chamber increases, causing flashback from boundary layer near wall. The flashback regime for reference and modified candidate configurations can broadly appear with increasing combustion chamber pressure. The later one can improve flashback-resist by compensating flow velocity at wall. Also, improved wall flow velocity profile of suggested contraction nozzle prevents entire flashback but causes local flashback at nozzle exit.

Analysis of the Flame Dynamic Characteristics in the ducted Combustor with Bluff Body (보염기가 존재하는 덕트형 연소기에서 화염의 동적 특성에 관한 연구)

  • Jeong, Chanyeong;Kim, Teasung;Song, Jinkwan;Yoon, Youngbin
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.351-354
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    • 2012
  • The characteristics of flame dynamics occurring near bluff body was experimentally investigated in a model combustor with V-gutter bluff body. Flashback occurs due to the change of pressure gradient in the combustor, and flashback distance depends on equivalent ratio. Unstable flames can be classified into three types depending on the flashback distance and structure. Re-stabilization takes place as the flame moves downstream. This process is supported by a strong vortex structure behind bluff body.

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An Experimental Study on the Flashback and Re-ignition Structure with a V-gutter type Flameholder (V-gutter형 보염기에서 발생하는 화염의 역화 및 재점화 구조에 관한 실험적 연구)

  • Jeong, Chan-Yeong;Kim, Tae-Sung;Song, Jin-Kwan;Yoon, Young-Bin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.603-607
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    • 2011
  • Structure of flashback and reignition occurring near flameholder was experimentally investigated in a model combustor with V-gutter flameholder. The combustor has a long duct shape with cross section of $40{\times}40mm$ and City Nature Gas(CNG) were used as fuel. Measurements of chemiluminescence with high speed camera was used for visualization of flame structure. In the lean case, flashback distance depend on equivalent ratio. New flame occurred at the front tip of flameholder when flashback. Flashback flame moved toward downstream direction of combustor because mixture flow velocity had increased, and then re-ignition was caused by entering flow into recirculation zone that is formed behind the flameholder.

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An Experimental Study on the Flame Dynamics in Ducted Combustor (덕트형 연소기에서 화염의 동특성에 관한 실험적 연구)

  • Jeong, Chanyeong;Kim, Taesung;Song, Jinkwan;Yoon, Youngbin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.5
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    • pp.121-131
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    • 2013
  • The characteristics of flame dynamics occurring near the bluff body was experimentally investigated in a model combustor with V-gutter bluff body. Measurements of chemiluminescence with high speed camera and PIV were performed for visualization of flame structure. Flashback occurs due to the change of pressure gradient in the combustor, and the flashback distance depends on equivalent ratio. Unstable flames can be classified into three types depending on the flashback distance and structure. When the flame goes over the bluff body, an unusual flame structure occurs at the front of the bluff body. Re-stabilization takes place as the flame moves downstream of the combustor. This process is supported by a strong vortex structure behind the bluff body.

Syngas-Oxygen Combustion Characteristics of a Swirl-Stabilized Premixed Flame (합성가스-순산소 예혼합 화염의 연소특성)

  • Cho, Ju-Hyeong;Park, Jun-Hong;Jeon, Choong-Hwan;Ahn, Koo-Kyoung;Kim, Han-Seok
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.6
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    • pp.561-569
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    • 2010
  • The present study deals with experimental investigations on the syngas-oxygen combustion characteristics of a swirl-stabilized premixed flame in a 10 kW combustor. The effect of hydrogen in syngas has been investigated with different swirl angles to identify the role of hydrogen and swirl strength on the flame stability and CO emissions. The results show that hydrogen addition extended the blowout limit while narrowing the flashback limit. The dependence of blowout on the swirl angle is negligible while the dependence of flashback on the swirl angle is evidenced by two regimes depending on the amount of hydrogen. CO emission is decreased with increasing excess $O_2$ supply or increasing hydrogen content. Chemiluminescence diagnostics is utilized to provide information on the structure of a swirl-stabilized premixed flame. The OH chemiluminescence intensity is more concentrated near the burner exit with an increase in the hydrogen content, which results from high reactivity of hydrogen.

A Study on Expression Method of Suspense in Restricted Space -Focused on Movies 『Buried』 and 『127 Hours』- (제한된 공간에서의 서스펜스 표현방식에 관한 연구 -영화 『베리드』와 『127 시간』을 중심으로-)

  • Lee, Kang Suk
    • The Journal of the Korea Contents Association
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    • v.16 no.6
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    • pp.103-113
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    • 2016
  • The suspense will be realized as various techniques influenced the perception of audience organically each other. These varied techniques induce isolation as well as a restricted space as formal system. Moreover, it could intensify emotional experience of audience that they will not escape in addition to the depth.. This study chose a movie (2010) and <127 hours> (2010) which used the limited space as the material as the analysis target to examine. It is the goal of this study to analyze the conversion of careful viewpoint and the flashback, and to raise the meaning of the suspense expression through this. The researcher would consider how the suspense is expressed based on the conversion of viewpoint and how the flashback delivers the psychology and emotion.

A Study on the Fire Suppression Characteristics of a Flame Arrester with Water Mist System (미분무 시스템이 장착된 화염방지장치의 화재 진화 특성에 관한 연구)

  • Kim, Hae-Ji;Lee, Kyung-Ro
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.15 no.5
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    • pp.117-124
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    • 2016
  • In this paper, we developed a breather valve with a water mist system for use near an oil storage tank. Our process applied a water mist system to the flame arrester to evaluate the fire suppression characteristics. For the fire suppression evaluation of the water mist system, we evaluated the angle of the nozzle, fire suppression, spray particle size, flashback, fire suppression time, and fire suppression test of antifreeze. Through the fire suppression test, the best fire suppression nozzle used an angle of $140^{\circ}$, and the flashback phenomenon of flame arrester did not occur. The fire suppression time of water mist system time was within three seconds, and the antifreeze was no problem with the fire suppression.

Numerical Study on the Stabilization of Turbulent Swirling Lifted Premixed Syngas Flames (석탄가스 난류선회유동 예혼합부상화염의 안정성 해석)

  • Kang, Sung-Mo;Lee, Jeong-Won;Kim, Yong-Mo
    • 한국신재생에너지학회:학술대회논문집
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    • 2008.05a
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    • pp.349-352
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    • 2008
  • This study has numerically modeled the combustion processes of the turbulent swirling premixed lifted syngas flames in the low-swirl burner (LSB). In these turbulent swirling premixed flames, the four tangentially-injected air jets induce the turbulent swirling flow which plays the crucial role of stabilizing the turbulent lifted flames. In the present approach, the turbulence-chemistry interaction is represented by the level-set based flamelet model. Numerical results indicate clearly that the present level-set based flamelet approach has realistically simulated the structure and stabilization mechanism of the turbulent swirling premixed lifted flames in the low-swirl burner. Computations are made for the wide range of the syngas chemical composition and the dilution level at two pressure conditions (1.0, 5.0 bar). Numerical results indicate that the lifted height in the LSB is increased by decreasing the H2 percentage and increasing the dilution level at the given equivalence ratio. It is also found that the flashback is occurred for the hydrogen composition higher than 80% at the equivalence ratio, 0.8. However, at the syngas composition range in the IGCC system, the stable lean-premixed lifted flames are formed at the low-swirl burner.

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Stability Characteristics of Syngas($H_2$/CO)/Air Premixed Flames using an Impinging Jet Burner (충돌제트 버너에서 합성가스($H_2$/CO)/공기 예혼합화염의 안정화 특성)

  • Park, Ju-Yong;Lee, Kee-Man;Hwang, Cheol-Hong
    • Journal of the Korean Society of Combustion
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    • v.16 no.1
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    • pp.15-21
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    • 2011
  • An experimental study was conducted to investigate the flame stability of the synthetic gas (syngas) using an impinging premixed jet burner. Since the syngas mainly consisted of $H_2$ and CO, the $H_2$/CO mixture was simulated as the syngas. $H_2$/CO mixture ratios, fuel/air mixture velocities and equivalence ratios were used as major parameters on the flame stabilitym The role of the impinging plate on the flame stability was also examined. In addition, laminar burning velocities of the $H_2$/CO mixture were predicted numerically to understand the characteristics of the flame stability for the syngas. The increase in the H2 concentration into the syngas brings about the extension of the blowout limit and the reduction in the flashback limit in terms of the stable flame region. The impinging jet plate broadened the blowout limit but does not play important role in changing of the flashback limit. Finally, it was found that the stability region of the flame using the syngas, which is expressed in terms of the mixture velocity and the equivalence ratio in this study, significantly differed from that of $CH_4$.