• 제목/요약/키워드: Hydrogen-Air Jet Flame

검색결과 45건 처리시간 0.023초

운동량에 의해 제어되는 수소 부양 제트 및 화염의 거동에 관한 이론적 해석 (Theoretical Study on the Behavior of Momentum-controlled Buoyant Jet and Flame of Hydrogen)

  • 양원;원상희;김민구;정석호;김종수
    • 한국연소학회지
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    • 제10권3호
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    • pp.34-41
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    • 2005
  • Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

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운동량에 의해 제어되는 수소 부양 제트 및 화염의 거동에 관한 이론적 해석 (Theoretical Study on the Behavior of Momentum-controlled Buoyant Jet and Flame of Hydrogen)

  • 양원;김종수;원상희;김민국;정석호
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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    • pp.207-214
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    • 2005
  • Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

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부상된 수소 난류확산화염의 화염구조 (Flame Structure of a Liftoff Non-Premixed Turbulent Hydrogen Jet with Coaxial Air)

  • 오정석;윤영빈
    • 대한기계학회논문집B
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    • 제33권9호
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    • pp.699-708
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    • 2009
  • To understand hydrogen jet liftoff height, the stabilization mechanism of turbulent lifted jet flames under non-premixed conditions was studied. The objectives were to determine flame stability mechanisms, to analyze coexistence of two different flame structure, and to characterize the lifted jet at the flame stabilization point. Hydrogen flow velocity varied from 100 to 300 m/s. Coaxial air velocity was changed from 12 to 20 m/s. Simultaneous velocity field and reaction zone measurements used, PIV/OH PLIF techniques with Nd:YAG lasers and CCD/ICCD cameras. Liftoff height decreased with the increase of fuel velocity. The flame stabilized in a lower velocity region next to the faster fuel jet due to the mixing effects of the coaxial air flow. The flame stabilization was related to turbulent intensity and strain rate assuming that combustion occurs where local flow velocity and turbulent flame propagation velocity are balanced. At the flame base, two different flame structures were found that was the partial premixed flames and premixed flame.

희석된 동축공기 수소 난류확산화염의 화염 길이 스케일링 (Flame Length Scaling in a Non-premixed Turbulent Diluted Hydrogen Jet with Coaxial Air)

  • 황정재;오정석;윤영빈
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2009년도 제33회 추계학술대회논문집
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    • pp.242-245
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    • 2009
  • 희석된 동축공기 수소 난류확산화염에서 연료의 구성이 화염 길이에 미치는 영향에 대한 연구를 수행하였다. 화염의 길이는 동축공기와 연료 제트의 속도비의 함수로 표현하였고, 이론적 예측과 비교하였다. 네 조건의 연료 구성에 대해 연구를 수행하였다. 동축공기 제트 화염의 길이 예측을 위해 near-field concept에서의 유효 직경을 이용한 스케일링 관계식을 유도하였다. 실험 결과 가시 화염의 길이는 이론적 예측과 크게 일치하였다. 여러 연료 조건에서의 희석된 수소 제트의 화염에서도 스케일링 분석은 유효하였다.

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수소 난류확산화염에서의 부상 메커니즘에 대한 연구 (Liftoff mechanisms in hydrogen turbulent non-premixed jet flames)

  • 오정석;김문기;최영일;윤영빈
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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    • pp.7-12
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    • 2007
  • To reveal the newly found liftoff height behavior of hydrogen jet, we have experimentally studied the stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition. The objectives of the present research are to report the phenomenon of a liftoff height decreasing as increasing fuel velocity, to analyse the flame structure and behavior of the lifted jet, and to explain the mechanisms of flame stability in hydrogen turbulent non-premixed jet flames. The velocity of hydrogen was varied from 100 to 300m/s and a coaxial air velocity was fixed at 16m/s with a coflow air less than 0.1m/s. For the simultaneous measurement of velocity field and reaction zone. PIV and OH PLIF technique was used with two Nd:Yag lasers and CCD cameras. As results, it has been found that the stabilization of lifted hydrogen diffusion flames is related with a turbulent intensity, which means that combustion occurs where the local flow velocity is valanced with the turbulent flame propagation velocity.

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질소 희석이 수소 난류확산화염의 화염안정성에 미치는 영향 (The Effect of N2 Dilution on the Flame Stabilization in a Non-Premixed Turbulent H2 Jet with Coaxial Air)

  • 오정석;윤영빈
    • 대한기계학회논문집B
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    • 제33권7호
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    • pp.477-485
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    • 2009
  • The study of nitrogen dilution effect on the flame stability was experimentally investigated in a non-premixed turbulent lifted hydrogen jet with coaxial air. Hydrogen gas was used as a fuel and coaxial air was used to make flame liftoff. Each of hydrogen and air were injected through axisymetric inner and outer nozzles ($d_F=3.65\;mm$ and $d_A=14.1\;mm$). And both fuel jet and coaxial air velocity were fixed as $u_F=200\;m/s$ and $u_A=16\;m/s$, while the mole fraction of nitrogen diluents gas was varied from 0.0 to 0.2 with 0.1 step. For the analysis of flame structure and the flame stabilization mechanism, the simultaneous measurement of PIV/OH PLIF laser diagnostics had been performed. The stabilization point was selected in the most upstream region of the flame base and defined as the point where the turbulent flame propagation velocity was equal to the axial component of local flow velocity. We found that the turbulent flame propagation velocity increased with the decrease of nitrogen mole fraction. We concluded that the turbulent flame propagation velocity was expressed as a function of turbulent intensity and axial strain rate, even though nitrogen diluents mole fraction was changed.

동축공기 수소 확산화염의 구조 및 화염길이 스케일링 (Flame Length Scaling and Structure in Turbulent Hydrogen Non-Premixed Jet Flames with Coaxial Air)

  • 윤상욱;오정석;김문기;윤영빈
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
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    • pp.105-110
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    • 2006
  • Many previous works have been performed to provide correlations of flame length, theoretically and experimentally. Most of these results studied were conducted in vertical turbulent flame with no coaxial air condition. The present study analyzes the flame length scaling with coaxial air. In turbulent hydrogen non-premixed jet flames with coaxial air, flame length scaling theoretically proposed so far has been related with the concept of a far-field equivalent source. At high coaxial air to fuel velocity ratio, $U_A/U_F$, however, this scaling theory has some difference with experimental flame length data. This difference is understood to be due to the fact that the theory is based on far-field notion, while the effect of coaxial air on jet flame occurs in the region near the nozzle exit. Therefore, we define effective jet density $P_{eff}$ involving the concept of near-field so that effective jet diameter can be extended to the near-field region. In this condition, we modify the correlation and compare with experimental data.

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수소 난류확산화염에서 NOx 생성특성에 대한 복사분율의 영향 (The Effect of Flame Radiation on NOx Emission Characteristic in Hydrogen Turbulent Diffusion Flames)

  • 김승한;김문기;윤영빈
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2000년도 제21회 KOSCO SYMPOSIUM 논문집
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    • pp.47-58
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    • 2000
  • The relationship among the flame radiation, NOx emissions, residence time, and global strain rate are examined for turbulent non-premixed jet flames with wide variations in coaxial air conditions. Measurements of NOx emission, flame geometry and flame radiation were made to explain the NOx emission scaling based on global parameters such as flame residence time, global strain rate, and radiant fraction. The overall 1/2-power scaling is observed in coaxial air flames, irrespective of coaxial air conditions, but the degree of deviation from the l/2-slope curve in each case differs from one another. From the comparison between the results of pure hydrogen flames and those of helium diluted hydrogen flames, it is observed that flame radiation plays a significant role in pure hydrogen flames with coaxial air and the deviation from 1/2-power scaling may be explained in two reasons: the difference in the flame radiation and the difference in jet similarity in coaxial air flames. From the radiation measurements, more detailed explanations on these deviations were suggested.

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동축공기 수소 난류확산화염에서의 화염안정성에 대한 실험적 연구 (Study of Hydrogen Turbulent Non-premixed Flame Stabilization in Coaxial Air Flow)

  • 오정석;김문기;최영일;윤영빈
    • 대한기계학회논문집B
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    • 제32권3호
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    • pp.190-197
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    • 2008
  • It was experimentally studied that the stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition to reveal the newly found liftoff height behavior of hydrogen jet. The objectives are to report the phenomenon of a liftoff height decreasing as increasing fuel velocity, to analyse the flame structure and behavior of the lifted jet, and to explain the mechanisms of flame stability in hydrogen turbulent non-premixed jet flames. The hydrogen jet velocity was changed from 100 to 300m/s and a coaxial air velocity was fixed at 16m/s with a coflow air less than 0.1m/s. For the simultaneous measurement of velocity field and reaction zone, PIV and OH PLIF technique was used with two Nd:Yag lasers and CCD cameras. As a result, it was found that the stabilization of lifted hydrogen diffusion flames is correlated with a turbulent intensity and Karlovitz number.

동축공기 수소확산 화염에서의 화염과 와류의 상호작용 실험연구 (Experimental Study on Flame-Vortex Interactions in Turbulent Hydrogen Non-premixed Flames with Coaxial Air)

  • 김문기;오정석;최영일;윤영빈
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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    • pp.86-94
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    • 2006
  • This paper investigates the effects of acoustic forcing on NOx emissions and mixing process in the near field region of turbulent hydrogen nonpremixed flames. The resonance frequency was selected to force the coaxial air jet acoustically, because the resonance frequency is effective to amplify the forcing amplitude and reduce NOx emissions. When the resonance frequency is acoustically excited, a streamwise vortex is formed in the mixing layer between the coaxial air jet and coflowing air. As the vortex develops downstream, it entrains both ambient air and combustion products into the coaxial air jet to mix well. In addition, the strong vortex pulls the flame surface toward the coaxial air jet, causing intense chemical reaction. Acoustic excitation also causes velocity fluctuations of coaxial air jet as well as fuel jet but, the maximum value of centerline fuel velocity fluctuation occurs at the different phases of $\Phi$=$180^{\circ}$ for nonreacting case and $\Phi$=$0^{\circ}$ for reacting case. Since acoustic excitation enhances the mixing rate of fuel and air, the line of the stoichiometric mixture fraction becomes narrow. Finally, acoustic forcing at the resonance frequency reduces the normalized flame length by 15 % and EINOx by 25 %, compared to the flame without acoustic excitation.

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