• Title/Summary/Keyword: hydrogen jet diffusion flame

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An Experimental Study for Combustion Characteristics of Hydrogen Jet Diffusion Flames (수소분류확산화염의 연소특성에 관한 실험적 연구)

  • Jung, Byong-Koog;Cho, Tae-Young;Song, Kyu-Keun;Jung, Jae-Youn;Kim, Hyung-Gon;Torii, Shuichi
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1310-1315
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    • 2004
  • The present study deals with the unique characteristics of hydrogen jet diffusion flames, such as split flames and reignition phenomenon. The split flames are composed of a small flamelet on the nozzle rim and a lifted main flame at downstream. When mass flow rates of fuel reach a critical point, a small-sized flamelet is found to remain in the vicinity of the nozzle exit and the flame reignition subsequent to blowout of main flame occurs repeatedly. In this study, the non-luminous hydrogen jet diffusion flames are visualized by using schlieren technique in order to analyze the combustion characteristics of hydrogen jet diffusion flames with focus on the flame reignition phenomenon.

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

  • Yang, Won;Won, Sang-Hee;Kim, Min-Kook;Chung, Suk-Ho;Kim, Jong-Soo
    • Journal of the Korean Society of Combustion
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    • v.10 no.3
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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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Theoretical Study on the Behavior of Momentum-controlled Buoyant Jet and Flame of Hydrogen (운동량에 의해 제어되는 수소 부양 제트 및 화염의 거동에 관한 이론적 해석)

  • Yang, Won;Kim, Jong-Soo;Won, Sang-Hee;Kim, Min-Kook;Chung, Suk-Ho
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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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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Numerical modelling for multicomponent diffusion in laminar hydrogen jet flame by using opensource OpenFOAM (오픈 소스 OpenFOAM을 이용한 층류 수소 제트 화염장 내의 다종 확산 수치해석 모델 개발)

  • Kim, Gunhong
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.335-338
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    • 2012
  • The present study focuses mainly on modeling the ordinary diffusion flux of species. According to CHEMKIN, both the mixture-averaged approach, Fick's formula, and the full multicomponent approach are implemented in the framework of opensource OpenFOAM. Also the Stefan-Maxwell approach is coded and validated together against measurements of laminar hydrogen jet flame. In the case of viscosity and conductivity of mixture, the mixture-averaged approach is applied and thermal diffusion is not considered in this work. Results show that there are no distinct deviations in three different approaches of diffusion of species in the present hydrogen flame condition.

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The Effect of Turbulence Intensity on the NOx Formation of Hydrogen Coaxial Jet Turbulent Diffusion Flames (난류강도가 수소 동축분류 난류 확산화염의 NOx 생성에 미치는 영향)

  • Han, Ji-Ung;Jeong, Yeong-Sik;Lee, Chang-Eon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.2
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    • pp.147-155
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    • 2001
  • Experimental investigations were conducted for two hydrogen-nitrogen coaxial jet diffusion flames. A flame was a conventional coaxial jet diffusion flame and the other was a coaxial jet diffusion flame of which ambient air-jet turbulence was intensified. In this study, firstly two kinds of NOx measuring system were campared by using different convertors, secondly the NOx formation characteristics were investigated in order to examine the effect of turbulence intensity. In this study it is known that stainless convertor has some problem in the converting process from NO$_2$to NO in fuel rich region but molybdenum convertor can detect the amount of NOx correctly. The increase of turbulence intensity reduces the thermal NOx less than a half in our experiment and this effect is conspicuous near the nozzle. The conversion rate from NO to NO$_2$and the portion of NO$_2$among NOx are increased with turbulence intensity. These NOx measurements will help to understand the influences of turbulence intensity on NOx formation.

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

  • Oh, Jeong-Seog;Kim, Mun-ki;Choi, Yeong-Il;Yoon, Young-Bin
    • 한국연소학회:학술대회논문집
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    • 2007.05a
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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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NOx Emission Reduction and Mixing Enhancement of Turbulent Hydrogen Diffusion Flame by An Acoustic Excitation (음파가진에 의한 수소 확산 화염의 NOx 배출저감 및 혼합증진)

  • Han, Jeong-Jae;Kim, Mun-Ki;Yoon, Sang-Wook;Yoon, Young-Bin
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.305-313
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    • 2005
  • Measurements of flame length, width and NOx emissions have been conducted to investigate the effect of an acoustic excitation on flame structure in turbulent hydrogen diffusion flames with coaxial air. The resonance frequency of oscillations was varied between 259 ,514 and 728 Hz with power rate of 0.405 and 2.88w. When these frequencies imposed to hydrogen flames, dramatic reduction of flame length and NOx emission was achieved. And acetone planar laser-induced fluorescence technique was used to measure a concentration of the near field of driven axisymmetric jet. The air-fuel stoichiometric line was plotted to investigate the mixing layer and development of air entrainment to fuel jet. Consequently, acoustic excitation on flame could enhance the air-fuel mixing resulting in abatement of NOx emission quantitatively.

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

  • Kim, Seung-Han;Kim, Mun-Ki;Yoon, Young-Bin
    • 한국연소학회:학술대회논문집
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    • 2000.12a
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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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Investigation of liftoff mechanisms in hydrogen turbulent non-premixed jet flames (수소 난류확산화염에서의 부상 메커니즘에 대한 연구)

  • Oh, Jeong-Seog;Kim, Mun-Ki;Choi, Yeong-Il;Yoon, Young-Bin
    • 한국가시화정보학회:학술대회논문집
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    • 2006.12a
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    • pp.135-140
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    • 2006
  • The stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition has been studied experimentally. The objectives are to explain the phenomenon of a liftoff height decreasing as increasing fuel velocity and to reveal the mechanisms of flame stability Hydrogen was varied from 100 to 300 m/s and a coaxial air was fixed at 16 m/s with a coflow air less than 0.1 m/s. The technique of PIV and OH PLIF was used simultaneously with CCD and ICCD cameras. It was found that the liftoff height of the jet decreased with an increased fuel jet exit velocity. The leading edge at the flame base was moving along the stoichiometric line. Finally we confirmed that the stabilization of lifted hydrogen diffusion flames is related with a turbulent intensity, which means combustion is occurred where the local flow velocity is equal to the turbulent flame propagation velocity.

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Effects of Lewis number on hydrogen diffusion flame structure (수소 확산화염의 구조에 미치는 Lewis 수의 영향)

  • Kim, Hu-Jung;Kim,Yong-Mo;An, Guk-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.9
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    • pp.1126-1138
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    • 1997
  • An axisymmetric laminar jet diffusion flame has been numerically modelled. The present study employs the refined physical submodels to account for the detailed chemical kinetics and the variable transport properties. It is found that preferential diffusion resulting from variable transport properties significantly influences the hydrogen diffusion flame structure in terms of the spatial distribution for temperature, species concentration, thermal and mass diffusivity, Lewis number, and NO concentration. The preferential diffusion effects on the diffusion flame in the high-pressure environment are also discussed in detail.