Hydrogen jet flames

Molkov, Vladimir; Saffers, Jean-Bernard

doi:10.1016/j.ijhydene.2012.08.106

Cited by 84 publications

(22 citation statements)

References 34 publications

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“…The hydrogen jet flame length (normalized by the release diameter) is linearly dependent on the square root of jet Reynolds number, for cryogenic, as well as room temperature sources of hydrogen. This observation is similar to the findings by Molkov and Saffers [27].The maximum radiative heat flux is emitted at approximately 70 -80% of the flame length. For a fixed hydrogen mass flow, the radiative heat flux increases as the release temperature decreases.…”

Section: Discussionsupporting

confidence: 92%

“…There is a large scatter of the current data around the line with, . This scatter was also reported by Molkov and Saffers [27] when comparing the flame lengths from a wider range of experimental data [25][26][27][28][29][30].…”

Section: Maximum Ignition Distancesupporting

confidence: 77%

“…Since previously reported literature data were atmospheric temperature hydrogen releases, the lack of variations in viscosity allowed the flame length to be shown to scale as, . Similar to the scaling analysis discussed by Molkov and Saffers [27] in this study we express a normalized flame length, , as a function of the more conventional Reynolds number, , (based on the throat density, viscosity, choked flow velocity, and diameter). Figure 10 shows the variation of normalized flame length of the cryogenic hydrogen jet flames from the current study, along with the data from literature [24][25][28][29][30][31], as a function of the square root of the Reynolds number.…”

Section: Maximum Ignition Distancementioning

confidence: 97%

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Ignition and flame characteristics of cryogenic hydrogen releases

Panda

Hecht

2017

International Journal of Hydrogen Energy

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In this work, under-expanded cryogenic hydrogen jets were investigated experimentally for their ignition and flame characteristics. The test facility described herein, was designed and constructed to release hydrogen at a constant temperature and pressure, to study the dispersion and thermo-physical properties of cryogenic hydrogen releases and flames. In this study, a nonintrusive laser spark focused on the jet axis was used to measure the maximum ignition distance. The radiative power emitted by the corresponding jet flames was also measured for a range of release scenarios from 37 K to 295 K, 2-6 bar abs through nozzles with diameters from 0.75-1.25 mm. The maximum ignition distance scales linearly with the effective jet diameter (which scales as the square root of the stagnant fluid density). A 1-dimensional (stream-wise) cryogenic hydrogen release model developed previously at Sandia National Laboratories (although this model is not yet validated for cryogenic hydrogen) was exercised to predict that the mean mole fraction at the maximum ignition distance is approximately 0.14, and is not dependent on the release conditions. The flame length and width were extracted from visible and infra-red flame images for several test cases. The flame length and width both scale as the square root of jet exit Reynolds number, as reported in the literature for flames from atmospheric temperature

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Section: Discussionsupporting

confidence: 92%

Section: Maximum Ignition Distancesupporting

confidence: 77%

Section: Maximum Ignition Distancementioning

confidence: 97%

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Ignition and flame characteristics of cryogenic hydrogen releases

Panda

Hecht

2017

International Journal of Hydrogen Energy

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“…More recently, Molkov and Saffers [63] have employed an original dimensionless group accounting for both Froude and Reynolds number effects for hydrogen jet flames, but this did not provide a suitable correlation for all the fuels in the present data base.…”

Section: The Q* Parametermentioning

confidence: 95%

Jet flame heights, lift-off distances, and mean flame surface density for extensive ranges of fuels and flow rates

Bradley

Gaskell

et al. 2016

Combustion and Flame

105

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An extensive review and re-thinking of jet flame heights and structure, extending into the choked/supersonic regime is presented, with discussion of the limitations of previous flame height correlations. Completely new dimensionless correlations for the plume heights, lift-off distances, and mean flame surface densities of atmospheric jet flames, in the absence of a cross wind, are presented. It was found that the same flow rate parameter could be used to correlate both plume heights and flame lift-off distances. These are related to the flame structure, jet flame instability, and flame extinction stretch rates, as revealed by complementary experiments and computational studies. The correlations are based on a vast experimental data base, covering 880 flame heights. They encompass pool fires and flares, as well as choked and unchoked jet flames of CH 4 , C 2 H 2 , C 2 H 4 , C 3 H 8 , C 4 H 10 and H 2 , over a wide range of conditions. Supply pressures range from 0.06 to 90MPa, discharge diameters from 4·10 -4 to 1.32 m, and flame heights from 0.08 to 110 m. The computational studies enabled reaction zone volumes to be estimated, as a proportion of the plume volumes, measured from flame photographs, and temperature contours. This enabled mean flame surface densities to be estimated, together with mean volumetric heat releases rates. There is evidence of a "saturation" mean surface density and increases in turbulent burn rates being accomplished by near pro rata increases in the overall volume of reacting mixture.

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“…For design purposes, predicting the flame height/length is desirable. Therefore, predictive models have been developed (e.g., [1][2][3][4][5][6][7][8]).…”

Section: Introductionmentioning

confidence: 99%