Hydrogen Safety Engineering

Molkov, Vladimir

doi:10.1016/b978-0-08-087872-0.00418-2

Cited by 43 publications

(27 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is "surprisingly" close to the flammability limit of 8.5e9.5% for downward and spherically propagating premixed hydrogen-air flames. This result [7] contradicts to previously published point of view [4e6], that the flame length may be calculated by substitution of the concentration corresponding to the stoichiometric mixture (29.5% by volume of hydrogen in air) into the equation of axial concentration decay for non-reacting jets.…”

contrasting

confidence: 78%

“…Indeed, our preliminary study [7] and conclusions of this complete work demonstrate that hydrogen non-premixed turbulent jet flame tip is located much farther from the nozzle as will be shown below, i.e. from 2.2 times (for shortest flame limit of 16% by volume of hydrogen in air mixture) to 4.7 times (for longest flame limit of 8%), compared to the axial location of stoichiometric concentration of hydrogen in air in non-reacting momentum-dominated jet.…”

Section: Introductionmentioning

confidence: 99%

“…This is important to underline that all experimental data on under-expanded jet fires are in the momentum-dominated regime due to high velocity of chocked flows and comparatively small diameters of piping for equipment working at pressures up to 100 MPa. Recently the similarity law for axial concentration decay in round unignited expanded momentum-dominated jets, suggested by Chen and Rodi [22], has been extended and thoroughly validated for underexpanded hydrogen jets [7] C ax…”

mentioning

confidence: 99%

“…The comparison between the Shevyakov's correlation (2) at the momentum-controlled limit and the similarity law for concentration decay in non-reacting expanded jets [22] has revealed recently [7] that the concentration of hydrogen in a non-reacting expanded jet at a distance equal to the flame tip location is about 8.5% by volume. This is "surprisingly" close to the flammability limit of 8.5e9.5% for downward and spherically propagating premixed hydrogen-air flames.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Hydrogen jet flames

Molkov

Saffers

2013

International Journal of Hydrogen Energy

View full text Add to dashboard Cite

Jet flame length The similarity law Dimensionless correlation Flame tip location a b s t r a c t A critical review and rethinking of hydrogen jet flame research is carried out. Froude number only based correlations are shown to be deficient for under-expanded jet fires. The novel dimensionless flame length correlation is developed accounting for effects of Froude, Reynolds, and Mach numbers. The correlation is validated for pressures 0.1e90.0 MPa, temperatures 80e300 K, and leak diameters 0.4e51.7 mm. Three distinct jet flame regimes are identified: traditional buoyancy-controlled, momentum-dominated "plateau" for expanded jets, and momentum-dominated "slope" for under-expanded jets. The statement "calculated flame length may be obtained by substitution the concentration corresponding to the stoichiometric mixture in equation of axial concentration decay for non-reacting jet"is shown to be incorrect. The correct average value for non-premixed turbulent flames is 11% by volume of hydrogen in air (range 8%e16%) not stoichiometric 29.5%. All three conservative separation distances for jet fire are shown to be longer than separation distance for non-reacting jet.

show abstract

contrasting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Hydrogen jet flames

Molkov

Saffers

2013

International Journal of Hydrogen Energy

View full text Add to dashboard Cite

show abstract

“…The f Ξ coefficient takes under account this phenomenon. Details about this coefficient can be found in [18]. As the combustion develops inside the enclosure, unburned mixture is pushed outside through the vent.…”

Section: Governing Equationsmentioning

confidence: 99%

CFD simulation of hydrogen deflagration in a vented room

Tolias

Venetsanos

Markatos

et al. 2015

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

The critical mass for the unconfined vapour cloud explosion of compressed and liquid hydrogen

Salzano

2023

Can J Chem Eng

View full text Add to dashboard Cite

The (unconfined) vapour cloud explosion (VCE) is a dramatic phenomenon that generates a severe pressure wave with a high potential to damage assets and produce injuries in the far field. This definition applies also to hydrogen. Nevertheless, no clear tools and methodology have been so far developed and tested for this highly reactive gas, and even advanced numerical simulations lack validation and suffer from large uncertainties. In this view, the comprehension of the physic which subtends this dramatic phenomenon for the specific case of hydrogen is still a central issue. This paper revises some of the most adopted theories on VCE based on classical acoustic theory and models for pressure wave propagation and provides a consequence‐based, threshold (minimum) value for the critical mass of hydrogen which is needed—at a stoichiometric concentration in air—for a vapour cloud to behave as a VCE. To this regard, any non‐stoichiometric hydrogen concentration in air or lower amount of hydrogen would decrease either the flame Mach number or the total energy, thus resulting in negligible overpressure. In this sense, the effects of buoyancy, diffusivity, and weather conditions on the dispersion of hydrogen should be taken into account. The results are valid either for compressed or cryogenic liquid tanks and can be adopted for the sake of distinction between hydrogen flash fire and VCE; for the hazard analysis of hydrogen production and storage; and more in general for the risk assessment of hydrogen systems.

show abstract

Hydrogen Safety Engineering

Cited by 43 publications

References 30 publications

Hydrogen jet flames

Hydrogen jet flames

CFD simulation of hydrogen deflagration in a vented room

The critical mass for the unconfined vapour cloud explosion of compressed and liquid hydrogen

Contact Info

Product

Resources

About