Limiting factor of flame propagation in low-volatility fuel clouds

Hayashi, Sachiko; Ohtani, Tomohito; Iinuma, Kazuo; Kumagai, S.

doi:10.1016/s0082-0784(81)80041-0

Cited by 15 publications

(9 citation statements)

References 7 publications

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“…In the third stage, the total area of the flames shrank at a rate of −79.25 cm 2 /s, which corresponds with the large flames splitting into smaller flames before quenching at the top. Different combustion modes of flames in aerosol systems have also been reported by previous researchers. ,, Among the three stages of flame propagation, the second stage, which is characterized by large yellow flames and rapid flame size expansion, is considered to be the most hazardous scenario of aerosol flames and may result in more severe damage to the plant environment if it occurs on a large scale.…”

Section: Resultsmentioning

confidence: 58%

“…In addition, the values of flame front speed were found to vary considerably with different test methods in the previous studies. For instance, velocity of the flame front was found to reduce with the existence of fuel droplets as compared to other experiments performed using a fuel vapor system with the same fuel concentration. ,,, In other studies, the flame front velocity in the aerosol system was found to be higher than that in the gaseous mixtures, and the phenomenon of flame speed oscillation was also reported. ,,− The seemingly contradictory results actually arose due to the complexity of flame characteristics in the aerosol system. For the case of flames in the current aerosol system, there was little uniformity or even discreteness in the flame shapes, followed by the observation of different stages of flame propagation.…”

Section: Discussionmentioning

confidence: 74%

“…Previous studies have shown that the flame characteristics of aerosol combustion are determined by the droplet evaporation. , The evaporation of droplets give rise to the fuel vapor concentration in the aerosol system, which may influence the flame front propagation speed. Subsequently, evaporation of droplets moving inside the flame determines the amount of fuel that is supplied by the droplets to support the combustion reactions, which may increase the fuel burning rate and influence propagation process of the flames.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Study on Flame Characteristics in Aerosols by Industrial Heat Transfer Fluids

Lian

Mejı́a

et al. 2011

Ind. Eng. Chem. Res.

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Due to the complexity of aerosol formation and the combustion process, fire and explosion hazards of flammable aerosols formed in the process industry are not fully understood. In this study, the flame propagation process of aerosolized industrial heat transfer fluids was investigated to understand the combustion phenomena in aerosol systems. Experimental observation shows different characteristics of flames propagation in aerosol systems, which are determined by the evaporated fuel vapor in aerosol system prior to encountering the flame and the amount of fuel vapor from droplets evaporating inside flames. Numerical modeling revealed that these factors were mainly determined by aerosol droplet size and velocity. The observed characteristics of the aerosol flames and the nature of continuous fuel evaporation that causes the reduction of droplet sizes suggest that ignition of flammable aerosols in the process plant might create more severe consequences than ignition of vapor mixtures. Results also imply that the aerosol dispersion conditions, as well as its formation conditions in scenarios of industrial fluid release, which determine the droplet size and movement velocity, need to be considered in assessment of fire hazard from the flammable aerosols.

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Section: Resultsmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 74%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Study on Flame Characteristics in Aerosols by Industrial Heat Transfer Fluids

Lian

Mejı́a

et al. 2011

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

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“…It is important to note, however, that optimum two-phase characteristics for successful ignition do not necessarily correspond to those for optimal fuel-mist flammability. An example of this was shown by Hayashi et al (1981) who established that the MIE generally correspond to < 30 µm droplet mists, dominated by evaporation timescales, whereas the lower flammability limit (LFL) reduces for droplet diameter > 40 µm due to the established inhomogeneouis droplet-droplet relay flame propagation mechanism. For this study, this potential source of confusion is allayed, as for all releases considered, those spray/mists that ignited also indeed propagated.…”

Section: Introductionmentioning

confidence: 99%

On flammability hazards from pressurised high-flashpoint liquid releases

Giles

Kay

Mouzakitis

et al. 2017

Journal of Loss Prevention in the Process Industries

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Hazardous area classification is well established for dust and vapours, however this is not the case for high flashpoint liquid fuels. This study highlights the limitations of current guidance in relation to flammable mists, through demonstration of flammability of a representative high flashpoint fuel for releases in the range of representative industrial operating pressure, complemented by a phenomenological analysis and semiquantification of the results observed. Flammability results are presented from low-pressure practical releases (< 20barg) of a representative fuel (gasoil with flashpoint > 61 °C), through a plain orifice, at temperatures well below its flashpoint. Based on a proposed two-phase flow-regime diagram, a semi-quantitiatve analysis of the results observed is offered via a simple 1-D phenomenological model, accommodating jet breakup length, spray quality, air entrainment and droplet dynamics. The complex scenario of liquid releases impinging onto an unheated flat surface is also considered. An impingement model is utilised to show the relative increase in volume of fine secondary spray induced postimpingement relative to the unobstructed case, resulting in a significant volume of flammable mist. This is demonstrated experimentally by showing flammability of a 5 barg release post impingement whereas the unobstructed 10 barg case would not ignite.

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“…The minimum ignition energy for a particular spray is then defined as the ignition energy which results in 50% probability of ignition (Danis et al, 1988). Another model for ignition probabililty in sprays has been developed by Hayashi et al (1981) based on a product of the probability for a droplet to ignite and the probability that a propagating flame would result. This was prompted by the realization that in real sprays the droplet spacing mayor may not be small relative to the spark gap.…”

Section: Introductionmentioning

confidence: 99%

Ignition Probability and Absolute Minimum Ignition Energy in Fuel Sprays

Wehe

1992

Combustion Science and Technology

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Ignition in a one dimensional spray by a short duration source is modeled numerically. The probabilistic nature of spray ignition is discussed using a deterministic approach. The ignition source is modeled by a hot gas region of a defined thickness simulating a pilot flame or a low tempera lure spark source. For a given drop spacing, the location of the droplet closest to the ignition source determines whether or not the spray ignites. The bounds of droplet location beyond which the spray will not ignite define a droplet location domain for successful spray ignition. The ratio of length of this domain to droplet spacing is defined to be ignition probability. Ignition probabilities and ignition energies are presented for different ignition source thicknesses and overall equivalence ratios. The absolute minimum ignition energy is then ohtained at the limit of zero probability. Temperature and fuel species profiles. along with droplet radii and location information, are also presented.

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Limiting factor of flame propagation in low-volatility fuel clouds

Cited by 15 publications

References 7 publications

Study on Flame Characteristics in Aerosols by Industrial Heat Transfer Fluids

Study on Flame Characteristics in Aerosols by Industrial Heat Transfer Fluids

On flammability hazards from pressurised high-flashpoint liquid releases

Ignition Probability and Absolute Minimum Ignition Energy in Fuel Sprays

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