Prediction of the Height of Turbulent Diffusion Buoyant Flames

Steward, F.R.

doi:10.1080/00102207008952248

Cited by 148 publications

(54 citation statements)

References 17 publications

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“…Fig. 7 Earlier theoretical and experimental studies of turbulent diffusion flames from porous gas burners have provided scaling laws for flame height and other important properties of the flame and the plume (Steward 1970, McCaffrey 1979, Zukoski & al 1981. The laws derived from these steady combustion regimes showed that the flame height scales as a 2/5 power of the heat release rate for axi-symmetric fires :…”

Section: Flame Heightmentioning

confidence: 99%

Fires from a cylindrical forest fuel burner: combustion dynamics and flame properties

Dupuy

Maréchal

Morvan

2003

Combustion and Flame

115

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Section: Flame Heightmentioning

confidence: 99%

Fires from a cylindrical forest fuel burner: combustion dynamics and flame properties

Dupuy

Maréchal

Morvan

2003

Combustion and Flame

115

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“…The problem reduces to finding a relation involving the amount of e ntrainme nt and the he igh t of the thermal discontinuity for a given fi re such tha t its locus will intersect the enclosure flow at the appropriate flow and height, i. e., the points on figure 13 . Several fire plume models exist; the one chosen here from reference [1] is an adaptation of work by Fang [9] and Stewart [10]. The total flow in the plume , Wp , is given as a fun ction of the fu el inj ection rate , WI; a fuel property, w; density ratio , ambient to fu el , PO /PI ; plume entrainment coeffi cient , ke, and finall y, th e height above the burner , D.…”

Section: Plume Entrainmentmentioning

confidence: 99%

Static pressure measurements of enclosure fires

McCaffrey¹,

Rockett²

1977

J. RES. NATL. BUR. STAN.

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Some enclosure-fire s tati c pressure me asurements are presented for both full a nd sca le mode l rooms and are compared with the present hydra uli cs-orifice flow model for fire induced flows into and out of enclosures. Results indicate that the vertical pressu re diffe renti al (enclosure to ambient) follow s the expected hydrostati c distribution qUite well and accura tely reflects the doorway Inflow and outflow gas velocities. .Measure me nt of ceiling a nd floor diffe rential pressure using different numbers of gas burners yields ins ight Int o gross plume e ntrainment and Illus trates how the neutra l p la ne and thermal di scontinuit y vary with upper gas temperature. Corre la ting upper gas tempe ra ture with fire s ize and enclosure he ight ma kes it possible to pred ict at wha t heat release rat e a give n enclosure mi ght become fully involved, i. e., by using the temperature at which the the rma l discontinuity approac hes th e floor.In te rms of present fire plume modeling la rge e ntra inment coeffi cie nt s (0 .3-0.4) are required in order to reproduce the e nc los ure fl ows for both the s ma ll and large scale resu lt s. A noted defi cie ncy in the plume mode l appears In the small sca le results wh e re the data suggest that the e ntrainment s hould exhibit a much stronger dependence on th e fu el injecti on rate tha n that pred icted by the th eory.Key words: Buoyancy pressure; e nclosure fires; entrai nme nt; fire ind uced flow s; models; physica l sca le; plumes.Nomenclature door opening area (m 2 ) orifice discharge coeffic ient gas specifi c heat (J/kg' K) height of thermal discontinuity above floor (m) plume Froude number = uJ/g'Yo gravitational accelerati on (9.8 m/s 2 ) height of enclosure (m) height of door opening (m) entrainmen t coeffi cient gas/air How rate (kg/s) height of ne utral plane above floor (m) pressure (torr, N/m 2 ) pressure difference, enclosure to ambient P-P AMB (torr, also given as N/m 2 ) heat release rate (k W) radial distance from plume axis gas temperature (OC, K) temperature difference eC) gas burner flow velocity (m/s) gas/air velocity (m/s) door opening width (m) entrained flow in plume (kg/s) gas burner flow rate = pf7T1o u f height above floor (m) radius of gas burner (m) distance above or below neutral plane gas densit y (kg/m 3 ) fu el property defined by equation (9) 1 . Introduction Present e nclos ure-fire modeling incorpora tes a hydrauli csorifice approach for calculation of th e How in a nd out of th e opening [1,2,3].1 Due to th e hot gases present in the upper portion of the room a pressure difference with respect to the ambient hydrostati c pressure is developed across the opening which is responsible for driving th e How. The gas in th e room is ass umed stationary and the How ra te is determined using Bernoulli's equation with an appropri a te orifice coefficient. Additionally th e gas Jlow in and ou t of th e e nclos ure is co upled via entra inmen t of th e [ire plume. Figures 1 a nd 2 illustrate th ese ideas sc he mati cally. A s tep functi...

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“…A similar assumption has been made by (Thomas, 1963) and (Steward, 1970); and results were suggested theoretically by (Townsend, 1966). Therefore, the Eq.…”

Section: Similarity Solutionsmentioning

confidence: 51%