Centre for Fire and Explosion StudiesCentre for Fire and Explosion Studies
SPRINKLER SPRAY MODELLING
Hamed Aghajani
Supervisors:Prof. Jennifer Wen and Dr. Siaka Dembele
CFES, Kingston University, London
3rd FM Global Open Source CFD Fire Modeling Workshop, Norwood MA
May 9-10
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Outline
β’ Objectives
β’ Modelling Approach
β’ Preliminary studies and results
β’ Conclusion
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Objectives
Sheppard, D. T. Spray characteristics of fire sprinklers. PhD Dissertation, Evanston, IL: North-western University, 2002.
Studying Available Modeling Approaches for Sprinklers and Understand their Limitations
Develop a Model to Study Droplets Transport and Interaction with Fire
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Modelling Approaches
β’ Deterministic Atomization ModelInitial
Sprinkler Condition
Sheet Breakup
Droplet size, location, Velocity
Ligament Breakup
Marshall, A. W., and M. Di Marzo. Process Safety and Environmental Protection 82 (2004): 97β104.
Film Formation
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Modelling Approaches
Film Formation
Sheet Breakup
ππΏh(π πππ‘ )2
+πhπ2(π πππ‘ )β 2πππ 2 β2ππ2=0 π= ππΌ π πβπππ π³π
hππ’=hππππ ππ’
πππ’=π π+π π hπππ‘ π‘ππ’
πΌ πππππ ππππ +π π πππ
π βππ π π ( π βπππ³π
ππΌ ππππππ )
π
=π
Sheet Tracking
hπ=πΆ2Γ(ππΏ
π )0 .25 π π
94 +π
94
ππ
hπ=π0
2π π
+πΆ1Γ( 7ππΏ
π 0)
0 .2
ππ0 . 8
Presently derived equation
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Modelling Approaches
Ligament Formation
π πππ=ππ πππ2 [2π (π ππ’+π πππ) ]
π πππ=π hππ’[(πππ’+ π2 )2
βπ ππ’2 ]
π ππ»
π ππππ + π
ππππ
π πππ ππππ β[(π ππ+
ππ )
π
βππππ ]=π
Drop Formation
πππππ‘ πππππππ=[ 12+ 3π
2βππΏπππππ]β 0 .5
43ππ π·πππ
3 =π π πππ2 πππππ‘πππ
π π«πππβ =πβ ππ
ππππππππ
π ππππ
Deterministic approach predicts a single droplet characteristic
Presently derived conservation equation
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Modelling Approachesβ’ Stochastic Modeling
Critical Breakup Amplitude (
Sheet Breakup Wavelength (
Ligament Breakup Wavelength (
Stochastic Model
Wu, Di, Delphine Guillemin, and Andre W Marshall. "A modeling basis for predicting the initial sprinkler spray." Fire Safety Journal 42 (2007): 283-294.
Droplet Size
Initial Location
Existing model is mainly for simple deflectors
Do not account for actual sprinkler configurations (Pendant, Upright)[There is no model for fluctuation intensity]
Normal distribution have been utilized for all 3 parameters.0.1 < I < 0.3
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Ibrahim, E A., and McKinney, T R., Proceedings of the Institution of Mechanical Engineers 220 (2006): 203-214.
Preliminary Studies and Results
Alternative Sheet Tracking Model
πππ (π π π’π πΏ )=0Mass
Momentum π π π’π
ππ’π
ππβπ π π’ ππ€ π
sin ππ
=ππ+π π πcosπ
π π π’π π’π
ππ’π
π πβπ ππ€ π π€ π
cosππ
=βππ π
ππβπ π πsin π
Geometryπππ π
=sinπ
ππ§ππ
=cosπ
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Preliminary Studies and Results
Implementation thoroughly satisfies the original paper
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Preliminary Studies and Results
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K=2
K=3
K=4
K=5
Preliminary Studies and Results
Wu, Di, Delphine Guillemin, and Andre W Marshall. "A modeling basis for predicting the initial sprinkler spray." Fire Safety Journal 42 (2007): 283-294.
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2/11min2.3
,25
psigalK
mmDdef
)3.0,1.0(
50,50,1000
randIII
pnm
dropligf
Preliminary Studies and Results
Ren, Ning. βAnalysis of the Initial Spray from Canonical Fire Suppression Nozzlesβ, Master Thesis, Maryland: University of Maryland, College Park, 2007.
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Preliminary Studies and Results
Dundas, P., FMRC serial no. 18792 RC73-T-40
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Preliminary Studies and Results
Normalized radial displacement Vs. Normalized Vertical displacement
AT 300K
P = 10 psi
P = 20 psi
P = 30 psi
P = 50 psi
P= 70 psi
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Normalized Velocity Vs. Normalized Vertical displacement
AT 300K
Preliminary Studies and Results
P = 10 psi
P = 20 psi
P = 30 psi
P = 50 psi
P= 70 psi
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Preliminary Studies and ResultsLiquid sheet deflection Vs. Normalized Vertical displacement
AT 300K
P = 10 psi
P = 20 psi
P = 30 psi
P = 50 psi
P= 70 psi
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Formerly introduced atomization models implemented as a frame tool for further investigations and improvements
Verification of the model against published research has been conducted Normally distributed stochastic parameters droplet size predicts droplet sizes in
range of , which are in range of published experimental work.
FURTHUR STUDIES Effect of surrounding air on spray parameters Explore the effects of some physical sprinkler parameters as boss and tine/space. Studying the interaction of different spray pattern with fire
Conclusion and Future Work
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Thank you.
Comments and Questions?