Centre for Fire and Explosion Studies Centre for Fire and Explosion Studies SPRINKLER SPRAY MODELLING Hamed Aghajani Supervisors: Prof. Jennifer Wen and Dr. Siaka Dembele CFES, Kingston University, London 3 rd FM Global Open Source CFD Fire Modeling Workshop, Norwood MA May 9-10
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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
Centre for Fire and Explosion Studies
Outline
• Objectives
• Modelling Approach
• Preliminary studies and results
• 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
• 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): 97–104.
Film Formation
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Modelling Approaches
Film Formation
Sheet Breakup
𝜌𝐿h(𝜕 𝑓𝜕𝑡 )2
+𝜇h𝑛2(𝜕 𝑓𝜕𝑡 )− 2𝜌𝜎𝑈 2 −2𝜎𝑛2=0 𝒇= 𝝆𝑼 𝟐 𝒕√𝟐𝒉𝝆 𝑳𝝈
h𝑏𝑢=h𝑑𝑟𝑑𝑟 𝑏𝑢
𝑟𝑏𝑢=𝑟 𝑑+𝑈 𝑠h𝑒𝑒𝑡 𝑡𝑏𝑢
𝑼 𝒔𝒉𝒆𝒆𝒕 𝒕𝒃𝒖𝟑 +𝒓 𝒅 𝒕𝒃𝒖
𝟐 −𝒉𝒅𝒓 𝒅( 𝒇 √𝟐𝝆𝑳𝝈
𝝆𝑼 𝒔𝒉𝒆𝒆𝒕𝟐 )
𝟐
=𝟎
Sheet Tracking
h𝑑=𝐶2×(𝜈𝐿
𝑄 )0 .25 𝑟 𝑑
94 +𝑙
94
𝑟𝑑
h𝑑=𝑟0
2𝑟 𝑑
+𝐶1×( 7𝜈𝐿
𝑈 0)
0 .2
𝑟𝑑0 . 8
Presently derived equation
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Modelling Approaches
Ligament Formation
𝑉 𝑙𝑖𝑔=𝜋𝑟 𝑙𝑖𝑔2 [2𝜋 (𝑟 𝑏𝑢+𝑟 𝑙𝑖𝑔) ]
𝑉 𝑙𝑖𝑔=𝜋 h𝑏𝑢[(𝑟𝑏𝑢+ 𝜆2 )2
−𝑟 𝑏𝑢2 ]
𝝅𝟒𝑻
𝒅𝒍𝒊𝒈𝟑 + 𝝅
𝟐𝒉𝒃𝒖
𝒓 𝒃𝒖𝒅𝒍𝒊𝒈𝟐 −[(𝒓 𝒃𝒖+
𝝀𝟐 )
𝟐
−𝒓𝒃𝒖𝟐 ]=𝟎
Drop Formation
𝑛𝑐𝑟𝑖𝑡 𝑙𝑖𝑔𝑑𝑙𝑖𝑔=[ 12+ 3𝜇
2√𝜌𝐿𝜎𝑑𝑙𝑖𝑔]− 0 .5
43𝜋𝑟 𝐷𝑟𝑜𝑝
3 =𝜋 𝑟 𝑙𝑖𝑔2 𝜆𝑐𝑟𝑖𝑡𝑙𝑖𝑔
𝒅𝑫𝒓𝒐𝒑❑ =𝟑√ 𝟑𝝅
𝒏𝒄𝒓𝒊𝒕𝒍𝒊𝒈
𝒅𝒍𝒊𝒈𝟐
Deterministic approach predicts a single droplet characteristic
Presently derived conservation equation
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Modelling Approaches• 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
𝜕𝜕𝜉 (𝜌 𝑓 𝑢𝑓 𝛿 )=0Mass
Momentum 𝜌 𝑓 𝑢𝑓
𝜕𝑢𝑓
𝜕𝜉−𝜌 𝑓 𝑢 𝑓𝑤 𝑓
sin 𝜃𝑟
=𝑆𝜉+𝜌 𝑓 𝑔cos𝜃
𝜌 𝑓 𝑢𝑓 𝑢𝑓
𝜕𝑢𝑓
𝜕 𝜉−𝜌 𝑓𝑤 𝑓 𝑤 𝑓
cos𝜃𝑟
=−𝜕𝑝 𝑓
𝜕𝜂−𝜌 𝑓 𝑔sin 𝜃
Geometry𝑑𝑟𝑑 𝜉
=sin𝜃
𝑑𝑧𝑑𝜉
=cos𝜃
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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.
Centre for Fire and Explosion Studies
2/11min2.3
,25
psigalK
mmDdef
)3.0,1.0(
50,50,1000
randIII
pnm
dropligf
Preliminary Studies and Results
Ren, Ning. “Analysis of the Initial Spray from Canonical Fire Suppression Nozzles”, 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