Advances in WaterBased Fire Suppression Modeling:

1
Advances in Water-Based Fire Suppression
Modeling Evaluating Sprinkler Discharge
Characteristics
June 24, 2008
7th International Fire Sprinkler Conference and
Exhibition Copenhagen, Denmark Students Ning
Ren, Andrew Blum, Di Wu, and Chi Do Faculty
Advisor Andre Marshall Sponsors NFSA, FM
Global, NSF
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Overview

• Introduction
• Motivation
• Project History
• Previous Work
• Global Objective
• Evaluate Discharge Characteristics
• Advanced Measurements
• SAM Development
• Approach
• Experimental
• Modeling (SAM)

• Results
• Sheet Formation (Deflector)
• Sheet Breakup
• Drop Formation
• Dispersion
• Summary
• Plans
• Experimental
• Modeling

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Motivation
Gain New Knowledge

• Physical models characterizing the break-up
  process and the associated initial spray in fire
  suppression devices have yet to be developed.

Develop Injector Technology

• The absence of this analytical capability impedes
  the development of fire suppression
  injectors/systems.

Understanding the relationship between
atomization physics and injector control
parameters would facilitate a transition away
from cut and try injector development.
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Motivation
D
inlet
L
inlet
D
o
L
jet
A
A
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boss
Section A-A
D
boss
t
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tine
arm
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space
D
def
Characterization
Cut and Try
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Motivation
Advance Fire Protection Engineering Practices

• CFD modeling tools of fire phenomena are becoming
  increasingly popular for fire protection analysis
  and performance based design.
• The absence of physical models describing
  atomization in sprinklers and water mist
  injectors results in uncertainties in CFD
  simulation of suppressed fires.
• Errors in the specification of the initial spray
  will be propagated and amplified during
  dispersion calculations.

The atomization model represents a critical
missing link in the modeling of suppressed fires.
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Project History
UM Fire Suppression Spray Research
FY2005
FY2006
FY2007
FY2008
FY2009
FY2012
FY2010
FY2011
NFSA
Sprinkler Atomization Modeling and FDS Integration
Betatti - U. Modena
DuPont
Surfactant Effects on Fire Suppression
HP Mist Modeling
FM Global
Scaling Laws and Models for Fire Suppression
Devices
NSF CAREER Award Exploring Atomization and Jet
Fragmentation in Combustion and Fire Suppression
Systems
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Previous Work
Previous Research
1
3
FD
Fs
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Global Objective
Evaluate discharge characteristics from fire
suppression devices using measurements and models.

• Parameter Space
• based on varied injector geometry and injection
  conditions.
• Experiments
• based on state-of-the art diagnostics focused on
  the initial spray.
• Analysis
• based on physics based models using
  semi-empirical approaches (e.g. scaling laws and
  wave dispersion analysis).

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Approach
Injected Flow
Injectors

J
e
t

TYCO TY4211
Gr
ow
t
h

o
f

W
a
v
e
s

D
e
f
le
ct
o
r

LP Nozzle 2 bar 700 ?m
Sh
e
e
t


F
or
m
a
t
io
n

TYCO AM4
Sh
e
e
t

L
igamen
t


?
Li
g
a
m
e
nt

Dr
o
p


?
MP Nozzle 15 bar 225 ?m
HP Nozzle 100 bar 60 ?m
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Approach
Geometric parameter space w/n LP injector
(sprinkler) configuration
3.2, 6.7, 9.7 mm
38 mm
Basis Nozzle
Sprinkler
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Approach
Trajectory Measurements (PLIF)
Camera FOV
texp 900 ?s
Cooke 16-bit cooled 2.0Mpixel High-Speed Digital
Video Camera.
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Approach
Sheet Break-up Measurements
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Approach
Drop Size Measurements
Malvern Spraytec Analyzer (Light Diffraction
Technique)
Local Measurements
Local Drop Size Distribution
P 2.07 bar r/R 0.45
Local
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Approach
Volume Flux Measurements
BasisDo 9.7 mm P 2.07 bar
BasisDo 9.7 mmP 2.07 bar
3.0 m
1.0 m
1.0 m
dv50 780 µm
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Approach
Radius where Wall Effects Reach Free Surface
Impinging Jet (Watson, 1964)
Viscous interactions with deflector important for
initial thickness and velocity of unstable free
liquid sheet.
Jet Radius
Deflector Radius
Arbitrary Length Scale Determined from Matching
Kinematic Viscosity
Jet Flow Rate
Annular Sheets (Ibrahim, 2004)
Transport equations for mass and momentum provide
the sheet trajectory.
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Approach
Dimensionless Wave Growth Rate
Viscous
Inviscid
Fastest Growing Wave
Most Unstable Wavelength
Gas
p-
p-
p-
U
p
p
Sinusoidal Waves
Viscous
Wave Growth (Sterling and Sleicher, 1975 Weber,
1931)
r
The most unstable wave is determined, which
breaks up the sheet at rbu,lig into a fragment
having characteristic length ?bu,lig.
r
Vjet
z
p
p-
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Results
Sheet Formation
Governing Equations
, b
Dimensionless Solution

• The thickness and velocity of the sheet is
  reduced by viscous effects depending on the
  nozzle geometry (not yet accounting for spaces).

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Results
Sheet Formation

• Two distinct streams are formed the jet is
  deflected radially outward along the tines and
  the jet is forced downward through the spaces
• The flow split between these streams governs the
  sheet thickness and the resulting drop size.

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Results
Sheet Breakup
Standard Nozzle, Do 6.35 mm, p 2 bar

• Sheet breakup locations occur several jet
  diameters away from the sprinkler.
• Data collapses well with appropriate theory

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Results
Drop Formation
p 2 bar

• Drop size in the space stream are siginificantly
  smaller than tine stream, but follow
  Rosin-Rammler
• Testing scaling law for drop size

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Results
Dispersion
The radial coordinate has been normalized with
the maximum theoretical radial value for each
condition.
Spatial Drop Size Distributions
Spatial Volume Flux Distributions
K 7.2 (0.5)
K 25.9 (1.8)
K 54.7 (3.4)
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Summary

• Viscous effects along the deflector can be
  important (for small K-factors).
• Two well characterized sheets (radially expanding
  and orthogonal fan) are formed through the tines
  and the spaces.
• SAM successfully models the tine stream. Space
  stream submodel in SAM currently under
  development.
• Sheet breakup locations are predicted well by SAM
  with We-1/3.
• Ligament break-up (high We) modes and rim
  break-up modes (low We) are observed. The We
  transition depends on nozzle geometry.
• Drop size predicted well by SAM when nozzle
  operates in ligament breakup mode with We-1/3.

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Experimental Plans
BREAKUP IMAGING
Tine Stream
Space Stream
QUANTITATIVE SHADOWGRAPH / PTV
DROP SIZE / VELOCITY
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Experimental Plans
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SAM Modeling Plans
Device Characterization
Space Stream Submodel
Fundamental Models
To Outer
Splitter
To Inner
Expanding Validated Parameter Space
CFD Integration
Standard Nozzle(Tyco D3 Nozzle)
Basis Nozzle
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Questions?