Assessment Of Fire Suppression Capabilities Of Water Mist

-Fighting Compartment Fires with the Cutting Extinguisher-

FIREFIGHT II Mid-term MeetingWednesday 24 – Friday 26 November 2010 in Prague

Pg. Dip. Msc. Fire Safety EngineeringAcademic year 2009/2010

Julien GSELLjuliengsell@orange.fr

Contents

• Introduction– Msc Fire Safety Engineering– The Master Thesis– Why on the Cutting Extinguisher?

Contents

• Introduction• Background

– Literature review– A Thesis to answer what?– Going further in the study

Contents

• Introduction• Background• Experimental framework

– Enclosure & type of fuel– Instrumentation– Methodology

Contents

• Introduction• Background• Experimental framework• Results

– Water mist behaviour– Fire suppression capabilities– Safety concerns

Contents

• Introduction• Background• Experimental framework• Results• Conclusion

– Publication– Translation in French– Haut-Rhin Fire Service

Introduction

• Msc Fire Safety Engineering– University of Ulster at Jordanstown

Belfast, Northern Ireland

• The Master Thesis– Assessment of the Fire Suppression Capabilities

of Water Mist

• Why on the Cutting Extinguisher?– Previous placement

• Study of the manufacturing, use, and development of the tool

Background

• Literature review

– The Cutting Extinguisher - Concept and Development: Swedish Rescue Services Agency, 1999

– Holmstedt, Göran. An assessment of the Cutting Extinguisher's Capabilities and limitations: Lund University, 1999

– Winkler, Thomas Karlsen & Henrik. Skärsläckaren som röjnings och släckverktyg för fartyg av kolfiberkomposit, 2000

– Olsson, Johannes Bjerregaard & Daniel. Skärsläckaren-experimentella försök och beräkningar, 2007

– Cutting Extinguishing concept-practical and operational use: Swedish Rescue Services Agency, 2010.

Background

• A Thesis to answer what? How this scenario with a focused jet of water and high flow rate, where

the beam is broken up into small droplets, affects the mixing of the fire gases has not so far as known been investigated

the impact of the ventilation openings on the cutting extinguishers ability to extinguish fires

the functioning of the cutting extinguisher in a well controlled fire in relation to various types of and ventilation

the importance for the efficiency of the cutting extinguisher of the water jet being able to break up

Cutting Extinguishing concept-practical and operational use: Swedish Rescue Services Agency, 2010.

Background

• Going further in the study

– Calibration of the water mist generated

– Water mist volumetric behaviour (situation without fire)

– Re-ignition probability

– Possible pressure variations in the compartment

– Consequences of spraying water mist

• Regarding the Fire fighters

• Regarding a potential victim

Experimental framework

• Enclosure & type of fuel– Characteristics & dimensions of the

compartment• 40 feet sea container• Fire area on the bottom• 2.71 m2 openings area to be used

– Type, properties & arrangement

Characteristics & dimensions of the compartment

Experimental framework

• Structure & type of fuel– Characteristics & dimensions of the

compartment

– Type, properties & arrangement• Chipboard panels• 12.8 or 8.4 m2 burning surface• Ceiling, lateral and bottom walls

Type, properties & arrangement

• Instrumentation– Bottle frame

• Every 0.5 m from 2.0 to 10.0 m• 144 bottles for a control surface of 324 cm2

– Thermocouple meshing– Radiometer– Pressure record– Video record

Experimental framework

Bottle frame

Experimental framework

• Instrumentation– Bottle frame– Thermocouple meshing

• 99 TC distributed over 8.8 m length,2.4 m width and 2.4 m height

• Control volume of 0.512 m3

– Radiometer– Pressure record

• 2 transducers– Video record

Temperature, pressure & heat flux

• Instrumentation– Bottle frame– Thermocouple meshing– Radiometer– Pressure record– Video record

Experimental framework

Video record

Methodology

• Scenarios– Location of the Cutting Extinguisher

• Front wall, mid-length, 1.65 m high– Studied parameter

• Experimental protocol– Exploit of the “Bottle frame”– Full scale burnings

Location of the Cutting Extinguisher

Methodology

• Scenarios– Location of the Cutting Extinguisher– Studied parameters

• Volumetric distribution of water• Influence of opening area, fuel surface, and

water flow rate• Experimental protocol

– Exploit of the “Bottle frame”– Full scale burnings

Studied parameters• Fire experiments

Designation of the scenario

Area of the openingsBurning SurfaceWater flow ratePossibles fire scenarios

Fire scenarios

Q = 56 L/min

Sf = 12.8 m2

Ac = 0.192 m2 1Ac = 0.192 m2 2Ao= 2.71 m2 3

Sr = 8.4 m2

Ac = 0.192 m2 4Ao= 2.71 m2 5

Qr = 28 L/min

Sf = 12.8 m2

Ac = 0.192 m2 6Ao= 2.71 m2 7

Sr = 8.4 m2

Ac = 0.192 m2 8

Ao= 2.71 m2 9

Methodology

• Scenarios– Location of the Cutting Extinguisher– Studied parameters

• Experimental protocol– Exploit of the “Bottle frame”– Full scale burnings

Exploit of the bottle frame

Methodology

• Scenarios– Location of the Cutting Extinguisher– Studied parameters

• Experimental protocol– Exploit of the “Bottle frame”– Full scale burnings

Full scale burnings

Results

• Water mist behaviour– Total flooding

• Water content: 44 g/m3

• Volumetric flow rate: 21.2 m3/s• Velocity: 7.13 m/s

– Spray pattern

Total flooding

Total flooding

Results

• Water mist behaviour– Total flooding– Spray pattern

• Inner core + outer ring• Initial diameter: 4.5 °• Break up point at 5.0 m• Widening following an angle of 9.0 °

– Application modes

Spray pattern

Results

• Water mist behaviour– Total flooding– Spray pattern– Application modes

• Spread droplets into the flames• Spread droplets in the smoke layer• Inerting by steam generation• Cool the burning fuel surface• Shield the fuel surfaces not yet involved

Results

• Fire suppression capabilities– Flame tackling time

• Fire extinguished every time• Below 15 seconds regardless to the scenarios• Major effect trough blowing and heat extraction

– Influence of parameters during gas cooling phase

– Re-ignition probability

Flame tackling time

0 200 400 600 800 1000 1200 1400 1600 1800 2000 22000

100

200

300

400

500

600

700

800

900

1000Fire Curves

Scenario 1

Scenario 2

Scenario 3

Scenario 4

Scenario 6

Time (in s.)

Tem

pera

ture

s (in

°C)

Results

• Fire suppression capabilities– Flame tackling time– Influence of parameters during gas cooling

phase• Initial “plateau”• Reducing fuel surface: faster to reach safe level• Increasing opening size: faster to reach safe level• Reducing water flow rate: cooling down more

difficult

– Re-ignition probability

Gas cooling phaseEntire fire development, shown 40 times faster

Gas cooling phaseExtinguishing phase, 4 times faster

Results

• Fire suppression capabilities– Flame tackling time– Influence of parameters during gas cooling

phase– Re-ignition probability

• Likely to occur• No significant temperature or fire rise within 3

min• Limited action of surface cooling• Requires to wet the remaining charring

material

Re-ignition probability

Results

• Safety concerns– Life safety

• Radiation shielding• Remaining of the “oxygen survival layer”• No high temperature or smoke feed back

– Property safety

Life safety• Radiation shielding

Radiation shielding

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

11

12Heat flux variations depending on time

rayonnement

Time (in s.)

Heat

flux

(in

kW/m

2)

Spraying period

Results

• Safety concerns– Life safety

• Radiation shielding• Remaining of the “oxygen survival layer”

– Also mixing & temperature destratification• No high temperature or smoke feed back

– Property safety

Mixing and temperature destratification

Scenario n°6

Results

• Safety concerns– Life safety

• Radiation shielding• Remaining of the “oxygen survival layer”• No high temperature or smoke feed back

– Property safety

Life safety

Results

• Safety concerns– Life safety– Property safety

• No water damage• No over pressure

Property safety

Conclusion

• Publication• Translation in french• Haut-Rhin Fire & Rescue Services• FIREFIGHT?

Thank you for listening

Questions?