8/11/2019 JDD - Alvin

1/49

A STUDYOFTHEPRECURSORSTOBACKDRAFT(SMOKE

EXPLOSION) INAMECHANICALLY-VENTILATED

COMPARTMENTANDTHEROLEOFSOOTINTHIS

PHENOMENON

PhD student : Alvin Si-Xian LOO

Supervisors: Prof. Alexis COPPALLE (CORIA), Philippe ANE (AREVA)

10meJourne des Doctorants du CORIA 2013

8/11/2019 JDD - Alvin

2/49

8/11/2019 JDD - Alvin

3/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

WHATISABACKDRAFT?

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

4/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

5/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

1 Ignition

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

6/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

1 Ignition

2 Fire growth

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

7/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

1 Ignition

2 Fire growth

3 Burning if all combustible materiels

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

8/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

1 Ignition

2 Fire growth

3 Burning if all combustible materiels

4 Fire decay due to lack of fuel

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

9/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

1 Ignition

2 Fire growth

3 Burning if all combustible materiels

4 Fire decay due to lack of fuel

5 Extinction of fire

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

10/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

Firepower(W)

Time (t)

Underventilated case + Backdraft

1 Ignition

2 Fire growth

3 Burning if all combustible materiels

4 Fire decay due to lack of fuel

5 Extinction of fire

1 2 3 4

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

11/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

Firepower(W)

Time (t)

Underventilated case + Backdraft

1 Ignition

2 Fire growth

3 Burning if all combustible materiels

4 Fire decay due to lack of fuel

5 Extinction of fire

1 2 3 4

1 Ignition

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

12/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

Firepower(W)

Time (t)

Underventilated case + Backdraft

1 Ignition

2 Fire growth

3 Burning if all combustible materiels

4 Fire decay due to lack of fuel

5 Extinction of fire

1 2 3 4

1 Ignition

2 Fire growth

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

13/49

Lets start by examining the different stages of the fire power development in a

compartment during an accidental fire:

Well-ventilated case

WHATISABACKDRAFT?

Firepower(W)

Time (t)

Firepower(W)

Time (t)

Underventilated case + Backdraft

1 Ignition

2 Fire growth

3 Burning if all combustible materiels

4 Fire decay due to lack of fuel

5 Extinction of fire

1 2 3 4

1 Ignition

2 Fire growth

3 Fire decay due to lack of air

+ accumulation of combustible

vapor and soot

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

14/49

8/11/2019 JDD - Alvin

15/49

WHATISABACKDRAFT?

Limited ventilation during an enclosure fire can lead to the production of largeamounts of unburnt pyrolysis products. When an opening is suddenlyintroduced, the inflowing air forms a gravity current and begins to mix withthe unburned pyrolysis products,creating a combustible mixture of gases insome part of the enclosure. Any ignition sources, such as a glowing ember, can

ignite this combustible mixture. Resulting in an extremely rapid burning ofgases/pyrolysis products forced out through the opening and causes a fireball

outside the enclosure. 15-- Fleischmann/Pagni/Quintiere

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

16/49

WHATISABACKDRAFT?

Limited ventilation during an enclosure fire can lead to the production of largeamounts of unburnt pyrolysis products. When an opening is suddenlyintroduced, the inflowing air forms a gravity current and begins to mix withthe unburned pyrolysis products,creating a combustible mixture of gases insome part of the enclosure. Any ignition sources, such as a glowing ember, can

ignite this combustible mixture. Resulting in an extremely rapid burning ofgases/pyrolysis products forced out through the opening and causes a fireball

outside the enclosure. 16-- (Fleischmann/Pagni/Quintiere)

Backdraft is sometimes called smoke explosion

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

17/49

CONTENTSOFTHISPRESENTATION

What is a Backdraft?

Context and Objectives of this study

Experimental apparatus for underventilated fires

Some Results of underventilated fires

Experimental apparatus for smoke deflagration

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

18/49

CONTEXTOFTHISSTUDY

To prevent radioactive substance leak, compartments are

sealedto ensure air-tightness. Mechanical ventilationsystems maintain an underpressureand renew the air ofthe compartment

Study fire scenarios in nuclear installations.

Air

Smoke

Journ

e

des

Do

ctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

19/49

CONTEXTOFTHISSTUDY

To prevent radioactive substance leak, compartments are

sealedto ensure air-tightness. Mechanical ventilationsystems maintain an underpressureand renew the air ofthe compartment

Study fire scenarios in nuclear installations.

Problem: Maintain confinement within thecompartments during fires Air

Smoke

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

20/49

CONTEXTOFTHISSTUDY

To prevent radioactive substance leak, compartments are

sealedto ensure air-tightness. Mechanical ventilationsystems maintain an underpressureand renew the air ofthe compartment

Study fire scenarios in nuclear installations.

Problem: Maintain confinement within thecompartments during fires

- Radioactive substance leak to the outside

- Damage of safety equipments in the compartment or in the ventilationnetwork (filters, doors, dampersetc)

What could happen:

Air

Smoke

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

21/49

CONTEXTOFTHISSTUDY

To prevent radioactive substance leak, compartments are

sealedto ensure air-tightness. Mechanical ventilationsystems maintain an underpressureand renew the air ofthe compartment

Study fire scenarios in nuclear installations.

Problem: Maintain confinement within thecompartments during fires

- Radioactive substance leak to the outside

- Damage of safety equipments in the compartment or in the ventilationnetwork (filters, doors, dampersetc)

Feared events: - Overpressure caused by the fire

- Temperatures inside the compartment becomes too high

- Backdraft

What could happen:

Air

Smoke

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

22/49

CONTEXTOFTHISSTUDY

Overpressure and high temperatures can be caused by the fire itself:

(Internal energy of the compartment)

Backdraft can happen:

- Smoke dilution in the ventilation network

- Opening of doors by rescue personnels

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

23/49

CONTEXTOFTHISSTUDY

Overpressure and high temperatures can be caused by the fire itself:

(Internal energy of the compartment)

Backdraft can happen:

- Smoke dilution in the ventilation network

- Opening of doors by rescue personnels

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

24/49

CONTEXTOFTHISSTUDY

Overpressure and high temperatures can be caused by the fire itself:

(Internal energy of the compartment)

Backdraft can happen:

- Smoke dilution in the ventilation network

- Opening of doors by rescue personnels

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

25/49

CONTEXTOFTHISSTUDY

Overpressure and high temperatures can be caused by the fire itself:

(Internal energy of the compartment)

So it is important to be able to predict correcly the power generated by the fire.

Backdraft can happen:

- Smoke dilution in the ventilation network

- Opening of doors by rescue personnels

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

26/49

CONTEXTOFTHISSTUDY

- Interaction between the fire and its confined environment

which is under-oxygenated and polluted.

- Aeraulic pertubation caused by the mechanical ventilation

Overpressure and high temperatures can be caused by the fire itself:

(Internal energy of the compartment)

So it is important to be able to predict correcly the power generated by the fire.

Difficulty:

Backdraft can happen:

- Smoke dilution in the ventilation network

- Opening of doors by rescue personnels

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

27/49

CONTEXTOFTHISSTUDY

- Interaction between the fire and its confined environment

which is under-oxygenated and polluted.

- Aeraulic pertubation caused by the mechanical ventilation

Overpressure and high temperatures can be caused by the fire itself:

(Internal energy of the compartment)

So it is important to be able to predict correcly the power generated by the fire.

Difficulty:

Backdraft can happen:

- Smoke dilution in the ventilation network

- Opening of doors by rescue personnels

Journ

e

des

Doctor

an

ts

CORIA

201

3

8/11/2019 JDD - Alvin

28/49

CONTEXTOFTHISSTUDY

- Interaction between the fire and its confined environment

which is under-oxygenated and polluted.

- Aeraulic pertubation caused by the mechanical ventilation

Overpressure and high temperatures can be caused by the fire itself:

(Internal energy of the compartment)

So it is important to be able to predict correcly the power generated by the fire.

Difficulty:

Backdraft can happen:

- Smoke dilution in the ventilation network

- Opening of doors by rescue personnels

Journ

e

des

Doctor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

29/49

1. Behavior of underventilated fires in a

mechanically-ventilated compartment. Underventilated fires in confined

compartments must occur before the

conditions favourable to Backdraft can

be created.

Experimental study using a reduced-

scale 1m3compartment (fire chamber)

OBJECTIVESOFTHISSTUDY

Journ

e

des

Doctor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

30/49

8/11/2019 JDD - Alvin

31/49

CONTENTSOFTHISPRESENTATION

What is a Backdraft?

Context and Objectives of this study

Experimental apparatus for underventilated fires

Some Results of underventilated fires

Experimental apparatus for smoke deflagration

Journ

e

des

Doctor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

32/49

Diagram of the experimental apparatus for studying underventilated fires in a

reduced-scale mechanically-ventilated compartment (fire chamber)

EXPERIMENTALAPPARATUSFORFIRES

Compartment made of steel - 1m2 steel plates are fixed onto a frame

Braids are crushed between the steel plates and the frame to ensure air-tightness

Refractory ceramic fibres on the inner wall to ensure thermal insulation.

Water seal between the scale and the fuel to ensure air-tightness

Journ

e

des

Doctor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

33/49

CONTENTSOFTHISPRESENTATION

What is a Backdraft?

Context and Objectives of this study

Experimental apparatus for underventilated fires

Some Results of underventilated fires

Experimental apparatus for smoke deflagration

Journ

e

des

Doc

tor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

34/49

Fuel Mass Loss Rate (MLR) estimation of pool fires (Hamins 1996) :

Smoke

Fuel

flameQ

reflectQ

smokeQ

SOMERESULTSFORUNDERVENTILATEDFIRES

One example of study: Determination of the fuelsMass Loss RateJourn

e

des

Doc

tor

an

ts

CORIA

2

01

3

Fuelsmass loss rate is caused by

the heat flux from various sources:

flame, smoke, compartment walls

The fuel reflects and reradiatessome part of the heat away.

wallQ

8/11/2019 JDD - Alvin

35/49

SOMERESULTSFORUNDERVENTILATEDFIRES

ARR = 5

ARR = 0,3

ARR =11

MLR at Free-burning (fire in non-enclosed area)

- Flames are extinguished due to lack of air

- MLR in these cases do not reach free burning rates

Development of the fuelsMass Loss Rate (MLR) at different ventilation rates:

Fuel : Heptane

Size of fuel pan: 2 x 10.8cm

*ARR = Air Renewal Rate

8/11/2019 JDD - Alvin

36/49

0.2s 0.2s 0.2s

Expanding flames

SOMERESULTSFORUNDERVENTILATEDFIRESVisual results:

Flames extend outside

the perimeter of the fuel

pan periodically

Journ

e

des

Doc

tor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

37/49

8/11/2019 JDD - Alvin

38/49

0.2s 0.2s 0.2s

Expanding flames

Wandering flames:

Ghosting flames:

0.2s 0.2s 0.2s

0.2s 0.2s 0.2s

SOMERESULTSFORUNDERVENTILATEDFIRESVisual results:

Flames extend outside

the perimeter of the fuel

pan periodically

Flames move around the

compartment towards

the opposite side of the

air inlet

Flames are lifted above

the fuel pan and float

around

Journ

e

des

Doc

tor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

39/49

CONTENTSOFTHISPRESENTATION

What is a Backdraft?

Context and Objectives of this study

Experimental apparatus for underventilated fires

Some Results of underventilated fires

Experimental apparatus for smoke deflagration

Journ

e

des

Doc

tor

an

ts

CORIA

2

01

3

8/11/2019 JDD - Alvin

40/49

8/11/2019 JDD - Alvin

41/49

8/11/2019 JDD - Alvin

42/49

Fresh air

Smoke from the fire chamber

EXPERIMENTALAPPARATUSFORBACKDRAFT

Diagram of the experimental apparatus (under construction):

Journ

e

des

Doc

tor

an

ts

CORIA

2

013

8/11/2019 JDD - Alvin

43/49

Methane gas

Fresh air

Smoke from the fire chamber

EXPERIMENTALAPPARATUSFORBACKDRAFT

Diagram of the experimental apparatus (under construction):

Journ

e

des

Doc

tor

an

ts

CORIA

2

013

8/11/2019 JDD - Alvin

44/49

E B

8/11/2019 JDD - Alvin

45/49

EXPERIMENTALAPPARATUSFORBACKDRAFT

What do we wish to study?

(thesis of Courty 2012)

1) Conditions of Backdraft :- Concentration of the different species

- Temperature

- Soot properties (size distribution, mass concentration)Gas analyser Testo 350

Thermocouples

2) Flame propagation

- Dynamic pressure (pressure increase during the

deflagration)

- Flame speed-Ombroscopy technique (thesis of Courty 2012)

-PIV technique (thesis of Varea 2013)

(thesis of Varea 2013)

Dynamic pressure sensor

Journ

e

des

Doc

tor

an

ts

CORIA

2

013

E B

8/11/2019 JDD - Alvin

46/49

EXPERIMENTALAPPARATUSFORBACKDRAFT

Role of soot -- What do we wish to determine?

We suspect that during the deflagration, the thermal radiation of soot cancontribute to the heating the fresh gases, thus increasing the flame speed.

+

?

Journ

e

des

Doc

tor

an

ts

CORIA

2

013

E B

8/11/2019 JDD - Alvin

47/49

EXPERIMENTALAPPARATUSFORBACKDRAFT

Role of soot -- What do we wish to determine?

We suspect that during the deflagration, the thermal radiation of soot cancontribute to the heating the fresh gases, thus increasing the flame speed.

Heating of the fresh gas can be caused by radiation

Combustion productsFresh gas

SL

Pre-heating zone Reaction zone

Flame propagation mecanism:

+

?

Journ

e

des

Doc

tor

an

ts

CORIA

2

013

E B

8/11/2019 JDD - Alvin

48/49

EXPERIMENTALAPPARATUSFORBACKDRAFT

Role of soot -- What do we wish to determine?

We suspect that during the deflagration, the thermal radiation of soot cancontribute to the heating the fresh gases, thus increasing the flame speed.

Heating of the fresh gas can be caused by radiation

The radiation emission and

absorption of soot increase the

radiated heat received by the freshcombustible mixture

More powerful deflagration ?

Combustion productsFresh gas

SL

Pre-heating zone Reaction zone

Flame propagation mecanism:

+

?

Journ

e

des

Doc

tor

an

ts

CORIA

2

013

8/11/2019 JDD - Alvin

49/49