Feasibility study

Feasibility study

A SMOKE EXTRACTION SYSTEM FOR FCC

EDMS No 1396658S. La Mendola DGS/SEEA. Henriques DGS/SEE 1

EDMS No 1396658S. La Mendola DGS/SEEA. Henriques DGS/SEE

Smoke propagation in case of longitudinal ventilation

2

Advantages for 100 % longitudinal ventilation system, with respect to Safety- Provides fresh air for occupants during access

Disadvantages for 100 % longitudinal ventilation system:- Propagation and contamination of smoke to others volumes of the tunnel, - Even if the ventilation is stopped , the smoke still propagates


Smoke propagation in case of longitudinal ventilation

u

Lb

Region IFr ≤ 0.9

Region II0.9 ≤ Fr ≤ 10

Region IIIFr > 10

H

Forc

edve

ntila

tion

Stratification Mixing

Fr = Froude number: ratio between flow inertia and buoyancy

The back layering length (Lb) is limited to a few tens of meters upstream the fire at worst

See also the presentation «A simplified model for tunnel fire dynamics predictions» by S. La Mendola EDMS 1278776

From the presentation by F. Corsanego EDMS 1236477 ver. 1

10 kW

50 kW

100 kW

500 kW

1 MW

5 MW

3

Ventilation ON – 1.2 m/s

https://edms.cern.ch/document/1278776/1



Smoke propagation in case of ventilation stop4 m2 petrol pool fire (about 10 MW),The handbook of tunnel fire safety

From the presentation by F. Corsanego EDMS 1236477 ver. 1

1 MW Fire

Smoke propagates along 300 m in both directions after about 12 minutes in a tunnel with a 6 m diameter

300 m

Fire origin

10 kW50 kW100 kW

500 kW1 MW5 MW

4



Smoke propagation in case of transverse ventilation

Advantages for 100 % transverse ventilation system, with respect to Safety- Limit the propagation and contamination of smoke to others volumes of the tunnel- Provide dynamic confinement localized near the fire

Disadvantages for 100 % transverse ventilation system:- Large ducts are needed occupy ~50 % of the tunnel volume- Tunneling costs

5


Smoke propagation in case of transverse ventilation

Fresh air supply duct

Vitiated air exhaust duct

Fresh air supply duct

Vitiated air exhaust duct

Smoke extraction solution proposed for CLIC,CLIC Conceptual Design Report – Geneva 2012

Normal operations Fire conditions

6

http://project-clic-cdr.web.cern.ch/project-clic-cdr/

http://project-clic-cdr.web.cern.ch/project-clic-cdr/

7

A proposal for a “Hybrid” smoke extraction system

- Longitudinal Ventilation for normal operations Provide the requirements for occupational health – Fresh air,

temperature, humidify

- Dedicated smoke extraction system Limit propagation and contamination of smoke to others volumes of

the tunnel Provide the dynamic confinement Reduce the cross section of the smoke extraction ducts.


Proposal - Dedicated extraction system- Example of a section of the FCC tunnel:

Nominal conditions

…

Shaft

Tunnel

Dedicated smoke extraction ductSmoke control dampers

Fresh air


Dedicated smoke extractor

Length of Smoke Compartment

…

Proposal - Dedicated extraction system- Example of a section of the FCC tunnel:

Accidental scenario – e.g. Fire Longitudinal ventilation is stopped Smoke extraction is ON

Dynamic Confinement



…

Proposal - Dedicated extraction system

- Fire Detection system : Shall be able to identify the fire location within a

certain length, to ensure that the dampers open in the correct location



…









…


Feasibility Assessment First approximation for extraction flow rate: 1 m3/s/100 m2 French “Code du travail ”

Velocity in the extraction duct of 10 m/s

0 100 200 300 400 500 6000

0.5

1

1.5

2

2.5

0

20000

40000

60000

80000

100000

120000

Ø duct [m]Q [m3/h]

Length Smoke Compartment [m]

Duc

t dia

met

er [m

]

Extr

actio

n flo

w ra

te [m

3/h]


Pressure Drop Linear pressure drop only, assuming maximum duct length of

8 km , where Q is the volume flow rate.

0 0.5 1 1.5 2 2.50

20000

40000

60000

80000

100000

120000

Duct diameter [m]

Pres

sure

dro

p [

Pa]

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.50

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Duct diameter [m]

Pres

sure

dro

p [

Pa]

Zoom


Evaluation of smoke volume production - Mathcad model

Smoke extraction flow rate = 11 m3/s for a tunnel diameter of 6 m and 8 m3/s for a diameter of 4.5 m.That gives a smoke compartment length of about 200 m taking into account the flow rate requirement from the code du travail (1 m3/s/100m2)


See “An introduction to fire dynamics”, D. Drysdale

Fire Dynamics Simulation (FDS) model


Fire Dynamics Simulator (FDS), developed by the National Institute of Standards and Technology (NIST) of the United States Department of Commerce, is a computational fluid dynamics (CFD) model of fire-driven fluid flow. The software solves numerically a large eddy simulation form of the Navier-Stokes equations appropriate for low-speed, thermally-driven flow, with an emphasis on smoke and heat transport from fires.

200 m to 600 m

Constant power 1 MW fire@ 100 m

No longitudinal ventilation

F = 6 m

Up to 1’372’800 cells

Virtual measurement stations (temperature, velocity, concentration of species, etc.)

Open ends boundary conditions, 4 smoke extraction dampers

http://en.wikipedia.org/wiki/Fire_Dynamics_Simulator

http://en.wikipedia.org/wiki/National_Institute_of_Standards_and_Technology

http://en.wikipedia.org/wiki/Large_eddy_simulation

http://en.wikipedia.org/wiki/Navier-Stokes_equations

http://en.wikipedia.org/wiki/Navier-Stokes_equations

Preliminary simulationsn D [m] Fire Type Peak HRR [MW] L [m] Vvent [m/s] xF [m] Extr. Flowrate [m3/s] Duration [s] Note Extr. Damp. Area [m2] extr. V. [m/s]1 6 Constant 1 200 0 100 12 600 1 m x 0.25 m 0.25 12.02 6 Constant 1 200 0 100 14 600 1 m x 0.25 m 0.25 14.03 6 Constant 1 200 0 100 16 600 1 m x 0.25 m 0.25 16.04 6 Constant 1 200 0 100 18 600 1 m x 0.25 m 0.25 18.05 6 Constant 1 200 0 100 20 600 1 m x 0.25 m 0.25 20.06 6 Constant 1 200 0 100 22 600 1 m x 0.25 m 0.25 22.07 6 Constant 1 200 0 100 22 600 Version a 1.5 m x 0.5 m 0.75 7.38 6 Constant 1 200 0 100 22 600 Version b 1.5 m x 1 m 1.5 3.79 6 Constant 1 200 0 100 36 600 1.5 m x 1 m 1.5 6.0

10 6 Constant 1 200 0 100 24 1200 12h 1.5 m x 1 m 1.5 4.011 6 Constant 1 200 0 100 24 2400 24h 1.5 m x 1 m 1.5 4.012 6 Constant 1 200 0 100 24 2400 Modeled duct 1.5 m x 1 m 1.5 4.0

13 6 Constant 1 200 0 100 12 2400Modeled duct + external fresh air

immission 1.5 m x 1 m 1.5 2.014 6 Constant 1 200 10 [m3/s] 100 12 2400 Simulation of longitudinal air 1.5 m x 1 m 2.5 1.215 6 Constant 1 400 7 200 12 2400


Q/4

50 m 50 m 50 m 25 m25 m

Constant 1 MW fireNo longitudinal ventilation

Q/4 Q/4 Q/4

Ope

n bo

unda

ry c

ondi

tion

Ope

n bo

unda

ry c

ondi

tion

Preliminary simulations results: the problem of extraction efficiency

12 m3/s

24 m3/s

36 m3/s (!)


Left tunnel opening Smoke extraction station

Smoke extraction station

Fire location

• For a smoke extraction flow rate up to 24 m3/s, smoke propagates beyond the smoke compartment.

• A flow rate of 36 m3/s would be necessary to confine smoke in this configuration (extraction efficiency between 1/2 and 1/3).

• In this configuration (36 m3/s ), the smoke extraction duct would be too big (φ ≈ 3 m) and that would reduce greatly the utility of the proposed system.

• Smoke curtains are proposed to keep the extraction flow rate at a feasible value (12 m3/s).

Smoke propagatesoutside the smoke compartment

Smoke confined

Smoke curtains (EN 12101-1): a possible solution

Pictures taken from the paper “Flexible Devices for smoke control in road tunnels”,

M. Bettelini et Al, AMBERG Engineering


http://www.google.ch/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&cad=rja&uact=8&ved=0CCMQFjAA&url=http://lampx.tugraz.at/~tunnel2014/history/Tunnel_2012_CD/PDF/38_Bettelini.pdf&ei=kKi6U5jYBMa60QWCiIDoAQ&usg=AFQjCNEt9xFU5crTfgsqwmG1_2j-GQmn3w&bvm=bv.70138588,d.d2k

Smoke curtains (EN 12101-1): a possible solution


EN 1

2101

-1EN

121

01-1

Fixed smoke curtain

Roller smoke curtain

Fire resistance test

Similar solution used for the ESS


Smoke curtains: a possible solution

Full confinement within the 200 m compartment for a 1 MW fire and 12 m3/s

Height from floor of design smoke layer = 2 m

Full confinement within the 200 m compartment for a 2 MW fire and 12 m3/s

Partial confinement within the 200 m compartment for a 5 MW fire and 12 m3/s

This system provides a good smoke confinement also in off-design conditionsEDMS No 1396658

S. La Mendola DGS/SEEA. Henriques DGS/SEE 22

Modeled smoke curtain.

H = 5 m

h = 2 m

Smoke curtainH - h = 3 m

Extraction duct Ø 1.2 m

Smoke extraction duct – cross section to scale


• Extraction flow rate of 12 m3/s;• Velocity in duct of 10 m/s;

• Linear pressure drop of ≈ 6 kPa;• Smoke compartment length of 200 m

Considering:

Provides an extraction duct of 1.2 m

Smoke extraction duct – smoke curtains layout


Roller curtainFixed curtain

Future activities

• Quantitative design optimization (n. of smoke extraction dampers, dimensions, distance, n. and dimension of smoke screens, etc.) with respect to soot propagation.

• System virtual test w.r.t to different “real” fires: electrical cabinet, cable trays (different length and height), etc.

• Take into account the delay of the fire detection system and the inertia of the ventilation system.

• Study on the compatibility of the smoke extraction system with a cryogenic release.


Documents

Feasibility study