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MECHANICAL SMOKE EXTRACTION FOR

LARGE FIRE LOADS IN THE GOTTHARD

BASE TUNNEL

6th International Conference

TUNNEL SAFETY AND VENTILATION

Graz, Austria: 23. – 25.04. 2012

Christoph Brander, Pöyry Infra AG, Switzerland

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

1


CONTENT

The exhaust system at the Gotthard Base Tunnel

Subject of investigation

Simulation and modeling

– Smoke exhaust plenum

Results

– Exhaust gas temperatures

– Concrete and rock temperatures

– Mass and volume flow, exhaust fan operating point

Measures

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

2


THE EXHAUST SYSTEM AT THE GOTTHARD BASE TUNNEL (1)

Two single-track tunnels,

length 57 km

2 multifunction stations

4 emergency stations

2 ventilation stations

(Faido, Sedrun)

8 fans, of which 4 smoke

exhaust fans with flow

rate of 250 m 3 /s

Installed mechanical

power up to 2500 kW

Lengt of smoke exhaust

plenums: 2150 – 4340 m

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

3


THE EXHAUST SYSTEM AT THE GOTTHARD BASE TUNNEL

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

4


SUBJECT OF INVESTIGATION

Scenario of the study: Activ smoke exhaust system with a fire on a…

– …passenger train. Fire load 20 MW within 70 min, up to 40 MW within 360 min.

Total fire length: 480 min.

– …freight train or a train carrying heavy good vehicles: Fire load 250 MW within 30

min. Total fire length: 180 min.

Subject of investigation:

– Air and concrete temperatures in the smoke exhaust plenums

– Aerodynamic behaviour of the system (pressure loss, fan operation point,

bouyancy…)

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

5


NUMERICAL SIMULATION

Boundary conditions

– Complex exhaust plenum

system

– High air temperatures

– Variation in air/smoke density

– Altitude difference

– Variation in pressure drop

– No regulation of the fans

(constant caracteristic)

Numerical simulation:

– Aerodynamic model 1D in flow

direction

– Combined thermodynamic

models for concrete and rock

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

6


RESULTS – EXHAUST GAS TEMPERATURE (1)

Significant cooling of the

exhaust gas

Large length of the

exhaust system

Maximum exhaust gas

temperature rises with

time due to lower mass

flow

(1) Partition wall, multifunctional station

(2) Access tunnel

(3) Exhaust fan

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

7


RESULTS – EXHAUST GAS TEMPERATURE (2)

Fire diminishes after

180 min

Increasing

temperatures

Large amounts of heat

stored in the concrete

surrounding

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

8


RESULTS – CONCRETE AND ROCK TEMPERATURE

Critical variable for assessing the impact of the fire on the concrete

Small fraction of heat arrives at a depth of 30 cm

Radial shell model and linear layer model lead to almost identical results,

distinction is important for longer observation periods and smaller

dimensions

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

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RESULTS – EXHAUST GAS DENSITY / VOLUME FLOW

Exhaust gas density > 1kg/m 3 at fan station

Decreasing mass flow with increasing temperatures

exhaust gas density

volume flow

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

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RESULTS – VOLUME FLOW, FAN OPERATION POINT

Increasing system pressure loss,

Aerodynamic and engine power capacity needed

Maximum bouyancy:1670 Pa (Faido) and 5000 Pa (Sedrun)

3 % system pressure change with 40 MW fire load

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

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THANK YOU FOR YOUR ATTENTION!

CONTACT:

Name: Christoph Brander

Mail: christoph.brander@poyry.com

Phone: 0041 76 356 2217

Mechanical smoke extraction for large fire loads in the Gotthard Base Tunnel

23.-25.April 2012

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