ICHS4, San Francisco, Sept. 12-14th, 2011Ruban, S.1, Heudier, L.2, Jamois, D.2, Proust, C.2, Bourhy-Weber, C.1 ,Jallais, S.1,Kremer-Knobloch, K.3,

Maugy C.3, Villalonga, S.4

1Air Liquide R&D, CRCD, Jouy en Josas, France 2 INERIS, Verneuil-en-Halatte, France

3 PSA PEUGEOT CITROEN, Carrières-sous-Poissy, France4 CEA, Le Ripault, Monts, France

Fire risk on high-pressure full

composite cylinders for automotive applications

PAN-HPAN-H

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 2

Epoxy resin/carbon

fiber composite wall (few cm)

Context

The high-pressure (70 MPa/10.1 kpsi) fully wrapped epoxy resin/carbon fiber composite cylinder is currently the preferred option for fuel cell electric vehicle

Epoxy resin/carbon fiber composites cylinder

Liner: H2 tightness (feu mm)

CostGravimetric

capacity

Volumetric capacity

Light weight Excellent mechanical performanceHigh capacity of H2 storageGood chemical and electrical resistance

H2 vehicle refilling station

Type 2Type 1 Type 4Type 3Type 2Type 1 Type 4Type 3

Cylinder connector

Fire safety strategy: preventing the cylinder from bursting

Releasing hydrogen through a thermal pressure release device (TPRD) and/or using a thermal

protection

Epoxy resin/carbon

fiber composite wall (a few cm) Liner: H2 tightness

(a few mm)

Cylinder connector

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 3

OBJECTIVE: DESIGN FOR SAFETY

TPRD Design: size of orifice and delay to opening avoiding cylinder burst Current TPRD orifice diameter: 3.6 to 6 mm => 11 to 18 m initial flame length

Safe H2 release through TPRD Reduce the H2 flow-rate released though TPRD or allow a longer release

duration in order to decrease the flame length

Increase knowledge on behavior of cylinder in fire without TPRD Current standard drafts (ISO/DIS 15869.3, CGH2R-12b, SAE J2579) and regulations (EC 79/2009) define

testing for fire impact on cylinders equipped with TPRD Current tests do not allow the proper design of the TPRD orifice and opening delay or thermal

protectionTests

Evaluation of the duration of cylinder resistance in fire, depending on initial pressure in the cylinder Influence of partial fire Validation of a smaller release rate through a TPRD

TPRD H2 DYNETEK 700b

TPRD H2 CIRCLE SEAL 700b

Suzuki, IEA Task 19 – SAE 2006-01-0129Bonfire Test in INERIS, 2009

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 4

Test conditions – Assessment of the net flux received by a metallic cylinder in this bonfire

Experimental set-up Gallery: 80 m long, 3 meters high, 10 m3/s ventilation to extract

fumes Bonfire: Heptane pan (0.6 x 1.2 m2), protected with baffles,

5.71 L/min consumption

Cylinder characteristics Steel cylinder sealed at both ends Diam: 330 mm, Length 900 mm, Thickness 12 mm Filled with air, pressure measurement

Results Themal load is reproducible and not constant with time Heat flux reached a maximum of 120 kW/m2 after 200 seconds The heat flux then decreased as the outside wall temperature

increased

INERIS Test Gallery

Steel cylinder over the pan

Bonfire in the gallery

Time (s)

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 5

Bonfire tests on composite cylinders

Composite cylinder: 70 Mpa, 36L, 34 kg, type IV, design coefficient: 3Experimental set-up

Cylinder pressured with Helium at 700 bar, 350 bar or 175 bar

Cylinder engulfed in fire or partially in fire (one half protected by a thermal shield)

No venting or venting with a 0.5 mm orifice opening 90 s after the start of the fire

5 Thermocouples (type IV – 1mm) positioned on the cylinder and one place 50 mm under the cylinder

Pressure inside the storage monitored

Global bonfire test

Partial bonfire test

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 6

Results

Test Type of fire Initial Pressure

Burst pressure

Time before burst Pressure ratio (P(t)/Pini) extreme

values

1 Global 703 bar 703 bar 6 min 32 s 0.99 – 1.00

2 Partial 706 bar 706 bar 5 min 20 s 0.98 – 1.00

3 Global 356 bar 378 bar 9 min 49 s 0.99 – 1.06

4 Global 178 bar N/A No burst – Leaks after 11 min 4s 1.00 – 1.125

5 Global 701 bar N/A No burst - Release at 1 min 30 s, no leak

0.99 – 1.00

No pressure increase inside the composite cylinder during the first 3 minutesBursting delays are of the same order of magnitude as found by Weyandt (6 to 12 min for cylinders type III and IV, 72 L and 88 L , 35 MPa)The pressure increase before cylinder rupture or leak is at the most 12.5% after 11 minutes of fire (and was null before the opening of the release valve in test N°5)The storage does not burst for an initial pressure of 178 bar or for an initial pressure of 701 bar with a gas release through a 0.5 mm orifice after 1 min 30 s.Slight pressure drop (factor 0.98) at the beginning due to the cooling of the gas after the filling procedure

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 7

Temperatures measured at cylinder surface vary between 500 and 900°C

Temperatures measured in the flame (TC6) were above 600°C after only a few secondsFor the partial fire test TC6 was placed in the immediate vicinity of the thermal shield explaining low temperatureNorm requirements:

Comply with ISO_DIS15869 (At least one thermocouple on the cylinder indicates a minimum temperature of 590 °C and is maintained for the remaining duration of the test as required in bonfire specification).

draft SAE J2579 : 800°C required was not systematically reached.

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200 250 300 350 400

time (s)

tem

pera

ture

(°C

) - p

ress

ure

(bar

)

Tc 1

Tc 2

Tc 3

Tc 4

Tc 5

Tc 6

pressure

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200 250 300 350

time (s)

tem

pera

ture

(°C

) - p

ress

ure

(bar

)

Tc 1

Tc 2

Tc 3

Tc 4

Tc 5

Tc 6

pressure

Global bonfire test

Partial bonfire test

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 8

Influence of the fire engulfing conditions

Under global fire conditions, the storage bursts one minute later than under partial fire conditions. Given the number of test involved (only one per condition) we can not rely on this unexpected resultBurst delay seems not to depend significantly on the size of the surface impacted by the fire, even if this size is divided by a factor of 2

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500

Time (s)

Pres

sure

(bar

)

Partial fire

Global fire

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 9

Influence of initial pressure

The higher the initial pressure, the shorter the resistance timeFor initial pressure under 178 bar, the gas leaks through the composite laminate and the cylinder does not burst

Global bonfire test

Composite after fire

Leak test after fire

0

0,2

0,4

0,6

0,8

1

1,2

0 500 1000 1500

Time (s)

P(t)

/ Pin

i

Pini=706 bar partial bonfirebarPini=703 bar bonfire bar

Pini=356 bar bonfire bar

Pini=178 bar bonfire bar

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 10

Controlled releaseThe 178 bar test gives a pressure/time threshold for the composite cylinder corresponding to the maximum pressure reached during the test : 200 bar and 11 minutes. To avoid a burst, a TPRD should detect the high temperature and allow the release of H2 to decrease the cylinder pressure down to 200 bar in less than 11 minutes. A 0.5 mm TPRD orifice opening at 90 s prevented the cylinder from bursting

Difference between the theoretical release and measured release (with or without fire) may be due to the temperature decrease in the cylinder induced by depressurization or to the reel orifice size being slightly different as specified (e.g. 0.6 mm)

0

100

200

300

400

500

600

700

800

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Time (s)

Cyl

inde

r pre

ssur

e (b

ar)

Threshold point

Theoretical Helium release at 90s through0,5mmTest bonfire - 700 bar with He release at 90sthrough 0,5mmTest without fire - 700 bar with He release at90 s through 0,5 mmTest bonfire - 175 bar without He release )1(2

15.0

01

1

11

12

)()()(

RTMW

AVC

Ctt

ExpttPtP

Theoretical release modeled as an isentropic release and sonic flow of ideal gas

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 11

CONCLUSION

The resistance time of a composite cylinder is of the same order of magnitude for a localized fire (where only half of the cylinder is exposed to fire) and for a global bonfire. The cylinder as a whole needs to be protected from localized fire impact, possibly achieved by a thermal protection.The release of hydrogen through an orifice with a diameter of 0.5 mm and opening at 90 seconds prevented the studied 36 L cylinder from bursting.This diameter represents a decreased factor of 10 compared to current practice, allowing the flame length and consequently the safety distance in case of fire to be decreased by the same factor. In order to be safer in case of TPRD release, one can adapt the design of the TPRD to the characteristics of the cylinder. Reducing the orifice diameter, we also reduce the safety margin to avoid burst, so we have to accurately design the storage protections.

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 12

Acknowledgements

To ANR (French National Research Agency) for its financial support through Plan d’Action National sur l’Hydrogène et les piles à combustibles program (project HYPE ref ANR07 PANH006)

To INERIS (Institut National de l’Environnement Industriel et des Risques) for the tests performed and their continuous support

PAN-HPAN-H

S. Ruban – ICHS2011, Paper No. 251, Sept. 14th 2011 13

Thank you!

Sidonie Rubansidonie.ruban@airliquide.com