Second International Conference on Hydrogen Safety, San Sebastian,

Spain, 11-13 September 2007

CFD for Regulations, Codes and Standards

A.G. VenetsanosNational Centre for Scientific Research “Demokritos”, Greece

A. KotchourkoResearch Centre Karlsruhe, Germany

C.D. MoenSandia National Laboratories, US

Slide 2

Presentation Outline

It will be shown that CFD is increasingly applied to provide the necessary support to RCS development: EIHP-2 project HyApproval project HyPer project

It will be shown that CFD tools are increasingly validated against H2 dispersion/combustion phenomena HySafe project

ICHS-2 Session 1 What we are going to see/listen

Venetsanos et al. (ICHS-2, 2007) An Inter-Comparison Exercise On the Capabilities of CFD Models to

Predict the Short and Long Term Distribution and Mixing of Hydrogen in a Garage

Slide 3

EIHP2 project: CGH2 bus in a city

Taken from Venetsanos et al. (2007) J. Loss Prevention in the Process Industry, In Press

Fuel-Pressure

(MPa)

Energy (MJ)

Fireball OverpressureAverage diameter

at 2.0m above ground (m)

Maximum diameter at any

height above ground (m)

Distance to 2kPa

overpressure (m)

Distance to 21kPa

overpressure (m)

Distance to 35kPa

overpressure (m)

H2-20 1460 12.7 a 18.8 75 7 3H2-35 1760 10.5 a 15 91 8 3H2-70 2220 16.0 a 21.5 100 9 5

CH4-20 754 11.0 a 15 65 L L

H2, 20MPa, 10.9s, 12.1 kg

LFL cloudsRelease of 40 kg H2 (168 kg CH4) through 4 outlet vents at the top of the bus (Stockholm accident site)

H2, 35MPa, 7.7s, 14.7 kg H2, 70MPa, 5.2s, 18.5 kg

CFD applications

CH4, 20MPa, 7.9s

Bus storage system

Urban site (Stockholm) showing assumed bus location

Slide 4

EIHP2 project: CGH2 bus in tunnel

Taken from Venetsanos et al. (2007) J. Loss Prevention in the Process Industry, In Press

H2, 35MPa, 30s, 2180m3, 32.5kg

H2, 20MPa, 40s, 2358m3, 32.4kg

CH4, 20MPa, 40s, 1756m3, 110kg

FUEL PRESSURE (MPa)

ENERGY (MJ)

FIREBALL OVERPRESSURELength Along The

Tunnel (m)Peak Overpressure

(kPa)

H220 3890 220a 42.535 3900 285a 150

NG 20 5380 198 45

LFL cloudsRelease of 40 kg H2 (168 kg CH4) through 4 outlet vents at the top of the bus

CFD applications

Slide 5

HyApproval project: Examined scenarios

Dispenser: rupture of dispensing line (CGH2 35 and 70 MPa, LH2)

Trailer: Hose disconnection during discharge (CGH2 20 MPa, LH2)

CFD applications

Luxemburg CGH2 site

Washington DC, LH2 site

Shell-HSL experimental site (2006)

Taken from HyApproval Deliverable 4.6, 2007

Slide 6

HyApproval project: LH2 dispenser leak

267g LH2 released in 5 seconds (hose id = 8mm)

CFD applications

5 m/s wind at 10m heightPredicted LFL clouds at 5 sec

South wind North wind

East wind

Scenario DL8

0

1

2

3

4

5

0 1 2 3 4 5time (s)

Max

ver

tica

l dis

tan

ce o

f L

FL

fr

om

so

urc

e (m

)

D5 EastD5 WestD5 SouthD5 NorthStagnant

Scenario DL8

0

5

10

15

20

0 1 2 3 4 5time (s)

Max

ho

rizo

nta

l dis

tan

ce o

f L

FL

fro

m s

ou

rce

(m)

D5 EastD5 WestD5 SouthD5 NorthStagnant

StagnantWest wind

Taken from HyApproval, NCSRD-JRC report, 2007

Slide 7

Fuego 3-D RANS simulation of

H2 Jet Flame Wall ImpingementSandia/SRI H2 Jet Flame

Wall Impingement Test (2500 psi)

625

- 625

X (cm)

Z (cm)767.3

0

Y (cm)

-122

625

Barrier

Jet Exit (0,0,0)

Symmetry Plane(Side)

Open Boundaries(Top and Sides)

No Slip Boundary(Bottom)

HYPER project: Barrier wall design● Jet flame experiments are used to validate CFD methodology for jet flames from

high-pressure sources.

● CFD calculations are used characterize consequences of unintended releases.

● Barrier walls are a potential mitigation strategy for jet releases.

Taken from Houf et al., 2nd ICHS, 2007

CFD applications

Slide 8

Hyper project: Fuel Cell Leak

14.8g H2 released in 60 seconds

CFD applications

Fuel cell located inside naturally ventilated test facility

Naturally Ventilated Test Facility (CVE)

Location and Interior of Fuel Cell

Slide 9

HySafe project: Dispersion CFD benchmarking

SBEP Description

Phenomena / Environmental Conditions

Low momentu

m jets

Sonic jets

Confinement

StratificationNatural

VentilationObstacles

Two-phase flow

V1Russian-2, 1988

and 2005

V3 INERIS-6C, 2007

V4 FZK jets, 2006

V5GEXCON-D27,

2007

V6BAM-5, LH2

close to buildings

E1NASA-6 LH2 in

open space

E2 Swain Hallway

V10 HSL jets

V11

Bus in an underpass QRA

exercise GEXCON

Slide 10

HySafe project: Combustion CFD benchmarking

SBEP Description

Phenomena / Environmental Conditions

Unconfined

combustion

Partial confinement/

Venting

Complete confinement

Slow flames

Fast flamesFlame

acceleration

DDTDetonation

Scale

V2 Fh-ICT balloon, 1985

V7HSL-SHELL HRS

tests, 2006

V8 FZK tube tests, 2006

V9Fh-ICT Jet ignition in a lane with DDT, 1984

V12Tunnel tests, Groethe

et al. 2005

V13KI DDT tests hyd5

and hyd9, 1995

V14Vented explosion

Pasman et al, 1974

V15Bus in an underpass

QRA exercise GEXCON

Main parameters important from the point of view of safety analysis:

Slide 11

Conclusions

CFD is increasingly applied for H2 safety studies and RCS support

Main reasons: CFD has the ability to treat complex scenarios, which simpler

integral tools cannot handle CFD cost is relatively lower than experiments CFD tools present generally realistic simulation times CFD tools/models are increasingly validated against H2

dispersion/combustion phenomena

Slide 12

ICHS-2 Session-1 Contents CFD applications

Analysis of naturally ventilated h2 from buildings, Barley et al. CFD simulations of h2 release and dispersion inside the storage room of a HRS,

Papanikolaou and Venetsanos Simulation of detonation after an accidental h2 release in enclosed envirnments, Bιdard-

Tremblay et al. CFD simulation study to investigate the risk from h2 vehicles in tunnels, Hansen et al. High pressure h2 jets in the presence of a surface, Benard et al

CFD validation HYSAFE SBEP-V3 results, Venetsanos et al HYSAFE SBEP-V5 results, Jordan et al Validation of CFD calculations against ignited impinging jet experiments, Middha et al. Numerical study of spontaneous ignition of pressurized h2 release into air, Xu et al. CFD modelling of h2 dispersion experiments for SAE J2578 test methods development,

Tchouvelev et al. Experimental work

Processes of the formation of large unconfined clouds following a massive spillage of liquid hydrogen on the ground, Proust et al.

Experimental study of jet-formed hydrogen-air mixtures and pressure loads from their deflagrations in low confined surroundings, Friedrich et al.

Experimental and numerical investigation of h2 Gas Auto-Ignition, Golub et al Unintended Releases of hydrogen, Houf et al