Large-Scale Testing: Part II - HySafe - Safety of Hydrogen ...€¦ · Hydrogen Release Experiments...

© 2008 SRI International

Large-Scale Testing: Part IIMark GroethePoulter LaboratorySRI InternationalMenlo Park, CAUSA

21-30 July 2008University of Ulster

Belfast, UK

3rd ESSHS

2© 2008 SRI International

Outline

•Experiments– Large Release

– Confined Explosions

•Summary


Release Experiments


Hydrogen Release Experiments

• Tests have been performed to simulate large-

and small-scale hydrogen accidents.

• Tests involve rapidly releasing and igniting

large amounts of hydrogen over a relatively

short period of time.

• Tests have been performed to study the blast

and thermal radiation produced by the ignition

of high-pressure hydrogen releases.

• Release rates are designed to match the

release from a rupture of hydrogen storage

facilities and vehicles.

• Tests have been done to study the interaction

of jets with barrier walls.

IR U

V

Visibl

e

IR

R. Schefer, W. Houf, B. Bourne, and J. Colton, “Experimental measurements to characterize the thermal and

radiation properties of an open flame hydrogen plume,” 15th NHA Meeting, Los Angeles, CA, 26-30 April 2004.


Flame Length Ratio

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 20 40 60 80 100 120

Luv/LIRave_time_HV_04/03.qpa

Horizontal Jet

Vertical Jet

L UV/L

IR

Time (sec)

• The ratio LUV/LIR is comparable

in horizontal and vertical flame

orientations.

• At early blow-down times UV

flame lengths are shorter.

• At later blow-down times UV

and IR flame lengths are

comparable.



Flame Length Ratio


Flame Width-to-Length Ratio

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 20 40 60 80 100 120

WIR/LIR_time_HV_04/03.qpa

Horizontal JetVertical Jet (0 deg)Vertical Jet (90 deg)

WIR

/ L IR

Time (sec)

0.17

• Flame width-to-length ratio for

H2 flames is 0.17 and is

independent of flow rate and

jet diameter.

• The value WIR/LIR = 0.17 agrees

well with literature values for a

range of fuels, jet diameters,

and flow rates.



Flame Width-to-Length Ratio


Visible Flame Length

Kalghatgi (1984) used flame

photographs (1/30 sec exposure)

to quantify average distance

between jet exit and visible flame

tip.

– Flame length increases

with mass flow rate.

– Flame length increases

with jet diameter.

– Flame lengths for H2

shown in plot. Results

for methane, propane,

and ethylene are similar.0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 20 40 60 80

Kalghatgi: d=5.0 mm

Kalghatgi: d=8.3 mm

Kalghatgi: d=10.0 mm

Present study: d=7.94 mm

Present study: d=7.94 mm

L vis

(m

m)

m (g/s)

d=5.0 mm

d=8.3 mm

d=10.0 mm

Lvis_mdot_lit.qpa2 : Lvis=0.89*LIR

Vertical jet

Horizontal jet





• Relative importance of jet momentum flux and buoyancy is given

by the flame Froude Number (Delichatsios, 1993)

Frf = ue fs1.5 / [ ( e/ inf)

0.25 Tf /Tinf g dJ) ]

• Define dimensionless flame length

L* = Lf fs / dJ( e/ inf)0.5

• Dimensionless flame length is a function of Frf

L* = 13.5 Frf0.4 / (1+0.07Frf

2) for Frf < 5

andL* = 13.5 for Frf > 5



Visible Flame LengthVisible Flame Length



• Frf = > 0 in natural convection limit• Frf = > in convective limit

• L* = 23 for Frf > 5

• L* = 13.5 Frf0.4 / (1+0.07Frf

2)0.2 for Frf < 5

• Flame length increases with Froude

Number

• Nondimensional flame lengths correlate

well for a variety of fuels

1

10

100

0.1 1 10 100

L*_vs_Fr.qpa2

CH4C3H8H2SRI FlameBarlow FlameLab FlameTheory

L*

FrR. Schefer, W. Houf, B. Bourne, and J. Colton, “Experimental measurements to characterize the thermal and


Visible Flame LengthL

*

Fr

L* should not exceed a value of 23. We

need to determine jet exit conditions.


Radiometer Locations: Plume Tests

10 Schmidt-Boelter-type heat flux transducers with ZnSe windows

– 6 longitudinal measurements at 2-ft intervals from nozzle

– 4 radial measurements 8 ft upstream of nozzle exit

0 2’ 4’ 6’ 8’ 10’ 12’

D D D D D D

R6 R5 R1 R2 R3 R4

8’

0

D

R1

DR2

D

R3

D

R4 3’

2’

1’



Radiometer Locations: Plume Tests


0.0

0.50

1.0

1.5

2.0

0.0 0.50 1.0 1.5 2.0 2.5 3.0

Siv&Gore_Fig2.qpa

C2H4 11.2C2H4 20.2CH4 12.5CH4 6.40C2H2 18.1C2H2 56.5i

C*

x/Lvis

Fuel S (kW)

• Experiments show C* is

independent of:

– burner diameter

– flow rate

– fuel type

– radial position

• C* only depends on axial

position

Flame Radiant Power Is Calculated Using Single Heat Flux Measurement

Sivathanu and Gore (1993)

C*(x/L) = 4 R2 qrad(x/L) / Srad

Srad = total radiative power

qrad = radiant flux at position x




Flame Radiant Power Is Calculated

Using Single Heat Flux Measurement

0.0

0.20

0.40

0.60

0.80

1.0

0.0 0.50 1.0 1.5 2.0 2.5

vert_prof_Med_4/17/03.qpa5

t=5 sect=20 sect=40 sect=60 sect=70 secBarlow (d

J=3.75 mm)

C*

x/LV I S



• Experiments show C* is

independent of:

– burner diameter

– flow rate

– fuel type

– radial position

• C* only depends on axial

position

C*(x/L) = 4 R2 qrad(x/L) / Srad

Srad = total radiative power

qrad = radiant flux at position x

Flame Radiant Power Is Calculated Using Single Heat Flux Measurement


• Radiant Fraction Xrad = Srad / mfuel Hc

• Flame Residence Time f = (rf Wf Lf ) / ( 3 ro dJ

2 uJ)

Estimate Radiant Power fromFlame Residence Time

Flame density, f

Flame width, Wf

Flame length, Lf

Jet diameter, dj

Jet velocity, uj

0

0.1

0.2

0.3

0.4

1 10 100 1000

Turns_vs_SRI/labH2 flames.qpa3

Xr_CO/H2Xr_CH4Xr_C3H8Xr_C2H4Xr_H2 (SRI Flame)Xr_H2 (Lab Flame)Xr_H2(Barlow Flame

Rad

ian

t F

ract

ion

, X

rad

Flame residence Time, G

(ms)

• Radiant fraction for H2 flames comparable to CH4 flames

• Sooty hydrocarbon flames have significantly higher Xrad



Turns and Myhr (1991)


• Characterize stabilization of H2 jet flames on barriers.

• Characterize thermal/structural integrity of barriers.

• Develop correlations for wall heights and wall stand-off

distances.

• [Verify the ability of Sandia Navier-Stokes code (Fuego)

to compute hydrogen jet flames and unignited jet

concentration.]

H2

(a)

(b)

(c)

Stabilized flame

Radiometers

H2 Jet Flames Barriers have been proposed as a mitigation

strategy for unintended releases to reduce

separation distances.

R. Schefer, M. Groethe, W. Houf, and J. Keller, “Experimental evaluation of barrier walls for risk reduction of unintended

hydrogen releases,” 17th World Hydrogen Energy Conference, Brisbane, Australia, 15-19 June 2008.

Barrier Walls: Effect of Barrier Walls on H2 Flames

Combine data and analysis with quantitative risk

assessment for barrier configuration guidance.


Nominal Delivery Pressure at Stagnation

Chamber: 140 bar

Maximum Mass Flow Rate: 0.05 kg/sec

Pst

ag (

psi

)M

ass

Flo

w R

ate

(kg

/sec

)Time (sec)

H2 Cylinder Blowdown



Schematic of Flow Delivery System


Barrier Wall Test Configurations

H2 Jet

Barrier Wall

Jet at Wall Center

H2 Jet

Barrier Wall

Jet at Wall Top

60 degrees

H2 Jet

BarrierWall

Ground

Inclined Wall

H2 Jet

Ground

Free Jet

H2 Jet

BarrierWall

Three-sided Wall

135 degrees

Inclined Wall1

Free Jet

Jet at Wall Center Jet at Wall Top

Three-sided Wall2

1 Based on NFPA 68 guidelines for barrier walls.2 Recommended by IFC 2006.




Barrier Wall Test Configurations

Free Jet

Jet at Wall Top

1 Based on NFPA 68 guidelines for barrier walls.2 Recommended by IFC 2006.

Inclined Wall1 Three-sided Wall2



Jet at Wall Center


Barrier Wall Tests: Temperature

• Effect of barrier wall on gas

temperature is limited to region

near wall surface.

• Heat transfer to wall reduces

adjacent gas temperature by

nearly 500 K.

Gas temperature for Test 1-07: Jet centered on vertical wall

2.4 m x 2.4 m cinderblock wall with jet centered on wall

Barrier Wall

Dashed line indicates freejet measurements




Barrier Wall Tests: Overpressure

• Overpressure in front of wall

exceeds 6 kPa.

• Barrier wall attenuates

pressure by factor of five.

Static and reflected pressure for Test 1-07: Jet centered on wall

2.4 m x 2.4 m cinderblock wall with jet centered on wall

Front of wall

Behind wall




Melted Cinderblock Wall

Melted cinderblock

Cracks

Wall Displacement

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

-2 -1 0 1 2 3 4 5

displacement_Test1&2.qpa

Disp1-07 (in) Displ 2-07 (in)

Dis

plc

em

en

t (i

n)

Time (sec)

Jet impacts the wall (pre-ignition)

Wall beginsd to tiltfrom heat loading

5 Hz ringoingwhen blast reaches the wall

Jet centered at top of wall



Barrier Wall Tests


InclinedWall

Igniter

Radiometers

Stagnation Chamber

Equipment setup for inclined wall atSRI test site

Inclined wall after flame impact



Barrier Wall Tests


Visible Video Image (early) Visible Video Image (late)

Inclined (60-degree) wall with jet centered

Flame extends fartherpast wall top at earlytimes.



Barrier Wall Tests


High Speed Video (500 fps)

Three-sided wall (135 degrees between sides)

t = 0.028 sec t = 0.004 sec t = 0.010 sec

t = 0.058 sec t = 0.098 sec t = 0.198 sec



Barrier Wall Tests


Barrier Wall Tests:Effect on Overpressure

• Wall-centered jet results in a factor of 2.5

increase in overpressure prior to wall.

• Overpressure generated by three-sided wall

is low at the ignition delay time studied

(variable ignition timing could change this).

• Maximum overpressure reduction was

achieved by three-sided wall (pressure

behind wall reduced by a factor of 14).

Pressure Before Wall

Pressure Attenuation




Barrier Wall Tests:Effect on Radiative Heat Flux

• Maximum radiative heat flux behind wall

occurs with jet at top of wall jet.

• Heat flux levels with all walls are well

below harmful levels.

• Walls are an effective mitigation strategy

for radiative heat flux hazards as long as

flame is confined by wall.

• Walls significantly increase heat flux levels

at leak origin.

• Heat flux levels at leak origin for jet

centered on wall exceed pain threshold

limit (19.87 kW/m2 for 2-sec exposure

time).

Heat Flux Behind Wall

Heat Flux at Jet Origin

0

1

2

3

4

5

1 2 3 4 5

R4_vs_Test.qpa

R4 (k

W/m

2 )

Test Number

Wall-topjet

Inclined wall

Wall-center jet Three-side

wall

t = 25 seconds

0

5

10

15

20

25

1 2 3 4 5

R1_vs_Test.qpa

R1 (k

W/m

2 )

Test Number

Free jet

Wall-topjet

Inclined wall

Wall-center jet

Three-side wall

t= 25 seconds




Rapid release of a large quantity of hydrogen that is ignited

Description and Summary

• 300 Nm3 H2 (27 kg) are released in about

30 sec.

• Spontaneous ignition occurs for all

experiments. Possible sources could be

static discharge, friction heating of

particulates, other?

• Significant overpressures result on ignition

Release

valve

EstimatedFlame Jet

18-m tower

Sample station

Sample station

NozzleIgniters (15mJ)

Pressure and heat flux gauges

Sample station

Large Release Experiments

M. Groethe, E. Merilo, J. Colton, S. Chiba, Y. Sato and H. Iwabuchi, “Large-scale hydrogen deflagrations and

detonations,” International Journal of Hydrogen Energy, Volume 32, Issue 13 (September 2007) pp. 2125-2133.


High-Speed Video Frames

Large Release Experiments

451.724 ms385.084 ms 404.124 ms 756.364 ms375.564 ms

18 m

Spontaneous

ignition




Heat FluxOverpressure

Flame Speed



Large-Release Test


Confined Explosion Experiments


Confined Explosion Experiments

• Studies of hydrogen release and deflagrations in confined areas

• Vehicle tunnels and buildings

• Homogeneous hydrogen-air mixtures and hydrogen releases representing leaks from

fuel-cell vehicles and fuel transports

• Models of vehicles and actual vehicles to investigate turbulent enhancement

• Passive and active ventilation approaches

Tunnel Garage


Parameters that were varied:

• Blockage ratio: 0.32, 0.47, & 0.65

• Obstacle spacing: 38 cm, 76 cm, & 152 cm

• H2 concentration: 20%, 30%, & 57%

• End conditions, closed or open

Tube

Closed endObstacle

Open end

Purpose: Assess confined turbulent combustion

Tube Experiments

Mixing

tube

Tube

M. Groethe, J. Colton, and S. Chiba, “Hydrogen deflagration safety studies in a confined tube,”

14th World Hydrogen Energy Conference, Montreal, Québec, 9-13 June 2002.


Tube Sensors

Obstacle

Thermocouple Pressuresensor

Ion probe

Ion pin




Tube End Conditions

• Ignition end was closed

• Output end was opened just prior to ignition by

rupturing a tightly stretched latex rubber diaphragm

Latex diaphragm Diaphragm ruptured Ignition of mixture




Flame Speed, Overpressure, and DDT

Turbulence from just a few obstacles produces a transition to detonation (DDT)



Obstacle


Deflagration, H2 release, obstacle-induced enhancement

~ 1/5 scale

Tunnel Experiments

Two types of experiments:

• Homogeneous deflagration experiments

• In-tunnel release experiments

– Scaled release and ventilation rates

M. Groethe, E. Merilo, J. Colton, S. Chiba, Y. Sato, and H. Iwabuchi, “Large-scale hydrogen deflagrations and



37 m3 tent

Tunnel Concrete floor20% H2

20% hydrogen in a 37 m3 volume

20% and 30% Hydrogen Experiment

Y. Sato, E. Merilo, M. Groethe, J. Colton, S. Chiba, and H. Iwabuchi, “Homogeneous hydrogen deflagrations in a sub-scale vehicle

tunnel,” National Hydrogen Association (NHA) Annual Hydrogen Conference 2006, Long Beach, California, 12-16 March 2006.

0 ms

100 ms

IR

20%

IR

20%


FC Bus Tunnel Experiments

- range | + range

Sam

ple

1

Sam

ple

2

Sam

ple

3

0

2

4

6

8

10

-15 -10 -5 0 5 10 15Range (m)

Hydro

gen C

oncentr

ation (

%)

Sample 1

Sample 2

Sample 3

Tunnel

No ventilation, no obstacles

Jet ignition occurred, overpressure ~ 0.25 kPa

Spark

Y. Sato, E. Merilo, M. Groethe, J. Colton, S. Chiba, and H. Iwabuchi, “Hydrogen release deflagrations in a

sub-scale vehicle tunnel,” 16th World Hydrogen Energy Conference, Lyon, France, 12-16 June 2006.


Garage Experiments

• Evaluate the effects of release rate and ventilation rate on hydrogen concentration.

• Characterize the resulting flame speed and overpressure when the mixture is ignited.

Dimensions

- Height: 2.72 m

- Width: 3.64 m

- Length: 6.10 m

- Volume: ~ 60 m3

- The open end was covered with

sheet of 0.0076-mm high-density

polyethylene (HDPE) for the tests.

- This allowed visible and infrared

cameras to capture images of the

flame.

- A ventilation intake hole was cut at

the bottom of the plastic sheet.

1.22 m

0.09 m

Y. Ishimoto, E. Merilo, M. Groethe, S. Chiba, H. Iwabuchi, and K. Sakata, “Study of hydrogen diffusion and deflagration in a

closed system,” 2nd International Conference on Hydrogen Safety (ICHS), San Sebastian, Spain, 11-13 September 2007.


Garage Instrumentation

Release

Point

Sample

StationsSample

Stations

Thermocouples

Release

Nozzle

Z

Y

X

Ventilation

Exhaust

Duct

P2

P1

P4

P3






• The maximum concentration is proportional

to the ratio of the hydrogen release rate

and the ventilation rate within the range of

parameters tested in the present study.

• Therefore, a required ventilation rate can

be estimated from the assumed hydrogen

leak rate within the present experimental

conditions.

• Further experiments in closed systems are

necessary, varying additional parameters

(volume, the direction of the nozzle,…).

The correlation between the ratio of the hydrogen

release rate to ventilation rate and the maximum

hydrogen concentration

0

5

10

15

20

0 0.05 0.1 0.15 0.2

Maximum hyrdgen c

The ratio of hydrogen release rate to

ventilation speed

M

ax

imu

m H

2 c

on

ce

ntr

ati

on

Hydrogen Concentration

The ratio of hydrogen release rate

to ventilation speed


Summary

• Open Space Experiments– Assess scaling effects, acquire free-field blast data

• Open Space with Obstacles– Small-scale obstacles have shown significant enhancement of explosions

– Large-scale obstacles have not significantly enhanced explosions

• Protective Blast Wall Experiments– Reduction in overpressures behind the walls

• Large Release Experiments– Spontaneous ignition

• Confined Explosions– DDT with only a few obstacles in the small tube

– Significant enhancement of explosions

– Ventilation has been successful at mitigating the risk


ReferencesR. Schefer, M. Groethe, W. Houf, and J. Keller, “Experimental evaluation of barrier walls for risk reduction of unintended hydrogen releases,”17th World Hydrogen Energy Conference, Brisbane,

Australia, 15-19 June 2008.

E. Merilo and M. Groethe, “Deflagration safety study of mixtures of hydrogen and natural gas in a semi-open space,” 2nd International Conference on Hydrogen Safety (ICHS), San Sebastian, Spain,

11-13 September 2007.

Y. Ishimoto, E. Merilo, M. Groethe, S. Chiba, H. Iwabuchi, and K. Sakata, “Study of hydrogen diffusion and deflagration in a closed system,” 2nd International Conference on Hydrogen Safety

(ICHS), San Sebastian, Spain, 11-13 September 2007.

M. Groethe, E. Merilo, J. Colton, S. Chiba, Y. Sato, and H. Iwabuchi, “Large-scale hydrogen deflagrations and detonations,” International Journal of Hydrogen Energy, Volume 32, Issue 13(September 2007) pp. 2125-2133.

E. Merilo, M. Groethe, J. Colton, and S. Chiba, “Experimental facilities for large-scale and full-scale study of hydrogen accidents,” Hydrogen & Fuel Cells 2007: International Conference and Trade

Show, Vancouver, Canada, 29 April - 2 May 2007.

Y. Sato, E. Merilo, M. Groethe, J. Colton, S. Chiba, and H. Iwabuchi, “Hydrogen release deflagrations in a sub-scale vehicle tunnel,”16th World Hydrogen Energy Conference, Lyon, France, 12-16June 2006.

Y. Suwa, H. Miyahara, K. Kubo, K. Yonezawa, Y. Ono and K. Mikoda, “Design of safe hydrogen refueling stations against gas-leakage, explosion and accidental automobile collision,” 16th World

Hydrogen Energy Conference, Lyon, France, 12-16 June 2006.

Y. Sato, E. Merilo, M. Groethe, J. Colton, S. Chiba, and H. Iwabuchi, “Homogeneous hydrogen deflagrations in a sub-scale vehicle tunnel,” National Hydrogen Association (NHA) Annual Hydrogen

Conference 2006, Long Beach, California, 12-16 March 2006.

Y. Sato, H. Iwabuchi, M. Groethe, J. Colton, and S. Chiba, “Experiments on hydrogen deflagration,” 8th Asian Hydrogen Energy Conference, Tsinghua University, Beijing, China, 26-27 May 2005.

ICMAT 2005 IUMRS-ICAM 2005, Symposium P, Materials for Rechargeable Batteries, Hydrogen Storage and Fuel Cells, Singapore, 3-8 July 2005. Selected to be published in Journal of Power

Sources.

R. Schefer, W. Houf, B. Bourne, and J. Colton, “Turbulent hydrogen-jet flame characterization,” International Journal of Hydrogen Energy, 2005.

M. Groethe, J. Colton, S. Chiba, and Y. Sato, “Hydrogen deflagrations at large scale,” 15th World Hydrogen Energy Conference, Yokohama, Japan, 27 June - 2 July 2004.

R. Schefer, W. Houf, B. Bourne, and J. Colton, “Experimental measurements to characterize the thermal and radiation properties of an open flame hydrogen plume,” 15th NHA Meeting, 26-30 April

2004, Los Angeles, CA.

Y. Inaba, T. Nishihara, M. Groethe, and Y. Nitta, “Study on explosion characteristics of natural gas and methane in semi-open space for the HTTR hydrogen production system,” Nuclear

Engineering and Design 232 (2004) p. 111-119.

M. Groethe and J. Colton, “Hydrogen explosion safety studies,” Poster presented at Towards a Greener World, Hydrogen and Fuel Cell Conference, Vancouver, B.C., Canada, 8-11 June 2003.

M. Groethe, J. Colton, and S. Chiba, “Hydrogen deflagration safety studies in a semi-open space,” 14th World Hydrogen Energy Conference, Montreal, Québec, 9-13 June 2002.

M. Groethe, J. Colton, and S. Chiba, “Hydrogen deflagration safety studies in a confined tube,” 14th World Hydrogen Energy Conference, Montreal, Québec, 9-13 June 2002.

M. Groethe, B. Peterson, and J. Colton, “Experimental facilities for hydrogen safety studies,” 11th Canadian Hydrogen Conference, Victoria, B.C., Canada, 17-20 June 2001.

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Large-Scale Testing: Part II - HySafe - Safety of Hydrogen ...€¦ · Hydrogen Release Experiments...

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