Poulter Laboratory MG 8/1/05 Large-Scale Hydrogen Deflagration and Detonations International Conference on Hydrogen Safety 8-10 September 2005 Pisa, Italy.

Poulter LaboratoryMG 8/1/05

Large-Scale Hydrogen Deflagration and

Detonations

International Conference on Hydrogen Safety8-10 September 2005

Pisa, Italy

M. GroetheE. MeriloJ. ColtonS. ChibaY. Sato

H. Iwabuchi

Poulter LaboratoryMG 8/1/05

• Objectives

• 300 m3 Open-Space Tests

• 1/5 Scale Tunnel Tests

• Partial Confinement Test

• Protective Blast Wall Test

• Large-Scale release (300 Nm3 H2)

• Summary

Outline

Poulter LaboratoryMG 8/1/05

• Acquire basic data on hydrogen deflagrations and detonations.

• Acquire hydrogen deflagration/detonation data for validation of computer simulations.

Objective

Studies were performed for IAE and administered through NEDO as part of the “Development for Safe Production and Utilization and Infrastructure of Hydrogen” program.

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300 m3

5.7 m

300 m3 Open-Space TestsObstacle-induced enhancement, scaling, free-field blast data.

• Deflagration tests with obstacles.

• Deflagration tests without obstacles.

• Detonation tests without obstacles.

Volume Blockage ratio: ~11%

Obstacle Test 0.46 m-diam X 3 m-tall

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Obstacle Test

~67 ms ~67 ms

~100 ms

• Standard and infrared video frames

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Obstacle Test

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Deflagration Data

Overpressure Heat Flux

Scaled Overpressure Scaled Impulse

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Stoichiometric Detonation

• High-Speed Video Frames

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Detonation Data

Heat fluxOverpressure

Scaled Overpressure Scaled Impulse

• Detonation data consistent with previous smaller scale tests

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Tunnel ExperimentsDeflagration, H2 release, Obstacle-induced enhancement.

• Homogeneous deflagration tests.

• Tests with and without scaled vehicles as obstacles.

• Scaled release and ventilation rates.

~ 1/5 scale

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Tunnel with Vehicle Models

Obstacles representingscaled vehicles.

Blockage ratio: 0.03

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Pressure and Impulse

Overpressure Impulse

Overpressure

•Overpressure and impulse unchanged by presence of vehicle models.

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H2 Release Tests

• Test 14 and Test 15: 0.1 kg H2 in 20 sec, no ventilation.

• Test 16: 0.1 kg H2 in 20 sec, 1.6 m3/sec ventilation rate.

• Test 17: 2.2 kg H2 in in 420 sec, 1.6 m3/sec ventilation rate.

H2 concentrationH2 concentration

• Ventilation significantly reduces H2 concentration

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Partial Confinement TestDeflagration enhancement from partial confinement.

• Narrow gap between two plates provides partial confinement

• Flame position measured by ionization pins.

• Overpressure measured inside and outside the source.

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Partial Confinement Test

Scaled Overpressure Scaled Impulse

~33 ms ~33 ms

Standard Video Frame IR Video Frame

• Confinement between plates does not enhance deflagration

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Protective Wall Tests Assess overpressure reduction by using a protective blast wall.

Test Layout

• 4 m-tall by 10 m-wide wall, 4 m from edge of the 5.3 m3 source• Stoichiometric deflagration (bottom, center spark ignition) • Pressure measured inside the source and in the free-field.

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Protective Wall Test Setup

Wall 5.3 m3 Source

Blastsensors

10 m

4 m

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Scaled Overpressure and Impulse

Scaled ImpulseScaled Overpressure

• Deflagration data suggests a reduction in overpressure and impulse.• Previous tests with a 2 m-tall wall show reductions up to 30%.

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Large-Release Test Rapid release of a large quantity of hydrogen that is ignited.

•300 Nm3 H2 (27 kg) released

in about 30 seconds.•Spontaneous ignition occurred

at ~360 milliseconds.

Tower

Nozzle

Releasevalve

Table with drywall insert

EstimatedFlame Jet

18-m tower

Sample station

Sample station

NozzleIgniters (15mJ)

Pressure and heat flux

Sample station

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Large-Release Test

• High-Speed Video Frames

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Large-Release TestHeat FluxOverpressure

Flame Speed

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Release to Free Field Static

Hydrogen Amount about 5 m ３ NTP 11 m ３ NTP

Hydrogen Concentration

heterogeneous homogeneous (30 vol ％ , 37 m3)

Status at Ignition Turbulent Static

Flame Propagation Velocity

about 100 m/sec 44 m/sec

Pressure Measurement

Range from Ignition Peak Overpressure

(kPa)

Impulse (Pa-s)

Peak Overpressure

(kPa)

Impulse (Pa-s)

(5.3m) 5.6 (5.3m) 40 (5.9m) 4.4 (5.9m) 122

11 m 3.8 25 2.9 82

21 m 2.3 13 1.7 44

Large-Release Test

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Summary

1 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.

• Large-scale 300 m3 open space deflagrations and detonations.- Large obstacles do not enhance the deflagration.- Detonation data consistent with smaller scale tests and analytic expressions.

• Partial confinement of mixture between two plates.- Deflagration was not enhanced for this geometry.

• 1/5 scale tunnel tests.- Homogeneous deflagrations show near constant overpressure and impulse - 30% H2 blast is much higher than the free-field case. - Vehicle models do not enhance deflagration (BR = 0.03, which is small)- Ventilation of the tunnel significantly reduces the H2 concentration.

• 4 m-tall protective blast wall.- Blast reduction is suggested to over twice the wall height.- Previous tests and calculations show a reduction that diminishes with

range1.

• Large-scale release of hydrogen.- Release spontaneously ignite producing a blast followed by a flame jet.

- Ignited release produced a higher blast pressure and lower impulse than astatic homogeneous deflagration.