1. Large-Scale Hydrogen Deflagration and Detonations
M. Groethe
E. Merilo
J. Colton
S. Chiba
Y. Sato
H. Iwabuchi
International Conference on Hydrogen Safety
8-10 September 2005
Pisa, Italy

2. Outline 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

3. Objective
Acquire basic data on hydrogen deflagrations and detonations.
Acquire hydrogen deflagration/detonation data for validation of computer simulations.
Studies were performed for IAE and administered through NEDO as part of the “Development for Safe Production and Utilization and Infrastructure of Hydrogen” program.

4. 300 m3 Open-Space Tests Volume Blockage ratio: ~11%
Obstacle-induced enhancement, scaling, free-field blast data.
Deflagration tests with obstacles.
Deflagration tests without obstacles.
Detonation tests without obstacles.
Obstacle Test
0.46 m-diam
X 3 m-tall
300 m3
5.7 m
Volume Blockage ratio: ~11%

5. Obstacle Test
Standard and infrared video frames
~67 ms
~67 ms
~100 ms

6. Obstacle Test

7. Deflagration Data Overpressure Heat Flux Scaled Overpressure
Scaled Impulse

8. Stoichiometric Detonation
High-Speed Video Frames

9. Detonation Data
Detonation data consistent with previous smaller scale tests
Overpressure
Heat flux
Scaled Overpressure
Scaled Impulse

10. Deflagration, H2 release, Obstacle-induced enhancement.
Tunnel Experiments
Deflagration, H2 release, Obstacle-induced enhancement.
Homogeneous deflagration tests.
Tests with and without scaled vehicles as obstacles.
Scaled release and ventilation rates.
~ 1/5 scale

11. Tunnel with Vehicle Models
Obstacles representing
scaled vehicles.
Blockage ratio: 0.03

12. Pressure and Impulse
Overpressure
Overpressure and impulse unchanged by presence of vehicle models.
Overpressure
Impulse

13. H2 Release Tests Ventilation significantly reduces H2 concentration
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 concentration
H2 concentration

14. Partial Confinement Test
Deflagration 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.

15. Partial Confinement Test
Confinement between plates does not enhance deflagration
Scaled Overpressure
Scaled Impulse
~33 ms
Standard Video Frame
IR Video Frame

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

17. Protective Wall Test Setup
Blast
sensors
10 m
4 m
Wall
5.3 m3
Source

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

19. Rapid release of a large quantity of hydrogen that is ignited.
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.
Sample station
18-m tower
Estimated
Flame Jet
Tower
Sample station
Sample station
Table with
drywall
insert
Igniters (15mJ)
Nozzle
Nozzle
Release
valve
Pressure and heat flux

20. Large-Release Test
High-Speed Video Frames

21. Large-Release Test
Heat Flux
Overpressure
Flame Speed

22. Large-Release Test
Release to Free Field
Static
Hydrogen Amount
about 5 m３NTP
11 m３ NTP
Hydrogen Concentration
heterogeneous
homogeneous
(30 vol％, 37 m3)
Status at Ignition
Turbulent
Flame Propagation Velocity
about 100 m/sec
44 m/sec
Pressure Measurement
Range from Ignition
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

23. Summary 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 a
static homogeneous deflagration.
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.