Context R&D activities in H2 technologies in France is driven by industrial research targeting real applications (DIMITHRY, H2E, HYPE, ...) Safety management is the “red line” and especially aiming at shaping mitigation techniques (avoid atex, control fire and explosion effects) Explosion venting need to be considered : Widely used in industry, Large body of experiments, Theory, standards, guidelines, ...

But, … Vent dimensioning remains difficult : Some key phenomena remain obscure : The role of flame instabilities Combustion of external cloud Interaction internal/external explosion ... Severe lack of experimental : ... evidence ... data about vented hydrogen explosion Purpose of this work : Providing additional results about vented hydrogen-air explosions in vessels of industrial sizes

Experimental devices 1 m3 chamber : Length : 1.85 m Diameter : 0.94 m Vent area : 0.15 m2 10 m3 chamber : Length : 5.73 m Diameter : 1.6 m Vent area : 2 m2

Instrumentation 1 m3 chamber : Injection device : 1 bottle of 5 l (filled with H2) Pressure : 5 piezoresistive gauges Inside : 2 gauges – (0-10 bar ± 0.01 bar) Outside : 3 gauges – (0-2 bar ± 0.002 bar) installed in lenses supports at 1, 3 and 5 m Ignition : pyrotechnical match (60 J) opposite to vent Propagation of the flame : 6 ionisation gauges

Instrumentation 10 m3 chamber : Injection device : 4 bottles of 8 l (filled with H2) Pressure : 2 piezoresistive gauges (0-10 bar ± 0.01 bar) Ignition : pyrotechnical match (60 J) opposite to vent Propagation of the flame : 4 ionisation gauges 4 optical sensors

Main results – 1 m3 chamber Test 1.0-05 (20%H2) Classical shape with a single dome End of combustion in the vessel Overpressure keeps on rising when the combustion is ended in the chamber External explosion : strong pressure burst and propagation at the speed of sound Acoustic effect : Fresh gases replaced by burnt gases – local effect Acoustic effect : External atmosphere accelerated by the emerging flow of fresh gases 20% H2 in air

Main results – 10 m3 chamber External explosion : Pressure rises sharply before the end of combustion in the tank Test 10.5-16 (23%H2) First pressure bulge : Combustion in the chamber End of combustion in the vessel First acoustic mode of the chamber Natural vibration of metallic envelope Pressure decrease 23% H2 in air

Conclusion Typical industrial question : How do the data compare to the standards ? Absolute necessity to refine our knowledge of the phenomenology and to produce much more data NEXT STORY Bauwens et al 64 m3 Pasman et al 1 m3 Kumar et al 6.85 m3 Present 10 m3 1 m3 NFPA 68

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