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•• 21/04/23 1DRA/LPe
Data for the evaluation of hydrogen RIsks onboard VEhicles : outcomes from the French
project DRIVE----
Gentilhomme O., Proust C., Jamois D., Tkatschenko I., Cariteau B., Studer E., Masset F., Joncquet G., Amielh M. et Anselmet F.
International Conference on Hydrogen Safety September 12-14, 2011
ICHS 2011 – OGe 2
Sources of motivation Hydrogen widely used in many industrial applications
with good safety records But current safety procedures and technologies will
provide only limited guidance for transport industry:– H2 used in “decentralized” infrastructure (= car)
– H2 used in relatively small amount (= several kg per user)
– H2 used by a large population with no special training regarding the handling of such flammable gas
To gain full public acceptance, important to identify all risks and to succeed in controlling them
ICHS 2011 – OGe 3
Sources of motivation Hydrogen widely used in many industrial applications with
good safety records But current safety procedures and technologies will
provide only limited guidance for transport industry:– H2 used in “decentralized” infrastructure (= car)
– H2 used in relatively small amount (= several kg per user)
– H2 used by a large population with no special training regarding the handling of such flammable gas
To gain full public acceptance, important to identify all risks and to succeed in controlling them
… but, despite all these vehicles, only limited data on safety aspects !!!
ICHS 2011 – OGe 4
DRIVE : Data for the evaluation of hydrogen RIsks onboard VEhicles
Duration : 2006 - 2009
Partners : CEA, IRPHE (CNRS centre), PSA Peugeot Citroën and INERIS
Total budget : 2000 kEuros (partly financed by the French national research agency)
Overall presentation of DRIVE
ICHS 2011 – OGe 5
To produce experimental data on the whole reaction chain leading to a hydrogen hazard onboard vehicle,
Main objective of DRIVE
LeakageH2 build up and ATEX
formationIgnition
Hydrogen jet flame
Explosion
ICHS 2011 – OGe 6
• “The range and frequencies of occurrence of leakage rates that will occur with hydrogen vehicles are unknown to us, despite our literature search” [BARLEY et al., ICHS in San Sebastian, 2007]
• Observation confirmed by the initial work of DRIVE
• Propose to classify the leakage in three types :
Leak quantification
Probability Gravity
ICHS 2011 – OGe 7
• “The range and frequencies of occurrence of leakage rates that will occur with hydrogen vehicles are unknown to us, despite our literature search” [BARLEY et al., ICHS in San Sebastian, 2007]
• Observation confirmed by the initial work of DRIVE
• Propose to classify the leakage in three types :
Leak quantification
Probability Gravity
Definitely an area where further data are required
ICHS 2011 – OGe 8
• Test rig to measure the leakage from key components of the H2 vehicle after they were submitted to various situations (ageing, bad fitting, damage…)
• Rig capable to measure leakage as low as 2.10-5 L/min
Leak quantification
H2
ICHS 2011 – OGe 9
Leak quantification
ICHS 2011 – OGe 10
Leak quantification
Most of the leakage arose due to insufficient tightness – pay
attention to the maintenance !
ICHS 2011 – OGe 11
ATEX formation
• Hydrogen leakage taking place within a vehicle parked in a domestic garage or underground parking = one of the most dreadful scenario !
• Important to understand all the mechanisms leading to the build-up of a potential ATEX
• Yet most of the previous studies were focused on the gas distribution within the garage (BARLEY et al., 2007, VENETSANOS et al., 2010, ADAMS et al., 2011…) but rarely on the vehicle itself (MAEDA et al., 2007).
ICHS 2011 – OGe 12
ATEX formation
• Tests carried out within a private garage ( 5,8 × 3,0 × 2,4 m) with a real car parked inside
• Leakage (diffuse source or jet) simulated with helium at various locations : under the bonnet, under the chassis and near the storage area
• Leak flow rates varying between 0,05 and 600NL/min it covers both the chronic and accidental leakages
• Concentration monitored by means of catharometers
ICHS 2011 – OGe 13
ATEX formationSaturated
concentration (% v/v)
measured in the engine
compartment vs the leakage
flow rate (NL/min)
ICHS 2011 – OGe 14
ATEX formationSaturated
concentration (% v/v)
measured in the engine
compartment vs the leakage
flow rate (NL/min)
X Q2/3
Variation of the saturated concentration resulting from a diffuse leak follows the displacement regime identified by LINDEN [1999]
ICHS 2011 – OGe 15
ATEX formationSaturated
concentration (% v/v)
measured in the engine
compartment vs the leakage
flow rate (NL/min) Insufficient tightness can
lead to a concentration under the bonnet on the order of 10 % v/v (in the flammable range of H2)
ICHS 2011 – OGe 16
Explosion under the bonnet
• Tests performed in two steps :
In a rig
In the real vehicle
ICHS 2011 – OGe 17
• Example of results : homogenous concentration of 12,7 % v/v
Explosion in the rig
ICHS 2011 – OGe 18
• Example of results : homogenous concentration of 12,7 % v/v
Explosion in the rig
ICHS 2011 – OGe 19
• Example of results : homogenous concentration of 12,7 % v/v
Explosion in the rig
ICHS 2011 – OGe 20
• Example of results : homogenous concentration of 12,7 % v/v
Explosion in the rig
ICHS 2011 – OGe 21
• Example of results : homogenous concentration of 12,7 % v/v
Explosion in the rig
ICHS 2011 – OGe 22
• Example of results : homogenous concentration of 12,7 % v/v
Explosion in the rig
Bear in mind the possible formation of a secondary
explosion (outside the engine compartment)
ICHS 2011 – OGe 23
• Comparison of the results between rig / real vehicle
Explosion under the bonnet
P1 : pressure measured inside the engine compartment
P3 : pressure measured outside the engine compartment
Overpressures in the real vehicle slightly higher that those in the rig (filling ratio under the bonnet not exactly the same)
Pressure effects negligible when averaged H2 concentration < 10 % v/v.
ICHS 2011 – OGe 24
• Description of the testing facility
Jet fires from the vehicle
ICHS 2011 – OGe 25
• Visible flame length as a function of the release flow rate
Jet fires from the vehicle
Flame width 1/6 of its length
Measured temperature within the flame as high as 1500°C (a person fully or substantially engulfed by the flame will suffer fatality)
Lethal and irreversible effects due to thermal radiation will be limited to 1 – 2 m from the flame surface
ICHS 2011 – OGe 26
• Visible flame length as a function of the release flow rate
Jet fires from the vehicle
Flame width 1/6 of its length
Measured temperature within the flame as high as 1500°C (a person fully or substantially engulfed by the flame will suffer fatality)
Lethal and irreversible effects due to thermal radiation will be limited to 1 – 2 m from the flame surface
Safety distances on the order of 10 m all around the H2 vehicle !
ICHS 2011 – OGe 27
• How to reduce the safety distances associated with the PRD functioning ?
Jet fires from the vehicle
Taken from [HOUF et al, 2008]
By impacting the PRD release on the road ?
ICHS 2011 – OGe 28
• How to reduce the safety distances associated with the PRD functioning ?
Jet fires from the vehicle
Taken from [HOUF et al, 2008]
By impacting the PRD release on the road ?
Probably not enough !
ICHS 2011 – OGe 29
Conclusions DRIVE = one of the rare projects focused on the safety use of
H2 onboard vehicle 3 types of leakages :
– Permeation leakage : permanent but release flow rate so low that passive safety means should be sufficient (design of engine compartment, detection…)
– Accidental leakage : massive leakage but very rare. Active safety means (calibrated orifice, excess flow valve…) will be required
– Chronic leakage : arises due to the ageing of the vehicle or bad maintenance. More problematic since it features a high probability of occurrence and a release flow rate as high as 50-100 NL/min
Pressure effects due to an explosion under the bonnet will not be significant if maximum H2 concentration limited to 10 % v/v. Concentration not exceeded if release flow rate less than 10 NL/min. But bear in mind the possible formation of secondary explosion !!!
