Safety
Guidelines and Recommendations for Indoor Use of Fuel Cells and Hydrogen Systems
Oct 2015
Publication
Deborah Houssin-Agbomson,
Simon Jallais,
Elena Vyazmina,
Guy Dang-Nhu,
Gilles Bernard-Michel,
Mike Kuznetsov,
Vladimir V. Molkov,
Boris Chernyavsky,
Volodymyr V. Shentsov,
Dmitry Makarov,
Randy Dey,
Philip Hooker,
Daniele Baraldi,
Evelyn Weidner,
Daniele Melideo,
Valerio Palmisano,
Alexandros G. Venetsanos,
Jan Der Kinderen and
Béatrice L’Hostis
Hydrogen energy applications often require that systems are used indoors (e.g. industrial trucks for materials handling in a warehouse facility fuel cells located in a room or hydrogen stored and distributed from a gas cabinet). It may also be necessary or desirable to locate some hydrogen system components/equipment inside indoor or outdoor enclosures for security or safety reasons to isolate them from the end-user and the public or from weather conditions.<br/>Using of hydrogen in confined environments requires detailed assessments of hazards and associated risks including potential risk prevention and mitigation features. The release of hydrogen can potentially lead to the accumulation of hydrogen and the formation of a flammable hydrogen-air mixture or can result in jet-fires. Within Hyindoor European Project carried out for the EU Fuel Cells and Hydrogen Joint Undertaking safety design guidelines and engineering tools have been developed to prevent and mitigate hazardous consequences of hydrogen release in confined environments. Three main areas are considered: Hydrogen release conditions and accumulation vented deflagrations jet fires and including under-ventilated flame regimes (e.g. extinguishment or oscillating flames and steady burns). Potential RCS recommendations are also identified.
Simulation of Shock-Initiated Ignition
Sep 2009
Publication
The scenario of detonative ignition in shocked mixture is significant because it is a contributor to deflagration to detonation transition for example following shock reflections. However even in one dimension simulation of ignition between a contact surface or a flame and a shock moving into a combustible mixture is difficult because of the singular nature of the initial conditions. Initially as the shock starts moving into reactive mixture the region filled with reactive mixture has zero thickness. On a fixed grid the number of grid points between the shock and the contact surface increases as the shock moves away from the latter. Due to initial lack of resolution in the region of interest staircasing may occur whereby the resulting plots consist of jumps between few values a few grid points and these numerical artifacts are amplified by the chemistry which is very sensitive to temperature leading to unreliable results. The formulation is transformed replacing time and space by time and space over time as the independent variables. This frame of reference corresponds to the self-similar formulation in which the non-reactive problem remains stationary and the initial conditions are well-resolved. Additionally a solution obtained from short time perturbation is used as initial condition at a time still short enough for the perturbation to be very accurate but long enough so that there is sufficient resolution. The numerical solution to the transformed problem is obtained using an essentially non-oscillatory algorithm which is adequate not only for the early part of the process but also for the latter part when chemistry leads to appearance of a shock and eventually a detonation wave is formed. A validation study was performed and the results were compared with the literature for single step Arrhenius chemistry. The method and its implementation were found to be effective. Results are presented for values of activation energy ranging from mild to stiff.
Detonation Dynamics in a Curved Chamber for an Argon Diluted Hydrogen-oxygen Mixture
Sep 2019
Publication
The dynamics of detonation transmission from a straight channel into a curved chamber was investigated as a function of initial pressure using a combined experimental and numerical study. Hi-speed Schlieren and *OH chemiluminescense were used for flow visualization; numerical simulations considered the two-dimensional reactive Euler equations with detailed chemistry. Results show the highly transient sequence of events (i.e. detonation diffraction re-initiation attempts and wave reflections) that precede the formation of a steadily rotating Mach detonation along the outer wall of the chamber. An increase in pressure from 15 kPa to 26 kPa expectedly resulted in detonations that are less sensitive to diffraction. Local quenching of the initial detonation occurred for all pressures considered. The location where this decoupling occurred along the inner wall determined the location where transition from regular reflection to a rather complex wave structure occurred along the outer wall. This complex wave structure includes a steadily rotating Mach detonation (stem) an incident decoupled shock-reaction zone region and a transverse detonation that propagates in pre-shocked mixture.
Computational Modelling of Pressure Effects from Hydrogen Explosions
Sep 2007
Publication
The statement of the problem and algorithm of computational modelling of the processes of formation of the hydrogen-air mixture in the atmosphere its explosion (taking into account chemical interaction) and dispersion of the combustion materials in the open space with complex relief are presented. The finite-difference scheme was developed for the case of the three-dimensional system of gas dynamics equations complemented by the mass conservation laws of the gas admixture and combustion materials. The algorithm of the computation of thermal and physical parameters of the gas mixture appearing as a result of the instantaneous explosion taking into account chemical interaction was developed. The algorithm of computational solution of the difference scheme obtained on the basis of Godunov method was considered. The verification of the mathematical model showed its acceptable accuracy in comparison with known experimental data. It allows using the developed model for the modelling of pressure and thermal consequences of possible failures at the industrial enterprises which store and use hydrogen. The computational modelling of an explosion of the gas hydrogen cloud appearing as a result of instantaneous destruction of high pressure containers at the fuelling station was carried out. The analysis of different ways of protection of the surrounding buildings from destructive effects of the shock wave was conducted. The recommendations considering the choice of dimensions of the protection area around the fuelling station were worked out.
Experimental Study of Hydrogen Releases Combustion
Sep 2009
Publication
The objectives of the presented experimental work were investigation of hydrogen release distribution and combustion modelling possible emergency situation at industry scale. Results of large scale experiments on distribution and combustion in an open and congested area are presented. The mass of hydrogen in experiments varied from 50g to 1000g with release rate from 180 to 220 g/s. Qualitative characteristics of high momentum hydrogen jet releases distribution and subsequent combustion were obtained. It is shown that obstacles slow down jet speed promote combustible mixture formation in a large volume and accelerate combustion process. The maximum overpressure in experiments with additional congested area reached ΔР = 0.4 atm. Using partial confinement of congested area turbulent combustion regime with the maximum overpressure more than 10 atm. was obtained.
Measurement of Hydrogen Mixing Process by High Response Hydrogen Sensor
Sep 2017
Publication
According to the Global technical regulation on hydrogen and fuel cell vehicles (FCV) fuel cell discharge system at the vehicle exhaust system`s point of discharge the hydrogen concentration level shall not exceed 4 % average by volume during any moving three-second time interval during normal operation including start-up and shut down [1]. FC stack need to washout by the concentrated hydrogen as the purge gas and how to exhaust gas without exceeding 4 % is the most concerns. Also how to measure hydrogen pulse of millisecond in exhaust is also the rising up issue. In this paper model of FCV hydrogen discharge system was composed and variety of simple experiments were carried out to control the H2 concentration and release. In the case which the semiconductor sensor with porous material (average size less than quench distance) were applied to check H2 concentration the short pulse of high concentration of H2 in millisecond was hard to find. In this experiment the simple exhaust gas model H2/N2 flow was used instead of Air/H2. In the exhaust gas test experiment was conducted under the atmospheric condition in room temperature with small pressure difference and the fast solenoid valve to create quick hydrogen control. Most of the experiments except the turbulent flow experiments laminar flow is expected to be dominated when steady state condition is satisfied but the most result discussed here is the measurement of H2 concentration during the start point at the time of discharge within seconds. The results showed when H2 was added to N2 flow the boundary layer between N2 and H2 contained the high concentration of H2 at the initial wave front and decrease to reach steady state. This H2 pulse is typical in the FCV exhaust gas and topics of this paper.
The Role of Trust and Familiarity in Risk Communication
Sep 2009
Publication
In socio-economics it is well known that the success of an innovation process not only depends upon the technological innovation itself or the improvement of economic and institutional system boundaries but also on the public acceptance of the innovation. The public acceptance can as seen with genetic engineering for agriculture be an obstacle for the development and introduction of a new and innovative idea. In respect to hydrogen technologies this means that the investigation compilation and communication of scientific risk assessments are not sufficient to enhance or generate public acceptance. Moreover psychological social and cultural aspects of risk perception have to be considered when introducing new technologies. Especially trust and familiarity play an important role for risk perception and thus public acceptance of new technologies.
Inhomogeneous Hydrogen Deflagrations in the Presence of Obstacles in 25 m3 Enclosure. Experimental Results
Sep 2019
Publication
Explosion venting is a frequently used measure to mitigate the consequence of gas deflagrations in closed environments. Despite the effort to predict the vent area needed to achieved the protection through engineering formulas and CFD tools work has still to be done to reliably predict the outcome of a vented gas explosion. Blind-prediction exercises recently published show a large spread in the prediction of both engineering formula than CFD tools. University of Pisa performed experimental tests in a 25 m3 facility in inhomogeneous conditions and with the presence of simple obstacles constituted by plates bolted to HEB beams. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated with different blockage ratio and repeated obstacles sets. Description of the experimental set-up includes all the details deemed necessary to reproduce the phenomenon with a CFD tool.
Fire Risk on High-pressure Full Composite Cylinders for Automotive Applications
Sep 2011
Publication
In the event of a fire the TPRD (Thermally activated Pressure Relief Device) prevents the high-pressure full composite cylinder from bursting by detecting high temperatures and releasing the pressurized gas. The current safety performance of both the vessel and the TPRD is demonstrated by an engulfing bonfire test. However there is no requirement concerning the effect of the TPRD release which may produce a hazardous hydrogen flame due to the high flow-rate of the TPRD. It is necessary to understand better the behavior of an unprotected composite cylinder exposed to fire in order to design appropriate protection for it and to be able to reduce the length of any potential hydrogen flame. For that purpose a test campaign was performed on a 36 L cylinder with a design pressure of 70 MPa. The time from fire exposure to the bursting of this cylinder (the burst delay) was measured. The influence of the fire type (partial or global) and the influence of the pressure in the cylinder during the exposure were studied. It was found that the TPRD orifice diameter should be significantly reduced compared to current practice.
Evaluation of Safety Distances Related to Unconfined Hydrogen Explosions
Sep 2005
Publication
A simple approximate method for evaluation of blast effects and safety distances for unconfined hydrogen explosions is presented. The method includes models for flame speeds hydrogen distribution blast parameters and blast damage criteria. An example of the application of this methodology for hydrogen releases in three hypothetical obstructed areas with different levels of congestion is presented. The severity of the blast effect of unconfined hydrogen explosions is shown to depend strongly on the level of congestion for relatively small releases. Extremely large releases of hydrogen are predicted to be less sensitive to the congestion level.
Attained Temperature During Gas Fuelling and Defueling Cycles of Compressed Hydrogen Tanks for FCV
Sep 2011
Publication
In this study we conducted hydrogen gas filling and discharging cycling tests to examine the thermal behaviour in hydrogen storage tanks under actual use conditions. As a result it was confirmed that the gas temperature in the tank varied depending on the initial test conditions such as the ambient temperature of the tank and the filling gas temperature and that the gas temperature tended to stabilize after several gas filling and discharging cycles.
Evaluation of the Protection Effectiveness Against Overpressure From Hydrogen-air Explosion
Sep 2017
Publication
The aim of this study is to assess the probability of the damage to hydrogen fuelling station personnel exposed to the hydrogen explosion shock wave. A three-dimensional mathematical model of the explosion of hydrogen-air cloud formed after the destruction of the high-pressure storage cylinders is developed. A computer technology how to define the personnel damage probability field on the basis of probit analysis of the generated shock wave is developed. To automate the process of computing the "probit function-damage probability" tabular dependence is replaced by a piecewise cubic spline. The results of calculations of overpressure fields impulse loading and the probability of damage to fuelling station personnel exposed to the shock wave are obtained. The mathematical model takes into account the complex terrain and three-dimensional non-stationary nature of the shock wave propagation process. The model allows to obtain time-spatial distribution of damaging factors (overpressure in the shock wave front and the compression phase impulse) required to determine the three-dimensional non-stationary damage probability fields based on probit analysis. The developed computer technology allows to carry out an automated analysis of the safety situation at the fuelling station and to conduct a comparative analysis of the effectiveness of different types of protective facilities.
Dynamic Load Analysis of Explosion in Inhomogeneous Hydrogen-air Mixtures
Sep 2017
Publication
This paper presents results from experiments on gas explosions in inhomogeneous hydrogen-air mixtures. The experimental channel is 3 m with a cross section of 100 mm by 100 mm and a 0.25 mm ID nozzle for hydrogen release into the channel. The channel is open in one end. Spectral analysis of the pressure in the channel is used to determine dynamic load factors for SDOF structures. The explosion pressures in the channel will fluctuate with several frequencies or modes and a theoretical high DLF is seen when the pressure frequencies and eigen frequencies of the structure matches.
The CALIF3S-P2remics Software – An Application to Underexpanded Hydrogen Jet Deflagration
Sep 2019
Publication
To assess explosion hazard the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) is developing the P2REMICS software (for Partially PREMIxed Combustion Solver) on the basis of the generic CFD solver library CALIF3S (for Components Adaptive Library for Fluid Flow Simulation). Both P2REMICS and CALIF3S are in-house IRSN softwares released under an open-source license. CALIF3S-P2REMICS is dedicated to the simulation of explosion scenarii (explosive atmosphere formation deflagration or detonation and blast waves propagation) for hydrogen as more generally for any explosive gas or gas/dust mixture. It is based on staggered space discretizations and implements fractional-steps time algorithms well suited for massively parallel computations. A wide range of experiments is used for the software validation. Among them we focus here on a free underexpanded hydrogen jet deflagration performed in two steps: first the hydrogen is released in air up to obtain a steady jet (dispersion phase) then the deflagration is triggered. For the dispersion phase simulation a notional nozzle approach is used to get rid of the description of the shocked zone located near the nozzle. Then a so-called turbulent flame velocity approach is chosen for the deflagration simulation. The computations allow to highlight the complex flow structures induced by the inhomogeneity fuel concentration in the jet. A large dispersion of results is observed depending on the chosen correlation for the turbulent flame speed.
Hydrogen Related Risks Within a Private Garage: Concentration Measurements in a Realistic Full Scale Experimental Facility
Sep 2007
Publication
Next generation of hydrogen energy based vehicles is expected to come into widespread use in the near future. Various topics related to hydrogen including production storage and application of hydrogen as an energy carrier have become subjects of discussion in the framework of various European and International projects. Safety information is vital to support the successful introduction into mainstream and public acceptance of hydrogen as an energy carrier. One of such issues which is seeking major attention is related to hydrogen powered vehicles parked inside a confined area (such as in a private garage). It is of utmost importance to predict if uncontrolled release of hydrogen from a vehicle parked inside a confined area can create an explosive atmosphere. Subsequently how the preventive measures can be implied to control these explosive atmospheres if present inside a confined area? There is a little guidance currently developed for confined areas accommodating hydrogen fuelled vehicles. It is essential that mitigation measures for such conditions become established.<br/>Characterization of different scenarios those may arise in a real situation from hydrogen fuelled vehicle parked inside a garage and furthermore the investigation of an optimal ventilation rate for hydrogen risk mitigation are some of the main objectives described in the framework of the present study. This work is an effort to provide detail experimental information’s in view of establishing guidelines for hydrogen powered vehicles parked inside a private garage. The present work is developed in the framework of a European Network of Excellence HySafe and French project DRIVE. Present paper describes a purpose built realistic Garage test facility at CEA to study the dispersion of hydrogen leakage. The studied test cases evaluate the influence of injected volumes of hydrogen and the initial conditions at the leakage source on the dispersion and mixing characteristics inside the free volume of the unventilated garage. The mixing process and build-up of hydrogen concentration is measured for the duration of 24 hours. Due to safety reasons helium gas is used to simulate the hydrogen dispersion characteristics.
Analysis of Composite Hydrogen Storage Cylinders under Transient Thermal Loads
Sep 2007
Publication
In order to ensure safe operation of hydrogen storage cylinders under adverse conditions one should be able to predict the extremities under which these cylinders are capable of operating without failing catastrophically. It is therefore necessary to develop a comprehensive model which can predict the behavior and failure of composite storage cylinders when subjected to various types of loading conditions and operating environments. In the present work a finite element model has been developed to analyze composite hydrogen storage cylinders subjected to transient localized thermal loads and internal pressure. The composite cylinder consists of an aluminium liner that serves as a hydrogen gas permeation barrier. A filament-wound carbon/epoxy composite laminate placed over the liner provides the desired load bearing capacity. A glass/epoxy layer or other material is placed over the carbon/epoxy laminate to provide damage resistance for the carbon/epoxy laminates. A doubly curved composite shell element accounting for transverse shear deformation and geometric nonlinearity is used. A temperature dependent material model has been developed and implemented in ABAQUS using user subroutine. A failure model based on Hashin's failure theory is used to predict the various types of failure in the cylinder. A progressive damage model has also been implemented to account for reduction in modulus due to failure. A sublaminate model has been developed to save computational time and reduce the complications in the analysis. A numerical study is conducted to analyze a typical hydrogen storage cylinder and possible failure trends due to localized thermal loading and internal pressure is presented.
Blending Ammonia into Hydrogen to Enhance Safety through Reduced Burning Velocity
Sep 2019
Publication
Laminar burning velocities (SL) of hydrogen/ammonia mixtures in air at atmospheric pressure were studied experimentally and numerically. The blending of hydrogen with ammonia two fuels that have been proposed as promising carriers for renewable energy causes the laminar flame speed of the mixture SL to decrease significantly. However details of this have not previously available. Systematic measurements were therefore performed for a series of hydrogen/ammonia mixtures with wide ranges of mole fractions of blended ammonia (XNH3) and equivalence ratio using a heat flux method based on heat flux of a flat flame transferred to the burner surface. It was found that the mixture of XNH3 = 40% has a value of SL close to that of methane which is the dominant component of natural gas. Using three chemical kinetic mechanisms available in the literature i.e. the well-known GRI-Mech 3.0 mechanism and two mechanisms recently released SL were also modelled for the cases studied. However the discrepancies between the experimental and numerical results can exceed 50% with the GRI-Mech 3.0 mechanism. Discrepancies were also found between the numerical results obtained with different mechanisms. These results can contribute to an increase in both the safety and efficiency of the coutilization of these two types of emerging renewable fuel and to guiding the development of better kinetic models.
Full Scale Experimental Campaign to Determine the Actual Heat Flux Produced by Fire on Composite Storages - Calibration Tests on Metallic Vessels
Oct 2015
Publication
If Hydrogen is expected to be highly valuable some improvements should be conducted mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign which will allow studying in future works the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire propane gas fire hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for reference of pure radiation heat transfer. The retained thermal load might be representative of accidental situations in worst case scenarios and relevant for a standardized testing protocol. The tests performed show that hydrogen gas fires and heptane pool fire allow reaching the target in terms of absorbed energy regarding the results of risk analysis performed previously. Other considerations can be taken into account that will led to retain an hydrogen gas fire for further works. Firstly hydrogen gas fire is the more realistic scenario: Hydrogen is the combustible that we every time find near an hydrogen storage. Secondly as one of the objectives of the project is to make recommendations for standardization issues it’s important to note that gas fires are not too complex to calibrate control and reproduce. Finally due to previous considerations Hydrogen gas fire will be retained for thermal load of composite cylinders in future works.
Hydrogen for Renewable Energy Export: Broadening the Concept of Hydrogen Safety
Sep 2019
Publication
Recently we have seen hydrogen (re)emerge as an important component of widespread decarbonisation of energy sectors. From an Australian perspective this brings with it an opportunity to store transport and export renewable energy—either as liquefied hydrogen or in a carrier such as ammonia. The growth of the hydrogen industry to now include the power and transport sectors as well as the notion of hydrogen export has broadened the range of safety considerations required and seen them extend into the realm of the consumer for the first time.<br/>Hydrogen as well as ammonia and other carriers such as methanol are existing industrial chemicals which have established protocols for their handling and use in the chemicals sector. As their use in energy and transport increases especially in the context of widespread domestic use their handling and use by inexperienced people in less-controlled environments expands shifting the risk profiles and management systems required. There is also the potential for novel hydrogen carriers such as methylcyclohexane/toluene to reach commercial viability at industrial scale.<br/>This paper will discuss some of these emerging applications of hydrogen and its carriers and discuss some of the technological innovations under development that may accompany a new energy industry— with some consideration given to their potential risks and the required safety considerations. In addition we will also provide an overview of global activity in this area and how new standards and regulations would need to be developed for the adaption of these technologies in an Australian context.
The Hydrogen Executive Leadership Panel (HELP) Initiative for Emergency Responder Training
Sep 2007
Publication
In close cooperation with their Canadian counterparts United States public safety authorities are taking the first steps towards creating a proper infrastructure to ensure the safe use of the new hydrogen fuel cells now being introduced commercially. Currently public safety officials are being asked to permit hydrogen fuel cells for stationary power and as emergency power backups for the telecommunications towers that exist everywhere. Consistent application of the safety codes is difficult – in part because it is new – yet it is far more complex to train emergency responders to deal safely with the inevitable hydrogen incidents. The US and Canadian building and fire codes and standards are similar but not identical. The US and Canadian rules are unlikely to be useful to other nations without modification to suit different regulatory systems. However emergency responder safety training is potentially more universal. The risks strategies and tactics are unlikely to differ much by region. The Hydrogen Executive Leadership Panel (HELP) made emergency responder safety training its first priority because the transition to hydrogen depends on keeping incidents small and inoffensive and the public and responders safe from harm. One might think that advising 1.2 million firefighters and 800000 law enforcement officers about hydrogen risks is no more complicated than adding guidance to a website. One would be wrong. The term “training” has specific legal implications which may vary by state. For hazardous materials federal requirements apply. Insurance companies place training requirements on the policies they sell to fire departments including the thousands of small all-volunteer departments which may operate as private corporations. Union contracts may define training and promotions may be based on satisfactorily completed certain levels of training. Emergency responders could no sooner learn how to extinguish a<br/>hydrogen fire by reading a webpage than a person could learn to ride a bicycle by reading a book. Procedures must be learned by listening reading and then doing. Regular practice is necessary. As new hydrogen applications are commercialized additional responder training may be necessary. This highlights another obstacle emergency responders’ ability to travel distances and take the time to undergo training. Historically fire academies established adjunct instructor programs and satellite academies to bring the training to firefighters. The large well-equipped academies are typically used for specialized training. States rarely have enough instructors and instructors often must take the time to create a course outline research each point and produce a program that is informative useful and holds the attention of responders. The challenge of training emergency responders seems next to impossible but public safety authorities are asked to tackle the impossible every day and a model exists to move forward in the U.S. Over the past few years the National Association of State Fire Marshals and U.S. Department of Transportation enlisted the help of emergency responders and industry to create a standardized approach to train emergency responders to deal with pipeline incidents. A curriculum and training materials were created and more than 26000 sets have been distributed for free to public safety agencies nationwide. More than 8000 instructors have been trained to use these materials that are now part of the regular training in 23 states. Using this model HELP intends to ensure that all emergency responders are trained to address hydrogen risks. The model and the rigorous scenario analysis and review used to developing the operational and technical training is addressed in this paper.
Defect Assessment on Pipe Used For Transport of Mixture of Hydrogen and Natural Gas
Sep 2009
Publication
The present article indicates the change of mechanical properties of X52 gas pipe steel in presence of hydrogen and its consequence on defect assessment particularly on notch like defects. The purpose of this work is to determine if the transport of a mixture of natural gas and hydrogen in the actual existing European natural gas pipe network can be done with a reasonable low failure risk (i.e. a probability of failure less than 10-6). To evaluate this risk a deterministic defect assessment method has been established. This method is based on Failure Assessment Diagram and more precisely on a Modified Notch Failure Assessment Diagram (MNFAD) which has been proposed for this work. This MNFAD is coupled with the SINTAP failure curve and allows determining the safety factor associated with defect geometry loading conditions and material resistance. The work described in this paper was performed within the NATURALHY work package 3 on ’Durability of pipeline material’.
Hydrogen Effect on Fatigue and Fracture of Pipe Steels
Sep 2009
Publication
Transport by pipe is one the most usual way to carry liquid or gaseous energies from their extraction point until their final field sites. To limit explosion risk or escape to avoid pollution problems and human risks it is necessary to assess nocivity of defect promoting fracture. This need to know the mechanical properties of the pipes steels. Hydrogen is considered to day as a new energy vector and its transport in one of the key problems to extension of its use. Within the European project NATURALHY it has been proposed to transport a mixture of natural gas and hydrogen. 39 European partners have combined their efforts to assess the effects of hydrogen presence on the existing gas network. Key issues are durability of pipeline material integrity management safety aspects life cycle and socio-economic assessment and end-use. The work described in this paper was performed within the NATURALHY work package on ’Durability of pipeline material’. This study makes it possible to emphasize the hydrogen effect on mechanical properties of several pipe steels as X52 X70 or X100 in fatigue and fracture and in two different environments: air and hydrogen electrolytic.
Hydrogen Safety- New Challenges Based on BMW Hydrogen 7
Sep 2007
Publication
The BMW Hydrogen 7 is the world’s first premium sedan with a bi-fuelled internal combustion engine concept that has undergone the series development process. This car also displays the BMW typical driving pleasure. During development the features of the hydrogen energy source were emphasized. Engine tank system and vehicle electronics were especially developed as integral parts of the vehicle for use with hydrogen. The safety-oriented development process established additional strict hydrogen-specific standards for the Hydrogen 7. The fulfilment of these standards were demonstrated in a comprehensive experimentation and testing program which included all required tests and a large number of additional hydrogen-specific crash tests such as side impacts to the tank coupling system or rear impacts. Furthermore the behaviour of the hydrogen tank was tested under extreme conditions for instance in flames and after strong degradation of the insulation. Testing included over 1.7 million km of driving; and all tests were passed successfully proving the intrinsic safety of the vehicle and also confirming the success of the safety-oriented development process which is to be continued during future vehicle development. A safety concept for future hydrogen vehicles poses new challenges for vehicles and infrastructure. One goal is to develop a car fuelled by hydrogen only while simultaneously optimizing the safety concept. Another important goal is removal of (self-imposed) restrictions for parking in enclosed spaces such as garages. We present a vision of safety standards requirements and a program for fulfilling them.
Real-gas Equations-of-State for the GASFLOW CFD Code
Sep 2011
Publication
GASFLOW is a finite-volume computer code that solves the time-dependent two-phase homogeneous equilibrium model compressible Navier–Stokes equations for multiple gas species with turbulence. The fluid-dynamics algorithm is coupled with conjugate heat and mass transfer models to represent walls floors ceilings and other internal structures to describe complex geometries such as those found in nuclear containments and facilities. Recent applications involve simulations of cryogenic hydrogen tanks at elevated pressures. These applications which often have thermodynamic conditions near the critical point require more accurate real-gas Equations-of-State (EoS) and transport properties than the standard ideal gas EoS and classical kinetic-theory transport properties. This paper describes the rigorous implementation of the generalized real-gas EoS into the GASFLOW CFD code as well as the specific implementation of respective real-gas models (Leachman's NIST hydrogen EoS a modified van der Waals EoS and a modified Nobel-Abel EoS); it also includes a logical testing procedure based upon a numerically exact benchmark problem. An example of GASFLOW simulations is presented for an ideal cryo-compressed hydrogen tank of the type utilized in fuel cell vehicles.
Evaluation of Optical and Spectroscopic Experiments of Hydrogen Jet Fires
Sep 2009
Publication
This paper reports results of evaluating joint experiments under the work programme of Hysafe occurring at HSL who provided the test facilities and basic measurements to generate jet fires whereas Fraunhofer ICT applied their equipment to visualise the jet fires by fast video techniques IR-cameras and fast scanning spectroscopy in the NIR/IR spectral region. Another paper describes the experimental set up and main findings of flame structures and propagation resolved in time. The spatial distribution of species and temperate as well as their time history and fluctuations give a basis of the evaluation of effects caused by such jet fires. Fraunhofer ICT applied their comprehensive evaluation codes to model the radiation emission from 3-atomic species in the flame especially H2O in the Infrared spectral range. The temperatures of the hydrogen flame were about 2000 K as found by least squares fit of the measured molecular bands by the codes. In comparison with video and thermo camera frames these might enable to estimate on a qualitative level species distribution and air entrainment and temperatures to identify hot and reactive zones. The risk analysis could use this information to estimate heat transfer and the areas of risk to direct inflammation from the jet fires by semi-empirical approaches.
Effect of Expansion Ratio on Flame Acceleration During Hydrogen Fueled Gas Explosions
Sep 2019
Publication
A precise understanding of the flame turbulence induced by cellular instabilities is indispensable to perform an appropriate risk assessment of hydrogen fuelled gas explosion. In this research Darrieus Landau instability (DL instability) whose effect on gas explosion is remarkable was experimentally examined. The DL instability is essentially caused by a volumetric expansion of burned gas at flame front. Therefore in order to examine the effects of volumetric expansion ratio the experiments were conducted using H2-O2-N2-Ar gas mixtures of various volumetric expansion ratio conditions by changing N2-Ar ratio. When Ar content ratio is increased the flame temperature becomes higher and volumetric expansion ratio is increased owing to lower specific heat of Ar. The experiments were conducted in nearly unconfined conditions of laboratory-scale and large-scale. Gas mixtures were filled in a 10 cm diameter soap bubble for the laboratory-scale and in a plastic tent of thin vinyl sheet of 1m3 for the large-scale. The gas mixtures were ignited by an electric spark and blast wave and flame speed were measured simultaneously by using a pressure sensor and a high-speed video camera. The DL instability owing to volumetric expansion accelerates flame propagation. In addition the intensity of blast wave was greatly raised depending on flame acceleration which can be explained by an acoustic theory. The effects of expansion ratio and experimental scales on flame propagation and blast wave were analyzed in detail. These results are quite important to perform an appropriate consequence analysis of accidental explosion of hydrogen.
Vented Explosion Overpressures From Combustion of Hydrogen and Hydrocarbon Mixtures
Sep 2009
Publication
Experimental data obtained for hydrogen mixtures in a room-size enclosure are presented and compared with data for propane and methane mixtures. This set of data was also used to develop a three-dimensional gas dynamic model for the simulation of gaseous combustion in vented enclosures. The experiments were performed in a 64 m3 chamber with dimensions of 4.6 × 4.6 × 3.0 m and a vent opening on one side and vent areas of either 2.7 or 5.4 m2 were used. Tests were performed for three ignition locations at the wall opposite the vent at the center of the chamber or at the center of the wall containing the vent. Hydrogen–air mixtures with concentrations close 18% vol. were compared with stoichiometric propane–air and methane–air mixtures. Pressure data as function of time and flame time-of-arrival data were obtained both inside and outside the chamber near the vent. Modelling was based on a Large Eddy Simulation (LES) solver created using the OpenFOAM CFD toolbox using sub-grid turbulence and flame wrinkling models. A comparison of these simulations with experimental data is discussed.
Effect of Microstructural and Environmental Variables on Ductility of Austenitic Stainless Steels
Sep 2019
Publication
Austenitic stainless steels are used extensively in harsh environments including for high-pressure gaseous hydrogen service. However the tensile ductility of this class of materials is very sensitive to materials and environmental variables. While tensile ductility is generally insufficient to qualify a material for hydrogen service ductility is an effective tool to explore microstructural and environmental variables and their effects on hydrogen susceptibility to inform understanding of the mechanisms of hydrogen effects in metals and to provide insight to microstructural variables that may improve relative performance. In this study hydrogen precharging was used to simulate high-pressure hydrogen environments to evaluate hydrogen effects on tensile properties. Several austenitic stainless steels were considered including both metastable and stable alloys. Room temperature and subambient temperature tensile properties were evaluated with three different internal hydrogen contents for type 304L and 316L austenitic stainless steels and one hydrogen content for XM-11. Significant ductility loss was observed for both metastable and stable alloys suggesting the stability of the austenitic phase is not sufficient to characterize the effects of hydrogen. Internal hydrogen does influence the character of deformation which drives local damage accumulation and ultimately fracture for both metastable and stable alloys. While a quantitative description of hydrogen-assisted fracture in austenitic stainless steels remains elusive these observations underscore the importance of the hydrogen-defect interactions and the accumulation of damage at deformation length scales.
CFD Benchmark Based on Experiments of Helium Dispersion in a 1m3 Enclosure–intercomparisons for Plumes
Sep 2013
Publication
In the context of the French DIMITRHY project ANR-08-PANH006 experiments have been carried out to measure helium injections in a cubic 1 m3 box - GAMELAN in a reproducible and quantitative manner. For the present work we limit ourselves to the unique configuration of a closed box with a small hole at its base to prevent overpressure. This case leads to enough difficulties of modelisations to deserve our attention. The box is initially filled with air and injections of helium through a tube of diameter 20 mm is operated. The box is instrumented with catharometres to measure the helium volume concentration within an accuracy better than 0.1%. We present the CFD (Fluent and CASTEM ANSYS-CFX and ADREA-HF) calculations results obtained by 5 different teams participating to the benchmark in the following situation: the case of a plume release of helium in a closed box (4NL/min). Parts of the CFD simulations were performed in the European co-funded project HyIndoor others were performed in the French ANR-08-PANH006 DimitrHy project.
First Responder Training Supporting Commercialization of Hydrogen and Fuel Cell Technologies
Oct 2015
Publication
A properly trained first responder community is critical to the successful introduction of hydrogen fuel cell applications and their transformation in how we use energy. Providing resources with accurate information and current knowledge is essential to the delivery of effective hydrogen and fuel cell-related first responder training. The California Fuel Cell Partnership and the Pacific Northwest National Laboratory have over 15 years of experience in developing and delivering hydrogen safety-related first responder training materials and programs. A National Hydrogen and Fuel Cell Emergency Response Training Resource was recently released. This training resource serves the delivery of a variety of training regimens. Associated materials are adaptable for different training formats ranging from high-level overview presentations to more comprehensive classroom training. This paper presents what has been learned from the development and delivery of hydrogen safety-related first responder training programs (online classroom hands-on) by the respective organizations. The collaborative strategy being developed for enhancing training materials and methods for greater accessibility based on stakeholder input will be discussed.
Material Testing and Design Recommendations for Components Exposed to Hydrogen Enhanced Fatigue – the Mathryce Project
Sep 2013
Publication
The three years European MATHRYCE project dedicated to material testing and design recommendations for components exposed to hydrogen enhanced fatigue started in October 2012. Its main goal is to provide an “easy” to implement methodology based on lab-scale experimental tests under hydrogen gas to assess the service life of a real scale component taking into account fatigue loading under hydrogen gas. Dedicated experimental tests will be developed for this purpose. In the present paper the proposed approach is presented and compared to the methodologies currently developed elsewhere in the world.
Hydrogen Fast Filling to a Type IV Tank Developed for Motorcycles
Oct 2015
Publication
If Hydrogen is expected to be highly valuable some improvements should be conducted mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign which will allow studying in future works the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire propane gas fire hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for reference of pure radiation heat transfer. The retained thermal load might be representative of accidental situations in worst case scenarios and relevant for a standardized testing protocol. The tests performed show that hydrogen gas fires and heptane pool fire allow reaching the target in terms of absorbed energy regarding the results of risk analysis performed previously. Other considerations can be taken into account that will led to retain an hydrogen gas fire for further works. Firstly hydrogen gas fire is the more realistic scenario: Hydrogen is the combustible that we every time find near an hydrogen storage. Secondly as one of the objectives of the project is to make recommendations for standardization issues it's important to note that gas fires are not too complex to calibrate control and reproduce. Finally due to previous considerations Hydrogen gas fire will be retained for thermal load of composite cylinders in future works.
LES Modelling Of Hydrogen Release and Accumulation Within a Non-Ventilated Ambient Pressure Garage Using The Adrea-HF CFD Code
Sep 2011
Publication
Computational Fluid Dynamics (CFD) has already proven to be a powerful tool to study the hydrogen dispersion and help in the hydrogen safety assessment. In this work the Large Eddy Simulation (LES) recently incorporated into the ADREA-HF CFD code is evaluated against the INERIS-6C experiment of hydrogen leakage in a supposed garage which provides detailed experimental measurements visualization of the flow and availability of previous CFD results from various institutions (HySafe SBEP-V3). The short-term evolution of the hydrogen concentrations in this confined space is examined and comparison with experimental data is provided along with comments about the ability of LES to capture the transient phenomena occurring during hydrogen dispersion. The influence of the value of the Smagorinsky constant on the resolved and on the unresolved turbulence is also presented. Furthermore the renormalization group (RNG) LES methodology is also tested and its behaviour in both highly-turbulent and less-turbulent parts of the flow is highlighted.
Influence of the Location of a Buoyant Gas Release in Several Configurations Varying the Height of the Release and the Geometry of the Enclosure
Sep 2013
Publication
The present work proposes a parametric study on the influence of the height of the release source on the helium dispersion regimes inside a naturally ventilated enclosure. Several configurations were experimentally addressed in order to improve knowledge on dispersion considering conditions close to hydrogen energy systems in terms of operating characteristics and design. Thus the varying parameters of the study were mainly the height of the release and also the releasing flow rate the volume and the geometry of the enclosure. Experimental results were compared to existing analytical models and considered through model improvements allowing a better approach of these specific cases for hydrogen systems risk assessment.
Simulation of the Efficiency of Hydrogen Recombiners as Safety Devices
Sep 2011
Publication
Passive auto-catalytic recombiners (PARs) are used as safety devices in the containments of nuclear power plants (NPPs) for the removal of hydrogen that may be generated during specific reactor accident scenarios. In the presented study it was investigated whether a PAR designed for hydrogen removal inside a NPP containment would perform principally inside a typical surrounding of hydrogen or fuel cell applications. For this purpose a hydrogen release scenario inside a garage – based on experiments performed by CEA in the GARAGE facility (France) – has been simulated with and without PAR installation. For modelling the operational behaviour of the PAR the in-house code REKO-DIREKT was implemented in the CFD code ANSYS-CFX. The study was performed in three steps: First a helium release scenario was simulated and validated against experimental data. Second helium was replaced by hydrogen in the simulation. This step served as a reference case for the unmitigated scenario. Finally the numerical garage setup was enhanced with a commercial PAR model. The study shows that the PAR works efficiently by removing hydrogen and promoting mixing inside the garage. The hot exhaust plume promotes the formation of a thermal stratification that pushes the initial hydrogen rich gas downwards and in direction of the PAR inlet. The paper describes the code implementation and simulation results.
Effect of Hydrogen Concentration on Vented Explosion Overpressures from Lean Hydrogen–air Deflagrations
Sep 2011
Publication
Experimental data from vented explosion tests using lean hydrogen–air mixtures with concentrations from 12 to 19% vol. are presented. A 63.7-m3 chamber was used for the tests with a vent size of either 2.7 or 5.4 m2. The tests were focused on the effect of hydrogen concentration ignition location vent size and obstacles on the pressure development of a propagating flame in a vented enclosure. The dependence of the maximum pressure generated on the experimental parameters was analyzed. It was confirmed that the pressure maxima are caused by pressure transients controlled by the interplay of the maximum flame area the burning velocity and the overpressure generated outside of the chamber by an external explosion. A model proposed earlier to estimate the maximum pressure for each of the main pressure transients was evaluated for the various hydrogen concentrations. The effect of the Lewis number on the vented explosion overpressure is discussed.
Hydrogen Storage: Recent Improvements and Industrial Prospective
Oct 2015
Publication
Efficient storage of hydrogen is crucial for the success of hydrogen energy markets (early markets as well as transportation market). Hydrogen can be stored either as a compressed gas a refrigerated liquefied gas a cryo-compressed gas or in hydrides. This paper gives an overview of hydrogen storage technologies and details the specific issues and constraints related to the materials behaviour in hydrogen and conditions representative of hydrogen energy uses. It is indeed essential for the development of applications requiring long-term performance to have good understanding of long-term behaviour of the materials of the storage device and its components under operational loads.
Use of Hydrogen Safety Sensors Under Anaerobic Conditions – Impact of Oxygen Content on Sensor Performance
Sep 2011
Publication
In any application involving the production storage or use of hydrogen sensors are important devices for alerting to the presence of leaked hydrogen. Hydrogen sensors should be accurate sensitive and specific as well as resistant to long term drift and varying environmental conditions. Furthermore as an integral element in a safety system sensor performance should not be compromised by operational parameters. For example safety sensors may be required to operate at reduced oxygen levels relative to air. In this work we evaluate and compare a number of sensor technologies in terms of their ability to detect hydrogen under conditions of varying oxygen concentration.
A National Set of Hydrogen Codes and Standards for the US
Sep 2009
Publication
In 2003 the US Department of Energy (DOE) initiated a project to coordinate the development of a national template of hydrogen codes and standards for both vehicular and stationary applications. The process consisted of an initial evaluation to determine where there were gaps in the existing hydrogen codes and standards and the codes and standards required to fill these gaps. These codes and standards were to be developed by several Standards Development Organizations (SDOs). This effort to develop codes and standards has progressed from a position in 2003 when there were relatively few codes and standards that directly addressed hydrogen technology applications to the position at the end of 2008 where requirements to permit hydrogen technologies have been implemented in primary adopted codes- building and fire codes in hydrogen specific codes such as National Fire Protection Association (NFPA) 52 NFPA 55 and NFPA 853 and in many of the hydrogen specific component standards that are referenced primarily in the NFPA codes and standards. This paper describes the three levels of codes and standards that address hydrogen technologies for the built environment:<br/>Level 1. Primary adopted building and fire codes<br/>Level 2. Hydrogen specific codes and standards references in primary adopted code<br/>Level 3. Hydrogen specific component standards referenced in hydrogen specific codes<br/>This paper also describes the progress to date in populating these three levels with the required hydrogen codes and standards. The first two levels are essentially complete and are undergoing refinement and routine revision. Level 3 the hydrogen specific component standards is the furthest from having first edition documents that address requirements for a hydrogen system component.<br/>The DOE is focusing much of their codes and standards development efforts on these hydrogen specific component standards with the expectation that a first edition of most of these standards will be issued by 2010.
Analysis of Transient Hydrogen Release, Dispersion and Explosion in a Tunnel with Fuel Cell Vehicles using All-Speed CFD Code
Sep 2019
Publication
Hydrogen energy is expanding world wide in recent years while hydrogen safety issues have drawn considerable attention. It is widely accepted that accidental hydrogen release in an open air environment will disperse quickly hence not causing significant hydrogen hazards. A hydrogen hazard is more likely to occur when hydrogen is accidentally released in a confined place i.e. parking garages and tunnels. Prediction the consequences of hydrogen detonation is important for hydrogen safety assessment and for ensuring the safety of installations during accidents. Hence an accident scenario of hydrogen release nd detonation in a tunnel is analysed with GASFLOW-MPI in this paper. GASFLOW-MPI is a well validated parallel CFD code focusing on hydrogen transport combustion and detonation. GASFLOWMPI solves compressible Navier-Stokes equations with a powerful all-speed Arbitrary-Lagrangian-Eulerian (ALE) method hence it can cover both the non-compressible flow during the hydrogen relesase and dispersion phases and the compressible flow during combustion and detonation. A 3D model of a tunnel including eight cars is modelled. Firstly the hydrogen dispersion in the tunnel is calculated. Then the detonation in the tunnel is calculated by manually igniting the hydrogen at the top of the tunnel when the λ criterion is maximum. The pressure loads are calculated to evaluate the consequence of the hazard.
Vented Hydrogen Deflagrations in Containers: Effect of Congestion for Homogeneous Mixtures
Sep 2017
Publication
This paper presents results from an experimental study of vented hydrogen deflagrations in 20-foot ISO containers. The scenarios investigated include 14 tests with explosion venting through the doors of the containers and 20 tests with venting through openings in the roof. The parameters investigated include hydrogen concentration vent area type of venting device and the level of congestion inside the containers. All tests involved homogeneous and initially quiescent hydrogen-air mixtures. The results demonstrate the strong effect of congestion on the maximum reduced explosion pressures which typically is not accounted for in current standards and guidelines for explosion protection. The work is a deliverable from work package 2 (WP2) in the project “Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations” or HySEA which receives funding from the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) under grant agreement no. 671461.
Safety Aspects in the Production and Separation of Hydrogen from Biomass
Sep 2011
Publication
Tecnalia is working in the development of gasification technology for the production of hydrogen from biomass. Biomass is an abundant and disperse renewable energy source that can be important for the production of hydrogen. The development of hydrogen system from biomass requires multifaceted studies on hydrogen production systems hydrogen separation methods and hydrogen safety aspects. Steam gasification of biomass produces a syngas with high hydrogen content but this syngas requires a post-treatment to clean and to separate the hydrogen. As a result of this analysis Tecnalia has defined a global process for the production cleaning enrichment and separation of hydrogen from the syngas produced from biomass gasification. But besides the technical aspects safety considerations affecting all the described processes have been identified. For that reason it is being developed a procedure to establish the technical requirements and the recommended practices to ensure the highest level of safety in the production and handing of hydrogen.
Real-size Calculation of High-pressure Hydrogen Flow and its Auto-ignition in Cylindrical Tube
Sep 2013
Publication
A real-size calculation is performed for high-pressure hydrogen release in a tube using the axisymmetric Navier–Stokes equations with the full hydrogen chemistry. A Harten–Yee-type total variation diminishing scheme and point-implicit method are used to integrate the governing equations. The calculated real-size results show that the leading shock wave velocity is similar to that calculated using a smaller tube. The mixing process and ignition behaviour of high-pressure hydrogen are explained in detail; the velocity shear layer and Kelvin–Helmholtz instability are the main causes of mixing of hydrogen with air and ignition in the high-temperature region behind the leading shock wave.
Predicting Radiative Characteristics of Hydrogen and Hythane Jet Fires Using Firefoam
Sep 2013
Publication
A possible consequence of pressurized hydrogen release is an under-expanded jet fire. Knowledge of the flame length radiative heat flux and fraction as well as the effects of variations in ground reflectance is important for safety assessment. The present study applies an open source CFD code FireFOAM to study the radiation characteristics of hydrogen and hydrogen/methane jet fires. For combustion the eddy dissipation concept for multi-component fuels recently developed by the authors in the large eddy simulation (LES) framework is used. The radiative heat is computed with the finite volume discrete ordinates model in conjunction with the weighted-sum-of-gray-gases model for the absorption/emission coefficient. The pseudo-diameter approach is used in which the corresponding parameters are calculated using the correlations of Birch et al. [22]. The predicted flame length and radiant fraction are in good agreement with the measurements of Schefer et al. [2] Studer et al. [3] and Ekoto et al. [6]. In order to account for the effects of variation in ground surface reflectance the emissivity of hydrogen flames was modified following Ekoto et al. [6]. Four cases with different ground reflectance are computed. The predictions show that the ground surface reflectance only has minor effect on the surface emissive power of the hydrogen jet fire. The radiant fractions fluctuate from 0.168 to 0.176 close to the suggested value of 0.16 by Ekoto et al.[6] based on the analysis of their measurements.
High Pressure Hydrogen Fires
Sep 2009
Publication
Within the scope of the French national project DRIVE and European project HyPER high pressure jet flames of hydrogen were produced and instrumented.<br/>The experimental technique and measurement strategy are presented. Many aspects are original developments like the direct measurement of the mass flow rate by weighing continuously the hydrogen container the image processing to extract the flame geometry the heat flux measurement device the thermocouples arrangement…<br/>Flames were observed from 900 bar down to 1 bar with orifices ranging from 1 to 3 mm. An original set of data is now available about the main flame characteristics and about some thermodynamic aspects of hydrogen releases under high pressure.<br/>A brief comparison of some available models is presented.
Application of the Validated 3D Multiphase-multicomponent CFD Model to an Accidental Liquid Hydrogen Release Scenario in a Liquefication Plant
Sep 2017
Publication
Hydrogen-air mixtures are flammable in a wide range of compositions and have a low ignition energy compared to gaseous hydrocarbons. Due to its low density high buoyancy and diffusivity the mixing is strongly enhanced which supports distribution into large volumes if accidentally released. Economically valuable discontinuous transportation over large distances is only expected using liquid hydrogen (LH2). Releases of LH2 at its low temperature (20.3 K at 0.1 MPa) have additional hazards besides the combustible character of gaseous hydrogen (GH2). Hazard assessment requires simulation tools capable of calculating the pool spreading as well as the gas distribution for safety assessments of existing the future liquid hydrogen facilities. Evaluating possible risks the following process steps are useful:
- Possible accident release scenarios need to be identified for a given plant layout.
- Environmental boundary conditions such as wind conditions and humidity need to be identified and worst case scenarios have to be identified.
- A model approach based on this information which is capable of simulating LH2 releases vaporization rates and atmospheric dispersion of the gaseous hydrogen.
- Evaluate and verify safety distances identify new risks and/or extract certain design rules.
Comparison of Solutions for a Liquid Pool Spreading Model with Continuous and Instantaneous Spills
Sep 2013
Publication
In this study a solution for a liquid pool spreading model with a continuous spill is compared with that for a liquid pool spreading model with an instantaneous spill under the same total release volume. As reducing spill time in completely releasing liquid from a tank it is evaluated whether the solution for a continuous spill approaches to that for an instantaneous spill or not. Also effects of the viscous term in the liquid pool spreading model with continuous and instantaneous spills on the liquid pool spreading behaviour are investigated.
Experimental Study of Hydrogen Releases in the Passenger Compartment of a Piaggio Porter
Sep 2011
Publication
There are currently projects and demonstration programs aiming at introducing Hydrogen powered Fuel Cell (HFC) vehicles into the market. Regione Toscana has been cofounder of the project “H2 Filiera Idrogeno” whose goal is to achieve a clean and sustainable mobility through HFC vehicle studies covering their production storage and use. Among the goals of the project was the substitution of the electric propulsion system with a hydrogen fuel cells propulsion system. This work presents a brief overview of the necessary modifications of the electric propulsion version of a Piaggio Porter to host a H2 fuel cell and experimental studies of realistic H2 releases from the vehicle. The scenarios covered H2 unintended releases underneath the vehicle when at rest and focused on three types of releases diffusive major and minor that might reach the interior of the vehicle and potentially pose a direct risk to the passengers.
Trends in Gas Sensor Development for Hydrogen Safety
Sep 2013
Publication
Gas sensors are applied for facilitating the safe use of hydrogen in for example fuel cell and hydrogen fuelled vehicles. New sensor developments aimed at meeting the increasingly stringent performance requirements in emerging applications are presented based on in-house technical developments and a literature study. The strategy of combining different detection principles i.e. sensors based on electrochemical cells semiconductors or field effects in combination with thermal conductivity sensor or catalytic combustion elements in one new measuring system is reported. This extends the dynamic measuring range of the sensor while improving sensor reliability to achieve higher safety integrity through diverse redundancy. The application of new nanoscaled materials nano wires carbon tubes and graphene as well as the improvements in electronic components of field-effect resistive-type and optical systems are evaluated in view of key operating parameters such as sensor response time low energy consumption and low working temperature.
Numerical Study on Spontaneous Ignition of Pressurized Hydrogen Release Through a Length of Tube
Sep 2009
Publication
The issue of spontaneous ignition of highly pressurized hydrogen release is of important safety concern e.g. in the assessment of risk and design of safety measures. This paper reports on recent numerical investigation of this phenomenon through releases via a length of tube. This mimics a potential accidental scenario involving release through instrument line. The implicit large eddy simulation (ILES) approach was used with the 5th-order weighted essentially non-oscillatory (WENO) scheme. A mixture-averaged multi-component approach was used for accurate calculation of molecular transport. The thin flame was resolved with fine grid resolution and the autoignition and combustion chemistry were accounted for using a 21-step kinetic scheme.<br/>The numerical study revealed that the finite rupture process of the initial pressure boundary plays an important role in the spontaneous ignition. The rupture process induces significant turbulent mixing at the contact region via shock reflections and interactions. The predicted leading shock velocity inside the tube increases during the early stages of the release and then stabilizes at a nearly constant value which is higher than that predicted by one-dimensional analysis. The air behind the leading shock is shock-heated and mixes with the released hydrogen in the contact region. Ignition is firstly initiated inside the tube and then a partially premixed flame is developed. Significant amount of shock-heated air and well developed partially premixed flames are two major factors providing potential energy to overcome the strong under-expansion and flow divergence following spouting from the tube.<br/>Parametric studies were also conducted to investigate the effect of rupture time release pressure tube length and diameter on the likelihood of spontaneous ignition. It was found that a slower rupture time and a lower release pressure will lead to increases in ignition delay time and hence reduces the likelihood of spontaneous ignition. If the tube length is smaller than a certain value even though ignition could take place inside the tube the flame is unlikely to be sufficiently strong to overcome under-expansion and flow divergence after spouting from the tube and hence is likely to be quenched.
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