France
An Intercomparison Exercise on the Capabilities of CFD Models to Predict Deflagration of a Large-Scale H2-Air Mixture in Open Atmosphere
Sep 2005
Publication
This paper presents a compilation of the results supplied by HySafe partners participating in the Standard Benchmark Exercise Problem (SBEP) V2 which is based on an experiment on hydrogen combustion that is first described. A list of the results requested from participants is also included. The main characteristics of the models used for the calculations are compared in a very succinct way by using tables. The comparison between results together with the experimental data when available is made through a series of graphs. The results show quite good agreement with the experimental data. The calculations have demonstrated to be sensitive to computational domain size and far field boundary condition.
An Inter-Comparison Exercise on the Capabilities of CFD Models to Predict the Short and Long Term Distribution and Mixing of Hydrogen in a Garage
Sep 2007
Publication
Alexandros G. Venetsanos,
E. Papanikolaou,
J. García,
Olav Roald Hansen,
Matthias Heitsch,
Asmund Huser,
Wilfried Jahn,
Jean-Marc Lacome,
Thomas Jordan,
H. S. Ledin,
Dmitry Makarov,
Prankul Middha,
Etienne Studer,
Andrei V. Tchouvelev,
Franck Verbecke,
M. M. Voort,
Andrzej Teodorczyk and
M. A. Delichatsios
The paper presents the results of the CFD inter-comparison exercise SBEP-V3 performed within the activity InsHyde internal project of the HYSAFE network of excellence in the framework of evaluating the capability of various CFD tools and modelling approaches in predicting the physical phenomena associated to the short and long term mixing and distribution of hydrogen releases in confined spaces. The experiment simulated was INERIS-TEST-6C performed within the InsHyde project by INERIS consisting of a 1 g/s vertical hydrogen release for 240 s from an orifice of 20 mm diameter into a rectangular room (garage) of dimensions 3.78x7.2x2.88 m in width length and height respectively. Two small openings at the front and bottom side of the room assured constant pressure conditions. During the test hydrogen concentration time histories were measured at 12 positions in the room for a period up to 5160 s after the end of release covering both the release and the subsequent diffusion phases. The benchmark was organized in two phases. The first phase consisted of blind simulations performed prior to the execution of the tests. The second phase consisted of post calculations performed after the tests were concluded and the experimental results made available. The participation in the benchmark was high: 12 different organizations (2 non-HYSAFE partners) 10 different CFD codes and 8 different turbulence models. Large variation in predicted results was found in the first phase of the benchmark between the various modelling approaches. This was attributed mainly to differences in turbulence models and numerical accuracy options (time/space resolution and discretization schemes). During the second phase of the benchmark the variation between predicted results was reduced.
Hydrogen Refueling Stations: Safe Filling Procedures
Sep 2005
Publication
Safety is a high priority for a hydrogen refueling station. Here we propose a method to safely refuel a vehicle at optimised speed of filling with minimum information about it. Actually we identify two major risks during a vehicle refuelling: over filling and overheating. These two risks depend on the temperature increase in the tank during refuelling. But the inside temperature is a difficult information to get from the station point of view. It assumes a temperature sensor in a representative place of the tank and an additional connection between the vehicle and the station for data exchange. The refuelling control may not depend on this parameter only. Therefore out objective was to effectively control the filling particularly to avoid the two identified risks independently of optional and safety redundant information from the vehicle. For that purpose we defined a maximum filling pressure which corresponds to the most severe following conditions: if the maximum temperature is reached in the tank or if the maximum capacity is reached in the tank. This maximum pressure depends on a few filling parameters which are easily available. The method and its practical applications are depicted.
Quantifying the Hydrogen Embrittlement of Pipeline Steels for Safety Considerations
Sep 2011
Publication
In a near future with an increasing use of hydrogen as an energy vector gaseous hydrogen transport as well as high capacity storage may imply the use of high strength steel pipelines for economical reasons. However such materials are well known to be sensitive to hydrogen embrittlement (HE). For safety reasons it is thus necessary to improve and clarify the means of quantifying embrittlement. The present paper exposes the changes in mechanical properties of a grade API X80 steel through numerous mechanical tests i.e. tensile tests disk pressure test fracture toughness and fatigue crack growth measurements WOL tests performed either in neutral atmosphere or in high-pressure of hydrogen gas. The observed results are then discussed in front of safety considerations for the redaction of standards for the qualification of materials dedicating to hydrogen transport.
Hydrogen Storage: Recent Improvements and Industrial Perspectives
Sep 2019
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.
Influence of Doping Element in Distributed Hydrogen Optical Fiber Densors with Brillouin Scattering
Sep 2013
Publication
Distributed hydrogen optical fiber sensor with Brillouin scattering is an innovative solution to measure hydrogen in harsh environment as nuclear industry. Glass composition is the key point to enhance the sensing parameter of the fiber in the target application. Several optical fiber with different doping element were used for measuring hydrogen saturation. Permeability of optical plays a major role to the kinetic of hydrogen diffusion. Fluorine doped fiber increase the sorption and the desorption of hydrogen.
Threshold Stress Intensity Factor for Hydrogen Assisted Cracking of Cr-Mo Steel Used as Stationary Storage Buffer of a Hydrogen Refueling Station
Oct 2015
Publication
In order to determine appropriate value for threshold stress intensity factor for hydrogen-assisted cracking (KIH) constant-displacement and rising-load tests were conducted in high-pressure hydrogen gas for JIS-SCM435 low alloy steel (Cr-Mo steel) used as stationary storage buffer of a hydrogen refuelling station with 0.2% proof strength and ultimate tensile strength equal to 772 MPa and 948 MPa respectively. Thresholds for crack arrest under constant displacement and for crack initiation under rising load were identified. The crack arrest threshold under constant displacement was 44.3 MPa m1/2 to 44.5 MPa m1/2 when small-scale yielding and plane-strain criteria were satisfied and the crack initiation threshold under rising load was 33.1 MPa m1/2 to 41.1 MPa m1/2 in 115 MPa hydrogen gas. The crack arrest threshold was roughly equivalent to the crack initiation threshold although the crack initiation threshold showed slightly more conservative values. It was considered that both test methods could be suitable to determine appropriate value for KIH for this material.
Helium Release in A Closed Enclosure- Comparisons Between Simple Models, CFD Calculations And Experimental Results
Sep 2011
Publication
In the prospect of a safe use of hydrogen in our society one important task is to evaluate under which conditions the storage of hydrogen systems can reach a sufficient level of safety. One of the most important issues is the use of such system in closed area for example a private garage or an industrial facility. In the scope of this paper we are mainly interested in the following scenario: a relatively slow release of hydrogen (around 5Nl/min) in a closed and almost cubic box representing either a fuel cell at normal scale or a private garage at a smaller scale. For practical reasons helium was used instead of hydrogen in the experiments on which are based our comparisons. This kind of situation leads to the fundamental problem of the dispersion of hydrogen due to a simple vertical source in an enclosure. Many numerical and experimental studies have already been conducted on this problem showing the formation of either a stably stratified distribution of concentration or the formation of a homogeneous layer due to high enough convective flows at the top of the enclosure. Nevertheless most of them consider the cases of accidental situation in which the flow rate is relatively important (higher than 10Nl/min). Numerical simulations carried out with the CEA code Cast3M and a LES turbulence model confirm the differences of results already observed in experimental helium concentration measurements for a same injection flow rate and two different injection nozzle diameters contradicting simple physical models used in safety calculations.
CFD Validation Against Large Scale Liquified Helium Release
Sep 2019
Publication
The ADREA-HF CFD code is validated against a large scale liquefied helium release experiment on flat ground performed by INERIS in the past. The predicted release and dispersion behavior is evaluated against the experimental using temperature time histories at sensors deployed at various distances and heights downstream the source. For the selected sensors the temperature predictions are generally in good agreement with the experimental with a tendency to under-predict temperature as the source is approached.
Fast Synthesis of TiNi by Mechanical Alloying and its Hydrogenation Properties
Mar 2019
Publication
Mechanical alloying is widely used for the synthesis of hydrogen storage materials. However amorphization and contamination triggered by long-time milling are serious drawbacks for obtaining efficient hydrogen storage. In this work short-time ball milling synthesis is explored for a representative hydride forming compound: TiNi. Through structural morphological and chemical characterizations we evidence that formation of TiNi is complete in only 20 min with minor Fe contamination (0.2 wt%). Cross-sectional analysis of powder stuck on milling balls reveals that alloy formation occurs through the interdiffusion between thin layers of co-laminated pure elements. Hydrogenation thermodynamics and kinetics of short-time mechanically alloyed TiNi are similar to those of coarse-grained compounds obtained by classical high-temperature melting. Mechanical alloying is a suitable method for fast and energy-efficient synthesis of intermetallic compounds such as TiNi.
Ia-HySafe Standard Benchmark Exercise Sbep-V21- Hydrogen Release and Accumulation within a Non-Ventilated Ambient Pressure Garage at Low Release Rates
Sep 2011
Publication
The successful Computational Fluid Dynamics (CFD) benchmarking activity originally started within the EC-funded Network of Excellence HySafe (2004-2009) continues within the research topics of the recently established “International Association of Hydrogen Safety” (IA-HySafe). The present contribution reports the results of the standard benchmark problem SBEP-V21. Focus is given to hydrogen dispersion and accumulation within a non-ventilated ambient pressure garage both during the release and post-release periods but for very low release rates as compared to earlier work (SBEP-V3). The current experiments were performed by CEA at the GARAGE facility under highly controlled conditions. Helium was vertically released from the centre of the 5.76 m (length) x 2.96 m (width) x 2.42 m (height) facility 22 cm from the floor from a 29.7 mm diameter opening at a volumetric rate of 18 L/min (0.027 g/s equivalent hydrogen release rate compared to 1 g/s for SBEP-V3) and for a period of 3740 seconds. Helium concentrations were measured with 57 catharometric sensors at various locations for a period up to 1.1 days. The simulations were performed using a variety of CFD codes and turbulence models. The paper compares the results predicted by the participating partners and attempts to identify the reasons for any observed disagreements.
Combustion Modeling in Large Scale Volumes
Sep 2013
Publication
This paper is devoted to a benchmarking exercise of the EUROPLEXUS code against several large scale deflagration and detonation experimental data sets in order to improve its hydrogen combustion modeling capabilities in industrial settings. The code employs an algorithm for the propagation of reactive interfaces RDEM which includes a combustion wave as an integrable part of the Reactive Riemann problem propagating with a fundamental flame speed (being a function of initial mixture properties as well as gas dynamics parameters). An improvement of the combustion model is searched in a direction of transient interaction of flames with regions of elevated vorticity/shear in obstacle-laden channels and vented enclosures.
Hydrogen Storage - Recent Improvements and Industrial Prospectives
Sep 2013
Publication
This paper gives a historical and technical overview of hydrogen storage vessels and details the specific issues and constraints of hydrogen energy uses. Hydrogen as an industrial gas is stored either as a compressed or as a refrigerated liquefied gas. Since the beginning of the last century hydrogen is stored in seamless steel cylinders. At the end of the 60s tubes also made of seamless steels were used; specific attention was paid to hydrogen embrittlement in the 70s. Aluminum cylinders were also used for hydrogen storage since the end of the 60s but their cost was higher compared to steel cylinders and smaller water capacity. To further increase the service pressure of hydrogen tanks or to slightly decrease the weight metallic cylinders can be hoop-wrapped. Then with specific developments for space or military applications fully-wrapped tanks started to be developed in the 80s. Because of their low weight they started to be used in for portable applications for vehicles (on-board storages of natural gas) for leisure applications (paint-ball) etc… These fully-wrapped composite tanks named types III and IV are now developed for hydrogen energy storage; the requested pressure is very high (from 700 to 1 000 bar) leads to specific issues which are discussed. Each technology is described in term of materials manufacturing technologies and approval tests. The specific issues due to very high pressure are depicted. Hydrogen can also be stored in liquid form (refrigerated liquefied gases). The first cryogenic vessels were used in the 60s. In the following the main characteristics of this type of storage will be indicated.
Modelling of H2 Dispersion and Combustion Phenomena Using CFD Codes
Sep 2005
Publication
Computational Fluid Dynamics codes are increasingly being considered for safety assessment demonstrations in many industrial fields as tools to model accidental phenomena and to design mitigation (risk reducing) systems. Thus they naturally complement experimental programmes which may be expensive to run or difficult to set up. However to trust numerical simulations the validity of the codes must be firmly established and a certain number of error sources (user effect modelling errors discretization errors etc) reduced to the minimum. Code validation and establishment of “best practice guidelines” in the application of simulation tools to hydrogen safety assessment are some of the objectives pursued by the HYSAFE Network of Excellence. This paper will contribute to these goals by describing some of the validation efforts that CEA is making in the areas of release dispersion combustion and mitigation thereby proposing the outline of a validation matrix for hydrogen safety problems.
Detonability of Binary H2/Ch4 - Air Mixture
Sep 2009
Publication
Abatement of greenhouse gas emissions and diversification of energy sources will probably lead to an economy based on hydrogen. In order to evaluate safety conditions during transport and distribution experimental data is needed on the detonation of Hydrogen/Natural gas blend mixtures. The aim of this study is to constitute detonation and deflagration to detonation transition (DDT) database of H2/CH4-air mixtures. More precisely the detonability of such mixtures is evaluated by the detonation cell size and the DDT run up distance measurements. Large experimental conditions are investigated (i) various equivalence ratios from 0.6 to 3 (ii) various H2 molar fraction x ( ( )2 2 4x H H CH= + ) from 0.5 to 1 (iii) different initial pressure P0 from 0.2 to 2 bar at fixed ambient temperature T0=293 K. Detonation pressures P velocities D and cell sizes ? were measured in two smooth tubes with different i.d. d (52 and 106 mm). For DDT data minimum DDT run up distances LDDT were determined in the d=52 mm tube containing a 2.8 m long Schelkin spiral with a blockage ratio BR = 0.5 and a pitch equal to the diameter. Measured detonation velocities D are very close to the Chapman Jouguet values (DCJ). Concerning the effect of detonation cell size ? follows a classical U shaped- curve with a minimum close to =1 and concerning the effect of x ? decreases when x increases. The ratio ik L?= obtained from different chemical kinetics (Li being the ZND induction length) is well approximated by the value 40 in the range 0.5 < x < 0.9 and 50 for x 0.9. Minimum DDT run up distance LDDT varies from 0.36 to 1.1m when x varies from 1 to 0.8. The results show that LDDT obeys the linear law LDDT ~ 30-40? previously validated in H2/Air mixtures. Adding Hydrogen in Natural Gas promotes the detonability of the mixtures and for x 0.65 these mixtures are considered more sensitive than common heavy Alkane-Air mixtures.
Hydrogen and Fuel Cell Stationary Applications: Key Findings of Modelling and Experimental Work in the Hyper Project
Sep 2009
Publication
Síle Brennan,
A. Bengaouer,
Marco Carcassi,
Gennaro M. Cerchiara,
Andreas Friedrich,
O. Gentilhomme,
William G. Houf,
N. Kotchourko,
Alexei Kotchourko,
Sergey Kudriakov,
Dmitry Makarov,
Vladimir V. Molkov,
Efthymia A. Papanikolaou,
C. Pitre,
Mark Royle,
R. W. Schefer,
G. Stern,
Alexandros G. Venetsanos,
Anke Veser,
Deborah Willoughby,
Jorge Yanez and
Greg H. Evans
"This paper summarises the modelling and experimental programme in the EC FP6 project HYPER. A number of key results are presented and the relevance of these findings to installation permitting guidelines (IPG) for small stationary hydrogen and fuel cell systems is discussed. A key aim of the activities was to generate new scientific data and knowledge in the field of hydrogen safety and where possible use this data as a basis to support the recommendations in the IPG. The structure of the paper mirrors that of the work programme within HYPER in that the work is described in terms of a number of relevant scenarios as follows: 1. high pressure releases 2. small foreseeable releases 3. catastrophic releases and 4. the effects of walls and barriers. Within each scenario the key objectives activities and results are discussed.<br/>The work on high pressure releases sought to provide information for informing safety distances for high-pressure components and associated fuel storage activities on both ignited and unignited jets are reported. A study on small foreseeable releases which could potentially be controlled through forced or natural ventilation is described. The aim of the study was to determine the ventilation requirements in enclosures containing fuel cells such that in the event of a foreseeable leak the concentration of hydrogen in air for zone 2 ATEX is not exceeded. The hazard potential of a possibly catastrophic hydrogen leakage inside a fuel cell cabinet was investigated using a generic fuel cell enclosure model. The rupture of the hydrogen feed line inside the enclosure was considered and both dispersion and combustion of the resulting hydrogen air mixture were examined for a range of leak rates and blockage ratios. Key findings of this study are presented. Finally the scenario on walls and barriers is discussed; a mitigation strategy to potentially reduce the exposure to jet flames is to incorporate barriers around hydrogen storage equipment. Conclusions of experimental and modelling work which aim to provide guidance on configuration and placement of these walls to minimise overall hazards is presented. "
Modelling Of Hydrogen Explosion on a Pressure Swing Adsorption Facility
Sep 2011
Publication
Computational fluid dynamic simulations have been performed in order to study the consequences of a hydrogen release from a pressure swing adsorption installation operating at 30 barg. The simulations were performed using FLACS-Hydrogen software from GexCon. The impact of obstruction partial confinement leak orientation and wind on the explosive cloud formation (size and explosive mass) and on explosion consequences is investigated. Overpressures resulting from ignition are calculated as a function of the time to ignition.
Comparison of Two Simplified Models Predictions with Experimental Measurements for Gas Release Within an Enclosure
Sep 2009
Publication
In this work the validity of simplified mathematical models for predicting dispersion of turbulent buoyant jet or plume within a confined volume is evaluated. In the framework of the HYSAFE Network of Excellence CEA performed experimental tests in a full-scale Garage facility in order to reproduce accidental gas leakages into an unventilated residential garage. The effects of release velocities diameters durations mass flow rates and flow regimes on the vertical distribution of the gas concentration are investigated. Experimental data confirm the formation for the release conditions of an almost well-mixed upper layer and a stratified lower layer. The comparison of the measurements and the model predictions shows that a good agreement is obtained for a relatively long-time gas discharge for jet like or plume like flow behaviour.
Experimental Study of the Effects of Vent Geometry on the Dispersion of a Buoyant Gas in a Small Enclosure
Sep 2011
Publication
We present an experimental study on the dispersion of helium in an enclosure of 1 m3 with natural ventilation through one vent. Three vent geometries have been studied. Injection parameters have been varied so that the injection Richardson number ranges from 2·10−6 to 9 and the volume Richardson number which gives the ability of the release to mix the enclosure content ranges from 8·10−4 to 900. It has been found that the vertical distribution of helium volume fraction can exhibit significant gradient. Nevertheless the results are compared to the simple analytical model based on the homogenous mixture hypothesis which gives fairly good estimates of the maximum helium volume fraction.
Delayed Explosion of Hydrogen High Pressure Jets in a Highly Obstructed Geometry
Sep 2017
Publication
Delayed explosions of accidental high pressure hydrogen releases are an important risk scenario in safety studies of production plants transportation pipelines and fuel cell vehicles charging stations. Such explosions were widely explored in multiple experimental and numerical investigations. Explosion of high pressure releases in highly obstructed geometries with high blockage ratio is a much more complicated phenomenon. This paper is dedicated to the experimental investigation of the influence of obstacles on a delayed deflagration of hydrogen jets. The computational fluid dynamics (CFD) code FLACS is used to reproduce experimental data. In the current study the computed overpressure signals are compared to the experimentally measured ones at different monitoring points. Simulations are in close agreement with experimental results and can be used to predict overpressure where experimental pressure detectors were saturated. For homogenous stationary clouds a new approach of equivalent mixture of H2/air (~16.5%) to stoichiometric mixture of CH4/air is suggested. This approach is validated versus experimental data from the literature in terms of overpressure maxima. A parametric study is performed using FLACS for various concentrations in the same geometry in order to identify a possible transition from deflagration to detonation.
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