Safety

We’ve studied the conditions enabling a detonation to be quenched when interacting with an obstruction and the propensity for establishing subsequent fast-flame. Oxy-hydrogen detonations were found quench more easily than oxy-methane detonations when comparing the ratio of gap size and the detonation cell size. High-speed turbulent deflagrations that re-accelerate back to a detonation were only observed in methane-oxygen mixtures. Separate hot-spot ignition calculations revealed that the higher detonability of methane correlates with its stronger propensity to develop localized hot-spots. The results suggest that fast-flames are more difficult to form in hydrogen than in methane mixtures.

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.

Currently the periodic inspection of composite tanks is typically achieved via hydrostatic test combined with internal and external visual inspections. Acoustic emission (AE) technology demonstrates a promising non destructive testing method for damage mode identification and damage assessment. This study focuses on AE signals characteristics and evolution behaviours for used 70 MPa Type IV hydrogen storage tanks during hydrostatic burst tests. AE-based tensile tests for epoxy resin specimen and carbon fiber tow were implemented to obtain characteristics of matrix cracking and fiber breakage. Then broadband AE sensors were used to capture AE signals during multi-step loading tests and hydrostatic burst tests. K-means ++ algorithm and wavelet packet transform are performed to cluster AE signals and verify the validity. Combining with tensile tests three clusters are manifested via matrix cracking fiber/matrix debonding and fiber breakage according to amplitude duration counts and absolute energy. The number of three clustering signals increases with the increase of pressure showing accumulated and aggravated damage. The sudden appearance of a large number of fiber breakage signals during hydrostatic burst tests suggests that the composite tank structure is becoming mechanically unstable namely the impending burst failure of the tank.

As hydrogen fuel cell vehicles become more widely adopted by consumers the demand for refuelling stations increases. Most vehicles require high-pressure (either 350 or 700 bar) hydrogen and therefore the refuelling infrastructure must support these pressures. Fast running reduced order physical models of releases from high-pressure sources are needed so that quantitative risk assessment can guide the safety certification of these stations. A release from a high pressure source is choked at the release point forming the complex shock structures of an under-expanded jet before achieving a characteristic Gaussian pro le for velocity density mass fraction etc. downstream. Rather than using significant computational resources to resolve the shock structure an equivalent source model can be used to quickly and accurately describe the ow in terms of velocity diameter and thermodynamic state after the shock structure. In this work we present correlations for the equivalent boundary conditions of a subsonic jet as a high-pressure jet downstream of the shock structure. Schlieren images of under-expanded jets are used to show that the geometrical structure of under-expanded jets scale with the square root of the static to ambient pressure ratio. Correlations for an equivalent source model are given and these parameters are also found to scale with square root of the pressure ratio. We present our model as well as planar laser Rayleigh scattering validation data for static pressures up to 60 bar.

In the present work CFD simulations of a large scale open deflagration experiment are performed. Stoichiometric hydrogen–air mixture occupies a 20 m hemisphere. Two combustion models are compared and evaluated against the experiment: the Eddy Dissipation Concept model and a multi-physics combustion model which calculates turbulent burning velocity based on Yakhot's equation. Sensitivity analysis on the value of fractal dimension of the latter model is performed. A semi-empirical relation which estimates the fractal dimension is also tested. The effect of the turbulence model on the results is examined. LES approach and k-ε models are used. The multi-physics combustion model with constant fractal dimension value equal to 2.3 using the RNG LES turbulence model achieves the best agreement with the experiment.

In order to achieve a high level of safety while using hydrogen as a vehicle fuel the possible hazards must be estimated. Especially hydrogen release tests with defined ignition represent a very important way to characterize the basics of hydrogen combustion in a potential accident. So ICT participated on a hydrogen jet release campaign at HSL (Buxton) in 2008 to deploy their measurement techniques and evaluation methods to visualize jets ignition and subsequent flames. The following paper shows the application of high speed cinematography in combination with image processing techniques the Background Oriented Schlieren (BOS) and a difference method to visualize the shape of hydrogen jet. In addition these methods were also used to observe ignition and combustion zone after defined initiation. In addition the combustion zone was recorded by a fast spectral radiometer and a highspeed-IR-camera. The IR-camera was synchronized with a rotating filter wheel to generate four different motion pictures at 100Hz each on a defined spectral range. The results of this preliminary evaluation provide some detailed information that might be used for improving model predictions.

During the filling of hydrogen tanks high temperatures can be generated inside the vessel because of the gas compression while during the emptying low temperatures can be reached because of the gas expansion. The design temperature range goes from −40 °C to 85 °C. Temperatures outside that range could affect the mechanical properties of the tank materials. CFD analyses of the filling and emptying processes have been performed in the HyTransfer project. To assess the accuracy of the CFD model the simulation results have been compared with new experimental data for different filling and emptying strategies. The comparison between experiments and simulations is shown for the temperatures of the gas inside the tank for the temperatures at the interface between the liner and the composite material and for the temperatures on the external surface of the vessel.

As of 2014 the majority of the Codes and Standards required to initially deploy hydrogen technologies infrastructure in the US have been promulgated1. These codes and standards will be field tested through their application to actual hydrogen technologies projects. CCSI is process of identifying code issues that arise during project deployment and then develop codes solutions to these issues. These solutions would typically be proposed amendments to codes and standards. The process is continuous because of technology and the state of safety knowledge develops there will be a need for monitoring the application of codes and standards and improving them based on information gathered during their application. This paper will discuss code issues that have surfaced through hydrogen technologies infrastructure project deployment and potential code changes that would address these issues. The issues that this paper will address include:

• Setback distances for bulk hydrogen storage
• Code mandated hazard analyses
• Sensor placement and communication
• The use of approved equipment
• System monitoring and maintenance requirements

HyRAM is a methodology and accompanying software toolkit which is being developed to provide a platform for integration of state-of-the-art validated science and engineering models and data relevant to hydrogen safety. As such the HyRAM software toolkit establishes a standard methodology for conducting quantitative risk assessment (QRA) and consequence analysis relevant to assessing the safety of hydrogen fueling and storage infrastructure. The HyRAM toolkit integrates fast-running deterministic and probabilistic models for quantifying risk of accident scenarios for predicting physical effects and for characterizing the impact of hydrogen hazards (thermal effects from jet fires thermal and pressure effects from deflagrations and detonations). HyRAM incorporates generic probabilities for equipment failures for nine types of hydrogen system components generic probabilities for hydrogen ignition and probabilistic models for the impact of heat flux and pressure on humans and structures. These are combined with fast-running computationally and experimentally validated models of hydrogen release and flame behaviour. HyRAM can be extended in scope via user contributed models and data. The QRA approach in HyRAM can be used for multiple types of analyses including codes and standards development code compliance safety basis development and facility safety planning. This manuscript discusses the current status and vision for HyRAM.

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.