Germany

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.

The flame velocities of unconfined gas explosions depend on the cloud size and the distance from the initiating source. The mechanisms for this effect are not fully understood; a possible explanation is turbulence generated by the propagating flame front. The molecular bands in the flame front are exposed to continuously increasing radiation intensity of water bands in the interior of the reaction product ball. A first approach to verifying this assumption is described in this paper. The flame propagation was observed by high speed video techniques including time resolved spectroscopy in the UV-Vis-NIR spectral range with a time resolution up to 3000 spectra/s. Ignition flame head velocity flame contours reacting species and temperatures were evaluated. The evaluation used video brightness subtraction and 1-dimensional image contraction to obtain traces of the movements perpendicular to the direction of propagation. Flame front velocities are found to be between 16m/s and 25 m/s. Analysis focused in particular on the flame front which is not smooth. Salients emerge on the surface to result in the well-known cellular structures. The radiation of various bands from the fire ball on the reacting species is estimated to have an influence on the flame velocity depending on the distance from initiation. Evaluation of OH-band and water band spectra might indicate might indicate higher temperatures of the flame front induced by radiation of the fireball. But it is difficult to verify the effect relative to competing flame acceleration mechanisms.

The effect of hydrogen atoms at grain boundaries in metals is usually detrimental to the cohesion of the interface. This effect can be quantified in terms of the strengthening energy which is obtained following the thermodynamic model of Rice and Wang. A critical component of this model is the bonding or solution energy of the atoms to the free surfaces that are created during decohesion. At a grain boundary in a multicomponent system it is not immediately clear how the different species would partition and distribute on the cleaved free surfaces. In this work it is demonstrated that the choice of partitioning pattern has a significant effect on the predicted influence of H and C on grain boundary cohesion. To this end the Σ3(112)[11¯0] symmetric tilt grain boundary in bcc Fe with different contents of interstitial C and H was studied taking into account all possible distributions of the elements as well as surface diffusion effects. H as a single element has a negative influence on grain boundary cohesion independent of the details of the H distribution. C on the other hand can act both ways enhancing or reducing the cohesion of the interface. The effect of mixed H and C compositions depends on the partition pattern. However the general trend is that the number of detrimental cases increases with increasing H content. A decomposition of the strengthening energy into chemical and mechanical contributions shows that the elastic contribution dominates at high C contents while the chemical contribution sets the trend for high H contents.

Liquid hydrogen (LH2) compared to compressed gaseous hydrogen offers advantages for large scale transport and storage of hydrogen with higher densities and potentially better safety performance. Although the gas industry has good experience with LH2 only little experience is available for the new applications of LH2 as an energy carrier. Therefore the European FCH JU funded project PRESLHY conducts pre-normative research for the safe use of cryogenic LH2 in non-industrial settings. The work program consists of a preparatory phase where the state of the art before the project has been summarized and where the experimental planning was adjusted to the outcome of a research priorities workshop. The central part of the project consists of 3 phenomena oriented work packages addressing Release Ignition and Combustion with analytical approaches experiments and simulations. The results shall improve the general understanding of the behavior of LH2 in accidents and thereby enhance the state-of-the-art what will be reflected in appropriate recommendations for development or revision of specific international standards. The paper presents the status of the project at the middle of its terms.

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.

The shipping industry is becoming increasingly visible on the global environmental agenda. Shipping's share of air pollution is becoming significant and public concern has led to ongoing political pressure to reduce shipping emissions. International legislation at the IMO governing the reduction of SOx and NOx emissions from shipping is being enforced and both the European Union and the USA are planning to introduce further regional laws to reduce emissions. Therefore new approaches for more environmental friendly and energy efficient energy converter are under discussion. One possible solution will be the use of fuel cell systems for auxiliary power or even main propulsion. The paper summarizes the legal background in international shipping related to the use of fuel cells and gas as fuel in ships. The focus of the paper will be on the first experiences on the use of fuel cell systems on board of ships. In this respect an incident on a fuel cell ship in Hamburg will be discussed. Moreover the paper will point out the potential for the use of fuel cell systems on board. Finally an outlook is given on ongoing and planed projects for the use of fuel cells on board of ships.

Metal hydrides are used for hydrogen storage. AlH3 shows a capacity to store about 10 wt% hydrogen. Its hydrogen is split-off in the temperature interval of 400–500 K. On dehydrogenation a nano-structured Al material emerges with specific surfaces up to 15–20 m2/g. The surface areas depend on the heating rate because of a temperature dependent crystallite growth. The resulting Al oxidizes up to 20–25% weight on air access forming an alumina passivation layer of 3–4 nm thickness on all exposed surfaces. The heat released from this Al oxidation induces a high risk to this type of hydrogen storage if the containment might be destroyed accidentally. The kinetics of the dehydrogenation and the subsequent oxidation is investigated by methods of thermal analysis. A reaction scheme is confirmed which consists of a starting Avrami-Erofeev mechanism followed by formal 1st order oxidation on unlimited air access. The kinetic parameters activation energies and pre-exponentials are evaluated and can be used to calculate the reaction progress. Together with the heat of the Al oxidation the overall heat release and the related rate can be estimated.

Liquid hydrogen carriers are considered to be attractive hydrogen storage options because of their ease of integration into existing chemical transportation infrastructures when compared with liquid or compressed hydrogen. The development of such carriers forms part of the work of the International Energy Agency Task 32: Hydrogen-Based Energy Storage. Here we report the state-of-the-art for ammonia-based and liquid organic hydrogen carriers with a particular focus on the challenge of ensuring easily regenerable high-density hydrogen storage.

The paper presents an overview of the main achievements of the internal project InsHyde of the HySafe NoE. The scope of InsHyde was to investigate realistic small-medium indoor hydrogen leaks and provide recommendations for the safe use/storage of indoor hydrogen systems. Additionally InsHyde served to integrate proposals from HySafe work packages and existing external research projects towards a common effort. Following a state of the art review InsHyde activities expanded into experimental and simulation work. Dispersion experiments were performed using hydrogen and helium at the INERIS gallery facility to evaluate short and long term dispersion patterns in garage like settings. A new facility (GARAGE) was built at CEA and dispersion experiments were performed there using helium to evaluate hydrogen dispersion under highly controlled conditions. In parallel combustion experiments were performed by FZK to evaluate the maximum amount of hydrogen that could be safely ignited indoors. The combustion experiments were extended later on by KI at their test site by considering the ignition of larger amounts of hydrogen in obstructed environments outdoors. An evaluation of the performance of commercial hydrogen detectors as well as inter-lab calibration work was jointly performed by JRC INERIS and BAM. Simulation work was as intensive as the experimental work with participation from most of the partners. It included pre-test simulations validation of the available CFD codes against previously performed experiments with significant CFD code inter-comparisons as well as CFD application to investigate specific realistic scenarios. Additionally an evaluation of permeation issues was performed by VOLVO CEA NCSRD and UU by combining theoretical computational and experimental approaches with the results being presented to key automotive regulations and standards groups. Finally the InsHyde project concluded with a public document providing initial guidance on the use of hydrogen in confined spaces.

Spontaneous ignition processes due to high pressure hydrogen releases into air are known phenomena. The sudden expansion of pressurized hydrogen into a pipe filled with ambient air can lead to a spontaneous ignition with a jet fire. This paper presents results of an experimental investigation of the visible flame propagation and pressure measurements in 4 mm extension tubes of up to 1 m length attached to a bulk vessel by a rupture disc. Transparent glass tubes for visual observation and shock wave pressure sensors are used in this study. The effect of the extension tube length on the development of a stable jet fire after a spontaneous ignition is discussed.