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Paper des Monats
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In order to reduce the human footprint of CO2 emissions and limit global warming effects hydrogen combustion is becoming increasingly important. To enable fuel cells and gas turbines to operates this carbon free fuel, unprecedently large amounts of hydrogen need to be produced and safely transported and stored. The investigation of the effects of accidents involving hydrogen is therefore becoming of outmost importance. Since hydrogen is usually stored and transported under pressure, one scenario to be considered is the release of hydrogen from a leakage with subsequent ignition. The resulting jet flame must be characterized with respect to the thermal radiation emitted into the environment to define safety regulations. Various models that characterize the resulting flame shape and radiation already exist in the literature, but these are mainly based on empirical data from hydrocarbon jet flames.[1-4] To verify these models, a H2 Jet Flame project conducted at BAM, is investigating the safety of momentum driven hydrogen jet flames. For this purpose, large-scale tests are carried out at the Test Site Technical Safety (BAM-TTS). The object of the investigations is to assess the effects of real scale release scenarios regarding flame geometry and the thermal radiation emitted. Parameters such as release angle, leakage diameter (currently 1 mm to 10 mm), pressure (currently up to max. 250 bar) and mass flow (up to max. 0.5 kg/s) are varied. In addition, influences such as the type of ignition, ignition location as well as delayed ignition can also be investigated. The gained knowledge will be compared with existing jet flame models, to validate these and identify a possible need for further development. In particular, the focus will be laid on the thermal radiation of hydrogen flames. The challenge here is the visualization and characterization of the flame geometry in an open environment. Visualization is performed using infrared (IR) camera systems from at least two viewing angles. Measurements of the heat radiation of jet flames, which can be found in the literature, are mostly based on unsteady outflow conditions.The experimental setup used here allows for the generation of a steady-state outflow for several minutes and thus a direct comparability with existing (steady-state) models. Furthermore, the tests can be carried out for comparative measurements with hydrocarbons (methane, etc.) as well as mixtures of hydrogen and hydrocarbons.
Interlaboratory studies are common tools for collecting comparable data to implement standards for new materials or testing technologies. In the case of construction materials, these studies form the basis for recommendations and design codes. Depending on the study, the amount of data collected can be enormous, making manual handling and evaluation difficult. On the other hand, the importance of the FAIR (findable, accessible, interoperable, and reusable) principles for scientific data management, published by Wilkinson et al. in 2016, is constantly growing and changing the view on data usage.
The benefits of using data management tools such as data stores/repositories or electronic laboratory notebooks are many. Data is stored in a structured and accessible way (at least within a group) and data loss due to staff turnover is reduced. Tools usually support data publishing and analysis interfaces. In this way, data can be reused years later to generate new knowledge with future insights. On the other hand, there are many challenges in setting up a data repository, such as selecting suitable software tools, defining the data structure, enabling data access, and understanding by others and
ensuring maintenance, among others.
This talk discusses the advantages and challenges of setting up and applying a data repository using the interlaboratory study on the mechanical properties of printed concrete structures carried out in RILEM TC 304-ADC as example. First, the definition of a suitable data structure including all information is discussed. The tool-dependent upload process is then described. Here, the data
management system openBIS (open source software developed by ETH Zurich) is used. Since in most cases an open compute platform allowing access from different organisations is not possible or available due to data protection and maintenance issues, tool-independent export options are discussed and compared. Finally, the different query and analysis possibilities are demonstrated.
In this presentation, the results of the determination of the diffraction and single-crystal elastic constants of laser powder bed fused Inconel 718 are presented. The analysis is based on high-energy synchrotron diffraction experiments performed at the Deutsches Elektronen-Synchrotron. It is shown that the characteristic microstructure of laser powder bed fused Inconel 718 impacts the elastic anisotropy and therefore the diffraction and single-crystal elastic constants. Finally, the consequences on the diffraction-based residual stress determination of laser powder bed fused Inconel 718 are discussed.
In this lecture, the safety assessment of hydrogen gas storage systems is presented using the example of composite pressure vessels. The main element is a probabilistic approval approach based on five steps. Firstly, the testing and evaluation of properties at the beginning of life are shown. Secondly, methods for artificial aging and the effect on the residual strength are presented. Thirdly, testing against dedicated accidents is introduced. Fourthly, effects on the surveillance of production quality are discussed. Finally, degradation and the end of life are estimated. Background information and examples are given for each step. The assessment presented is a method applicable for many safety-related systems.
In this lecture, the safety assessment of hydrogen gas storage systems is presented using the example of composite pressure vessels. The main element is a probabilistic approval approach based on five steps. Firstly, the testing and evaluation of properties at the beginning of life are shown. Secondly, methods for artificial aging and the effect on the residual strength are presented. Thirdly, testing against dedicated accidents is introduced. Fourthly, effects on the surveillance of production quality are discussed. Finally, degradation and the end of life are estimated. Background information and examples are given for each step. The assessment presented is a method applicable for many safety-related systems.
In this lecture, the safety assessment of hydrogen gas storage systems is presented using the example of composite pressure vessels. The main element is a probabilistic approval approach based on five steps. Firstly, the testing and evaluation of properties at the beginning of life are shown. Secondly, methods for artificial aging and the effect on the residual strength are presented. Thirdly, testing against dedicated accidents is introduced. Fourthly, effects on the surveillance of production quality are discussed. Finally, degradation and the end of life are estimated. Background information and examples are given for each step. The assessment presented is a method applicable for many safety-related systems.
Homochirality is an obvious feature of life on Earth. On the other hand, extraterrestrial samples contain largely racemic compounds. The same is true for any common organic synthesis. Therefore, it has been a perplexing puzzle for decades how these racemates could have formed enantiomerically enriched fractions as a basis for the origin of homochiral life forms. Numerous hypotheses have been put forward as to how preferentially homochiral molecules could have formed and accumulated on Earth. In this article, it is shown that homochirality of the abiotic organic pool at the time of formation of the first self-replicating molecules is not necessary and not even probable. It is proposed to abandon the notion of a molecular ensemble and to focus on the level of individual molecules. Although the formation of the first self-replicating, most likely homochiral molecule is a seemingly improbable event, on a closer look, it is almost inevitable that homochiral molecules have formed simply on a statistical basis. In this case, the non-selective leap to homochirality would be one of the first steps in chemical evolution directly out of a racemic “ocean”. Moreover, most studies focus on the chirality of the primordial monomers with respect to an asymmetric carbon atom. However, any polymer with a minimal size that allows folding to a secondary structure, would spontaneously lead to asymmetric higher structures (conformations). Most of the functions of these polymers would be influenced by this inherently asymmetric folding. To summarize, simple and universal mechanisms may have led to homochiral self-replicating systems in the context of chemical evolution. A homochiral monomer pool is deemed unnecessary and probably never existed on primordial Earth.
Manipulating ceramic powder compacts and ceramic suspensions (slurries) within their volume with light requires a minimum transparency of the materials. Compared to polymers and metals, ceramic materials are unique as they offer a wide electronic band gap and thus a wide optical window of transparency. The optical window typically ranges from below 0.3 µm up to 5µm wavelength. Hence, to penetrate with laser light into the volume of a ceramic powder compound its light scattering properties need to be investigated and tailored. In the present study we introduce the physical background and material development strategies to apply two-photon-polymerization (2PP) for the additive manufacture of filigree structures within the volume of ceramic slurries.
Manipulating ceramic powder compacts and ceramic suspensions (slurries) within their volume with light requires a minimum transparency of the materials. Compared to polymers and metals, ceramic materials are unique as they offer a wide electronic band gap and thus a wide optical window of transparency. The optical window typically ranges from below 0.3 µm up to 5µm wavelength. Hence, to penetrate with laser light into the volume of a ceramic powder compound its light scattering properties need to be investigated and tailored. In the present study we introduce the physical background and material development strategies to apply two-photon-polymerization (2PP) for the additive manufacture of filigree structures within the volume of ceramic slurries.
Die Präsentation gibt einen Überblick über die Arbeiten im German Pilot des EU-Projekts TREEADS. Es werden klein-, mittel- und großskalige Versuche an Waldboden mit einheimischer Vegetation durchgeführt. Begleitend werden numerische Untersuchungen durchgeführt, die eine Variation der Parameter, wie Bodenfeuchte, Temperaturen und Wind über die Experimente hinaus erlauben. Die gemessenen Materialparameter dienen als Input für die numerischen Berechnungen. Die numerischen Modelle werden mit den mittel- und großskaligen Experimenten validiert.