2.1 Sicherheit von Energieträgern
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In order to assess the thermal radiation emanating from hydrogen jet flames, experiments under real scale conditions were carried out at the Test Site Technical Safety of BAM. Herein, the behavior of inclined hydrogen jet flames was investigated. The aim of the work is to determine the Surface Emissive Power and radiant heat fraction of these flames and to provide a reliable dataset for model evaluation purposes. Since the aforementioned values are not directly measurable, the incident heat radiation was measured at defined distances from the flame, as well as the flame's shape and size. The required values were then derived from these measurements. The hydrogen releases ranged from 0.005 kg/s to 0.175 kg/s with a 30 mm orifice. The mass flows were held constant during the releases, nevertheless a transient behavior of the flame could be observed since the experiments were carried out under open field conditions, with unsteady wind fields. In the literature, the flame lengths are often determined using visible light imaging, either by injecting coloring substances in the low light emitting hydrogen jet flame or by carrying out the measurements in darkness. In this work the jet flames were visualized using infrared (IR) and OH* imaging. The recorded flame shapes and resulting flame lengths are compared. Results from this showed that the flame lengths determined with OH* and IR recordings differ greatly. A flame length ratio l_(f OH*)/l_(f IR) in the range of 0.47-0.62 can be found. In addition, the SEP differ also in the range of 10 kW/m²-16 kW/m² (IR) and 40 kW/m²-80 kW/m² (OH*) for hydrogen jet flames due to differences in the determined flame surface. Conclusions regarding the determined x_(RAD )values for IR and OH* result in approximately the same range of 0.031-0.043.
In order to assess the thermal radiation emanating from hydrogen jet flames, experiments under real scale conditions were carried out at the Test Site Technical Safety of BAM. Herein, the behavior of inclined hydrogen jet flames was investigated. The aim of the work is to determine the Surface Emissive Power and radiant heat fraction of these flames and to provide a reliable dataset for model evaluation purposes. Since the aforementioned values are not directly measurable, the incident heat radiation was measured at defined distances from the flame, as well as the flame's shape and size. The required values were then derived from these measurements. The hydrogen releases ranged from 0.005 kg/s to 0.175 kg/s with a 30 mm orifice. The mass flows were held constant during the releases, nevertheless a transient behavior of the flame could be observed since the experiments were carried out under open field conditions, with unsteady wind fields. In the literature, the flame lengths are often determined using visible light imaging, either by injecting coloring substances in the low light emitting hydrogen jet flame or by carrying out the measurements in darkness. In this work the jet flames were visualized using infrared (IR) and OH* imaging. The recorded flame shapes and resulting flame lengths are compared. Results from this showed that the flame lengths determined with OH* and IR recordings differ greatly. A flame length ratio l_(f OH*)/l_(f IR) in the range of 0.47-0.62 can be found. In addition, the SEP differ also in the range of 10 kW/m²-16 kW/m² (IR) and 40 kW/m²-80 kW/m² (OH*) for hydrogen jet flames due to differences in the determined flame surface. Conclusions regarding the determined x_(RAD )values for IR and OH* result in approximately the same range of 0.031-0.043.
The presentation starts with general slides on BAM, its location, mission, tasks and focus areas. It provides the fields of activity in the focus area “Energy” and explains the structure of the competence Centre and its focus on building trust in hydrogen. The test sides at TTS on hydrogen are explained in combination with the H2Safety@BAM’s products in a nutshell.
Then the major H2-applications of H2Safety@BAM are explained by deep dives on the Living Lab “Hydrogen Networks”, the Living Lab „Hydrogen Refuelling Station“, on Explosion Protection, on Reference Materials and Procedures, on Material Compatibility, on Storage Systems for Compressed Gases and Storage of Liquid Hydrogen as well as on the Training and Further Education.
The presentation ends with an overview about our international work on H2Safe-Collaboration.
Eine Frage der Technik? Verfahren und Kriterien für den sicheren Betrieb von Wasserstoffanlagen
(2025)
Das Webinar wird im Rahmen von TransHyDE Systemanalyse (AP5.3 Akzeptanzbewertungen) durchgeführt und adressiert aus einer interdisziplinären Perspektive relevante Aspekte der Sicherheit und öffentlichen Risikowahrnehmung von Wasserstoffprojekten. Dabei erfolgt ein Überblick über Standards der sicherheitstechnischen Forschung, Einblicke aus der Projektkommunikation mit Akteuren und Bürger*innen sowie die Vorstellung aktueller Forschungsergebnisse zur öffentlichen Wahrnehmung der Risiken von Wasserstofftechnologien. Die Diskussion geht den u.a. Fragen nach, welche Rolle das Thema Sicherheit in der aktuellen Planungspraxis spielt, wie transparent über Risiken kommuniziert werden kann, ohne Vertrauen zu gefährden und welche Kommunikationsansätze sich als zielführend zeigen, um gesellschaftlichen Unsicherheiten zu begegnen. Der Vortrag zeigt auf, dass der sichere Betrieb von Anlagen nicht nur mit der Technologie alleine gewährleistet werden kann.
In combination with new types of drive technologies, more and more flammable gases could be introduced into the traffic area “road tunnel” in future. If these vehicles have an accident and the gases are subsequently released, there is the possibility that the mentioned substances show a heavy gas behavior due to their storage conditions. From a safety point of view, this scenario has to be assessed with regard to its effects on the tunnel structure and the people involved. The aim of the experimental investigations carried out in this work is to create the basis for such an analysis by investigating the spreading behavior of the gases after they have been released in the tunnel and determining the influence of individual geometric and operational parameters on this behavior. Specifically, this work is based on the scenario of a continuous, momentum-free release of propane within a vaulted road tunnel with active longitudinal ventilation. The tunnel-specific boundary conditions that are relevant to this scenario are first worked out by a theoretical analysis. The basis of the subsequent experimental part is formed by two test rigs built as part of the work, which are similar in their essential features, but differ in scale. In both facilities, the aforementioned release scenario was simulated under various boundary conditions based on an idealized tunnel segment. The dispersion behavior is primarily assessed by the averaged concentration distribution near the ground, which results from a large number of detectors arranged in the experimental area. The detectors operate on the principle of weakening infrared light in the presence of hydrocarbons. Measurements of the flow field properties accompany the concentration measurements. The conception of the test rig on a scale of 1:12 is based on dimensional analysis. The actual release campaign comprises a large number of individual experiments in which selected parameters were varied over the tunnel-relevant range. The predicted heavy gas behavior for propane emerged clearly in the experiments. In cases in which the cloud laterally reaches the tunnel walls, the gases are channeled, which is accompanied by reduced longitudinal dilution. It was possible to identify the release rate and the flow velocity as the factors that have the greatest influence. The former basically increased the concentration, while the latter decreased it. All other tested parameters resulted in more complex propagation situations, which force a differentiated consideration of the influence. Lifting the source from the ground also reduced the concentration. In the case of an eccentrically arranged source and a transverse slope of the roadway, the influence is largely limited to the lateral concentration distribution in the immediate vicinity of the source. Nevertheless, both parameters plus a possible longitudinal slope of the roadway only showed a slight effect on the area far-downstream from the source. In addition, the phenomenon of backlayering, which is known from the spreading of fire smoke in the tunnel, could be demonstrated with a steep longitudinal slope. Obstacles increased the complexity of the situation. While globally the dilution of the cloud is partly invariant to obstacles, locally an increase as well as a decrease in concentration can be observed under certain conditions. For the unobstructed tunnel, it was finally possible to define a dimensionless parameter that describes the curve of the longitudinal dilution on the ground within the heavy gas cloud. From this, a simple graphical nomogram is derived for the continuous release of heavy gases in an unobstructed tunnel environment, which can be used to estimate the concentration in relation of a dimensionless source distance. For exploring the real, undistorted behavior experiments were also carried out in original scale. Due to the similarity of both test rigs in terms of scale, the test results can also be used to check the scalability of the spreading situations. For that, two configurations that have already been examined in small scale were selected. The main limitation for test execution and regarding the scalability comparison was the dependence of the flow conditions within the test rig from external wind conditions which occurred despite of taken countermeasures. The large-scale release was associated with pronounced fog formation. The near-ground spreading corresponding to the heavy gas behavior could be confirmed. However, in detail the spread was far more unsteady. Looking at the time-averaged concentrations, the processes already known from the small-scale test were qualitatively well approximated. Remaining quantitative differences, however, require critical consideration. This discrepancy is more likely a consequence of the experimental compromises have to be made in the specific case. From the observed gas behavior, the development of a surface fire initiated by ignition of the re-leased gases is considered to be the most likely subsequent scenario for the release of heavy, flam-mable gases in tunnel-like enclosures. The thesis concludes with recommendations on the methodological approach to be favored in the future.
Geräte und Maschinen, die zur bestimmungsgemäßen Verwendung in explosionsgefährdeten Bereichen gemäß 2014/34/EU konstruktiv vorgesehen sind, muss in der europäischen Union eine Zündgefahrenbewertung durchgeführt werden. Dabei müssen alle 13 Zündquellen betrachtet werden. Eine Teilmenge der 13 Zündquellen sind die Gefahren von nichtelektrischen Zündquellen, zu denen auch die mechanischen Schlag-, Schleif- und Reibvorgänge gehören. Bei mechanischen Schlagvorgängen kommt es infolge des Zusammenstoßes zweier Werkstücke bzw. Bauteile zu einer Umwandlung der kinetischen Energie. Dabei erhöht sich die Temperatur der Werkstoffe an der Kontaktstelle und es kommt unter Umständen zu einem Abtrennvorgang kleiner Partikel erhöhter Temperatur. Sowohl die heißen Kontaktstellen (Zündquelle "heiße Oberflächen") als auch die abgetrennten Partikel (Zündquelle "mechanisch erzeugte Funken") können eine wirksame Zündquelle für ein explosionsfähiges Gasgemisch darstellen. Zur Festlegung von Grenzwerten wurden in der Norm DIN EN ISO 80079-36:2016 die Gasgemische anhand ihrer Explosionsgruppe klassifiziert und zu jeder Gruppe die maximale Energie des Schlagvorgangs festgelegt, unter derer die Entstehung einer wirksamen Zündquelle als unwahrscheinlich angenommen werden kann. Weitere Festlegungen von Grenzwerten für die kinetische Schlagenergie und geeignete Werkstoffpaarungen finden sich u.a. in der DIN EN 1755 (ex-geschützte Flurförderzeuge) und in der DIN EN 14986 (ex-geschützte Ventilatoren).
Flame Arrestors are safety relevant devices in chemical plants. If despite all the safety measures an explosion is initiated, they prevent damage, fatalities, and complete losses of production plants by hindering the explosion from propagating throughout the complete installation. Depending on the explosion propagation characteristics of the gas or gas mixture in question, the flame arrestors need to fulfil certain different operating requirements. In case of decomposable gases like acetylene and tetrafluoroethylene in some respect it might become necessary to violate the advice given in the standards concerning flame arrestor’s design.
In dem Vortrag werden die aktuellen Herausforderungen für die Sicherheit von Wasserstofftechnologien skizziert, die sicherheitstechnischen Eigenschaften und physikalischen Eigenschaften von Wasserstoff im Vergleich zu anderen Energieträgern vorgestellt sowie Gefahren spezifisch im Zusammenhang mit Flüssigwasserstoff aufgezeigt. Im zweiten Teil wird ein kurzer Überblick über Regelwerke gegeben und typische Unfallszenarien anhand eines Fallbeispiels illustriert. Abschließend werden die von nationalen und internationalen Expertengruppen identifizierten Forschungslücken zusammengefasst und es wird auf relevante Datenbanken und Portale zur Wasserstoffsicherheit verwiesen.
The paper presents the results of the experimental and reaction kinetic investigation of hydrogen ignition at different pressures, highlighting its non-linear behaviour and effects of radical wall termination. The reaction kinetic simulation predicts the three characteristic ignition limits caused by radical and thermal auto-ignition and is in close agreement with the experimental measurements. The introduction of radical wall termination in the reaction mechanism allowed us to investigate the effect of the autoclave wall and vessel size on the hydrogen ignition behaviour. The first ignition limit is determined by the chain initiation reaction H_2+O_2→2 OH and shows a strong sensitivity towards wall termination of O, H and OH radicals. The third ignition limit is dominated by the reaction paths HO_2+HO_2→H_2 O_2+O_2 and H_2 O_2+M→2 OH+M which is why it shows a strong sensitivity towards wall termination of HO₂ and H₂O₂ radicals. The second ignition limit is influenced by the wall termination of O, H, OH, HO2 and H2O2 radicals. Increasing the radical wall termination rate by increasing the adsorption rate of the radicals at the wall leads to an increase of the auto-ignition temperature at the same pressure.