Filtern
Dokumenttyp
- Zeitschriftenartikel (6)
- Vortrag (6)
- Beitrag zu einem Tagungsband (3)
Schlagworte
- Composite pressure vessel (2)
- Distribution function (2)
- F-N-diagram (2)
- Monte-Carlo Simulation (2)
- Pressure-volume product (2)
- Safety assessment (2)
- Weibull Distribution (2)
- Acceptance rate (1)
- Ageing (1)
- Anderson Darling - GoF Test (1)
Organisationseinheit der BAM
Eingeladener Vortrag (wissenschaftliche Konferenzen)
- nein (6)
The combustion characteristics and explosive hazard of syngas (H2/CO)/air mixtures are affected by its exact composition and equivalence ratios. In this paper, the explosion pressure and spectral radiant intensity of free radicals were quantitatively examined for syngas with different H2 proportions ([H2 in syngas] = 0, 30, 50, 70, 100 vol%) and equivalence ratios (φ = 0.8, 1.0, 1.2, 1.4, 1.6, 2.0, 2.5). The results show that the explosion process of syngas/air mixtures can be separated into the initial slow combustion stage, the violent deflagration stage and the deflagration ending stage. The peaks of explosion pressure, pressure rise rate, OH*spectral intensity and rise rate of spectral intensity first increase and then decrease with increasing the equivalence ratio, and they reduce gradually with the decrease of H2 proportion in syngas. The H2 content in syngas greatly affects the heat release and the concentration of excited state OH*, especially for the syngas/air mixtures with smaller proportion of H2. Additionally, the presence of H2 greatly increases the deflagration index and spectral radiant index of OH* for syngas/air mixtures. The average rise rates of explosion pressure and spectral intensity of free radicals are introduced and the coupling model between them is established based on the first law of thermodynamics and the principle of chain reaction. The established model is furthermore verified by the experimental results. It is indicated that there is a linear relationship between average rise rates of explosion pressure and spectral intensity (OH*). The results can be used to improve the combustion efficiency of syngas and to guide theoretically the prevention, mitigation and control of syngas explosions.
Um ein verlässliches Ergebnis der Monte-Carlo-Simulation zu garantieren, muss die Zuverlässigkeit des Tools vor dessen Anwendung sorgfältig geprüft werden. In diesem Vortrag werden die Validierung der angenommenen Verteilungsfunktionen, die Vertrauensbereiche und die Grenzwerte der generierten Grundgesamtheit vorgestellt. Darauf aufbauend wird der Ablauf der gesamten Simulation von der Erzeugung der Zufall-Variablen bis hin zur Akzeptanzrate gezeigt.
In solids, chemical short‐range order (CSRO) refers to the self‐organization of atoms of certain species occupying specific crystal sites. CSRO is increasingly being envisaged as a lever to tailor the mechanical and functional properties of materials. Yet quantitative relationships between properties and the morphology, number density, and atomic configurations of CSRO domains remain elusive. Herein, it is showcased how machine learning‐enhanced atom probe tomography (APT) can mine the near‐atomically resolved APT data and jointly exploit the technique's high elemental sensitivity to provide a 3D quantitative analysis of CSRO in a CoCrNi medium‐entropy alloy. Multiple CSRO configurations are revealed, with their formation supported by state‐of‐the‐art Monte‐Carlo simulations. Quantitative analysis of these CSROs allows establishing relationships between processing parameters and physical properties. The unambiguous characterization of CSRO will help refine strategies for designing advanced materials by manipulating atomic‐scale architectures.
Hydrogen is an attractive energy carrier that requires high effort for safe storage. For ensuring safety, storage cylinders must undergo a challenging approval process. Relevant standards and regulations for composite cylinders used for the transport of hydrogen and for its onboard storage are currently based on deterministic (e.g. ISO 11119-3) or to some respect semi-probabilistic criteria (UN GTR No. 13; with respect to burst strength).
This paper provides a systematic analysis of the load cycle properties resulting from these regulations and standards. Their characteristics are compared with the probabilistic approach of the Federal Institute for Materials Research and Testing BAM. The most important aspect of comparing different concepts is the rate for accepting designs with potentially unsafe or critical safety properties. This acceptance rate is analysed by operating Monte-Carlo simulations over the available range of production properties.
The test data for static burst strength and load cycle fatigue strength of pressure vessels can often be well described by Gaussian normal or Weibull distribution functions. There are various approaches which can be used to determine the parameters of the Weibull distribution function; however, the performance of these methods is uncertain. In this study, six methods are evaluated by using the criterion of OSL (observed significance level) from Anderson-Darling (AD) goodness of Fit (GoF), These are: a) the norm-log based method, b) least squares regression, c) weighted least squares regression, d) a linear approach based on good linear unbiased estimators, e) maximum likelihood estimation and f) method of moments estimation. In addition, various approaches of ranking function are considered. The results show that there are no outperforming methods which can be identified clearly, primarily due to the limitation of the small sample size of the test data used for Weibull analysis. This randomness resulting from the sampling is further investigated by using Monte Carlo simulations, concluding that the sample size of the experimental data is more crucial than the exact method used to derive Weibull parameters. Finally, a recommendation is made to consider the uncertainties of the limitations due to the small size for pressure vessel testing and also for general material testing.
Safe onboard storage is clearly one of the greatest challenges for the hydrogen economy. Even if hydrogen vehicles offer better efficiency, technological barriers remain for short-term implementation. Hydrogen storage difficulties stem from its low density, necessitating very high pressure for storage. In addition, the weight, volume, efficiency, safety of storage as well as the cost of the hydrogen must be considered. Safety is of paramount importance for deployment of hydrogen technologies as it is flammable in a wide range of concentrations with air, more sensitive to ignition due to its low minimum ignition energy, deflagrates faster due to higher burning velocity, and is prone to deflagration-to-detonation transition. Various safety measures must be implemented in order to prevent accidental leakage and ensure inherent safety.
Today, the strategy of the OEM’s prioritises the development of a single electrical drivetrain platform where the battery pack is mounted in the underbody of the vehicle. The automotive industry aims to use this same space for hydrogen storage systems, with the expectation that such conformable hydrogen storage systems will be available in the next 3-5 years.
The main innovations of BAM’s specialist divisions 3.5 and 8.6 in this project are, firstly, the integration of optical fibres in the filament winding of complete pressure to gain a deeper understanding of the structural behaviour under the different hydraulic and pneumatic loading conditions, and secondly, the development of a fire test platform to test the assembly of 9 tubular vessels under the fire test requirements of GTR13. Therefore, a wind damping and splinter-protecting cage was built from protection modules specifically developed for this project. Extensive safety-related tests are to be carried out at BAM during the project period.
Safety criteria for the transport of hydrogen in permanently mounted composite pressure vessels
(2020)
The recent growth of the net of hydrogen fuelling stations increases the demands to transport compressed hydrogen on road by battery vehicles or tube-trailers, both in composite pressure vessels. As a transport regulation, the ADR is applicable in Europe and adjoined regions, and is used for national transport in the EU. This regulation provides requirements based on the behaviour of each individual pressure vessel, regardless of the pressure of the transported hydrogen and relevant consequences resulting from generally possible worst case scenarios such as sudden rupture. In 2012, the BAM (German Federal Institute for Materials Research and Testing) introduced consequence-dependent requirements and established them in national transport requirements concerning the “UN service life checks” etc. to consider the transported volume and pressure of gases. This results in a requirement that becomes more restrictive as the product of pressure and volume increases. In the studies presented here, the safety measures for hydrogen road transport are identified and reviewed through a number of safety measures from countries including Japan, the USA and China. Subsequently, the failure consequences of using trailer vehicles, the related risk and the chance are evaluated. A benefit-related risk criterion is suggested to add to regulations and to be defined as a safety goal in standards for hydrogen transport vehicles and for mounted pressure vessels. Finally, an idea is given for generating probabilistic safety data and for highly efficient evaluation without a significant increase of effort.
Determination of Distribution Function used in MCS on Safety Analysis of Hydrogen Pressure Vessel
(2019)
The test data of static burst strength and load cycle strength of composite pressure vessels are often described by GAUSSian normal or WEIBULL distribution function to perform safety analyses. The goodness of assumed distribution function plays a significant role in the inferential statistics to predict the population properties by using limited test data. Often, GAUSSian and WEIBULL probability nets are empirical methods used to validate the distribution function; Anderson-Darling and KolmogorovSmirnov tests are the mostly favorable approaches for Goodness of Fit. However, the different approaches used to determine the parameters of distribution function lead mostly to different conclusions for safety assessments. In this study, six different methods are investigated to show the variations on the rates for accepting the composite pressure vessels according to GTR No. 13 life test procedure. The six methods are: a) NormLog based method, b) Least squares regression, c) Weighted least squares regression, d) A linear approach based on good linear unbiased estimators, e) Maximum likelihood estimation and f) The method of moments estimation. In addition, various approaches of ranking function are considered. In the study, Monte Carlo simulations are conducted to generate basic populations based on the distribution functions which are determined using different methods. Then the samples are extracted randomly from a population and evaluated to obtain acceptance rate. Here, the “populations” and “samples” are corresponding to the burst strength or load cycle strength of the pressure vessels made from composite material and a plastic liner (type 4) for the storage of hydrogen. To the end, the results are discussed, and the best reliable methods are proposed.
Safety criteria for the transport of hydrogen in permanently mounted composite pressure vessels
(2019)
The recent growing of the net of hydrogen fuelling stations increases the demands to transport compressed hydrogen on road by tube-trailers in composite pressure vessels. As transport regulation the ADR is applicable in Europe and adjoined regions and used for national transport in EU. This regulation provides requirements based on the burst pressure of each individual pressure vessel, regardless the capabilities of the transported hydrogen and relevant consequences resulting from worst case scenarios. In 2012, BAM (German Federal Institute for Materials Research and Testing) introduced consequence-dependent requirements and established them in national requirements concerning the “UN service life checks” etc.) to consider the transported volume and pressure of gases. However, this results in a stringent requirement in case of using large pressure vessels (tubes) on tube-trailers. In the studies presented here, the key safety factors for using hydrogen trailers are identified and reviewed through some safety measures from some countries like Japan, USA and China. Subsequently, the risk, chance, failure consequences of using trailers are evaluated, in addition, the difficulties for approving huge pressure vessels (large tubes) are addressed. There, a maximum acceptable pressure-volume product is defined. Finally, a performance-based criterion for the balance of chance and risk of hydrogen trailers is suggested to add into regulations and consequently into standards for hydrogen trailers.
