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Organisationseinheit der BAM
Rückendeckung
(2013)
Neben herkömmlichen Stahlflaschen, die seit Jahrzehnten in fast unveränderter Bauform für Flüssiggase (Propan-Butan-Gemische) eingesetzt werden, etablieren sich immer mehr Flaschen aus Faserverbundwerkstoffen (GFK) mit einer geringeren Masse. Die Bundesanstalt für Materialforschung und -prüfung (BAM) wurde beauftragt, das Verhalten dieser Gasflaschen unter den extremen Bedingungen eines Unfallfeuers zu untersuchen. In einem Brandprüfstand der BAM auf dem Testgelände Technische Sicherheit (TTS) in Horstwalde wurden deshalb beide Typen von Propangasflaschen einem simulierten Unfallfeuer ausgesetzt.
Gefahrguttanks
(2016)
Gefahrguttanks werden primär gegen betriebliche Belastungen dimensioniert. Unfallbelastungen spielen hierbei keine Rolle. In der Vergangenheit gab es immer wieder einige katastrophale Unfälle, die nicht nur materielle Schäden zur Folge hatten sondern bei denen auch Todesopfer zu beklagen waren. Zur Ermittlung möglicher Sicherheitsreserven werden Untersuchungen zum Abtrag auslegungsüberschreitender Belastungen durchgeführt. Mit dem Grenzlasttragverfahren steht ein leistungsfähiges Analysewerkzeug zur Verfügung, mit dem nichtlineare Beanspruchungsszenarien bewertet werden können. Der Vergleich der numerischen mit den experimentellen Ergebnissen zeigt dies eindeutig.
Dangerous goods are transported as air freight in commercial aircrafts. Using plastic jerrycans or plastic containers, liquids or gases can escape by leakage or permeation effects. Prior research by the German Federal Institute for Materials Research and Testing (BAM) showed that the lower explosion limit can be reached when transporting dangerous goods in sea-freight containers under normal transportation situations. This motivated the presented study of the transportation situation of dangerous goods in cargo compartments of commercial airplanes. The scope of this paper is to present the experimental method used for validating a numerical model for CFD (Computational Fluid Dynamics) simulations. The CFD model will be used in a future study to evaluate the potential risk from transporting dangerous goods.
The objective of this paper is to present the model mock-up of an aircraft cargo compartment and some examples of three dimensional velocity profiles of the air flow in the mock-up. The velocity profiles are calculated using numerical simulations and measured by Laser-Doppler-Anemometry (LDA) experiments. The mock-up is a generic model of a wide-body aircraft lower deck cargo compartment in a 1:10 scale. Geometry, air exchange rates and inlet as well as outlet flow conditions in the cargo compartment are modeled using realistic boundary conditions. The commercial CFD (Computational Fluid Dynamics) code ANSYS CFX 14 is used for numerical flow simulations applying RANS (Reynolds-Averaged-Navier-Stokes) equations and turbulence models. The turbulence models studied are the renormalization group k-ε-model (RNG), the Reynolds-Stress model by Launder, Reece and Rodi (LRR) and the SST-k-ω-model by Menter (SST).
The flow measurement with LDA in the mock-up of a cargo compartment proves to be a feasible method for producing data to validate CFD simulations. Qualitative evaluation of the results shows a good overall agreement between numerical and experimental results. The experimental validation indicates that the implemented CFD model is capable of reproducing the flow situation in the model mock-up.
How can the risk of a BLEVE be reduced? That is the main question based on different research projects. In various large scale fire tests fire protection coating systems were used of different manufacturers. The degree of the coating as well as the layer thickness and the processing were varied. These experimental configurations were partly tested with and without pressure relief valve. The pressure relief valves were not protected again the thermal Load from the test fire. The ambition is to find a minimum of the thickness from the fire protection coating witch delay a BLEVE up to 90 minutes. Here are given the most interested configurations of tanks in fire and a description of the test-rigs.
Full engulfment fire tests have been conducted on total containment pressure vessels filled to 50% and 98 % capacity with water. The tests included an unprotected tank and tanks with two different levels of thermal protection. Total containment in this context means there was no pressure relief device. The tests were conducted with 1/3rd linear scale rail tank cars similar to the DOT 111 tank cars used in North America. The 2.4 m3 model tanks were subjected to 100 % engulfing fires fuelled by liquid propane. The fire heat flux was approximately 80 % by radiation and 20 % by convection with a total heat flux to a cool surface of approximately 100 kW/m2.
Pressurisation of full-containment pressure vessels in fire is known to be driven by thermal stratification. The predominant mode of heat transfer to the contents (convection from the shell to the liquid phase) results in formation of „hot“ boundary layers. Sub-cooled boiling may also be present. The warm layer rises to the surface through buoyancy and bubble flow, increasing the surface of the liquid above that of the bulk temperature, and hence driving a pressure rise.
For reliable prediction of the complex effects governing vessel pressurization a three-dimensional numerical model is required. Work is being undertaken on such a model by other institutions in cooperation with this project.
