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- Pool fire (14)
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Eingeladener Vortrag
- nein (1)
Data and prediction for the mass burning rate of a tert-butyl-peroxy-benzoat (TBPB) pool fire (pool diameter = 3 m) is presented. The mass burning rates of TBPB fires are up to six times higher and less dependent on pool diameter compared to hydrocarbon pool fires caused by an additional heat release rate due to exothermic decomposition reaction in the liquid phase. This heat release rate is calculated using a 1st order reaction kinetic obtained from micro calorimetric measurements. A new model is derived considering the heat release rate due to the decomposition reaction which is shown to be 100 % of the heat release rate radiated to the pool surface. With the presented model, including also physical quantities, especially the limiting fuel concentration for upward flame propagation, it is possible to predict the mass burning rates of large TBPB pool fires. The predicted values are in very good agreement with the experiments.
Data and predictions for the mass burning rates of di-tert-butyl peroxide (DTBP) pool fires (0.003 m < pool diameter < 3 m) are presented. The mass burning rates of DTBP fires are up to five times higher and are less dependent on pool diameter compared to hydrocarbon pool fires caused by an additional heat release rate due to exothermic decomposition reaction in the liquid phase. This heat release rate is calculated using a first-order reaction kinetic obtained from microcalorimetric measurements. A new model is derived considering the heat release rate due to the decomposition reaction, which is shown to be 40% of the heat release rate radiated to the pool surface. With the presented model, which also includes physical quantities, especially the limiting fuel concentration for upward flame propagation, it is possible to predict the mass burning rates of large DTBP pool fires. The predicted values are in very good agreement with the experiments.
Es werden Experimente zur Bestimmung der Massenabbrandraten von multiplen Poolfeuern präsentiert. Als Modellsubstanzen dienen n-Heptan und Di-tert-butylperoxid (DTBP). Es werden Versuche im Labormaßstab mit Durchmessern von d = 6 cm und relativen Abständen von 0.08 ≤ D/d ≤ 4 beschrieben und durch Feldversuche mit Pooldurchmessern d = 1.5 m und relativen Abständen zwischen den Pool von 0.17 ≤ D/d ≤ 1 ergänzt. Es kann gezeigt werden, dass die Massenabbrandraten multipler Feuer im Vergleich zu Einzelfeuern mit gleicher Brennstoffoberfläche bis zu einem Faktor 5.9 (n-Heptan) und 1.6 (DTBP) erhöht sind. Die Erhöhung ist abhängig vom relativen Abstand zwischen den Pools D, der Anzahl der Pools N und vom jeweiligen Brennstoff und zeigt ein lokales Maximum, welches mit dem Merging-Bereich der Flammenverschmelzung zusammenfällt. Die Massenabbrandrate als Funktion des relativen Abstandes zwischen den Pools kann durch eine Vergrößerung der Flammenbodenoberfläche infolge Flammenverschmelzung erklärt werden.
Limiting distances for flame merging of multiple n-heptane and di-tert-butyl peroxide pool fires
(2013)
Experiments to determine the limiting distances for flame merging of multiple pool fires are presented. As model substances n-heptane and di-tert-butyl peroxide are used. Laboratory scale tests with a Diameter d = 6 cm and relative distances between the pools of 0.08 ≤ D/d ≤ 4 are described and complemented with field experiments with a diameter d = 1.5 m and relative distances between the pools of 0.17 ≤ D/d ≤ 1.
Three regions for flame merging are observed and limiting distances are determined. A merging Region with the limiting distance Dmerg/d within which all flames merge together over the complete burning time. A transition region with the limiting distance Dtran/d within which some flames merge together while other flames are separated from each other. A separated region within which all flames are completely separated from each other. A correlation against the number of burning pools is presented to predict the limiting distances Dmerg/d und Dtran/d.
Most of the measurements of temperatures in large pool fires are indirect and present a number of complexities due to the interactions of convection, radiation and soot blockage. In the present work these influences for two organic peroxide [tert-butyl peroxybenzoate (TBPB) and tert-butyl peroxy-2-ethylhexanoate (TBPEH)] pool fires are analysed.
Thermocouple measured temperature in the clear flame zone i.e. combustion zone are found to be 250-400 K lower than from the thermographic measurements. The convective and radiative heat flux contributions from the fire on temperature measurements are discussed. CFD (Computational Fluid Dynamics) simulations have been performed for large pool fires and the predicted time averaged flame temperatures were found to be in qualitative agreement with
measurements due to the stoichiometric combustion model used in the present simulations.
Flame temperature (T), surface emissive power (SEP) of Liquefied Natural Gas (LNG) pool fires (d = 1 m, 6.1 m, 30 m) are investigated by CFD (Computational Fluid Dynamics) simulation and compared with experimental results.
Time averaged flame temperatures of T = 1320 K, T = 1298 K and T = 1281 K are obtained. Surface emissive power (SEP) of 55 kW=m2, 130 kW=m2 and 230 kW=m2 are predicted.
Pool fires and spill fires
(2012)
The flame temperatures T of a multiple n-heptane pool fire d = 6 cm, N = 5, D/d = 0.33 are measured with type S thermocouples and predicted with Large Eddy Simulation (LES) and an assumed pdf-approach containing a detailed kinetic with 112 species and 800 elementary reactions. Multiple pool fires show higher flame temperatures up to ≈ 200 K in comparison to single pool fires. CFD simulation is in good agreement with the experimental results and a validation is performed. It can be shown that multiple fires have an enhanced air-entrainment leading to an increased formation of OH radicals and consequently to the observed higher flame temperatures.
In verfahrenstechnischen Anlagen kann es während des Umgangs, des Transports und der Lagerung durch Freisetzung und anschliesender Zündung von brennbaren Flüssigkeiten zu Lachen-, Pool- oder Tankfeuern kommen. Die sich ausbildenden Feuer konnen große Schäden an benachbarten verfahrenstechnischen Anlagen und Personen verursachen. Im Unterschied zu Einzelfeuern sind multiple Pool- und Tankfeuer aufgrund ihrer Wechselwirkungseffekte sicherheitstechnisch von besonderer Bedeutung. Mit Di-tert-butyl-peroxid (DTBP) und n-Heptan als Leitsubstanzen werden Labor- und Feldexperimente (d ≤ 1.5 m) mit wechselwirkenden Poolflammen (N ≤ 9) in einer Matrixanordnung bei relativen horizontalen Abständen D/d zwischen den Pools im Bereich 0.16 ≤ D/d ≤ 4 durchgeführt.
Die Phänomene der Flammenverschmelzung (Flammenfusion) in Abhängigkeit vom Poolabstand D/d werden experimentell untersucht und modelliert.
Bisher ist das Sicherheitsniveau verfahrenstechnischer Anlagen in Deutschland hoch. Die Anzahl der Institute, die auf dem Gebiet der technischen Sicherheit forschen und damit zum Kompetenzerhalt beitragen, geht kontinuierlich zurück. Dies liegt zum einen an der aktuellen Forschungspolitik, zum anderen daran, dass die neuen Themen wie Life Sciences, Nano-, Umwelt- oder Informations- und Kommunikationstechnologien insbesondere für junge Menschen, die gerade dabei sind, sich beruflich auszurichten, eine hohe Attraktivität besitzen. Der Staat und die Wirtschaft sind aufgerufen gemeinsam etwas dagegen tun.