Filtern
Dokumenttyp
Sprache
- Englisch (4)
Schlagworte
- Computational fluid dynamics (CFD) (1)
- Evacuation (1)
- Fire modeling (1)
- Fire safety (1)
- Furniture (1)
- Gas analysis (1)
- Modern (1)
- Room fire (1)
- Smoke (1)
- Smoke toxicity (1)
Organisationseinheit der BAM
Fire smoke contains a variety of highly toxic substances and can lead to unconsciousness within a few minutes and to death for critical concentrations. Currently the engineer’s methods of fire safety include various procedures to calculate the fire propagation and smoke spread in buildings.
However, up to now the evaluation and calculation of smoke concerning its optical properties and toxic potential on the basis of a detailed combustion is still a field of research. Since smoke composition is highly variable and not fully characterised it has to be examined whether and how the Chemical composition and the optical properties of smoke are correlating. A method has been developed that establishes the relation between the smoke components and smoke toxicity.
About 80% of all fire fatalities in Germany occur because of fires in homes. It has been known for some time that modern materials (synonym for materials consisting mostly of synthetic polymers) tend to burn differently from older materials (synonym for materials consisting mostly of fibrous cellulosic substances) and it has been acknowledged that the amount of combustible plastics in homes has increased significantly over the last decades. To investigate the influence of modern furniture and ventilation conditions of fires in homes, a series of four large-scale tests in two Living rooms (LRs) with adjacent rooms (ARs) was performed by BAM and the Frankfurt fire service. Two LRs, one with older furniture and one with modern furniture, were tested twice each. Each test started with the ignition of a paper cushion on an upholstered chair. The influence of modern materials on the fire development was investigated, as well as the influence of the ventilation on the fire development. In all settings, an upholstered chair was the first burning item. Results of the test series show that fires in rooms with modern furniture develop faster than fires in rooms with older furniture.
This is true for temperature development in the rooms as well as for smoke production.
CFD modeling approach of smoke toxicity and opacity for flaming and non-flaming combustion processes
(2016)
Current engineer’s methods of fire safety design include various approaches to calculate the fire Propagation and smoke spread in buildings by means of computational fluid dynamics (CFD). Because of the increased computational capacity, CFD is commonly used for prediction of time-dependent safety parameters such as critical temperature, smoke layer height, rescue times, distributions of chemical products, and smoke toxicity and visibility. The analysis of smoke components with CFD is particularly complex, because the composition of the fire gases and also the smoke quantities depends on material properties and also on ambient and burning conditions. Oxygen concentrations and the temperature distribution in the compartment affect smoke production and smoke gas toxicity qualitatively and quantitatively. For safety designs,
it can be necessary to take these influences into account. Current smoke models in CFD often use a constant smoke yield that does not vary with different fire conditions. If smoke gas toxicity is considered, a simple approach with the focus on carbon monoxide is often used. On the basis of a large set of experimental data, a numerical smoke model has been developed. The developed numerical smoke model includes optical properties, production, and toxic potential of smoke under different conditions. For the setup of the numerical model, experimental data were used for calculation of chemical components and evaluation of smoke toxicity under different combustion conditions. Therefore, averaged reaction equations were developed from experimental measurements and implemented in ANSYS CFX 14.0.
Crisis management, particularly the evacuation of handicapped People during a fire scenario presents a highly demanding challenge for nursing staff and rescue forces on site. The German research Project SiME is an interdisciplinary cooperation of university and non-university research institutions as well as medium-sized companies, which work together to develop strategies to manage such critical scenarios. In the SiME project, which is funded by the German Federal Ministry of Education and Research, evacuation characteristics of pedestrians with physical, mental or age-related disabilities are investigated to fit consisting numerical evacuation models with data. One of the major tasks of the OvGU was to set up a database of scenarios related to fire, explosion or substance releases in the working and living environment of handicapped people. Therefore, more than 463 fire Events occurring over the last decade in Germany were documented in this database and categorized by a suitable assignment of characteristics e.g. location of fire, ignition source, number of fatalities and injured.
The evaluated data were the basis for carrying out a quantitative risk analysis. Thus event trees were set up for different integrative infrastructures with which occurrence probabilities for different scenarios could be calculated for each path. The extent of damage, as a quantity describing the impact, was assumed to be personal injury or death or serious injury. By a risk assessment critical Scenarios could be derived from the risk analysis.