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Mogelijke onderzoeksprojecten

FSE topics in the mastertrack BPB

1. Numerical simulation of local fires with local flames:
Is a reliable simulation of local flames and/or external flames possible in CFD? If so, is RANS or LES technique more suitable for this simulation and what gridsizes are needed? Compare (and fit) simulationresults to empirical flamemodels and empirical models for the local heat flux (radiation and convection). A sensitivity analysis on boundary conditions and assumptions would be very welcome.
2. Physiological aspects in personal safety:
What is the resistance of humans to heat flux, convective heat and toxicity of smoke gases? Is it possible to define the resistance of the human body in a mean value with a standard deviation, related tot different damage levels (1st degree, 2nd degree, lethality) for different ages and physical conditions? For the human skin a multilayer model might be possibel. But not only the human skin, also the respiration system is relevant in relation to this research question.
3. Oxygen-controlled fires in zonemodels:
Most post-flashover fires are oxygen (ventilation) controlled. With oxygen controlled fires there are two different, almost opposite combustion models possible:
a) Extended fire duration: Reduction of the RHR by lack of oxygen means that it will take more time before all fuel has been combusted. In this case, the pyrolysis rate is linked to the RHR and will bereduced in the same way as the RHR. All combustion energy remains in the compartment.
b) External flaming: Reduction of the RHR by lack of oxygen means that combustion partly takes place outside the compartment in exernal flames. Reduction of RHR doesn’t automatically lead to reduction of pyrolysis of the fuel. The gas mass in the compartment contains both combustion products and fuel. Not all combustion energy remains in the compartment.
In general, the external flaming combustion model seems most realistic. However, in case of small openings in the external separation construction of a fire compartment, the RHR of the external flames exceeds the RHR in the compartment. In practice, that is not possible, due to the airflow resistance of the openings. Is itpossible to combine the external flaming and extended combustion model to a more realistic combustionmodel?
4. Application of the standard fire curve in a natural fire concept:
The thermal load according to the natural fire concept depends on fuel properties and building properties.
Basicly, the thermal load by the gastemperature in the fireroom is a result from the heat release scenario.
This project-specific thermal load differs from the standard fire curve. In case of testing the fire resistance of constructions the standard fire curve is used. To value the performance of tested constructions in a natural fire concept the project-specific natural fire curve has to be compared to the standard fire curve. What comparison makes sense and in what translation from a project-specific fire curve into the standard firecurve will this comparison result?
5. Consequences of changing boundary conditions in building and building users:
In both new buildings and renovation of existing buildings the boundary conditions by the building envelope will change (e.g. higher thermal insulation, more airtight, etc.). In very well insulated buildings, like passive or active house concepts, the building envelope influences the fire scenario. A local fire may become ogygen controled before the flashover conditions are reached. The probability of a compartment fire decreases. This advantage for loadbearing and separation constructions is a disadvantage for building users or residents. The smothered fire produces a lot of carbon monoxide, while there is hardly any oxygenleft in the compartment.
When we take into account an ageing population, which is less alert and will need more time for escape, the victim risk will increase in the near future. Do we need more stringent fire safety rules and regulations or do we need explicit fire safety objectives?
6. Design of pressurized stairwells:
What strategies are possible for pressurized stairwells? Normally, in a pressurized stairwell an overpressure is maintained in comparison with the compartments in the building. However, then many doors are open in case of evacuation of the building occupants, the failure probability of a pressurized stairwell is relatively high. Is it possible to apply other techniques, like pressurizing the lobbies of the staircase?
7. Prevention and suppression – Linking fire suppression strategy to preventive 'Lines of Defense':
Fire suppression tactics are divided in 4 main strategies: defensive outdoor attack, offensive outdoor attack, defensive indoor attack and offensive indoor attack. Fire suppression is only effective when suppression stratgy fits with the preventive lines of defense in the building. Preventive lines of defense are commonly represented in a ‘cascade riskmodel’. Is it possible to link fire suppression also to this cascade riskmodel?
8. Fire safety concept without building evacuation ('Stay-in-place' concept):
Is it possible to create a fire safety concept for a building, without evacuating the building? Then escape routes are no longer necessary. But what are the consequences for building constructions (separation constructions and load bearing elements), fire safety installations and emergency assistance?
9. Heat release rate and fire development in residential functions:
In residential functions the fire load depends on furniture, furnishings and decoration. This variable fire load is very sensitive to trends. The fire development depends on both the variable fire load and the permanent fire load caused by the building envelope and internal separation constructions. The design curves for different building functions (e.g. Eurocode) are based on a uniform distributed fire load. In most building functions this assumption makes sense. In residential buildings with relatively small compartments the fire load cannot be considered uniformly distributed. For residential buildings a new design curve is necessary.
10. Reliability of fire safety objectives
In fire (safety) engineering we follow a project-specific approach to realize the required fire safety objectives. In a generic rule based approach the assessment is very simple, you only have to a check if all requirements are fulfilled. In an objective based approach the objectives are quantified in an acceptable failure probability (or failure risk). To determine the failure probability, uncertainties in boundary conditions (building and fuel characteristics) have to be taken into account. Is it possible to quantify the safety objectives of the Building Code and how do you set up a sensitivity analysis for assessment to these acceptable failure probabilities?
11. Underventilated (localized) fires
Normally, a localized fire is fuel controlled. In some cases, localized fires become oxygen controlled. In case of an airtight building envelope without any openings that’s nog very surprising. But even with open windows a localized fire becomes sometimes oxygen controlled. What is the explanation for this and what boundary conditions are significant fot this type of localized fire?
Is it possible to simulate underventilated localized fires in zonemodels or CFD-models? Is it possible to set up an experimental model for simulation?
More info and more topics:
Ruud van Herpen
fellow Fire Safety Engineering TU/e
Email: R.A.P.v.Herpen@tue.nl