Fire Protection Engineering

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    SPILL AND BURNING BEHAVIOR OF FLAMMABLE LIQUIDS
    (2010) Benfer, Matthew; Quintiere, James G; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Unconfined liquid spill depths were measured for two liquid fuels and three non-flammable liquids atop a smooth concrete pad. Unconfined liquid spill thicknesses were found to be less than 0.1 cm in all fuels and liquids similar to fuels. Spill fires were conducted with volumes ranging from 0.2 ml to 450 ml for gasoline and denatured alcohol. Average burning rates for both unconfined liquid fuel spill fires increased linearly with increasing volume spilled. A liquid spill thickness model was developed and compared to experimental data. Comparisons showed good predictions for half of the liquids used. In addition, a liquid spill fire burning rate model was also developed and checked with experimental data. This model provided good qualitative results, however further development is still needed.
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    Numerical Simulation of Ignition and Transient Combustion in Fuel Vapor Clouds
    (2007-07-31) Wiley, Jennifer; Trouvé, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Large-Eddy Simulation (LES) approach is used to model partially-premixed combustion (PPC) in confined and unconfined fuel vapor clouds. The model is based on the concept of a filtered reaction progress variable to describe the premixed combustion. The premixed combustion model is implemented into the Fire Dynamics Simulator (FDS), developed at the National Institute of Standards and Technology, USA, and is coupled with either an equilibrium-chemistry, mixture-fraction based model (FDS Version 4) or an eddy dissipation model (FDS Version 5) for non-premixed combustion. Modifications to the model are developed and implemented with the goal of reducing the grid resolution requirement while still producing physically sound results. The modified formulation is tested using both versions of the non-premixed combustion model, and the results are compared. It is found that the modifications are capable of reducing errors associated with poorly-resolved simulations in both versions of the model.
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    Flame Extinction and Air Vitiation Effects In FDS In Poorly Ventilated Compartment Fires
    (2005-08-15) Hu, Zhixin; Trouvé, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Compartment fires with different ventilation conditions exhibit different dynamical behaviors, ranging from steady fuel-limited fires to unsteady air-limited fires. Numerical simulations are here performed to study compartment fires in a configuration corresponding to a scaled-down model developed at University of Maryland, in which experimental data are available. The simulations use Fire Dynamics Simulator (FDS) developed by National Institute of Science and Technology (NIST). Four different cases are studied that are representative of different fire conditions: steady over-ventilated fires; steady under-ventilated fires; and unsteady fires with partial flame quenching; unsteady fires leading to total flame quenching. To account for air vitiation and flame extinction effects, a new flame extinction model is developed and integrated into FDS. It is found that the new model improves the numerical predictions and offers the potential of a better representation of the flame dynamics and upper-layer gas composition.
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    Atomization Model Development for Fire Suppression Devices
    (2005-05-04) Wu, Di; Marshall, Andre; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The performance of water-based fire suppression systems is governed by the dispersion of the droplets in the spray. Characterization of the spray is essential for predicting and evaluating the performance of these suppression systems. The accuracy of the spray characterization is quite sensitive to the initial spray specification when using particle tracking method to model spray dispersion. An atomization model based on first principles has been developed for predicting the distributed properties for the initial spray. Inputs to this model include injector geometry, operating conditions, and suppressant fluid properties. This modeling approach has also been integrated with drop dispersion models in FDS 4.0 to characterize spray dispersion behavior. The effect of initial spray specification on spray dispersion behavior in a quiescent environment has also been addressed. The drop size predictions using the proposed atomization model have demonstrated favorable agreement with actual sprinkler spray measurements over a range of operating conditions.