Fire Protection Engineering Theses and Dissertations

Permanent URI for this collection

http://hdl.handle.net/1903/2772

Browse

Now showing 1 - 20 of 201

Predicting the Ignition Time and Burning Rate of Thermoplastics in the Cone Calorimeter
(1995) Hopkins, Donald Jr.; Quintiere, James G.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
Ignition and burning rate data are developed for Nylon 6/6, Polyethylene, and Polypropylene in a Cone Calorimeter heating assembly. The objective is to examine a testing protocol that leads to the prediction of ignition and burning rate for thermoplastics from Cone data. The flame heat flux is not measured, but is inferred from Cone data. The constancy of the flame heat flux for thermoplastics in the Cone calorimeter is due to the geometry of the flame. The burning rate model is shown to yield good accuracy in comparison to measured transient values. Ignition and burning rate data are developed for Redwood and Red Oak in a Cone Calorimeter heating assembly. Measurements of the flame plus external heat flux are presented. The data is intended to be used for future work to develop a testing protocol and burning rate model for charring materials.
Radiant Auto-Ignition of Wood
(2001) Boonmee, Nathasak; Quintiere, James G.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Although piloted-ignition is well studied, auto-ignition is not, and under some conditions the latter may initiate the former. For that reason, the dynamics and mechanisms in the auto-ignition of redwood by radiant heating were experimentally studied. An open-cone radiant source heated an insulated cubical vertical sample 4 cm on a side. Infrared (IR) and normal video cameras were used to view the surface of the wood. Surface temperature (by thermocouple and IR) and mass loss were continuously recorded. The wood grain orientation was aligned either perpendicular or parallel to the incident heat flux. The time for flaming ignition is measured up to 70 kW/m2 and compared to piloted ignition results of Spearpoint and Quintiere [28,29] with little difference above 40 kW/m2. With no visible flame, the surface temperature of the wood can achieve 700 C, while the corresponding inert fibrous insulation achieves only 500 C. This is indicative of surface oxidation, which likely plays a role in the naming ignition or redwood. For example, at 40 kW/m2, heating perpendicular to the grain, flaming ignition occurs in 1000 s. The initiation of flaming ignition is seen in the gas phase above the sample consistent with the observations of Simms [25]. The purpose of this study is to examine experimentally and theoretically the auto-ignition of wood. The important parameters for ignition: ignition time, ignition temperature, mass loss rate, critical heat flux, and thermal inertia are examined and compared with the piloted ignition. The ignition contributed by glowing ignition, and flaming ignition is also discussed.
The Evaluation of a Performance-Based Design Process for a Hotel Building: The Comparison of Two Egress Models
(2003-12-15) Kuligowski, Erica Dawn; Milke, James A; Bryan, John L; Notarianni, Kathy A; Fire Protection Engineering
This work emphasizes the importance for egress model users to choose a model for each project with the appropriate input features and simulation capabilities. This report also gives model users a mechanism for choosing the appropriate model by providing a detailed egress model review (Chapter 2). Specifically this report focuses on the ability of two egress models, EXIT89 and Simulex, to simulate a high-rise hotel building evacuation. When EXIT89 and Simulex are used to 1) simulate the same design scenarios and 2) perform a bounding analysis of the hotel building, significant differences in egress times were identified. EXIT89's evacuation times were found to be 25-40% lower than Simulex for the design scenarios, attributed to differences in unimpeded speeds, movement algorithms, methods of simulating slow occupants, density in the stairs, and stair configuration input between the models. For the bounding analysis, EXIT89 produced maximum evacuation times 30-40% lower than Simulex.
Evaluation of Smoke Detector Response Estimation Methods
(2003-12-16) Geiman, Justin Aaron; Milke, James A; Mowrer, Frederick W; Gottuk, Daniel T; Fire Protection Engineering
Approximation methods exist to provide estimates of smoke detector response based on optical density, temperature rise, and gas velocity thresholds. The objective of this study was to assess the uncertainty associated with these estimation methods. Experimental data was used to evaluate recommended alarm thresholds and to quantify the associated error. With few exceptions, less than 50 percent of the predicted alarm times occurred within ± 60 seconds of the experimental alarms. At best, errors of 20 to 60 percent (in under-prediction) occurred for smoldering fires using an optical density threshold. For flaming fires, errors in predicted alarm times on the order of 100 to 1000 percent in over-prediction of the experimental alarms were common. Overall, none of the approximation methods distinguished themselves as vastly superior. Great care must be exercised when applying these approximation methods to ensure that the uncertainty in the predicted alarm times is appropriately considered.
Analysis of Fire Conditions in a Closed-End Tunnel
(2004-05-18) DeJoseph, Joelle; Mowrer, Frederick W; Fire Protection Engineering
Many studies have addressed fires in tunnels. For the most part, these previous studies have addressed fires that might occur during operation of the tunnel, when the tunnel has openings at both ends. During construction of a tunnel, the tunnel has only one opening as the tunnel is being bored. Analysis of fire conditions that might develop during construction of a tunnel is addressed here. A number of analyses are presented to assess tenability conditions in a closed-end subsurface environment as a result of different postulated fire scenarios. The purpose of these analyses is to develop fire tenability criteria for use in evaluating subsurface life and fire safety.
Predicting Smoke Detector Responce Using a Quantitative Salt-Water Modeling Technique
(2004-06-16) jankiewicz, sean; Marshall, Andre; Roby, Richard; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This investigation provides a detailed analysis of the hydraulic analogue technique used as a predictive tool for understanding smoke detector response within a complex enclosure. There currently exists no collectively accepted method for predicting the response of smoke detectors; one of the most important elements in life safety. A quantitative technique has been developed using salt-water modeling and planar laser induced fluorescence (PLIF) diagnostics. The non-intrusive diagnostic technique is used to temporally and spatially characterize the dispersion of a buoyant plume within a 1/7th scale room-corridor-room enclosure. This configuration is geometrically similar to a full-scale fire test facility, where local conditions were characterized near five ionization type smoke detectors placed throughout the enclosure. An evaluation of the scaled local conditions and dispersive event times for both systems was used to formulate a preliminary predictive detector response model for use with the hydraulic analogue.
FLAMMABILITY PROPERTIES OF CLAY-NYLON NANOCOMPOSITES
(2004-08-18) Liu, Xin; Quintiere , James G.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
A Cone Calorimeter device has been used to measure the flammability properties of samples with different clay dispersion on the nanometer (molecular) scale. Specifically, chemical energy release rate, mass loss rate, and time to ignite (melt and char also) are measured. Samples consisting of pure Nylon 6 and Nylon with nano-clay additives up to 5 % are used in the study. In addition, the effect of thickness is considered for 1 to 24 mm. Data obtained over a range of radiant heat flux are analyzed to illustrate the effect of clay loading and thickness on heat of combustion, heat of gasification and ignition temperature.
NITROGEN FOAM FIRE SUPPRESSION SYTEM FOR AUTOMOBILE UNDER-HOOD POST-COLLISION FIRE PROTECTION
(2004-08-19) Gunderson, John David; di Marzo, Marino; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This thesis describes the development and testing of a Nitrogen Foam fire suppression system. The purpose of the system is to contain or extinguish fires that originate in the engine compartments of automobiles after front-end collisions. The Nitrogen foam creates an inert environment within the engine compartment that is sustainable for a period of at least 10 minutes. Thus, the system is capable of extinguishing fires that have already started at the time of system activation and prevent fires from starting after the foam has been deployed. Testing shows that at an expansion ratio of 220 the Nitrogen foam will fill all of the voids within an engine compartment without freely flowing down and out of the engine compartment. Full-scale burn tests show that the system is capable of containing and extinguishing fires that originate within the engine compartment at the location of the battery.
Characterizing Cigarette Lighter Flames to Reduce Unwanted Ignition
(2004-09-14) Williamson, Justin Wade; Marshall, Andre W; Quintiere, James G; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This investigation provides detailed measurements and analysis for improved understanding of ignition from the 'small' flames produced by cigarette lighters. This research program is motivated by the need to improve the fire safety of cigarette lighters in response to the juvenile firesetter problem. A novel cigarette lighter concept for improved ignition safety has been developed, characterized, and compared with conventional lighters. Diagnostics were performed to measure laminar near-field plume behavior and turbulent far-field behavior in these small-scale (75W) flames. Plume diagnostics include centerline temperature, heat flux to a horizontal flat plate, and ignition of filter paper. Data was scaled and compared to plume theory and measurements. Other practical cigarette lighter performance related properties were also noted, such as lighter surface temperatures and cigarette ignition effectiveness.
Extreme Geotechnical Response to High Heat From Tunnel Fires
(2004-12-03) yong, meng wah; Marshall, Andre W; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This study investigates the effects of heating on the transient behavior of the geologic media surrounding the tunnel involved in a severe fire, which typically involve extreme temperature and prolonged duration. Currently, there is little research being done in this area. An analytical model has been developed to predict the temperature rise of dry soil in the experimental soil column configuration and there is good agreement between analytical and experimental results. In water-saturated soils, the onset of convection happens in soil of higher permeability and there is propagation of a saturation temperature front at the onset of boiling, with greater propagation speed as permeability increases. There is also significant increase (~500%) in the pore water pressure building up in finer-grained saturated soil. This project then examines how these thermal transport modes and the pore water pressure increase in the soil medium can affect the stability of the tunnel lining.
A Methodology for Flammability Diagrams
(2004-12-09) Panagiotou, Joseph; Quintiere, James G; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The current state of fire safety regulations in the United States Department of Transportation is examined, along with some of the associated flammability test methods. The applicability and overall usefulness of these tests is evaluated along with their ability to accurately capture and describe fire performance. Theoretical relationships are shown for the fire phenomena ignition, energy release and flame spread in terms of incident flux to demonstrate the ability to extract meaningful data from calorimetry and flame spread tests. This is done for sample materials to obtain a general overview of their fire performance. This general overview is presented in the form of a Flammability Diagram. A Flammability Diagram is a single plot showing the energy release rate, time to ignition and flame spread rates for a material all as a function of the incident heat flux. Effects of melting, dripping, thickness, sooting and other factors may not be fully described, but the experimental framework captures the overall result of such effects. This study shows the feasibility of developing a measurement methodology that can be followed for the creation of Flammability Diagrams, providing a clear picture of a material's fire performance.
Characterization of the MIL-F-24385F Nozzle
(2005-01-25) Hoskins, Bryan Lawrence; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Aqueous Film Forming Foam has been a fire suppression agent in use for nearly forty years. During this period, there has been little emphasis on characterizing the flow from nozzles that have a throw of only a few meters. With environmental concerns starting to appear, it is important to understand how the foam behaves. The research presented in this document attempts to quantify the mass flux and momentum of the foam. This was done using both experimental data and hand calculations. A range of nozzle angles were examined in an attempt to set bounds of the minimum and maximum expected values.
AN INVESTIGATION ON THERMAL CHARACTERISTICS OF PREMIXED COUNTERFLOW FLAMES USING MICRO-THERMOCOUPLES
(2005-05-03) Ghoddoussi, Roya; Marshall, Andre W; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Hydrogen addition is known to improve the stability of highly strained hydrocarbon premixed flames. Since the flame temperature is an important factor associated with extinction, it is of interest to study the thermal characteristics of the hydrogen-doped flames near extinction. Temperature profiles of highly strained lean-premixed pure CH4 and CH4/H2 flames were measured in a counterflow configuration at strain rates far from and close to extinction. Point temperature measurements were made utilizing a micro-thermocouple probe. To improve the measurements, the thermocouple support design was enhanced and corrections were made for measurement errors where appropriate. Trends observed in experimental and modeling temperature profiles with changes in fuel composition and strain rate, agree favorably. However, there are some discrepancies between the measured and predicted absolute temperatures. Factors contributing to these discrepancies and the methods to reduce the thermocouple measurement errors are discussed.
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.
A STUDY ON TOTAL EVACUATION VERSUS SELECT EVACUATION FOR HIGH-RISE OFFICE BUILDINGS
(2005-05-31) Hartmann, Suzette Marina; Milke, James; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Over the past hundred years, high-rise office buildings have been evacuated primarily due to fire incidents and terrorism attacks. Due to these incidents, there has been attention given on how to evacuate high-rise buildings more efficiently. Therefore, this thesis focuses on evaluating the evacuation strategies of high-rise buildings, with particular attention directed to how these strategies are affected by a building's size and occupant density. It discusses and demonstrates the issue of evacuation time as it relates to high-rise office buildings through the use of an evacuation model, EXIT89, and reviews the resulting times established by the model for each total and select evacuation. Overall, this research results in identifying that there are differences in the performance of the total and select evacuation strategies, with a greater penalty in the overall evacuation case than in the local (time to get evacuees out of the affected area).
Scale Modeling of the Transient Behavior of Wood Crib Fires in Enclosures
(2005-08-08) Perricone, Jonathan Andrew; Quintiere, James G; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Scale modeling affords engineers the ability to appreciate the dynamic enclosure fire environment of larger than life structures in the laboratory. Conventional approaches to scaling have expressed results in terms of time-averaged values. Transient scaling accuracy must be achieved in order to reasonably assess the interaction of the fire environment with the structural components of a prototype building. A wood crib is used to represent a typical fuel arrangement. The parameters of the wood crib and its surrounding enclosure are designed based on length scale relationships derived from the governing conservation equations. Experiments conducted at three model scales, in ventilation limited enclosures, demonstrate a high degree of both transient and spatial accuracy in the prediction of burning rates, temperatures and gas concentrations. Although it seems that a global energy balance is achieved, some inconsistencies in the scaling of local radiant heat fluxes are highlighted for future attention.
Analysis of Hold Times for Gaseous Fire Suppression Agents in Total Flooding Applications
(2005-08-12) O'Rourke, Sean Thomas; Mowrer, Frederick W; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Many of the clean agents currently used in total flooding fire suppression applications have vapor densities greater than ambient air. The denser agent-air mixture creates hydrostatic pressure differences causing flow of the mixture out of the enclosure as well as flow of ambient air in through leakage paths inherent in building construction. Hold time refers to the amount of time it takes for the concentration of the agent-air mixture to drop below a specified concentration at a designated height within the protected enclosure. In this study an experimental test enclosure was used to evaluate an analytical model of agent-air mixture leakage and to investigate the effects of different leakage areas on agent hold times. The analytical model, known as the descending interface model, demonstrated favorable agreement with experimental measurements for heights greater than one-half the height of the enclosure for the agent used in this investigation.
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.
FLAMMABILITY CHARACTERISTICS OF WATER-BASED POLYCRYLIC AND OIL-BASED POLYURETHANE COATED OAK VENEER PLYWOOD SAMPLES SUBJECTED TO INCIDENT HEAT FLUXES
(2005-12-13) Thompson, Sarah Elizabeth; Mowrer, Frederick W.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The flammability characteristics of oak veneer plywood were evaluated in the Cone Calorimeter. Samples of 6.35 mm (1/4 in.) thick and 19.05 mm (3/4 in.) thick oak veneer plywood were coated with 3, 6, and 9 coats of either oil-based polyurethane or water-based polycrylic clear finishes and tested at incident heat fluxes of 35, 50, and 75 kW/m2 along with uncoated samples. Both the type of finish and the number of coatings were found to influence the ignition time, the measured peak heat release rate, and the minimum flux for ignition of the samples. The ignition times for the coated samples were 2 to 3 times lower than the unfinished samples. Predicted times to ignition differed by a factor of 2 to 3 from the measured values (with the exception of the samples with nine coats of finish.) The predicted ignition temperatures differed by as much as 100 ºC from the measured temperatures. The Quintiere flammability parameter, b, was found to be positive for all testing scenarios, suggesting a propensity for flame spread at the incident heat fluxes evaluated.
Evaluation of the Ability of Fire Dynamic Simulator to Simulate Positive Pressure Ventilation in the Laboratory and Practical Scenarios
(2005-12-13) Kerber, Steve Ira Newton; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Positive Pressure Ventilation (PPV) is a tactic that is used on fire grounds across the world everyday, both to improve tenability after the extinguishment of a fire and/or offensively during fire attack to improve firefighting conditions. PPV has proven that it can be a useful tool on the fire ground, but it can also kill or injure fire fighters and civilians if used improperly. Data from three full-scale experiments are compared with simulations completed with the computational fluid dynamic model Fire Dynamic Simulator (FDS). The full-scale experiments characterize a Positive Pressure Ventilation (PPV) fan in an open atmosphere, in a simple room geometry and in a room fire. All experiments qualify and quantify the comparison of the experimental results with the FDS results. A concluding scenario is modeled utilizing the calibration of the full-scale experiments to examine the effects of PPV on a fire in a two-story, colonial style house.

Browse

Browsing Fire Protection Engineering Theses and Dissertations by Issue Date

Results Per Page

Sort Options