Fire Protection Engineering Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2772

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Analysis and Measurement of Candle Flame Shapes
(2008-05-07) Tabaka, Gregory Allen; Sunderland, Peter B; Quintiere, James G; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
A combined analytical and experimental study was performed to produce and validate a method by which the lengths and widths of flames burning on wax candles can be predicted. Two analogies are drawn: first, that heat transfer from the wick can be modeled as a slender vertical rod undergoing a natural convection process surrounded by a stagnant film; and second, that fuel pyrolyzed from the wick surface that remains unburned until above the wick can be modeled as flow from a circular port burner. Empirical correlations applied to the theoretical equations have produced reasonable agreement with measured flame lengths and widths for paraffin candles.
ANALYSIS AND QUANTIFICATION OF HAZARDS ASSOCIATED WITH CASCADING THERMAL RUNAWAY PROPAGATION IN LITHIUM ION BATTERY CELL ARRAYS
(2018) Lee, Christopher Patrick; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Lithium ion batteries are among the most common and efficient electrical energy storage devices despite the thermal, fire, and chemical hazards they pose upon thermal failure due to abnormal conditions. The hazards are intensified when thermal failure propagates from a single cell to neighboring cells in a battery pack. A new wind tunnel experimental setup was designed and built to investigate the dynamics, gaseous emissions, and energetics of cascading failure propagation in 18650 form factor, 2600 mA h, lithium cobalt oxide cathode cell arrays. Ambient environment (N2 / air), cell state of charge (SOC; 50% / 100%), and cell arrangement (without 5 mm gaps between cell rows / with 5 mm gaps between cell rows) were all varied during tests to investigate different aspects of battery pack failure and quantify the impact of different failure mitigation strategies. On average, failure propagation speed was 7.5 times faster in air than in nitrogen, 8.5 times slower at 50% SOC than at 100% SOC, and three times slower with a 5 mm gap between cells than without it. All tested cell arrays ejected minor mass yields of O2 and H2, as well as comparatively large mass yields of total unburned hydrocarbons, CO and CO2. At 100% SOC, approximately 59 kJ of energy per cell was produced from the chemical reactions between cell components during failure. An additional 62.8 ± 18.4 kJ per cell was produced when the ejected battery materials during failure combusted in a reacting medium, but the combustion in the wind tunnel setup was highly incomplete due to the development of under-ventilated conditions. In a separate experimental setup with near complete combustion, combustion energy of 107 ± 17.7 kJ per cell was measured.
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.
An Analysis of Heat Flux-Induced Arc Formation in Residential Electrical Cables
(2011) Novak, Cameron James; Stoliarov, Stanislav I; Quintiere, James G; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The mechanisms by which fire environments may trigger electrical arcs in household wiring are often misunderstood. A thorough knowledge of these mechanisms may assist fire investigators to determine whether a given arcing event was the cause or result of a fire. In this study, both unenergized and energized cables were tested under a variety of conditions to observe the behavior and breakdown of cable insulation. This research may have applications for the fire protection community and, in particular, the field of fire investigation. The data collected during testing indicates that electrical cables must be exposed to minimum heating conditions before a fault will occur, aiding in the analysis of the electrical system and tracing the progression of a fire.
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.
Analysis of Propane Gas Burner Experiments and FDS Simulations in a Two-Story Residential Structure with HVAC
(2020) Quiat, Adam; Milke, James; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
To further our knowledge of fire dynamics in a residential structure with a heating, venitilation, and air conditioning (HVAC) system, a series of live fire gas burner experiments were conducted and modeling simulations were completed to compare the results. 29 full-scale experiments were conducted in a single story ranch structure on a basement with fire from a single propane fed gas burner. The structure was instrumented to measure temperatures, oxygen and carbon dioxide concentrations, water vapor concentrations, and gas velocities. In addition to the full-scale experiments, six experiments were selected and modeled for comparison. A numerical simulation program, known as a Fire Dynamics Simulator (FDS) (version 6.7.10), was used to complete the computational fluid dynamics (CFD) calculations. The FDS HVAC submodel was incorporated into the modeled experiments to compare how heat and fire gases transversed the modeled HVAC system as compared to the experimental results. Results from experimental and simulated data showed that heat and fire gases were transferred through the HVAC system during the experiments. Comparison of simulation data to the experimental data showed that FDS over predicted heat transfer through the HVAC system. However, there was sufficient agreement between data points to support FDS modeling as a more severe set of outcomes in the event of a fire.
Analysis of Propane Gas Fire Experiments and Simulations in Residential Scale Structures
(2017) Willi, Joseph; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Nine full-scale fire experiments were conducted in two residential-sized structures with a fire source provided by three propane gas burners. Five of the experiments were conducted in a single-story structure, and four were conducted in a two-story structure. The structures were instrumented to measure temperature; oxygen and carbon dioxide gas concentrations; gas velocity; and heat flux. Various doors and vents were opened and closed during the experiments to change the ventilation through the structures. Numerical simulations of the nine experiments were conducted using Fire Dynamics Simulator (FDS) (version 6.5.3). The model data were compared to the corresponding experimental data, and the temperature, gas species concentration, and heat flux data produced by the simulations were within the expected agreement range based on the values of experimental relative standard deviation, model relative standard deviation, and model bias factor provided by the FDS Validation Guide for each specific data type. The one significant discrepancy between the simulation data and experimental data occurred with the gas velocity measurements, which produced a model relative standard deviation that was 0.18 larger than the value from the FDS Validation Guide. Overall, comparing the FDS simulation output to the experimental data shows sufficient agreement between the predicted and measured data, thus indicating that FDS is capable of accurately modeling different aspects of fire scenarios in residential-sized structures.
Analysis of the Effects of Temperature and Velocity on the Response Time Index of Heat Detectors
(2010) Pomeroy, Andrew Tom; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Recent revisions to NFPA 72, the National Fire Alarm Code, have specified the response time index (RTI) as the sensitivity listing for heat detectors. Originally derived as a sprinkler sensitivity rating, there has been little work performed to validate the use of the RTI rating for heat detectors. RTI values are determined by plunging the devices into a hot wind tunnel at 200 C (392 F) and 1.5 m/s (4.9 ft/s). These test conditions are unrealistically severe for the majority of expected ceiling jet profiles. While the RTI correlation is purported to be independent of temperature and velocity, data from previous studies indicates otherwise. This study examined the effects of low temperature and low velocity plunge test conditions on the constancy of the RTI for several common heat detectors. The RTI correlation was found to be inconsistent across temperature and velocity test conditions.
Analysis of the initial spray from canonical fire suppression nozzles
(2007-08-10) Ren, Ning; Marshall, André W; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The performance of a fire suppression spray is governed by injector discharge characteristics. An atomization model based on the theoretical evolution of a radially expanding sheet generated by an impinging jet has been established in this study. The atomization model predicts characteristic initial drop location, size, and velocity based on injector operating conditions and geometry. These model predictions have been compared with measured discharge characteristics from three nozzle configurations of increasing geometrical complexity over a range of operating conditions. Differences between the predicted and measured initial spray are critically evaluated based on the experimentally observed atomization behavior.
THE ANALYSIS OF THE TRANSITION FROM SMOLDERING TO FLAMING IN POLYURETHANE CONTAINING ASSEMBLIES REPRESENTATIVE OF UPHOLSTERED FURNITURE
(2019) Knapp, Graham Michael; Stoliarav, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The smoldering and ignition of upholstered furniture is the leading cause of loss of life in accidental residential fires. Due to these fatal incidents, a new smoldering apparatus experimental setup was designed and built to investigate the temperature profile, the gaseous products, and the probability of transition from smoldering-to-flaming in polyurethane foam based upholstered furniture when subjected to a high intensity cartridge heater representative of a cigarette. The measurement locations in which the gaseous products and the temperatures from smoldering combustion were determined (2.5 – 22.5 cm above the heater) and the materials that made up each upholstered furniture assembly (cotton and polyester fabrics and battings with both fire retardant or non-fire retardant polyurethane foams) were both varied during the tests to investigate the specific gaseous quantities compared with temperature readings as a smolder front propagates and how varying materials affect the transition from smoldering-to-flaming, respectively. On average, the rate in which the smolder front propagates near the end of the test is 2 times faster than the rate at the start of the test. All tests performed produced large amounts of Carbon Dioxide and Carbon Monoxide, which is representative of 95% of the Oxygen that was consumed. During the moments directly before the sample transitions from smoldering-to-flaming, there is a noticeable increase in Oxygen consumption as the distance from the heater increases past the smolder front and into the Oxygen limited pyrolysis zone. The anaerobic pyrolysis zone produces the combustible fuels required for transition, and once a substantial amount of combustible fuel is produced, the high temperature smoldering reaction ignites the fuel. In varying the materials used in each upholstered assembly, it was confirmed that the probability of transition increased substantially with the use of cotton fabric and cotton batting, while the use of polyester fabric and polyester batting greatly reduced the probability of transition. The presence of fire retardants in fabrics and polyurethane foam can greatly reduce (or even eliminate) the probability of transition, but when paired with cotton batting, higher levels of fire retardants (BS 5852 rated) were required.
An Analysis of Thermally Induced Arcing Failure of Electrical Cable
(2013) Fisher, Ryan Patrick; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Arc failure of Southwire Romex Simpull non-metallic sheathed 14/2 American wire gauge (AWG) with ground cable due to external heat was examined. This type of cable was selected due to its widespread use in residential building wiring. This research is motivated by the fact that currently there are no widely accepted methods or models used to predict electric arc failure in cables exposed to thermal conditions or to determine whether an arc failure event was the cause or result of a fire. A variety of tests were performed at various temperatures to learn more about the arc failure of these cables. The cables were exposed to precise temperatures with a steady heating rate in a convection oven in order to best attempt to eliminate heat transfer through the cable. In order to explore the effect current may have on the time to arc failure of the cable, experiments at different temperatures were performed in both loaded and unloaded scenarios. During many of these tests, voltage and current measurements were collected during an arcing event. As part of the process of exploring the events leading up to arc failure, electrical resistance tests of the cable's insulation components were examined. A model was developed to predict time to arc failure at a variety of temperatures based on thermal degradation of the PVC insulation. The purpose of the developed model is to be able to predict cable failure based on known thermal conditions. The proposed values of the model developed are in examining a prior thermally induced electrical arcing incident or in determining the suitability of a cable in an abnormal thermal environment. The results of this research will be useful in continuing the research and education of the arc failure of electrical cables.
Analysis of Underventilated Compartment Fires
(2009) Wolfe, Andrew John; Mowrer, Frederick; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Little research has been done to examine full-scale unventilated fires despite their common occurrence and relevance. This project was conducted to characterize the fire dynamics of unventilated and partially ventilated compartment fires. A series of fifteen full-scale fires were performed within an instrumented, four room, apartment style enclosure measuring 41.8 m2 (450 ft2). Three different fuel sources, including sofas, kitchen cabinets, and cotton batting, were tested using different ventilation and ignition schemes to analyze the effect of ventilation on fire growth and tenability. The results of these tests allowed for the examination of the effects of ventilation on: general fire dynamics, including fire growth, smoke and gas production, and vitiation; tenability factors including temperature, heat flux and carbon monoxide FED levels; and the ability to utilize forensic tools to determine the cause and progression of a fire.
An Analysis of Vehicle Fires and Potential Methods to Reduce Their Severity Through More Stringent Material Standards
(2008-06-17) Patronik, Evan; Mowrer, Frederick; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
In the United States, more than 1 in every 12 fire fatalities occurs in a passenger road vehicle; vehicle fires claim roughly 1200 injuries, $1.3 billion in property loss, and 490 lives annually. Very little progress has been made over the last several decades to confront the hazards of vehicle fires, but recently researchers and standards organizations have begun addressing these challenges. A literature review of the progress made and methods of reducing fire severity through technologies and standards was conducted. NFPA 556 is one proposed standard aimed at mitigating the hazards to occupants of vehicle fires; it was used to analyze the fire retardancy of a new, fire-resistant acoustic insulation material through small, bench, and large-scale testing. The feasibility of the use of this material in new vehicles for the reduction of losses was assessed through a cost-benefit analysis. Upon review of the results, it was determined that the new insulation did not pass all the requirements of NFPA 556. However, the standard does include stringent requirements, so the improved performance of the material should not be underappreciated. Based on the literature search and experiments, this standard, in combination with other fire protection technologies, provides a basis for improved vehicle fire safety.
Analyzing Photo-Electric Smoke Detector Response Based On Aspirated Smoke Detector Obscuration
(2010) Miller, John Herbert Thomas; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Accurate obscuration levels at the response time of photo-electric smoke detectors are needed for proper detection modeling and analysis. In recent works, obscuration meters were used to measure the obscuration level at photo-electric detector response. In this study, aspirated smoke detectors (VESDA) were used to measure this same obscuration level. These detailed measurements were used to reduce the ambient light and the technology difference error associated with the obscuration meters. The use of aspirated smoke detection (VESDA) instead of light obscuration meters displayed increased accuracy for a majority of the experiments conducted in the 2008 report titled "Validation of a Smoke Detection Performance Prediction Methodology" involving flaming and non-flaming incipient fire sources at 3 different ventilation conditions.
Assessing the Validity of the Verification Method as a Design Tool
(2018) Antonsen, Maibritt; Torero, José L; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The Verification Method (VM) as a design tool is becoming more widespread, result-ing in a need for a critique of the concepts behind the method. This project provides the critique by extracting examples from the design processes and solutions of a building being designed using three different approaches: Performance-Based Design, Prescriptive Methods and the VM. The main perceived advantages of the VM is its time efficiency, accessibility and flexibility, while the observed weaknesses include substitution of the designer, the level of under- and over-design and its lack of robustness of the performance criteria and guidance in areas such as fire modeling. It is uncovered how the VM is a design method rather than a tool to demonstrate compliance with the performance require-ments of building codes, which was the original objective of the VM. The Verifica-tion Method must return to its original intentions in order to ensure its validity as a design tool.
Assessment of Duct Leakage Rates on Stairwell Pressurization System
(2014) Taricska, Jerry Richard; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This study aims to evaluate the effects duct leakage had on a stairwell pressurization system in a high-rise residential building by using a network model, CONTAM. The network model was used to determine if the pressurized system was capable of being balanced and perform as intended during a fire incident. The subject building had two stairwells, each fed by a fan located on the 2nd and 29th floors of a 31-story building. Each fan fed a multi-injection duct system which ran through a mechanical shaft located next to each stairwell. This study evaluated the effects that building leakages and temperatures (stack effect) had on air leakage out of the duct system by comparing fan capacities to stairwell pressurization requirement. CONTAM was used to simulate these effects by running both a duct balance method and steady state method. The results from this study determined that as duct leakage rates increased, fan capacities increased to meet the stairwell pressurization requirements for a high-rise building. Additionally, the results determined that the building leakage and exterior temperatures increased the air flow leaking out of the duct system.
ASSESSMENT OF NATURAL VERTICAL VENTILATION FOR SMOKE AND HOT GAS LAYER CONTROL IN A RESIDENTIAL SCALE STRUCTURE
(2012) Opert, Kelly; Milke, James; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
In firefighting, ventilation tactics are used to increase visibility for firefighter rescue and fire suppression operations, to increase survivability of the occupants of the structure, and to decrease property damage. Improperly implemented ventilation tactics or unplanned, fire-induced ventilation can lead to rapid changes in fire behavior creating fatal conditions inside a building for occupants and firefighters. In this set of experiments, measurements were made within a single, full scale compartment varying the fire size and the ceiling vent conditions between no vents, one 1.2 m by 1.2m (4' by 4') vent, and two combined 1.2 m by 1.2m (4' by 4') vents. The objective was to assess the vents' ability to relieve smoke and the hot gas layer. Thirty-two experiments were conducted using natural gas. These fires were allowed to burn until conditions within the enclosure reached steady state. With one open vent, the hot gas layer was not fully vented. With two open vents, the hot gas layer was fully vented for all three fires sizes. Simulations of the natural gas experiments were produced using the National Institute of Standards and Technology's Fire Dynamics Simulator in order to explore how well the experiments were simulated based on the same fire sizes and vent conditions. The simulated steady state hot gas layer depths were significantly less than the experimental depths in the doorway when both vents were open, due to a discrepancy in whether or not a hot gas layer existed. The steady state hot gas layer temperatures were significantly under-predicted near the burner when both vents were open (meaning the simulated temperatures were cooler than the measured temperatures) and over-predicted in the doorway when one vent was open and two vents were open (meaning the simulated temperatures were hotter than the measured temperatures). Two additional experiments were conducted using sleeper sofas as fuel, in order to evaluate the differences between controlled natural gas fires and furniture. Neither one open vent nor two open vents was enough to raise the hot gas layer interface height. In the experiment with two sofas, two open vents did reduce the hot gas layer temperature at the doorway by as much as 300 °C (600 °F), but the temperature was still in excess of 200 °C (400 °F). In conclusion, the minimum vertical vent size of one 1.2 m by 1.2m (4' by 4') that firefighters are instructed to use does not remove all hazards, even in a 0.5 MW fire. More discussion is needed in the fire service to define the goals of vertical ventilation and how to best address each goal. More validation of the Fire Dynamics Simulator is needed before vertical ventilation can be accurately simulated in a multi-room structure fire.
An Assessment of the Use of Flame Retardant Plastics for Museum Applications
(2007-12-18) Leikach, Danielle Caryn; Mowrer, Frederick; Brostoff, Lynn; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Halogenated flame retardant plastic sheeting may help to reduce flame spread in museums; however, the plastics contain chemicals that may be harmful to museum objects in situ, particularly metals. This study assesses historical and contemporary problems and benefits associated with flame retardant plastics with respect to museum applications. This issue was addressed by pairing statistical data on museum fires with standard and novel methods for assessing corrosivity, while also creating a format for future assessments of fire-safety related practices as they are applied in museum settings. Flame retardant plastics were found to cause small rates of corrosion in copper, approximately 1.2 milli-inches per year (mpy), compared to pure polyethylene which corrodes at approximately 0.83 mpy. Conventional testing methods show that flame retardant plastics can be considered safe for limited museum use and that they delay ignition from small heat sources, but they must be assessed for each individual scenario.
AN ASYMPTOTIC ANALYSIS OF SPONTANEOUS IGNITION OF HYDROGEN JETS
(2007-04-26) lim, kianboon; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Analytical work is presented for the spontaneous ignition of a hydrogen jet emanating from a slot into air. A similarity solution of the flowfield was obtained. This was combined with the species and energy conservation equations, which were solved using activation energy asymptotics. Limits of spontaneous ignition were identified as functions of slot width, flow rate, and temperatures of the hydrogen jet and ambient air. Two scenarios are examined: a cool jet flowing into a hot ambient and a hot jet flowing into a cool ambient. For both scenarios, ignition is favored with an increase of either the ambient temperature or the hydrogen supply temperature. Moreover, for the hot ambient scenario, a decrease in local fuel Lewis number also promotes ignition. The Lewis number of the oxidizer only has a weak effect on ignition. Because spontaneous ignition is very sensitive to temperature, ignition is predicted to occur near the edge of the jet if the hydrogen is cooler than the air and on the centerline if the hydrogen is hotter than the air.
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.