Fire Protection Engineering Theses and Dissertations

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

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    DETECTION OF SIGNATURES FROM INTERNAL CONTAMINANT SOURCES USING INTELLIGENT ALGORITHMS
    (2023) Anthrathodiyil, Saleel; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Electrical odors and smoke incidents in aviation have become a pressing concern, with over half of the detector activations resulting in false alarms, leading to uncertainties for flight crews. The escalating costs of diversions and growing awareness of associated health risks underscore the need for more reliable detection and discrimination from false alarms. This study harnesses advanced multi-sensor array technologies, intelligent algorithms, and Metal Oxide Sensors (MOS) sensors equipped with AI capabilities to detect and analyze signatures from candidate internal contaminant sources located in the cockpit. Printed circuit boards from avionics, aviation cables of different insulation, and external contaminant sources were put to failure testing to analyze the early fire signatures. These signatures were subsequently assessed using clustering algorithms and multivariate analysis to pinpoint distinct markers. Comprehensive gas analysis and light obscuration measurements further characterized the environment. Experiments were executed at both the University of Maryland and the Federal Aviation Administration (FAA) tech center, replicating diverse conditions, including an altitude simulation of 8000 ft. The focus was on the capability to distinguish between samples during the smoldering phase, leveraging a multivariate approach and gas analysis. The study also incorporated Aspirating Smoke Detection (ASD) to characterize the responses during large-scale testing. The findings pave the way for identifying and integrating innovative technologies, achieving accurate detection of early-stage signatures from internal contaminants during potential aircraft smoke events.
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    COMPARISON OF IGNITION AND COMBUSTION CHARACTERISTICS OF PRESSURE TREATED WOOD AND TREX EXPOSED TO THERMALLY CHARACTERIZED GLOWING FIREBRAND PILES
    (2023) Lauterbach, Alec; Stoliarov, Stanislov I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In recent decades, the intensity of wildfires worldwide has escalated, leading to a rise in the destruction of structures and loss of lives within the Wildland-Urban Interface (WUI). Firebrands are small fragments of ignited vegetation or structural material that are carried by the plume of a wildfire, traveling in advance of the main fire front. Firebrand exposure has been recognized as the primary mechanism for the propagation of wildfires as well as a source of ignition of structural elements. However, this complex ignition process of structural elements in the WUI has yet to be fully understood. The ignition and combustion characteristics of a thermoplastic-wood composite (Trex) and Pressure Treated Wood (PTW), two frequently used WUI decking materials, when exposed to glowing firebrand piles were studied using a bench scale wind tunnel. An inert insulation material, ii Kaowool PM, was also used as a deposition substrate to quantify the heat feedback and combustion characteristics of solely the firebrand pile. Firebrand pile densities of 0.16 g cm-2 and 0.06 g cm-2 were deposited on each substrate in rectangular 10 cm x 5 cm orientations and exposed to air flow velocities of 0.9 m s-1, 1.4 m s-1, 2.4 m s-1, and 2.7 m s-1. Infrared camera measurements were used to determine the back surface temperatures of Kaowool PM tests. Using DSLR cameras, surface ignitions of the decking material in front of the firebrand pile (preleading zone ignition events), ignitions on top of the firebrand pile (pile ignition events), and surface ignitions of the decking material behind the firebrand pile (downstream ignition events) were visually quantified via their probability of ignition, time to ignition, and burn duration at each testing condition. A gas analyzer was used to compare combustion characteristics of Trex, PTW, and Kaowool PM tests through heat release rate (HRR) and modified combustion efficiency (MCE). Peak back surface temperatures of the firebrand pile were found to increase with increased air flow up to 2.4 m s-1, and then plateau. The same trend was observed for the ignition probabilities of preleading zone and pile ignition events. The probability of downstream ignition events increased with increasing air flow velocity. Peak HRR increased with increasing air flow velocity. Trex exhibited significantly less smoldering combustion than PTW yet was prone to more intense flaming combustion. When the rectangular 5 cm x 10 cm firebrand pile (10 cm edge facing the airflow), of which the majority of tests were conducted on, was rotated 90 degrees so that the 5 cm edge faced the airflow, the result was a significant decrease in the probability of ignition for both Trex and PTW, along with notable reductions in their HRR and MCE profiles.
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    SPHERICAL GAS-FUELED COOL DIFFUSION FLAMES
    (2022) Kim, Minhyeng; Sunderland, Peter B.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    An improved understanding of cool diffusion flames could lead to improved engines. These flames are investigated here using a spherical porous burner with gaseous fuels in the microgravity environment of the International Space Station. Normal and inverse flames burning ethane, propane, and n-butane were explored with various fuel and oxygen concentrations, pressures, and flow rates. The diagnostics included an intensified video camera, radiometers, thin-filament pyrometry, and thermocouples. Spherical cool diffusion flames, transitioned from hot flames, burning gases were observed for the first time. However, these cool flames were not readily produced and were only obtained for normal n-butane flames at 2 bar with an ambient oxygen mole fraction of 0.39. The sizes of hot and cool diffusion flames were investigated with the intensified camera images. The hot flames that spawned the cool flames were 2.6 times as large. An analytical model is presented that combines previous models for steady droplet burning and the partial-burning regime for cool diffusion flames. The results identify the importance of burner temperature on the behavior of these cool flames. They also indicate that the observed cool flames reside in rich regions near a mixture fraction of 0.53.
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    Effects of Fire Whirl Generator Dimensions on Flame Length and Burning Rate
    (2020) Dowling, Joseph Lee; Gollner, Michael J; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In-situ burning remains an efficient method of oil spill cleanup, but the implementation of fire whirls over the spilled fuel has the potential increase the speed and efficacy of the process by increasing burning rate and temperature. Logistical requirements would then be placed on the size of the fire whirl generator. A range of wall heights between 0 and55 cm were tested for a fixed-frame fire whirl generator with a liquid fuel source 10.5cm in diameter to analyze the effect on the burning rate and flame length of resulting fire whirls. For very short walls, with heights approximately equal to the fuel pool diameter,an increase of almost double was shown in the mass loss rate. The flame length for the fire whirl increased drastically for wall heights above a critical value of 35 cm, forming stable on-source fire whirls. This indicates that the inflow boundary layer of the fire whirl is a crucial feature causing an increase in the burning rate, while a critical wall height is necessary for aerodynamic effects to form stable on-source fire whirls with extended flame engths.
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    Pressure Measurements for Refrigerant Flammability Limit Testing Using ASTM E681 Apparatus
    (2017) Klieger, Alexandra Eve; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Improvements to the ASHRAE 34 and ASTM E681 standard test apparatus and procedure have been identied to make the test more repeatable and reproducible. Currently, the test apparatus centers around a glass flask with visual flammability criteria that can be subjective and dependent on a wide variety of factors. Additionally, the current test apparatus vents close to the time where the visual criteria is evaluated which can impact flame propagation. A high frequency pressure transducer was added to the testing apparatus to understand the pressure development in the test vessel throughout flame propagation. Initial test pressures below atmospheric were studied to reduce the likelihood of premature venting. Quenching effects from the electrode rods of the test apparatus were quantied as well. Ultimately, a fractional pressure rise of 40% from a mixture starting at 91.2 kPa was proposed as a new pressure-based flammability criteria to potentially replace the current visual criteria. This new criteria would result in an lower flammability limit of 14.0% for R32.
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    Laboratory Studies on the Generation of Firebrands from Cylindrical Wooden Dowels
    (2016) Caton, Sara; Gollner, Michael J; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Wildland urban interface (WUI) fires are increasing in size and severity in the United States. These fires are a major concern because they spread into communities and ignite thousands of homes every year. The main source of home ignitions is not through direct flame contact or radiation; rather, firebrands are the primary pathway for fire to spread into WUI communities. Firebrands are pieces of a burning material that break off and then can be lofted and carried large distances to ignite subsequent fires. The purpose of this thesis is to study the breakage process to better understand how firebrands are produced. Cylindrical wooden dowels are used to represent vegetative fuels in WUI fires. The dowels were exposed to various heating conditions and then three-point bending tests were performed on each dowel to study the effect of combustion on strength properties. It has been found that there are two distinct regimes that describe the breakage. The size of the dowel and the final density of the dowel both control the transition between regimes. A scaling analysis was performed to show that the two regimes and transition point are the same for all species. Predictions of wind velocities needed to produce the measured critical stresses were calculated, because a connection needs to be drawn between the combustion and the wind to fully understand firebrand generation.
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    Development of the ASTM E681 Standard
    (2016) Lomax, Peter; Sunderland, Peter; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    ASHRAE 34, based on ASTM E681, was improved by identifying and rectifying deficiencies in ASTM E681. An ASTM E681 apparatus and procedure was developed with gaseous refrigerant testing in mind. The plumbing was improved by ensuring that the pressure readings could be constantly monitored while decreasing leakage potential. An original electrical system was designed and constructed for the ignition system. Additionally, a control panel was constructed to isolate hazardous electrical elements, and facilitate the testing, while simultaneously organizing the critical plumbing and ignition components. 3D printing efficiently produced heat-resistant, nonreactive, and structurally stable lower electrode spacers, propellers, and propeller bars. The heating system was designed to ensure even temperature throughout the apparatus. The humidity system was designed to accurately condition the air. Recommendations to improve ASTM E681 are provided. The research can be built on to improve the accuracy and reproducibility of ASTM E681.
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    Interaction of Acoustic Waves with a Laminar Line-Flame
    (2016) Friedman, Adam Neal; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A systematic study was conducted to elucidate the effects of acoustic perturbations on laminar diffusion line-flames and the conditions required to cause acoustically-driven extinction. Flames were produced from the fuels n-pentane, n-hexane, n-heptane, n-octane, and JP-8, using fuel-laden wicks. The wicks were housed inside of a burner whose geometry produced flames that approximated a two dimensional flame sheet. The acoustics utilized ranged in frequency between 30-50 Hz and acoustic pressures between 5-50 Pa. The unperturbed mass loss rate and flame height of the alkanes were studied, and they were found to scale in a linear manner consistent with Burke-Schumann. The mass loss rate of hexane-fueled flames experiencing acoustic perturbations was then studied. It was found that the strongest influence on the mass loss rate was the magnitude of oscillatory air movement experienced by the flame. Finally, acoustic perturbations were imposed on flames using all fuels to determine acoustic extinction criterion. Using the data collected, a model was developed which characterized the acoustic conditions required to cause flame extinction. The model was based on the ratio of an acoustic Nusselt Number to the Spalding B Number of the fuel, and it was found that at the minimum speaker power required to cause extinction this ratio was a constant. Furthermore, it was found that at conditions where the ratio was below this constant, a flame could still exist; at conditions where the ratio was greater than or equal to this constant, flame extinction always occurred.
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    ZONE MODELING OF VERY-LOW-FREQUENCY UNSTABLE BEHAVIOR IN MECHANICALLY-VENTILATED COMPARTMENT FIRES
    (2015) Pi, Xiaoyue; Trouvé, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A zone model is developed to simulate the oscillatory behavior occasionally observed in compartment fires. This oscillatory behavior is the result of an unstable coupling between the liquid fuel evaporation rate, the combustion process, the compartment pressure and the ventilation of the compartment. The governing equations use a classical zone modeling approach combined with a (N-τ) model description of the variations of the fuel evaporation rate. The equations are solved with an in-house Matlab solver. The model is evaluated by comparisons with experimental data previously obtained at Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in France. Three different variations of the (N-τ) model are evaluated, corresponding to a coupling between liquid fuel evaporation and bulk oxygen, bulk temperature or admission flow rate. It is found that the variation corresponding to a coupling between liquid fuel evaporation and bulk oxygen provides the more realistic results.
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    Pyrolysis of Reinforced Polymer Composites: Parameterizing a Model for Multiple Compositions
    (2015) Martin, Geraldine Ellen; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A single set of material properties was developed to describe the pyrolysis of fiberglass reinforced polyester composites at multiple composition ratios. Milligram-scale testing was performed on the unsaturated polyester (UP) resin using thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) to establish and characterize an effective semi-global reaction mechanism, of three consecutive first-order reactions. Radiation-driven gasification experiments were conducted on UP resin and the fiberglass composites at compositions ranging from 41 to 54 wt% resin at external heat fluxes from 30 to 70 kW m-2. The back surface temperature was recorded with an infrared camera and used as the target for inverse analysis to determine the thermal conductivity of the systematically isolated constituent species. Manual iterations were performed in a comprehensive pyrolysis model, ThermaKin. The complete set of properties was validated for the ability to reproduce the mass loss rate during gasification testing.