Fire Protection Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2772
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Item HEALTH IMPACTS OF THERMAL RUNAWAY EVENTS IN OUTDOOR LITHIUM-ION BATTERY ENERGY STORAGE SYSTEM INSTALLATIONS(2024) Zhao, Zelda Qijing; McAllister, Jamie; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study aimed to develop a methodology for characterizing health impacts of large-scale, outdoor, lithium-ion battery energy storage systems (BESS) thermal runaway events. A literature review was conducted to identify toxic gas yields produced during flaming and non-flaming thermal runaway, as well as mass loss rates, gas temperature, typical BESS unit capacity and dimensions, and event durations. Lithium-iron-phosphate and nickel-manganese-cobalt cell chemistries were assessed. The BESS unit thermal runaway events were modeled in Fire Dynamics Simulator with a bounding analysis for wind and ambient temperature. Concentrations were evaluated using Immediately Dangerous to Life or Health values for occupational exposure and the Protective Action Criteria for Chemicals hierarchy values (Acute Exposure Guideline Levels- Level 1, Emergency Response Planning Guidelines- Level 1, Temporary Emergency Exposure Limits- Level 1) for community exposure. Through application of the methodology, a relationship between exposure limit distance and wind speed, ambient temperature, event duration, cell chemistry, and toxic gas species can be assessed. Under the conditions modeled in this project, exposure limits were exceeded at longer distances in the non-flaming scenarios when compared to the flaming scenarios. Wind speed, ambient temperature, event duration, cell chemistry, and toxic gas species were the controlling factors for non-flaming exposure limit distances. Wind speed was the primary controlling factor for flaming exposure limit distances; however, event duration had some influence.Item DEVELOPMENT AND VALIDATION OF A PYROLYSIS MODEL FOR FLEXIBLE POLYURETHANE FOAM(2024) Kamma, Siriwipa; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Flexible polyurethane foam (FPUF) is a common material contained in household goods such as upholstered furniture and mattresses, which are known to significantly contribute to fire growth. An accurate prediction of fire development on FPUF containing items requires knowledge of FPUF pyrolysis and combustion properties. These properties include reaction kinetic parameters, thermodynamic parameters, and thermal transport properties. While many past studies focused on the thermal decomposing mechanism and thermodynamic properties of the reactions, the thermal transport properties have not been determined. In this study, a complete pyrolysis model of FPUF was developed by extending the thermal decomposition model from a previous study. The thermal transport properties were obtained using inverse modeling of the Controlled Atmosphere Pyrolysis Apparatus II experimental data. The complete model was validated against cone calorimetry data and found to perform in an adequate manner.Item DESIGN AND PERFORMANCE EXPLORATION OF A SCALED-UP MILLIGRAM-SCALE FLAME CALORIMETER(2024) Cromwell Reed, Kyra; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fire causes thousands of lost lives and injuries, as well as billions of dollars of property damage, each year. It is critical to understand the fire hazard associated with materials used in the built environment. One method to evaluate the flammability properties of a material is through bench- scale and milligram-scale testing with apparatus such as the Milligram-Scale Flame Calorimeter (MFC). The MFC has previously been used to test samples ranging from 30 mg – 50 mg in mass. The small samples were useful for testing materials under development or materials cost prohibitive to test at larger sizes, but presented some difficulties in testing, including in sample preparation and as inconsistency in the results of testing on inhomogeneous materials. Furthermore, the small size of the MFC caused difficulty in heater manufacturing, requiring laborious by-hand construction. The size of the MFC crucible and apparatus was increased in this work to allow testing on larger sample masses, ranging in size from 90 mg – 150 mg, and for the exploration of five alternate heater manufacturing techniques. The MFC was rebuilt with a larger heater and optimized to create the best possible test conditions for this work. Tests were conducted on five polymers: polymethyl methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), and polyether ether ketone (PEEK), and on a wood-based material: oriented strand board (OSB). The tests showed general consistency when materials were tested at different sample masses and sample presentations. The results for the heat release rate and heat of combustion of the materials also aligned well with testing conducted using the previous version of the MFC apparatus. The updates to the MFC conducted in this work constitute an improvement to the versatility of the apparatus, allowing for testing on larger sample masses, but future work is needed to resolve flow and exhaust issues that caused some inconsistency in the test results and to further explore and develop alternate heater manufacturing techniques.Item Experimental Characterization of the Thermal Response of Firefighter Protective Ensembles Under Non-Flaming Convective Exposure(2024) DiPietro, Thomas Phillip; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Thermal burns are one of the most serious injuries a firefighter can sustain while operating in a structure fire despite being fully covered in gear designed to protect them from thermal exposure. Extensive experimentation has been conducted into the performance of a firefighter’s protective ensemble when caught in a high radiative heat flux environment to ensure the wearer has enough time to escape to safety. High heat flux tests are beneficial in estimating safe operating times, but firefighters are also getting burned in fire environments that are thought to be routine exposures. The current study explored the thermal response of three-layer firefighter protective ensembles exposed to a majority convective, low-level heat flux in an oven. Through experimentation, the temperature of a copper calorimeter simulating skin beneath two different protective ensembles were measured while exposed to temperatures of 100°C, 150°C, 200°C, 250°C, and 300°C. The time for the copper calorimeter to reach a temperature of 55°C (the temperature a second-degree burn has the potential to occur to human skin) was recorded and compared to currently accepted thermal operating time limits for firefighters. Results show that once exposure reached above 100°C the time for a potential burn injury to occur fell below the predicted safe operational time for firefighters of 15–20 minutes when the PPE was in contact with the copper disk. The time to potential burn injury and test temperature exhibited an exponentially decaying relationship which is expected to continue as temperatures increase beyond those tested in the current study. Although consisting of different layers of material, both types of protective ensembles tested responded similarly and demonstrated no significant differences in time to potential burn injury at every temperature. Additional tests were conducted in the oven with an air gap placed below the protective ensemble as well as using the original test set up with a mostly radiative heat source to compare results and evaluate different exposures and conditions for future experimentation.Item A study of Cool Diffusion Flames utilizing Ignition Delay Characteristics of N-Heptane Autoignition Simulations(2024) Pimple, Shubham; Sunderland, Peter; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Gaining deeper insights into cool diffusion flames (CDFs) can significantly enhance engine efficiency and reduce emissions, while also filling in knowledge gaps relating to explosion initiation and the transition from smoldering to flaming fires. While detailed computational fluid dynamic (CFD) models can simulate CDFs, they require substantial computational resources due to the need for detailed chemistry and transport resolution. To circumvent these challenges, this study utilizes an alternative approach using Cantera autoignition simulations, which presumes isobaric, adiabatic conditions. The fuel, n-heptane, is analyzed through six kinetic mechanisms that capture the spectrum of low and high temperature chemistry. The observed ignition process – manifesting as single, two, or three-stage ignition – is observed to vary with initial conditions. Analysis of ignition delay times unveils the Negative Temperature Coefficient (NTC) behavior, crucial for the existence of stable cool flames. The critical transition temperatures, such as the lower and upper turnover and the crossover temperature are also identified, along with the key chemical species produced during the two-stage ignition process. The peak temperature range for stoichiometric n-heptane CDFs is determined to be between 653 and 804 K, aligning favorably with previous experimental measurements. While the first-stage ignition delay time remains nearly constant, the second-stage ignition delay time noticeably decreases as the mixture becomes richer, up to an equivalence ratio of 32. This reduction is attributed to the rapid temperature increase caused by a larger fuel quantity, which accelerates high-temperature chemical reactions. The NTC temperature range is also seen to shorten as the mixture composition gets richer. While the six chemical kinetic models examined concur about the existence of an NTC regime, variations are observed in the threshold temperatures. The insights gained from this study enhance the understanding of CDFs, setting a foundation for future research into different fuels and varying conditions.Item 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.Item USE OF MILLIGRAM-SCALE FLAME CALORIMETRY FOR CHARACTERIZING FLAMMABILITY OF FABRIC SAMPLES WITH FLAME RETARDANT TREATMENTS(2023) Roche, Thomas William; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The fire hazard associated with fabrics threatens everyone’s safety, and the current standards used to reduce those hazards are expensive and time-consuming. Fabrics are a key component in clothing, upholstery, and carpentry and are present in nearly every built environment. The inherent flammability of fabrics leads to the application of flame-retardant treatments on nearly all commercial fabric products. Recently, environmental, economic and performance concerns have driven research to develop new flame retardants across a variety of materials. The military industry in particular has focused recent research efforts on flame retardant treatments for fabrics, given the challenging environments that military uniforms must endure. Current methods for testing performance of novel flame retardants, such as the Cone Calorimeter and Microscale Combustion Calorimeter can be prohibitively expensive or only provide a limited understanding of flame-retardant action. Fabrics present additional testing challenges due to their low density and thickness, effectively reducing the amount of fuel available for testing. A novel apparatus, the Milligram-scale Flame Calorimeter (MFC), has been used to test flame retardants in polymeric materials, successfully capturing gas-phase activity and with favorable comparison to Cone Calorimeter results. This study aims to expand the use of the MFC to the testing of fabrics and flame-retardant treated fabrics. Optimization tests were run to find the optimal number of fabric layers and best method for preparing samples for use in MFC. Subsequently, cotton fabrics (untreated and treated with phosphoric acid), as well as Nylon fabrics (untreated and treated with tannic acid) were characterized with MFC, and results were compared to those from the Microscale Combustion Calorimeter and Cone Calorimeter. The MFC showed similar trends in the onset of ignition, peak heat release rate, average heat release rate, char yield, and heat of combustion for the untreated fabrics with the Cone Calorimeter and Microscale Combustion Calorimeter results. The results for the flame-retarded fabrics are inconclusive and require additional testing, though the observations of the condensed-phase and gas-phase activity for the MFC samples does provide important insights on how the mechanism for the flame retardants operate.Item DEVELOPING A VELOCITY-DENSITY CURVE FOR HIGH-DENSITY CROWD SIMULATION BY ANALYZING FOOTAGE VIDEOS(2023) Zhang, Zilin; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Crowds with densities higher than 2 persons/m2 can be defined as high-density crowds. High-density crowds presenting in daily life like concerts and sports events can lead to serious people and property loss. This research work focuses on developing a new speed-density relationship for high-density crowds. The applicability of the new speed-density relationship is tested in Pathfinder, an agent-based evacuation simulation software developed by Thunderhead Engineering, to determine the impact of updating such data on the model's performance. This research also discusses several parameters and functions in Pathfinder including acceleration time and reduction factor to help model high-density crowds.Previous work is available for analyzing crowds with densities lower than 3 persons/m2. However, densities as high as 9 persons/m2 are common in many high-density crowd scenarios. The disparity between previous work and real-world situations presents a challenge for engineers to understand the crowd dynamics of high-density crowds. Developing evacuation models to predict the behavior of high-density crowds is crucial to improving the predictive ability of crowd simulation. By doing so, it helps to reduce the number of casualties in future emergencies. Real-world footage videos are analyzed in this research. With the open-source experimental footage videos provided by Jülich, a national research institution, a new speed-density curve is summarized by collecting and analyzing data from the videos. The assessment of the applicability of the new speed-density in Pathfinder focuses on four aspects: evacuation time, flow density, flow velocity, and occupants’ arrangement. Per case examined, by applying the new speed-density curve, the predicted evacuation time from Pathfinder simulation is improved from 12.6% to within 4.9% of the experimental video time. The predicted flow density is improved from 6.2% to within 0.7% of the average video density. The predicted flow velocity is improved from 25.9% to within 3.3% of the average video velocity. At the same time, it is observed that occupants in the model behave more realistically.Item EVALUATION OF LOW-PRESSURE WATER-BASED TRENCH DRAIN FIRE SUPPRESSION SYSTEMS IN AIRCRAFT HANGARS USING FDS MODELING(2023) Braddock, Sofia Le; Milke, James A; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The 2020 National Defense Authorization Act (NDAA) prohibition of PFAS-containing AFFF fire protection systems by 2024 has motivated the U.S. Department of Defense to study other alternatives. In this study, the current low-expansion AFFF foam fire suppression systems with trenches layout in NAVFAC facilities are modeled as water-based systems to determine the scale, coverage, and extinguishment times that can be expected from such systems. A reduced spacing of the trenches is then simulated to determine how spacing of the floor nozzles affects fire suppression and control. Additionally, a model of a previously identified floor-level low-pressure water mist nozzle with the incorporation of trenches is studied to validate its possibility of being a replacement option for the current NAVFAC systems. Each simulation consists of three components: fire model, sprinkler/water mist model, and extinction model. Each model is evaluated separately before inputting into the final simulations to determine the most accurate representation and minimize uncertainties. The final simulations with sprinkler nozzles show successful extinguishment up to 23 MW and better performance at earlier activation time and in setups with the current trench spacing. Little to no difference is observed between the two fuel spill fire scenarios at the same activation time and trench spacing. On the other hand, the low-pressure water mist systems do not meet adequate performance in the final hangar simulations.Item 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.