Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Burning Emulations of Condensed Phase Fuels Aboard The International Space Station(2022) Dehghani, Parham; Sunderland, Peter B; Quintiere, James G; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Little is known about the fire hazards of solids and liquids in microgravity. Ground-based tests are too short to overcome ignition transients and testing dozens of condensed fuels in orbit is prohibitively expensive. Burning rate emulation is one way to address this gap. It involves emulating condensed fuels with gases using a porous burner with embedded heat flux gages. This is a study of microgravity burning rate emulation aboard the International Space Station. The burner had porous round surfaces with a diameter of 25 mm. The fuel mixture was gaseous ethylene, and it was diluted with various amounts of nitrogen. The resulting heats of combustion were 15 – 47.2 kJ/g. The flow rate, oxygen concentration in the ambient, and pressure were varied. Heat flux to the burner was measured with two embedded heat flux gages and a slug calorimeter. The effective heat of gasification was determined from the heat flux divided by the fuel flow rate. Radiometers provided the radiative loss fractions. A dimensional analysis based on radiation theory yielded a relationship for radiative loss fraction. RADCAL, a narrow-band radiation model, yielded flame emissivities from the product concentrations, temperature, flame length, and pressure. Previously published analytical solutions to these flames allowed prediction of flame heights and radius, and when combined with the radiation empirical relationship led to corrections of total heat release rate from the flames due to radiative loss. Average convective and radiative heat flux were obtained from the analytical solution and a model based on the geometrical view factor of the burner surface with respect to the flame sheet, that was used to calculate the heat of gasification. All flames burning in 21% by volume oxygen self-extinguished within 40 s. However, steady flames were observed at 26.5, 34, and 40% oxygen. The analytical solution was used to quantify flame steadiness just before extinction. The steadiest flames reached more than 94% of their steady-state heat fluxes and heights. A flammability map as a plot of the heat of gasification versus heat of combustion was developed based on the measurement and theory for nominal ambient oxygen mole fractions of 0.265, 0.34, and 0.4.Item IMAGING PYROMETRY OF WOOD EMBERS UNDER SIMULATED MOVEMENT(2022) Baldwin, James H; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A major mechanism for wildland fire spread are spot fires, where small combusted organic particulate (firebrands) are lofted and transported to a remote location where they can then ignite new fires. The modeling of these spot fire ignitions is limited by the unknown surface temperature and emissivity of firebrands, which is challenging to measure due to the small size of firebrands (precluding the use of intrusive temperature methods such as thermocouples) as well as the dependency of conventional non-intrusive temperature measurements (e.g. Infrared Imagers) on emissivity. A solution to this is presented in Color Pyrometry, which uses color pixel intensities to determine an object's temperature based on a calibration against an object of known temperature/emissivity. The presented method is a Ratio Pyrometry approach between green and red pixel intensities normalized to camera settings, which demonstrates the benefit of being independent of object emissivity as validated by Planck's Law, and is based on a Blackbody Furnace calibration. To determine the method's applicability to realistic firebrand imaging conditions, which would provide the most comprehensive understanding of firebrand ignition, the individual impact of firebrand movement speed on the pyrometry's surface temperature predictions is considered. An apparatus is developed that decouples firebrand movement speed from the surface wind speed (which is known to impact firebrand surface temperature) as well as allows for modulation of the firebrand's simulated movement speed, and involves rotating the imaging device about a fixed axis relative to a stationary firebrand. Five trials at a set orientation were conducted to verify the apparatus' repeatability, and subsequent trials of varying rotation speed, distance, applied wind speed, and mounting orientation were conducted. Both qualitatively and through a statistical analysis consisting of ANOVA and non-parametric distribution testing, firebrand movement speed and orientation are shown to have no individual impact on surface temperature. Average ember surface temperatures were found to be 922.1 ± 20.4 °C with a 1 m/s applied wind speed and 955.0 ± 20.2 °C with a 2 m/s applied wind speed, which is in agreement with previous studies. It is proven that the presented Pyrometry method's results are independent of a major complicating factor associated with realistic firebrands, which thereby further supports future efforts into wildland fire spread modeling.Item 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.Item Development of a Cyber Physical System for Fire Safety(2015) Wills, Rosalie Faith; Marshall, Andre; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this study a cyber physical system (a system of collaborating computational elements that monitor and control physical entities) test bed was developed to demonstrate the viability of real-time decision support for smart firefighting and to provide validation data for continued cyber physical system (CPS) development. This CPS utilizes current technologies in the modern built environment and emerging virtualization tools. The smart networked fire test bed consisted of a multi-story instrumented building, a variety of fire and non-fire networked sensors, and a computational framework anchored by a Building Information Modeling (BIM) representation of the building. Well-controlled full-scale fire experiments were conducted (physical domain) and represented in the three-dimensional BIM (computational domain) allowing for visualization of critical static and dynamic building and fire information needed to support firefighter decisions. The CPS test bed produced remarkable evidence about the opportunities for fire safety created by the communication between sensors, BIM, and fire.