Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

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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Author: search.filters.author.Williamson, Justin Wade

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    Measurements and Analysis of Extinction in Vitiated Flame Sheets
    (2009) Williamson, Justin Wade; Marshall, Andre W; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Accidental fires present many challenging hazards to people and property. The thermal and toxic effects of fires are significantly affected by the ventilation conditions supplied to the fire. Vitiation is a consequence of limited ventilation, where the products of combustion mix with the unburned reactants prior to reaction. Vitiation results in diluting and preheating the reactants, significantly enhancing the behavior of the fire. An interesting effect of vitiation is the increased propensity of the flame to experience extinction, either locally or globally. Likewise, there are other factors that can increase the propensity for extinction, including losses due to incomplete chemical kinetics, radiation, and conduction. These extinction events have a direct impact on the thermal and toxic hazards associated with accidental fires by creating holes in the reaction surface. This research provides a detailed analysis of local flame extinction by examining the behavior of counterflow flames undergoing kinetic losses, radiation losses, and vitiation. A thorough review of flame extinction theory was conducted to determine the appropriate parameters necessary for characterizing local flame extinction conditions. Simple scaling arguments are presented to demonstrate that each of these parameters is significant in accidental fires. Counterflow methane-air diffusion flames have been studied experimentally and numerically with OPPDIF to systematically examine the effects of each parameter on local flame extinction. Furthermore, a model is presented, which uses reactant composition and temperature in the vicinity of the flame, net radiation losses from the flame, and the local scalar dissipation rate as inputs to model local extinction conditions. The proposed model is suitable for integration into Computational Fluid Dynamics (CFD) codes used to predict the hazards associated with accidental fires.
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    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.