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.

Browse

Filters

2009 - 200912010 - 20201

Settings

Subject: search.filters.subject.fuel

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A STUDY OF INTERMITTENT CONVECTIVE HEATING OF FINE LIVE WILDLAND FUELS
    (2020) Orcurto, Ashlynne Rose; Gollner, Michael; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Recent studies have investigated the role of convective heating advancing wildland fire spread through intermittent bursts or pulses of flames onto unburned fuels. This study seeks to expand on initial experiments investigating the role of this intermittent convective heating by exploring the ignition of live fuels with different moisture contents under these conditions. A modified Rubens' tube is used to generate periodic pulses of a small-scale diffusion flame over the surface of a fuel sample. Infrared imaging is used to track the surface temperature of the fuel leading up to ignition while the intermittent temperature is characterized using a fine-wire thermocouple. Ponderosa pine needles with a variety of moisture contents are tested at different heating frequencies to determine patterns in the process of ignition. The fuel moisture content is seen to have a significant effect on the ignition times of fuels, while the temperature at ignition is seen to vary with heating frequency. Ignition results are compared with past tests of dried dead fuels using the same apparatus. Model predictions of ignition times as a function of ignition temperature and moisture content are also compared to experimental values and discussed.
  • Thumbnail Image
    Item
    PERFORMANCE OF Ni/CEO2/YSZ SOFC ANODES WITH CARBONACEOUS FUELS
    (2009) Patel, Siddharth; Jackson, Gregory S; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This study explores the impact of ceria incorporation into Ni/YSZ cermet anode support layers on the performance of button-cell solid oxide fuel cells operating with syngas and n-butane/steam fuel feeds. Ceria is incorporated into the porous anode support by co-firing ceria powders with NiO, YSZ, and graphite pore formers. Comparison of the performance with and without the co-fired ceria indicated improvements for operation with doped ceria for both syngas (by almost 20% higher power density) and direct n-butane/steam feeds (by over 25% higher power density). For initial cell performance, ceria addition to the support layer offered improved performance at high current densities with syngas suggesting that ceria enhanced water-gas-shift reactions, thereby increasing H2 availability for more effective electrochemical oxidation in the functional layer. For longer-term testing with direct-butane feeds, ceria doped cells not only showed better performance, but also indicated suppression of carbon deposition thus improving long term operability. Ex situ characterization of the ceria-doped anodes using SEM and Raman spectroscopy indicated that ceria addition helped the anodes maintain their structural integrity. To better understand the experiments, a previous through-the-MEA 1-D model has been updated and used with C-H-O microkinetics for Ni/YSZ anodes to characterize the experimentally observed cell performance. The model was enhanced by developing a leakage mechanism to account for leakage through the electrolyte and by incorporating non-isothermal effects to account for temperature gradients due to endothermic internal reforming and exothermic oxidation within the anode layers. Studies with internal methane reforming in a Ni/YSZ anode showed that the non-isothermal effects in 1-D button cell experiments are very small. This through-the-MEA model was used to fit experimental data and provided a basis for assessing key micro-structural parameters for the Ni/YSZ cells tested in this study. The model fits with syngas at various compositions provided a basis for assessing the most sensitive micro-structural parameters on the fuel cell performance such as anode support layer porosity and tortuosity.