A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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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.Item The Effects of Liquid Alkane Fuel Structure on Catalyst-Enhanced Combustion(2018) Dube, Grant; Oran, Elaine S; Lee, Ivan C; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The U.S. Army is developing micro-combustors for use in soldier-portable power generation systems. Many of the challenges associated with micro-combustion can be potentially overcome using a catalyst, but the effects of the catalyst on ignition under the low temperature, atmospheric conditions seen in the field are not well understood. To better understand catalytic ignition phenomena under these conditions, a Catalytic Ignition and Emissions Tester (CIET) was developed and used to investigate the effects of liquid alkane fuel structure during catalyst enhanced ignition. Various mixtures of n-octane and iso-octane, as well as single component n-dodecane and n-hexadecane, were chosen as simple, surrogate test fuels to represent gasoline, jet fuel, and diesel, respectively. Fuel reactivity was shown to decrease with increased branching for all metrics tested while the effects of chain length were less definitive. The global apparent activation energies of all fuels tested were found to be in the range of 41-61 kJ/mol with 95% confidence, significantly lower than those previously reported for non-catalytic hydrocarbon combustion (>100 kJ/mol).Item 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.Item FLAMMABILITY CHARACTERISTICS OF WATER-BASED POLYCRYLIC AND OIL-BASED POLYURETHANE COATED OAK VENEER PLYWOOD SAMPLES SUBJECTED TO INCIDENT HEAT FLUXES(2005-12-13) Thompson, Sarah Elizabeth; Mowrer, Frederick W.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The flammability characteristics of oak veneer plywood were evaluated in the Cone Calorimeter. Samples of 6.35 mm (1/4 in.) thick and 19.05 mm (3/4 in.) thick oak veneer plywood were coated with 3, 6, and 9 coats of either oil-based polyurethane or water-based polycrylic clear finishes and tested at incident heat fluxes of 35, 50, and 75 kW/m2 along with uncoated samples. Both the type of finish and the number of coatings were found to influence the ignition time, the measured peak heat release rate, and the minimum flux for ignition of the samples. The ignition times for the coated samples were 2 to 3 times lower than the unfinished samples. Predicted times to ignition differed by a factor of 2 to 3 from the measured values (with the exception of the samples with nine coats of finish.) The predicted ignition temperatures differed by as much as 100 ºC from the measured temperatures. The Quintiere flammability parameter, b, was found to be positive for all testing scenarios, suggesting a propensity for flame spread at the incident heat fluxes evaluated.