Fire Protection Engineering
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Item Effects of Fire Whirl Generator Dimensions on Flame Length and Burning Rate(2020) Dowling, Joseph Lee; Gollner, Michael J; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In-situ burning remains an efficient method of oil spill cleanup, but the implementation of fire whirls over the spilled fuel has the potential increase the speed and efficacy of the process by increasing burning rate and temperature. Logistical requirements would then be placed on the size of the fire whirl generator. A range of wall heights between 0 and55 cm were tested for a fixed-frame fire whirl generator with a liquid fuel source 10.5cm in diameter to analyze the effect on the burning rate and flame length of resulting fire whirls. For very short walls, with heights approximately equal to the fuel pool diameter,an increase of almost double was shown in the mass loss rate. The flame length for the fire whirl increased drastically for wall heights above a critical value of 35 cm, forming stable on-source fire whirls. This indicates that the inflow boundary layer of the fire whirl is a crucial feature causing an increase in the burning rate, while a critical wall height is necessary for aerodynamic effects to form stable on-source fire whirls with extended flame engths.Item Effect of Microgravity on the Development and Structure of Fire Whirls(2020) Jones, Michael Robert; Gollner, Michael J; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fire whirls have long fascinated the scientific community due to their unique structure and behavior. When swirl is added to a traditional diffusion flame, a dramatic intensification of combustion occurs increasing flame lengths and burning rates, producing a more vigorous state of combustion. While fire whirls have long been studied, many aspects of their behavior remain unsolved, such as the precise mechanisms by which circulation and buoyancy interact to lengthen diffusion flames in swirling flows. Microgravity presents an opportunity to directly investigate these aspects, isolating the influence of ambient circulation from buoyancy on the flame. Results are presented from tests performed at the NASA Glenn Research Center Zero Gravity Research Facilities’ 5.18 s drop tower. Fire whirls were generated over a paraffin wax wick in 1 g using two offset half cylinders. A vertical bank of fans was placed at each inlet to provide continuous circulation, which was held constant throughout the microgravity drop test. Results show that the lengthening effect observed in 1 g dramatically reduces in microgravity, even under the influence of continuous ambient circulation. Some similarities are still observed between 1 g fire whirls with strong circulation and microgravity fire whirls, with flames shrinking and expanding into a more cylindrical form. Interesting phenomena is also observed in higher-g conditions following the drop test.Item THE INFLUENCE OF WIND ON THE STRUCTURE OF INCLINED FLAMES(2020) Heck, Michael; Gollner, Michael J; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Experiments were performed using stationary gas burners in order to characterize the flame geometry and downstream heating from stationary flames under inclined configurations under an applied forced flow. Stationary flames exhibit behavior similar to spreading wildland fires but are an ideal configuration for carefully studying fundamental wildland fire behavior characteristics that play a critical role in downstream heating, which subsequently drive fire spread. Two conditions were applied to a small-scale apparatus during experimentation, a sloped surface and forced-flow wind. The experiments were performed at multiple heat-release rates for angles from 0 to 28 degrees from the horizontal and wind speeds of 0 to 0.5 m/s.Flame geometry such as center-line flame length, flame tilt angle, and flame attachment length along the downstream surface were determined from side-view video imaging. Downstream heating was also measured through fine-wire thermocouple temperature measurements and surface total heat heat flux measurements. The measurements provided a heating profile depicting the magnitude of heating that would be applied to unburned fuels at distances in front of a spreading fire. These profiles were compared to the flame attachment observed from imaging, and to one another. While the surface heat flux cannot be scaled to larger fires, it’s relation to temperature profiles will be useful to further interpret large-scale experiments and as validation data for numerical modeling of fire behavior of the combined effects of slope and wind