Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Firebrands, small pieces of burning vegetation or debris generated by fires, are one of the primary ways wildfires ignite structures. Due to their small size, firebrands can be carried several kilometers by high winds before landing on combustible surfaces such as decks or roofs and potentially igniting homes. Until recently, little has been known about the heat transfer capabilities of firebrands to the surfaces on which they land. Understanding the heat transfer from firebrands is an essential step in engineering for greater fire resilience. In the first phase of this research, heat transfer from individual firebrands to horizontal surfaces was investigated using oak firebrands made from commercially available lumber. The firebrand shape, wind speed, and wind direction were varied to see how these variables affect the heat transfer. A method of inverse heat transfer analysis based on infrared thermographs was used to measure distributed heat fluxes from firebrands to the surfaces through time. This measurement technique provided spatial resolutions of < 0.5 mm, approximately 10 times higher than previous experiments in this field. Results showed that localized heat transfer was significantly higher than had previously been reported, reaching as high as 80 kW/m2 in some cases. It was also found that wind speed, wind direction, and firebrand shape all affected the heat transfer from individual firebrands. Firebrands have also been shown to accumulate in piles on decks or roofs creating complex systems that have different ignition capabilities than individual firebrands. Potentially many factors could influence the heat transfer from firebrand piles including wood moisture content, wood type (hardwood or softwood), wood density, wood state (live, dead, or artificial), wind speed, pile mass, firebrand diameter, and firebrand length. The second phase of this research used the same method of high-resolution heat transfer measurement to assess which of these factors significantly impacted the heat transfer from firebrand piles. Design of experiments was used to develop the test matrices and a rigorous statistical framework was employed to evaluate results at the α=0.05 level. It was found that wind speed, firebrand length, and an interaction between firebrand length and diameter were important. Additionally, it was found that there was a difference between the heat transfer from piles made with artificial and real firebrands, suggesting that using dowels as surrogate firebrands may produce higher heat fluxes than expected from real firebrands. Pile mass did not appear to significantly impact the heat flux from firebrand piles. The last phase of this research developed a simple engineering model to predict the ignition of common building materials by firebrand piles. The model used time-varying heat transfer data from firebrand pile tests and material properties developed by testing on select building materials in a cone calorimeter. The model predicted the surface temperature rise of the material due to an exposure heat flux with ignition being predicted when the surface temperature exceeded the ignition temperature of the material. The model was used to predict ignition for a number of pile/fuel combinations and experiments were run to validate the predictions. It was found that the model did an excellent job in predicting ignition for materials which did not melt. Together this research provides an important step in understanding heat transfer from firebrands and firebrand piles, predicting ignition, and engineering for greater fire resilience. / Master of Science / Uncontrolled wildfires burning close to human civilizations result in hundreds of deaths, the destruction of thousands of structures, and billions of dollars in economic damages each year. One of the primary ways wildfires ignite structures is through firebrands: small pieces of burning vegetation or debris generated by the fire. These firebrands can be carried great distance by strong winds, eventually landing on decks or roofs and potentially igniting homes. Until recently, little has been known about the heat transfer from firebrands to the surfaces on which they land. Understanding firebrand heat transfer will allow building materials to be selected that are resistant to ignition by firebrands and reduce the number of structures destroyed by wildfires. In the first phase of this research, heat transfer from individual firebrands was investigated. The firebrand shape, wind speed, and wind direction were varied to see how these variables affect the heat transfer. A high-resolution measurement technique was used, allowing heat transfer to be measured with approximately 10 times higher resolution than previous experiments. Results showed that localized heat transfer was significantly higher than had previously been reported and indicated that wind speed, wind direction, and firebrand shape all affected the heat transfer from individual firebrands. Firebrands have also been shown to accumulate in piles on decks or roofs creating complex systems that have different ignition capabilities than individual firebrands. Potentially many factors could influence the heat transfer from firebrand piles including wood moisture content, wood type (hardwood or softwood), wood density, wood state (live, dead, or artificial), wind speed, pile mass, firebrand diameter, and firebrand length. It was found that wind speed, firebrand length, and an interaction between firebrand length and diameter were important. Additionally, it was found that there was a difference between the heat transfer from piles made with artificial and real firebrands. The last phase of this research developed a simple engineering model to predict the ignition of common building materials by firebrand piles. The model used time-varying heat transfer data, and material properties developed by experimental testing. The model was used to predict ignition of select building materials with different firebrand piles, and experiments were run to validate the predictions. It was found that the model did an excellent job in predicting ignition for materials which did not melt.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 28, 2008) Includes bibliographical references (p. 170-176).

Thesis (MEngSc)--University of Melbourne, Dept. of Mechanical and Manufacturing Engineering, 2009. / Typescript. Includes bibliographical references (leaves 140-149)

Siemens Industrial Turbomachinery AB produce five gas turbines models. The SGT-700 can currently only start on gases which contain low amounts of inert gases. It is therefore of interest to widen the fuel range which the SGT-700, as well as other gas turbines, can start on. This report investigates the maximum limit of inert gases the SGT-700 will be able to start on, but also investigates if it is possible to start on liquid fuel (diesel) by making a few modifications to the gas turbine. To investigate this, the atmospheric combustion rig available at Siemens in Finspång has been used with a standard burner, igniter and ignition unit for the SGT-700. For the liquid fuel, the igniter was replaced by a torch igniter specially made for liquid fuels. Four different gases were evaluated; methane, propane, CO2 and N2 in order to see the effect of both various hydrocarbons and various inert gases. A model was developed for the gaseous experiments to estimate the limit for the maximum amount of inert gases the gas turbine would be able to start on. The model suggested that CO2 would require a larger amount of energy than N2 for the same amount in the composition, but that varying hydrocarbons did not have any effect if looking at the mass % of inert gas in the composition. The model was also extended with ethane and hydrogen but no experiments were performed with these gases. The model gave satisfying results. It overestimated the maximum amount of inert gases which could be mixed with propane, but agreed well when comparing the two inert gases with each other. Other interesting results were that an increased fuel flow decreased the minimum ignition energy and that an increased air flow gave a minor decrease in the maximum amount of inert gases that was possible to ignite. The torch igniter for the liquid fuel worked in a satisfying way. The ignition energy was however too low, so the ignition reliability was low. A new ignition unit with larger energy output therefore needs to be implemented. The igniter was fairly insensitive to variations in burner air flow and the ignition delay was small enough to provide a sustainable flame.

No description available.

Grassland fuels quickly respond to moisture changes in the environment, and successfully ignite more readily compared with other wildland fuel types. In recent years in New Zealand grasslands, wildfire ignitions have increased due to recreational activities on public conservation land. Ignition sources have included off-road vehicles, sparks from machinery, and campfires, cooking stoves, etc. This research investigated ignition thresholds for fully cured tussock (Festuca novae-zelandiae) and exotic (Agrostis capillaris) grasses, with the aim of providing a scientific basis for wildfire prevention through decision-support tools for activity controls. Five ignition sources of concern to the Department of Conservation were tested in the laboratory, and results were validated against field experiments. Experiments were innovative, and were designed to simulate ignitions from: hot exhaust systems on off-road vehicles (hot metal); sparks from vehicle exhausts (carbon emissions); grinding operations (metal sparks); smouldering debris dropped onto grass fuels from hot vehicle parts (organic embers); and ordinary cigarette lighters (open flame). Fuel moisture content (MC), and wind speed were varied, but ambient temperature and relative humidity were kept relatively constant in the laboratory. Logistic regression was used to analyse data for each ignition source, except organic embers because no ignitions occurred. Ignition thresholds were determined for a probability of ignition success of 50%, and all models were statistically significant. The thresholds are listed in terms of model accuracy for each experiment: open flame was 28% MC without wind, and 55% MC with light wind (1 m/s); metal sparks was 37% MC; hot metal, with a wind speed of 2 m/s and MC of 1%, was 398ºC hot metal temperature; and carbon emissions was 65% MC. The results represent a significant contribution to knowledge of the ignition behaviour of grassland fuels. Further research is required to verify and extend the results; but, initial findings provide a scientific basis for management, investigations of wildfire causes, and decisions around controls on recreational activities to protect highly sensitive ecosystems and natural areas from damaging wildfires.

Thesis (Ph.D.)--University of Melbourne, Dept. of Mechanical and Manufacturing Engineering, 2006. / Typescript. Includes bibliographical references (p. 251-276).

Thesis (Ph.D.)--University of Melbourne, Dept. of Mechanical Engineering, 2009. / Typescript. Includes bibliographical references (leaves 231-245)

No description available.