1. 152-52662339Paper 141-49759319Ceanothus 88-53474311Oak 164-52861346Manzanita Range (+/- 3*σ) Standard Deviation (σ) Average Ignition Temperature (ºC) Ignition Temperature Statistics The Experimental Design Apparatus designed to closely resemble forest fire flame front Modes of heat transfer Radiation: 6000W, 10”-square quartz heating panel (center) Convection: Flat-falme burner (FFB) (lower left) Fuel sample attached to a cantilever-type mass balance (top right) Infrared Images Optimal sample placement determined with IR camera (FLIR) Sharp interface between the post-flame gases and surrounding air Sample height of 2” is well within the hot zone of the post-flame gases Vertically Oriented Manzanita Sample Shape and orientation effects studied with video monitoring Samples cut in square and rounded shapes Horizontally oriented square-shaped samples ignite first at corners Horizontally oriented round-shaped samples ignite along the entire edge Vertically oriented samples ignite at edge closest to the flame Thermocouple placed at ignition location Temperature Profiles of Manzanita with Varying Thickness Thicker manzanita samples have slower heat-up times We want to develop a correlation to describe these and other effects J. D. Engstrom, J. K. Butler, T. H. Fletcher, L. L. Baxter Department of Chemical Engineering, Brigham Young University and D. R. Weise USDA Forest Service, Pacific Southwest Research Station, Forest Fire Laboratory This project is sponsored by the USDA/USDI National Fire Plan administered through a Research Joint Venture Agreement No. 01-CR-11272166-168 with the Forest Fire Laboratory, Pacific Southwest Research Station, Riverside, CA. Ignition Temperature Histograms Ignition temperature determined for live samples Ignition temperature defined when a flame is first visible Distributions of ignition temperatures measured (see figure above) Time to Ignition Histograms Ignition times determined for each samples Ignition time defined as time for sample to ignite Paper demonstrates experimental repeatability Gas Temperature Profiles CH 4, H 2, N 2, and air fed into FFB Post-flame conditions ~ 10 mol% O 2 127  m diameter type K thermocouple 2” above the FFB Demonstrates great repeatability Average Temperature 987 ºC Standard Deviation 11.9 ºC Purpose To better understand the combustion behavior of live fuels To add physics into forest fire modeling Conclusion Sample types are important in determining ignition temperature Heat and mass transfer effects play an important role in sample heat-up time Time to ignition significantly affected by size, shape and orientation Future Work Improve technique to determine accurate ignition temperature and time to ignition Incorporate knowledge of leaf burning into models of bush burning Develop heat transfer correlations to avoid excessive computational costs Representative California Chaparral Samples Manzanita (Arctostaphylos densiflora) Scrub Oak (Quercus berberidifolia) Hoaryleaf Ceanothus ( Ceanothus crassifolius) Chamise