Effects of fuel characteristics on ember generation characteristics at branch-scales
Tyler R. Hudson A B and David L. Blunck AA School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, 2000 SW Monroe Avenue, 204 Rogers Hall, Corvallis, OR 97331, USA.
B Corresponding author. Email: tyler.robert.hudson@gmail.com
International Journal of Wildland Fire 28(12) 941-950 https://doi.org/10.1071/WF19075
Submitted: 21 May 2019 Accepted: 8 September 2019 Published: 17 October 2019
Abstract
Spot fires caused by lofted embers (i.e. firebrands) can be a significant factor in the spread of wildfires. Embers can be especially dangerous near the wildland–urban interface (WUI) because of the potential for the fire to be spread near or on structures. This work sought to identify how ember generation changes for different fuel characteristics and environmental conditions. Samples were burned in a heated wind tunnel and the time required for the ember(s) to form was measured using a DSLR camera. A factorial analysis of variance was used to determine the sensitivity of the time to generation to species, diameter, moisture content, fuel condition (i.e. dowel v. natural sample), crossflow temperature and crossflow velocity. Four fuel species were evaluated: Douglas fir (Pseudotsuga menziesii), western juniper (Juniperus occidentalis), ponderosa pine (Pinus ponderosa) and white oak (Quercus alba). The diameter of the samples had the greatest effect on the time to generation and the fuel species had the second greatest effect. The small diameter samples were relatively insensitive to changes in other parameters. Natural samples required significantly longer time than dowels to generate an ember. These conclusions suggest that fuel morphology is one of the most significant factors influencing ember generation.
Additional keywords: firebrand, spot fire.
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