DEVELOPMENT AND USE OF PIXEL-BY-PIXEL PYROMETRY METHODS ON SMOLDERING WOOD EMBERS AND PILES
DEVELOPMENT AND USE OF PIXEL-BY-PIXEL PYROMETRY METHODS ON SMOLDERING WOOD EMBERS AND PILES
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Date
2022
Authors
Tlemsani, Mahdi
Advisor
Sunderland, Peter B
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Abstract
Wildfire, especially along the Wildland Urban Interface (WUI), presents a large threatto life and property globally. Firebrands can increase the size and spread of wildfires
rapidly. More than half of spot fires and WUI fires are caused by firebrands. Firebrand
generation, transport, and morphology has been studied in recent literature, but few papers
have reported firebrand temperatures, even fewer on groups of firebrands across varying
configurations. Those that have reported temperatures have typically relied on expensive IR
and thermocouple data that may not be as accurate at determining temperature or emissivity.
Color camera pyrometry presents a high resolution alternative to previous pyrometry methods
and can be done using a cheap color camera, and with certain techniques can derive temperature
independent of emissivity. This research builds on previous color camera pyrometry, automating
the process to allow for large datasets to be analyzed as opposed to single images. Two-color,
grayscale, and hybrid pyrometry [20] were used to recreate pyrometry results of previous
literature. Similar average single firebrand temperatures in the range of 900-950C were
reported. A novel Pixel-by-Pixel hybrid pyrometry was developed to incorporate more data
into established hybrid pyrometry methods. This method introduced large amounts of noise
into the temperature results, making them unreliable. Additionally, a method was developed
for determining the temperature of 8-gram ember piles at various wind speeds of 1.4, 2.4,
and 2.7m/s through a borosilicate glass window. Modified grayscale temperatures assuming
constant emissivity were used for these experiments and were fit to firebrand temperature
data from Kim and Sunderland [20]. A total of 720 ember pile images were analyzed in
the final dataset at an effective emissivity of 0.76. Peak ember pile average temperatures
ranged from 700-900C. Normalized temperature (T /Tmean) PDFs were produced. Data was
approximated as a normal distribution with mean of 1 and standard deviation ranging from
0.048 - 0.057.