Sung, K.
, Mueller, E.
, Bundy, M.
, Fernandez, M.
and Hamins, A.
(2025),
Global Burning Properties of Little Bluestem, Excelsior and Douglas Fir, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.TN.2314, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958825
(Accessed April 19, 2025)
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Global Burning Properties of Little Bluestem, Excelsior and Douglas Fir
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Abstract
A series of experiments were conducted to better understand the burning characteristics of three types of vegetative fuels: Little Bluestem grass, Douglas fir trees, and Excelsior. The measurements included the transient heat release rate (HRR) determined using oxygen consumption calorimetry, the mass loss rate, the yields of CO and smoke, and the radiative emission to the surroundings. An estimate of the average radiative fraction during the fires was obtained from radiative heat flux measurements made in the far field. Experiments were also conducted on extensions of excelsior positioned horizontally and vertically with controlled bulk density. The measurement results characterize the global combustion properties of the vegetative samples and offer insight into their complex burning behavior. A number of key findings are reported: 1. The ratio of the peak heat release rate to the initial mass of the test specimens as a function of their (dry) moisture content was consistent with previously published fire measurements on a variety of trees and bushes. A fit to all the data showed that a power law was an adequate representation of the results. 2. The moisture content significantly affected the Douglas fir tree fires. As the tree moisture content increased, the radiative fraction significantly decreased. The radiative fraction of the Douglas fir tree fires was observed to decrease from 0.34 to 0.13 as the moisture content increased from 7 % to 46 %. 3. The mean radiative fractions for Bluestem, Excelsior, and Douglas fir were similar, varying from 0.28±0.03, to 0.30±0.08, and 0.23±0.07, respectively. This is even more apparent when considering samples of similar moisture content (e.g. <15%). Considering the overlapping error bars, there is no statistically significant difference among the fuel types. The average radiative fraction for all the tests was 0.28±0.04. 4. The soot yields had a high degree of scatter, but statistically were also similar for all sample types, with mean values of 0.46% for Bluestem, 0.11% for excelsior, and 0.24% for Douglas fir. On the other hand, the CO yield varied more clearly as a function of specimen type, with mean values of 6.2%, 3.3%, and 8.9% for Bluestem, excelsior, and Douglas fir, respectively. These measurements of the global burning properties of these vegetative fuel types can provide guidance for fire modeling efforts.Citation
Technical Note (NIST TN) - 2314
Report Number
2314
NIST Pub Series
Pub Type
NIST Pubs
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Keywords
burning rate, heat release rate, radiative fraction, vegetation fires
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Created April 15, 2025