Fig 4 - uploaded by Michael John Gollner
Content may be subject to copyright.
Back surface temperature maps obtained for a 0.16 g cm -2 firebrand pile deposited onto Kaowool PM and exposed to 2.4 m s -1 air flow at 60 s (a) and 480 s (b) after the start of the test. The airflow-facing edge of the glowing firebrand pile is marked using a dashed line.
Source publication
A series of experiments was carried out in a bench-scale wind tunnel where firebrand piles of controlled coverage density and geometry were deposited onto a flammable and non-flammable substrate, Western Red Cedar (WRC) and Kaowool PM, respectively. Back substrate temperature, combustion heat release rate, modified combustion efficiency, and gaseou...
Contexts in source publication
Context 1
... these temperature maps significantly evolved in time with the hottest zone gradually shifting from the front of the pile facing the air flow toward the tail end of the pile. This traveling behavior was also noted in earlier studies [34,36]. To capture this evolution, the back surface of the sample was divided into three zones, as shown in Fig. 4. All zones were 4 cm in width (the dimension perpendicular to the direction of the air flow), slightly narrower than the pile deposition area width, which was 5 ...
Context 2
... preleading zone (zone 1 in Fig. 4) was located at the air flow facing edge of the pile and was 1.5 cm long. It extended 1 cm outside of the firebrand deposition area. The leading and middle zones (zones 2 and 3 in Fig. 4) were 3 cm in length and were located underneath the pile deposition area. The locations of these zones were selected to approximately match locations ...
Context 3
... preleading zone (zone 1 in Fig. 4) was located at the air flow facing edge of the pile and was 1.5 cm long. It extended 1 cm outside of the firebrand deposition area. The leading and middle zones (zones 2 and 3 in Fig. 4) were 3 cm in length and were located underneath the pile deposition area. The locations of these zones were selected to approximately match locations of ignition events, whose detection is discussed in Section 3.3. The airflow-facing edge of the glowing firebrand pile is marked using a dashed ...
Context 4
... factor of 2.7) did not result in a proportional increase in the peak-average HRRPUA. This is primarily because only a portion of the firebrands engaged in intense burning at any given time, as apparent from Fig. 5 showing that only the portion of the firebrand pile facing the air flow is visibly glowing. The back surface temperature maps shown in Fig. 4 further corroborate this observation indicating that the firebrand pile temperature is not uniform along the length of the pile. The hottest temperature zone travels from the front of the pile facing the air flow toward the back of the pile with time. The peak-average HRRPUA increases by less than 2.7 times because the portion of the ...
Similar publications
Tree mortality and partial canopy dieback are increasing in many forest ecosystems from unfavorable climate conditions. Examining how tree growth and mortality are affected by climate variability can help identify proximate causes of tree mortality and canopy dieback. We investigated anomalously high mortality rates and partial canopy dieback of we...
Forest tree canopies have a critical influence on water cycles through the interception of precipitation. Nevertheless, radial patterns of canopy interception may vary interspecifically. We analyzed canopy interception using catchments along radial transects underneath four common forest tree species (Acer macrophyllum, Alnus rubra, Pseudotsuga men...
Citations
Background Wildfires represent a significant threat to peatlands globally, but whether peat fires can be initiated by a lofted firebrand is still unknown. Aims We investigated the ignition threshold of peat fires by a glowing firebrand through laboratory-scale experiments. Methods The oven-dried weight (ODW) moisture content (MC) of peat samples varied from 5% ODW to 100% ODW, and external wind (ν) with velocities up to 1 m/s was provided in a wind tunnel. Key results and conclusions When MC < 35%, ignition is always achieved, regardless of wind velocity. However, if MC is between 35 and 85%, an external wind (increasing with peat moisture) is required to increase the reaction rate of the firebrand and thus heating to the peat sample. Further increasing the MC to be higher than 85%, no ignition could be achieved by a single laboratory firebrand. Finally, derived from the experimental results, a 90% ignition probability curve was produced by a logistic regression model. Implications This work indicates the importance of maintaining a high moisture content of peat to prevent ignition by firebrands and helps us better understand the progression of large peat fires.
