A series of experiments were carried out to identify and better understand the thermal mechanisms which govern the ignition propensity of firebrands. This work leverages the temperature-sensitive phosphorescence of YAG:Dy to non-intrusively measure and spatially resolve firebrand contact temperature along a 6.1 cm diameter area. The highly coupled firebrand heat transfer problem is studied by depositing smoldering firebrands onto a flat inert substrate and subjecting them to flow speeds of (1.5 ± 0.15) m/s. The temporal evolution of the thermal footprint is described and analyzed. Quasi-steady peak contact temperatures ranged between 500 K and 850 K while brief peaks exceeding 1150 K were also observed. The large difference in contact temperatures alludes to the significance in factors such as firebrand-fuel contact resistance, firebrand geometry, firebrand-flow orientation, fuel type (density and heat of combustion), and mass. Furthermore, the findings shed light on secondary heating events associated with shifting of the firebrand contact area and/or fragmenting, which can impart peak net heat flux equivalent to 70 % of the initial deposition. Lastly, considering the sensitivity of ignition on temperature, the work provides a brief discussion on the presence of unimodal and bimodal contact temperature distributions.

进行了一系列实验，以识别并更好地了解支配火种着火倾向的热机制。这项工作利用了YAG：Dy对温度敏感的磷光，沿直径6.1 cm的区域非侵入性地测量和空间分辨了火印接触温度。通过将阴燃的烙印沉积到平坦的惰性基材上并使其经受（1.5±0.15）m / s的流速，研究了高度耦合的烙印传热问题。描述并分析了热足迹的时间演变。准稳定的峰值接触温度介于500 K和850 K之间，同时还观察到短暂的峰值超过1150K。接触温度的巨大差异暗示着诸如火炭燃料接触电阻，火炭几何形状，火斑流动方向，燃料类型（密度和燃烧热）和质量。此外，研究结果揭示了与火印接触面积的移动和/或破碎相关的二次加热事件，这可以产生相当于初始沉积量70％的峰值净热通量。最后，考虑到点火对温度的敏感性，这项工作对单峰和双峰接触温度分布的存在进行了简要讨论。