Properties opposed flow flame spread

The LIFT apparatus can be used for obtaining opposed-flow flame spread properties. The apparatus is briefly discussed in Section 14.3.2.3.2 and is described in detail in ASTM E 1321. A schematic is shown in Figure 14.7. 

The main objective of conducting LIFT flame spread experiments is to obtain material properties for predicting opposed-flow flame spread. On the basis of the analysis by deRis (see Equation 14.8), the flame heating parameter can be determined from the slope of a linear fit of l/yjvp(y) plotted as a function of qe (y), where y is the distance from the hot end of the specimen. The minimum surface temperature for spread, Tsmin, is calculated according to an expression akin to Equation 14.4 from the incident heat flux at the maximum distance from the hot end reached by the flame. 

Table 8.1 Opposed flow properties for lateral flame spread on a vertical surface [16]...

This follows by a steady state energy balance of the surface heated by qe, outside the flame-heated region S. It appears that a critical temperature exists for flame spread in both wind-aided and opposed flow modes for thin and thick materials. Tstmn has not been shown to be a unique material property, but it appears to be constant for a given spread mode at least. Transient and chemical effects appear to be the cause of this flame spread limit exhibited by 7 smln. For example, at a slow enough speed, vp, the time for the pyrolysis may be slower than the effective burning time ... 

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