Upward Turbulent Flame Spread

Abstract

Mechanisms and rates of upward spread of turbulent flames along thermally thick vertical sheets are considered for both noncharring and charring fuels. By addressing the time dependence of the rate of mass loss of the burning face of a charring fuel, a linear integral equation of the Volterra type is derived for the spread rate. Measurements of spread rates, of flame heights and of surface temperature histories are reported for polymethylmethacrylate and for Douglas-fir particle board for flames initiated and supported by a line-source gas burner, with various -rates of heat release, located at the base of the fuel face. Sustained spread occurs for the synthetic polymer and not for the wood. Comparisons of measurements with theory aid in estimating characteristic parameters for the fuels.

Upward flame spread over discrete fuels

“…Significant experimental research has already been conducted on flame spread in the vertical direction over homogeneous sheets of PMMA. Vertical flame spread presents one of the most dangerous fire hazards because the natural buoyancy allows for concurrent flame propagation and accelerating flame spread [22]. Drysdale and MacMillan studied effects of fuel orientation on the flame spread rate, and found substantially higher velocities as the angle of orientation approached the vertical [23].…”

“…Initially, experimentalists simply took the flame height by eying an appropriate value (occasionally from video footage) [10][11][12][13]. In 1995, Audouin et al developed an image processing technique for pool fires where they averaged 160 images and obtained a flame presence probability [14].…”

Upward Flame Spread: Heat Transfer To The Unburned Surface

“…Brehob et al [8] suggested another form for the correlation of w q ′ ′ & with height based on the data reported by Quintiere et al [7] and Kim [9], viz. [11] 30 Delichatsios and Delichatsios [12] 25 Delichatsios and Chen [13] 25…”

“…However, to simplify the problem, most of these models [9][10][11][12][13][14][15][16][17][18] assume that " w q & is constant over the preheating region, becoming zero at heights above X f . Saito et al [9] took 25 kW/m 2 as the constant heat flux exposed to which mass loss rate was obtained for their steady-state model. Good consistency has been shown with their PMMA flame spread rate measurement.…”

Flame Spread Analysis Using a Variable B-Number

“…These correlations are based on test data like the Radiant Panel Rate of Flame Spread Test [26]. Other experimental correlations are developed from test data by Saito et al [27,28], Delichatsios et al [29], Quintiere and Harkleroad [30], Brehob and Kulkarni [31], and many other researchers; additional reviews are given by Joulain [32] and Brehob et al [33]. Given the extensive amount of available data, these correlations work well for most materials that are tested.…”