Surface flame position

Three parameters are generally evaluated the mass burning rate (evaporation), the flame position above the fuel surface, and the flame temperature. The most important parameter is the mass burning rate, for it permits the evaluation of the so-called evaporation coefficient, which is most readily measured experimentally. 

Theories relating the combustion of NC based proplnts to pressure are fairly well developed, the most successful being those proposed by Daniels(Ref 1), Rice (Ref 2), Crawford(Ref 3), Boys 8cCorner-(Ref 5), and others(Ref 4). The classification of these theories is contingent on the proposed position of the rate-determining step in the surface-flame structure... 

Equations 22-29 for the gas-phase profiles, temperature gradient, flame position, and vaporization rate depend only on the temperature at the surface of the droplet, Tg. (The Clausius-Clapeyron equation relates to Tg.) An iterative numerical procedure for satisfying the continuity of Tg at the liquid/gas interface is described in the Appendix. 

ASTM 3894 [139] is the standard that tests the flammability of the specimen arranged as two walls only, each 1220 mm x 610 mm high, or two walls plus a ceiling 1220 mm X 610 mm high, or two walls plus a ceiling 1220 mm square, which are exposed to a premixed propane flame positioned in the lower corner. A specified temperature time calibration is specified, and results are assessed in terms of flame spread. Thermocouples are positioned at specified locations on the specimen surface, and the times to maximum temperatures and the maximum temperatures are recorded. 

The solid-flame model can be used to overcome the inaccuracy of the point-source model. This model assumes that the fire can be represented by a solid body of a simple geometrical shape, and that all thermal radiation is emitted from its surface. To ensure that fire volume is not neglected, the geometries of the fire and target, as well as their relative positions, must be taken into account because a portion of the fire may be obscured as seen from the target. 

In addition to flame height, other flame dimensions must also be known. In general, flame shape must be assumed. A flame s surface area and position both vary during the course of the flash fire, so, if based on manual calculations, flame shape... 

Radiation heat flux is graphically represented as a function of time in Figure 8.3. The total amount of radiation heat from a surface can be found by integration of the radiation heat flux over the time of flame propagation, that is, the area under the curve. This result is probably an overstatement of realistic values, because the flame will probably not bum as a closed front. Instead, it will consist of several plumes which might reach heights in excess of those assumed in the model but will nevertheless probably produce less flame radiation. Moreover, the flame will not bum as a plane surface but more in the shape of a horseshoe. Finally, wind will have a considerable influence on flame shape and cloud position. None of these eflects has been taken into account. 

A freshly prepared flame-annealed Au(100) surface has been found to be reconstmcted188,487,534,538 and the surface atoms exhibit a hexagonal close-packed structure to yield the (hex)-stmcture. One-directional long-range corrugation of 1.45 nm periodicity and 0.05 nm height has been found on the Au( 100) surface.188,488 When the reconstruction is lifted due to specific adsorption of SO - anions at more positive , the surface changes to a (1 x 1) structure.538... 

In the film oxygen diffuses to the flame front, and combustion products and heat are transported to the surrounding atmosphere. The position of the boundary designated by °o is determined by convection. A stagnant atmosphere places the boundary at an infinite distance from the fuel surface. 

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