Heat balance at the burning surfac

The heat balance at the burning surface, i. e., at the interface between the soHd phase and zone I, is represented by... 

Referring to Eq. (3.49), the temperature gradient in the fizz zone, represented by is given by the heat balance at the burning surface ... 

The authors argue that the lower bum rate in air is due to competing oxidation that is less exothermic than fluoridation and, hence, influences the heat balance at the surface of the pyrolant. At higher pressures, these effects are compensated by better heat transfer as can be seen by the convergent lines in Figure 8.8 [13, 14]. Ladouceur explained the lower burn rate with preferred CF4 formation in oxygeneous atmosphere. CF4 reacts slower with Mg than that with CF2 and, thus, is held responsible for the observed lower burn rate [15]. The pressure dependence of a stoichiometric binary Mg/PTFE (32/68) formulation made with fine particles... 

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 ... 

An implicit relationship for the burning rate at low pressure may now be found by substituting Lnf ch from Equation 8 for Ln in the heat balance (Equation 3a). Inherent in this step is the assumption that the pyrolyzed fuel and oxidizer gases start to react immediately on leaving the propellant surface. When = Ts (e.g., where the first gaseous reaction stage is very fast) the burning rate at low pressure where it is chemical-reaction rate controlled can be written as ... 

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