Dark zone length

Fig. 6.8 Dark zone length (flame stand-off distance) decreases with increasing pressure.

Since the final gas-phase reaction to produce a luminous flame zone is initiated by the reaction in the dark zone, the reaction time is determined by the dark zone length, L4, i. e., the flame stand-off distance. Fig. 6.8 and 6.9 show data for the dark zone length and the dark zone temperature, T, respectively, for the propellants listed in Table 6.3. The luminous flame front approaches the burning surface and... 

The dark zone length of liF-catalyzed propellants is increased by the addition of LiF in the region of super-rate burning, similar to the case of Pb-catalyzed propellants, as shown in Fig. 6.28. Table 6-11 shows the dark zone lengths and reaction times Xg in the dark zone producing the luminous flame at two different pressures,... 

Table 6.11 Dark zone lengths and reaction times in the dark zone.

Since the final gas phase reaction to produce a luminous flame zone is initiated by the reaction in the dark zone, the reaction time is determined from the dark zone length Ld, i.e., the flame standoff distance. Figures 6-7 and 6-8 show the results for the dark zone length and dark zone temperature, Td, of the propellants listed in Table 6-1, respectively. The luminous flame front approaches the burning surface and the dark zone length decreases as pressure increases for the propellants. There is no clear difference between the propellants with respect to the dark zone length and the pressure exponent of the dark zone, d = n - m, defined in Eq. (3.70) is determined to be approximately -2.0. The overall order of the reaction in the dark zone is also determined to be m= 2.6 for all the propellants. However, the dark zone temperature increases as pressure increases at constant (N02) and also increases as (N02) increases at constant pressure. 

Figure 6-7. Dark zone length (flame standoff distance) decreases as pressure increases.

The flame structures of the noncatalyzed and catalyzed propellants shown in Fig. 6-25 are similar except for the flame standoff distance, i.e., dark zone length, as shown in Fig. 6-26. The dark zone lengths of both propellants decrease with increas-... 

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