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larger than that of FAP particles. And it suggests that the
position products, is not considered to occur at the pro-
location of each ame of Propellant E is brought closer to
pellant surface, but to extend from the surface. The primary
the burning surface, and (dT=dx)s of Propellant E is larger
ame is a premixed ame with the oxdizer and binder
than that of Propellant F. In order to conrm this, the
decomposition products mixing completely before reaction
burning surface of Propellants G and H extinguished was
occurs. And the nal diffusion ame follows the primary
observed under a scanning electron microscope (SEM). The
ame. On the other hand, the burning rate is given by the
SEM photographs of the burning surface of both propellants
heat balance equation at the burning surface as follows:
extinguished at atmospheric pressure are shown in Figure 4.
lgdT=dxs
In Figure 4, holes exist at the burning surface of Propellant
r 1
G, and AP remains in the hole on the burning surface of
cprpTs To Qs=cp
Propellant H. It is found that the regression rate of FPAP
where r is burning rate, l is thermal conductivity, (dT=dx) is particles is larger than that of FAP particles, even at a low
temperature gradient in the vicinity of the burning surface, c pressure. As mentioned above, at a lower pressure the AP
is specic heat, r is density, Ts is temperature at the burning particles protruded above the exposed surface of the binder
surface, To is initial temperature of propellant, and Qs is to greater height and at a higher pressure they recessed.
heat per unit mass generated at the burning surface. Sub- Therefore, the burning surface of Propellant G extinguished
scripts g, p, and s mean gas phase, propellant, and gas at atmospheric pressure was similar to the burning surface
phase at the burning surface, respectively. When the com- of the propellant extinguished at a high pressure. The result
positions of propellant are constant, it can be assumed that supports the above consideration.
lg, cp, rp, and Ts of the propellants are almost the same
values, respectively, at the same pressure. When To is
constant, Eq. (1) indicates that the burning rate increases
with increasing (dT=dx)s. Consequently (dT=dx)s is a
dominant factor on the burning rate. It can be considered
that (dT=dx)s is dependent on the location of each ame;
and when the location of each ame is brought close to the
burning surface, (dT=dx)s increases. In general, the burn-
ing rate increases with increasing pressure. This can be
explained as follows. The diffusion distance to react with
the oxidizer and binder decomposition products decreases
with increasing pressure, and the location of each ame is
brought closer to the burning surface. This implies that
(dT=dx)s increases with increasing pressure. On the other
hand, when the burning surface of a propellant extinguished
Figure 4. SEM micrographs of the burning surface of Propellants G
and H extinguished.
by rapid depressurization was observed, it was found that at
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