AP propellant

Combustion Wave Structure of Oxidizer-Rich AP Propellants... 

Fig. 7.13 shows the effect of the particle size of AP on burning rate.I l The propellants have the composition ap(0-80) and htpb(0-20). The AP particles are bimodal large-sized, with a 350 pm/200 pm mixture ratio of 4 3, and bimodal small-sized, with a 15 pm/3 pm mixture ratio of 4 3. The burning rate of the smaU-sized AP propellant is more than double that of the large-sized AP propellant. The pressure exponent of burning rate is 0.47 for the large-sized AP propellant and 0.59 for the small-sized AP propellant... 

Though the detailed mechanism of the action of SrC03 on AP propellants has yet to be fully understood, the results of the thermograms indicate that the site and mode of the action of SrCOj are in the condensed phase rather than in the gas phase. The decomposition process of AP particles is substantially altered by the addition of SrCO,. 

When sodium nitrate (NaN03) is incorporated into an AP propellant, the concentration of HCI molecules is reduced by reaction according to ... 

Thus, the number of HCI molecules is reduced when sodium nitrate particles are incorporated into AP propellants. This class of propellants is termed scavenged propellants . Fig. 12.18 shows the results of thermal equibbrium computations of scavenged AP propellants as a function of the mass fraction of sodium nitrate. 

Fig. 12.18 Mole fractions of HCI and NaCI produced by scavenged AP propellants as a function of (NaNOj).

NaN03). The AP propellant without NaNOj, (0.0), is composed of mass fractions of (AP) = 0.85 and (HTPB) = 0.15. The HCI gas among the combustion products of the AP propellant is converted into NaCl, which is a stable and environmentally benign material. 

When magnesium particles are incorporated into AP propellants, these react with HCI molecules generated in the combustion chamber according to ... 

The surface decomposition process of AP propellants is net exothermic, with heat absorbed at the AP and fuel surfaces by endothermic pyrolysis but with more heat liberated in the gas phase close to the AP crystals. In detail, decomposition at the AP surface consists of endothermic pressure-independent solid-to-gas phase dissociative sublimation, followed by exothermic pressure-dependent gas-phase oxidation. The over-all reaction for the AP decomposition is pressure dependent. 

The mere presence of the ash seems responsible for the ability of the LP3—AP propellant to undergo self-sustained combustion to pressures as low as 0.005 atm., an order of magnitude less than PBAA-AP and PB(CT)-AP propellants, and to maintain a relatively high burning rate at such low pressures. Two questions are of interest why does it form, and how does it sustain the burning rate It is not clear why the ash forms. It may be related to Bircumshaw and Newman s (14,15) discovery that only 30% of the original AP decomposes when the temperature is below ca. 350 °C. and that the remaining 70% is unreacted solid AP, and to the fact that the surface temperature and the temperature in the ash were measured by Most (60) as 250° 300°C. (The GDF theory with a collapsed A/PA flame indeed predicts a low surface temperature, ca. 400°C. below 0.01 atm.)... 

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