AP-CMDB Propellants

When crystalline AP particles are mixed with nitropolymers, ammonium perchlorate composite-modified double-base (AP-CMDB) propellants are formulated. A nitropolymer such as NC-NG or NC-TMETN double-base propellant acts as a... 

Fig.4.24 Specific impulse and adiabatic flame temperature of AP-CMDB propellants.

When nitramine particles such as HMX or RDX particles are mixed with a doublebase propellant, nitramine composite-modified double-base propellants are formulated. Since HMX and RDX are stoichiometrically balanced materials, the use of these nitramine particles leads to a somewhat different mode of combustion as compared to AP-CMDB propellants. Since each nitramine particle can burn independently of the base matrix at the burning surface, a monopropellant flamelet is formed in the gas phase from each particle. The monopropellant flamelet diffuses into the reactive gas of the base matrix above the burning surface and a homogeneously mixed gas is formed. 

When large spherical AP particles dg = 3 mm) are added, large flamelets are formed in the dark zone.Pl Close inspection of the AP particles at the burning surface reveals that a transparent bluish flame of low luminosity is formed above each AP particle. These are ammonia/perchloric acid flames, the products of which are oxidizer-rich, as are also observed for AP composite propellants at low pressures, as shown in Fig. 7.5. The bluish flame is generated a short distance from the AP particle and has a temperature of up to 1300 K. Surrounding the bluish flame, a yellowish luminous flame stream is formed. This yellowish flame is produced by in-terdiffusion of the gaseous decomposition products of the AP and the double-base matrix. Since the decomposition gas of the base matrix is fuel-rich and the temperature in the dark zone is about 1500 K, the interdiffusion of the products of the AP and the matrix shifts the relative amounts towards the stoichiometric ratio, resulting in increased reaction rate and flame temperature. The flame structure of an AP-CMDB propellant is illustrated in Fig. 8.1. 

Fig. 8.2 Flame photographs of AP-CMDB propellant (a) and RDX-CMDB propellant (b) showing that the luminous flame front of the RDX-CMDB propellant is distended from the burning surface ...

Region (2) is assumed to regress at approximately the same rate as the AP particles, as given by Eq. (8.1). Thus, the burning rate of an AP-CMDB propellant is expressed as the fractionally weighted sum of the two different regression rates ... 

Fig. 8.4 Computed and experimental burning rates of AP-CMDB propellants.

Fig. 13.31 Burning rate augmentation of an NC-NG double-base propellant and an AP-CMDB propellant along silver wires.

Fig. 13.32 Effect of silver wire diameter on burning rate augmentation of an AP-CMDB propellant.

Typical crystalline-energetic-particles are AP and nitramines such as HMX and RDX. The use of AP leads to an AP-CMDB propellant and the use of HMX leads to an HMX-CMDB propellant. These particles burn as a monopropellant at the burning surface of the CMDB propellant, and the combustion products react again with the combustion products of the base matrix. 

AP-CMDB propellants bum with a different mode from that of nitramine-CMDB propellants, namely that of AP composite propellants, a diffusion-flame mode. On the other hand, nitramine-CMDB propellants bum with a mode of double-base pro-... 

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