NP pyrolant

The mass fraction of nickel powder incorporated into the NP pyrolant was 0.01 and the diameter of the nickel particles was 0.1 pm. The NP pyrolants with and without nickel particles were pressed into pellet-shaped grains 1 mm in diameter and 1 mm in length. The BK pyrolant was pressed into pellet-shaped grains 3 mm in diameter and 3 mm in length. 

Fig. 12.2 Burning rate characteristics of BK and NP pyrolants, showing that the burning rate of the NP pyrolant remains unchanged by the addition of nickel particles.

NP pyrolant is caused by incomplete combustion at about 4 MPa and that the increased of the NP-Ni pyrolant is caused by a catalytic effect on the gas-phase re-... 

Nitropolymers composed of -O-NO2 functions and hydrocarbon structures are pyrolants that produce fuel-rich products accompanied by exothermic reaction. Typical nitropolymers are mixtures of nitrocellulose, nitroglycerin, trimethylolethane trinitrate, or triethylene glycol dinitrate, similar to the double-base propellants used in rockets and guns. Mixtures of these nitropolymers are formulated as fuel-rich pyrolants used in ducted rockets. This class of pyrolants is termed NP pyrolants. 

Typical gas-generating pyrolants include (1) AP pyrolant composed of AP, ap(0.50), and HTPB, htpb(0-50), which is cured with isophorone diisocy-anate(lPDl) (2) NP pyrolant composed of NC, nc(0-70) and NG, ng(0-30), which is plasticized with diethyl phthalate (DEP) and (3) GAP pyrolant composed of gly-cidyl azide copolymer, qap(0-85), which is cured with hexamethylene diisocy-anate(HMDl) and cross-linked with trimethylolpropane (TMP). 

The specific impulse of each pyrolant is computed as a function of air-to-fuel ratio, as shown in Fig. 15.7. In the computations, the pressure in the ramburner is assumed to be 0.6 MPa at Mach number 2.0for a sea-level flight When GAP pyrolant is used as a gas-generating pyrolant, the specific impulse is approximately 800 s at e = 10. It is evident that AP pyrolant and NP pyrolant are not favorable for use as gas-generating pyrolants in VFDR. However, the specific impulse and burning rate characteristics of these pyrolants are further improved by the addition of energetic materials and burning rate modifiers. 

The heats of explosion, of the pyrolants are shown as a function of pressure in Fig. 12.3. It is evident that H p of the NP pyrolant is increased by the addition of nickel particles in the low-pressure region below about 2 MPa. The measured of the NP-Ni pyrolant becomes less pressure-dependent and reaches approximately 97 % of the theoretical value. The results indicate that the lower value of H p of the NP pyrolant is caused by incomplete combustion at about 4 MPa and that the increased H p of the NP-Ni pyrolant is caused by a catalytic effect on the gas-phase reaction which increases the temperature. The gas-phase reduction of NO to N2 in the dark zone of the NP pyrolant in the low-pressure region is promoted by the addition of the nickel particles. 

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