GAP-AN pyrolants

In general, pyrolants composed of a polymeric material and AN particles are smokeless in character, their burning rates are very low, and their pressure exponents of burning rate are high. However, black smoke is formed as i decreased and carbonaceous layers are formed on the burning surface. These carbonaceous layers are formed from the undecomposed polymeric materials used as the matrix of the pyrolant. When crystalline AN particles are mixed with GAP, GAP-AN pyrolants are formed. Since GAP burns by itself, the GAP used as a matrix for AN particles decomposes completely and bums with the oxidizer gases generated by the AN particles. 

The combustion products of aluminized GAP-AN pyrolants at 10 MPa are HjO, Hj, Nj, GO, GOj, and AI2O3. The mass fraction of AljOj increases linearly while that of HjO decreases linearly with increasing Iai- This is caused by the overall reaction of 2A1 -I- 3H2O AI2O3 -t 3H2. 

The AN particles incorporated into GAP-AN pyrolants form a molten layer on the burning surface and decompose to form oxidizer fragments. The fuel-rich gas produced by the decomposition of GAP interdiffuses with these oxidizer fragments on and above the burning surface and produces a premixed flame. A luminous flameis formed above the burning surface. 

When AP particles are added to GAP-AN pyrolants, a number of luminous flame-lets are formed above the burning surface. These flamelets are produced as a result of diffusional mixing between the oxidizer-rich gaseous decomposition products of the AP particles and the fuel-rich gaseous decomposition products of the GAP-AN pyrolants. Thus, the temperature profile in the gas phase increases irregularly due to the formation of non-homogeneous diffusional flamelets. 

When A1 particles are added to GAP-AN pyrolants, agglomerated A1 fragments are formed on the burning surface. However, when A1 particles are mixed with pyrolants composed of GAP, AN, and AP, numerous flame streams are formed in the gas phase. The A1 particles are oxidized by the gaseous decomposition products evolved by the AP particles. The combustion efficiency of the A1 particles is improved significantly by the addition of the AP particles. 

The first trend involves the "blackening" of the char while discrete absorptions decline in intensity as the temperature is increased, an IR continuum grows and begins to level off above about 700°C. The explanation, briefly, is that as the material is pyrolized, polyaromatic networks grow and tend in structure toward that of graphite. Following Kmeto [ 1J], the band gap... 

The highest flame temperature for a B-GAP pyrolant is obtained at b( 0.2), whereupon BN is produced, while that for an Al-GAP pyrolant is obtained at ai( 0.4), whereupon AIN is produced. Al reacts with N2 generated by the decom-... 

The results of thermochemical experiments reveal that an exothermic reaction of GAP occurs at about 526 K and that no other thermal changes occur. When Mg or Ti parhcles are incorporated into GAP to formulate Mg-GAP or Ti-GAP pyrolants, two exothermic reactions are seen the first is the aforementioned exothermic decomposihon of GAP, and then a second reachon occurs at 916 K for the Mg-GAP pyrolant and at 945 K for the Ti-GAP pyrolant There is no reaction between either Mg or Ti and GAP at the temperature of the first exothermic reaction. Both Mg and Ti particles within GAP are ignited by the heat generated by the respechve second exothermic reactions. 

Boron particles are incorporated into GAP pyrolants in order to increase their specific impulse.[8-i2] xhe adiabatic flame temperature and specific impulse of GAP pyrolants are shown as a function of air-to-fuel ratio in Fig. 15.10 and Fig. 15.11, respectively. In the performance calculation, a mixture of the combustion products of the pyrolant with air is assumed as the reactant. The enthalpy of the air varies according to the velocity of the vehicle (or the relative velocity of the air) and the flight altitude. The flight conditions are assumed to be a velocity of Mach 2.0 at sea level. An air enthalpy of 218.2 kj kg is then assumed. 

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