Burning rate of AP-HTPB composite propellant

Fig. 7.19 shows the burning rates of AP-HTPB composite propellants at 243 K and 343 K. The propellants are composed of bimodal fine or coarse AP particles. The chemical composihons of the propellants are shown in Table 7.2. The burning rates of both propellants are seen to increase linearly in an In r versus In p plot in the pressure range 1.5-5 MPa, and also increase with increasing initial propellant temperature at constant pressure.Ii l The burning rate increases and the temperature sensitivity decreases with decreasing AP particle size. 

As shown in Fig. 7.20, the burning rate of the AP composite propellant is increased approximately twofold by the addihon of 1 % BEFP. In general, the degree of the burning rate increase is proportional to the amount of catalyst added when the catalyst conshtutes less than about 3 % of the total mass, and the effect of the catalyst addihon shows saturation behavior at about 5% by mass. Fig. 7.23 shows the burning rates of AP-HTPB composite propellants composed of ap(0-80) and... 

Figure 7-4 shows the effect of (AP) on burning rate of AP-HTPB composite propellants 3. The chemical compositions of the propellants are shown in Table 7-1. The burning rate of the propellant composed of (0.86) is higher than that of (0.80) at constant pressure. However, the pressure exponent is 0.60 for both (0.86) and (0.80) propellants and the burning rate is represented by r - p ° 6. 

The burning rates of AP-RDX composite propellants are dependent on the physicochemical properhes of the AP, RDX, and fuel used, such as particle size, as well as on mixture raho and the type of binder. The results of burning rate measurements are reported in AlAA Paper No. 81-1582.125] Various combinahons of AP and RDX parhcles are used to formulate AP-RDX composite propellants, as shown in Table 7.6.125] pjjg particles incorporated into the propellants have bimodal combinations of sizes, where large RDX particles (RDX-I), small RDX particles (RDX-S), large AP particles (AP-I), and small AP particles (AP-S) are designated by d, d, dj, and da, respectively. HTPB binder is used in all of the propellants shown in Table 7.6. 

If the binder (BDR) concentration of AP-HTPB composite propellants is less than the stoichiometric ratio, the burning rate increases as (BDR) increases, as shown in Fig. 7.6. The burning rate of a propellant with the composition bdr(0-08) is... 

Figure 7-6. Burning rate and temperature sensitivity of AP-HTPB composite propellants composed of fine or coarse AP particles.

Fig. 7.3 Burning rates of three AP-HTPB composite propellants at low pressures below 1 MPa.

Various types of binders are used to formulate AP composite propellants. Binders such as HTPB and HTPE decompose endothermically or exothermically at the burning surface. The burning rates of AP composite propellants thus appear to be dependent on the thermochemical properties of the binders used. Figs. 7.17 and 7.18 show In r versus In p plots for AP composite propellants made with five differ-... 

Fig. 7.7 Burning rate of an oxidizer-rich AP-HTPB propellant with the composition htpb(0 08) if low-pressure region.

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... 

In addition, a few other publications also address this issue of ballistic modification of composite propellants. The cobalt, nickel and zinc hexammine perchlorates have been studied by Gurdip Singh and coworkers for this purpose. The generated data indicate that cobalt complex accelerates burn rate three-fold when used at 2% level in HTPB-AP-based composite propellant [277]. Another study on transition metals (copper, iron, cobalt and nickel) salts of NTO as BRMs for HTPB-AP-based... 

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