Uncatalyzed propellants

The heat of explosion of the uncatalyzed NC-NG propellant decreases rapidly when the pressure is decreased below about 4 MPa, as shown in Fig. 13.12. However, the heat of explosion of the catalyzed NC-NG propellant remains relatively unchanged, even below 2 MPa. 

Substituting the measured H xp data into Eqs. (13.32) and (13.28), one obtains an experimentally determined m value as a function of pressure. The results indicate that m of the uncatalyzed NC-NG propellant is approximately 0.35 at 0.6 MPa, gradually decreases with increasing pressure, and becomes zero at 5 MPa and above m of the catalyzed NC-NG propellant is approximately zero over the same tested pressure range. Substituting the results for m and n into Eq. (13.35), one gets... 

The combustion tests conducted for a rocket motor show that the combustion becomes unstable below 1.7 MPa and that the burning acquires a chuffing mode in the case of the uncatalyzed propellant. However, as expected, the combustion is stable even below 0.5 MPa for the nickel-catalyzed NC-NG propellant, as shown in Fig. 13.13. Propellants for which the flame temperature decreases with decreasing pressure tend to exhibit T combustion instability. 

The steady combustion behavior of two common energetic materials are discussed in the context of the foregoing simplified model uncatalyzed NC/NG double base propellant and cyclo-tetramethylene-tetranitramine (HMX). 

Fig. 11 Temperature profiles and volumetric heat release for double base NC/NG propellant-N (uncatalyzed, medium heat of explosion) along with model predictions for Eg 1 and Eg 1.

Figure 11 shows near-surface, gas phase temperature measurements for steady burning of uncatalyzed, medium energy NC/NG propellant (designated propellant-N following Russian notation) at 5 MPa (50 atm) from thermocouples [23]. At this pressure there is a distinct two-stage gas flame structure but only the primary stage closest to the surface, where temperature increases from 7j = 668 K to around... 

Catalysts have been rarely nsed in pyrotechnic compositions over the years, although there has been considerable interest in the nse of catalysts to accelerate the decomposition of oxidizers in propellant formulations. Catalysts work by providing an alternate reaction pathway of lower activation energy than the primary (uncatalyzed) pathway. In energetic mixtures, the role of the catalyst is frequently to accelerate the... 

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