Combustion Mechanisms of Super-Rate Burning

Combustion Mechanisms of Super-Rate Burning 6.4.2.1 Burning Rate Characteristics 

The effect of the addition of metallic lead and copper powders on super-rate burning is shown in Fig. 6-24. Pb powder is more effective than Cu powder in increasing the burning rate. When these powders are mixed into the noncatalyzed propellant, there is no drastic burning rate increase, i.e., no super-rate burning is observed. However, when PbO powder (1 %) is added, the burning rate is increased approximately 250 %, i.e., there is super-rate burning. 

The effectiveness of lead compounds in producing super-rate burning decreases as the propellant s heat of explosion increases1101. This implies that propellants with a lower content of NG or lower nitrated NC are strongly influenced by lead compounds. 

The propellants composed of NC-NG and HMX show super-rate and plateau burning rate characteristics as shown in Fig. 6-25 201. The chemical compositions on noncatalyzed and catalyzed propellants are shown in Table 6-6. 

The flame structures of the noncatalyzed and catalyzed propellants shown in Fig. 6-25 are similar except for the flame standoff distance, i.e., dark zone length, as shown in Fig. 6-26. The dark zone lengths of both propellants decrease with increas- 

---