The effect of radiative heat feedback on burning rate of metalized propellants.

摘要

Metalized solid propellants have higher final flame temperatures and higher flame radiant intensities than non-metalized propellants. However, the importance of radiative heat feedback in metalized propellant combustion is still unknown. In this study, radiative effects in metalized composite AP-HTPB propellants containing aluminum, boron, and magnesium were examined by embedding optical fibers and micro-thermocouples in propellants to measure radiative and conductive feedback. Extinguishment by rapid depressurization was used to determine the condition and location of the thermocouple and optical fiber at the burning surface. Hemispherical reflectivity measurements were also made to determine propellant absorptivity. The reflectivity measurements showed that even a small amount of a metal powder in a propellant increases the absorptivity significantly. Incident radiative flux of non-metalized and metalized propellants is dependent on pressure in the pressure range less than 2 MPa. In non-metalized propellant, the effect of radiative feedback on burning rate was negligible because of low incident flux from flame and low absorptivity of the propellant. In the metalized propellants, radiative heat feedback is a significant fraction of the total feedback and is strongly dependent on pressure and metal loading. In the aluminum and boron propellants, radiative feedback increased the burning rate by approximately 20%. In magnesium propellant, radiative feedback increased the burning rate by approximately 10%. In addition, the importance of radiative feedback increases as metal loading increases. A sensitivity analysis was performed to determine the sensitivity of burning rate on radiative feedback, condensed phase heat release and other processes. The aluminized propellant was found to be rather sensitive to radiative feedback while the boron propellant was more sensitive to condensed phase heat release.