Characterization of the influence of aluminum particle size on the temperature of composite-propellant flames using CO absorption and AlO emission spectroscopy

Understanding the temperature of aluminized, composite-propellant flames is critical to achieving robust rocket motor designs and developing accurate, predictive models for propellant combustion. This work presents measurements (1) CO (within flame bath gas) (2) AlO (located primarily within regions surrounding burning aluminum particles) as a function height above surface. Three ammonium-perchlorate (AP), hydroxyl-terminated polybutadiene (HTPB) composite propellants with varying particle size (nominally 31 ?m, 4.5 or 80 nm) one non-aluminized AP-HTPB were studied while in air at 1 atm. A wavelength-modulation-spectroscopy technique was utilized measure mole fraction via mid-infrared wavelengths conventional emission-spectroscopy AlO. The bath-gas varied significantly between propellants, particularly 2 cm smallest particles (nano-scale aluminum) had highest average temperatures far less variation measurement location. At all locations, increased initial decreased, likely due results support arguments that larger can act heat sink near surface require more time space ignite burn completely. On time-averaged basis, measured from agreed uncertainty 2650 K nano-aluminum flame, however, often exceeded by ? 250 800 micron-aluminum flames. result suggests here, on diffusion-controlled combustion regime, whereas very close kinetically controlled regime.