The temperature in an aluminized propellant is determined as a function of height and plume depth from diatomic AlO and thermal emission spectra. Higher in the plume, 305 and 508 mm from the burning surface, measured AlO emission spectra show an average temperature with 1σ errors of 2980 ± 80 K. Lower in the plume, 152 mm from the burning surface, an average AlO emission temperature of 2450 ± 100 K is inferred. The thermal emission analysis yields higher temperatures when using constant emissivity. Particle size effects along the plume are investigated using wavelength-dependent emissivity models.
The study of aluminum particle ignition in an open atmosphere propellant burn is of particular interest when considering accident scenarios for rockets carrying high-value payloads. This study investigates the temperature of an open atmosphere Atlas V solid propellant burn as a function of height from the burning surface. Two instruments were used to infer this temperature: a two-color pyrometer and a spectrometer. The spectra were fitted to a model of energy states for aluminum monoxide. The temperature which provided the best match between the model and data was taken as the reaction temperature. Emissions above 30 inches from the surface of the propellant were not sufficiently strong for data reduction, perhaps obscured by the alumina smoke cloud. The temperature distribution in the plume increased slightly with distance from the burning surface, presumably indicating the delay in ignition and heat release from the larger aluminum particles in the propellant. The pyrometer and spectrometer results were found to be in excellent agreement indicating plume temperatures in the range of 2300K to 3000K.
This article examines potential use of a new device called multi-directional heat flux and velocity probe for simultaneous measurement of heat flux and flame speed in a diffusion flame. The probe consists of a thin-wall spherical shell with internal insulation to mitigate internal convection. Both pressure and temperature distributions around the sphere are used to indicate local velocity and heat flux. The multi-directional heat flux and velocity probe appears to be a more promising device than the bidirectional velocity probe in the sense that the sphere is a regular geometry with minimum flow separation and should lead to more predictable behavior. However, an outcome of this study is that the device must be used in conjunction with a fire code computational fluid dynamics model because the boundary layer is not isothermal so that the conventional pressure coefficient for a sphere leads to erroneous results.
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