Species and temperature profiles of propellant flames obtained from FTIR absorption spectroscopy

The use of Fourier transform infrared absorption spectroscopy to obtain species and temperature profiles within solid-propellant flames is described. Measurements were performed at a spectral resolution of 2 cm^-1 and a spatial resolution of 1 mm within the flame zone of an RDX-composite propellant. A nonlinear, least-squares routine was developed to deduce the absolute species concentrations of CO, NO, H₂O, CO₂, HCN, CH₄ and N₂O as well as the rotational temperature. The deduced temperature profile revealed the presence of dark-zone/luminous flame-zone structures. The mole fraction of CO increased while the mole fraction of HCN decreased from the beginning of the dark zone to the luminous flame zone. Data on the spatial variation of species concentration and temperature within these zones are important for the development and validation of chemical kinetic mechanisms describing the combustion of solid propellants.