Measurement of Temperatures and Oh Concentrations of Solid Propellant Flames Using Absorption Spectroscopy

Multi-parameters least-squares analysis of rotationally resolved absorption spectroscopy in the A2Σ − X2Π(0, 0) vibrational band system of OH from 307 to 311 nm was performed to determine the flame temperatures and OH concentrations of JA-2 double-base propellant under steady-state burning at elevated pressures with a spatial resolution of 50–100 µm. Deduced flame temperatures were 2754 ± 124 K, 2836 ± 147 K, 2852 ± 179 K, and 2873 ± 188 K at pressures of 1.60, 3.55, 5.62, and 6.99 MPa, respectively; the corresponding OH number densities were (1.09 ± 0.34) × 1017,(2.31 ± 0.48) × 1017,(3.31 ± 0.27) × 1017,and (3.44 ± 0.30) × 1017 molecules/c.c., respectively. The results at 1.60 MPa agree well with data in the literature, and deduced flame temperatures at high pressures agree well with chemical equilibrium calculations. OH mole fractions are about 40% lower than the equilibrium analysis. This work represents the first set of optical absorption measurements performed on solid propellants at pressures above 2.0 MPa.