Combustion chemistry of HAN, TEAN, and XM46

Combustion characteristics and related chemical processes were investigated for a HAN-based liquid propellant, XM46, and its ingredients, HAN and TEAN. Experiments were conducted over the pressure range of 0.1 to 1 atmosphere and at the heat fluxes from 50 to 400 W/cm² in air and inert gas environments. Flame behavior was observed using a high magnification video system. A triple quadrupole mass spectrometer (TQMS) and micro-thermocouples were applied for the temporal measurements of gas-phase species and temperature profiles. Species in the XM46 residue left after burning were analyzed using a gas chromatograph/mass spectrometer (GC/MS). No visible flame was observed from XM46 or its ingredients at 1ATM and 100 W/cm². However, at 1ATM and 400 W/cm², HAN and TEAN showed distinctive flame behaviors, and XM46 exhibited three flames in sequence with the white HAN flame appearing first, followed by the blue and yellow TEAN flames. Gaseous products evolved from HAN and TEAN exhibited a distinctive set of species profiles for each ingredient, corresponding to its flame behavior. Species measurements of XM46 showed the same sequential characteristics as the flame behavior; however, a significant portion of the HAN and TEAN flames in XM46 was found to involve HAN+TEAN mixed reactions. The maximum temperatures for XM46 combustion in air were found to be approximately 1250 and 2050 K at 100 and 400 W/cm², respectively. Species found in the residues of XM46 varied according to the stage where the residue was formed.