Assessment of Combustion Characteristics and Mechanism of Hydroxylammonium Nitrate-Based Liquid Monopropellant

Abstract

The combustion characteristics and reaction mechanism of a HAN-based liquid monopropellant (HANGLY26, consisting of 60% HAN, 14% glycine, and 26% water by weight ) were investigated. Combustion tests of liquid strands formed in test tubes were performed in an optically accessible strand burner. Fine-wire thermocouples were also installed in the strand to measure the temperature distribution of the reaction zone. The burning rate of HANGLY26 exhibited four burning rate regimes for pressures ranging from 1.5 to 18.2 MPa. No luminous e ame was observed in any combustion tests. The temperatures of combustion products in the test tube were found to be near the water boiling points at pressures below 8.8 MPa. For pressures above 8.8 MPa, the product temperatures were found to be lower than the boiling points of water. Slope break points for burning rate vs pressure were found to coincide with those of concentration curves of recovered residues vs pressure. The observed slope breaks in burning rates are shown to be associated with the reaction mechanism changes between adjacent pressure regimes. Major species detected from the recovered liquid residues are nitrogen, nitric oxide, carbon dioxide, and formaldehyde. The pyrolysis of the fresh unburned liquid propellant was also studied. The results were compared with those of the recovered liquid residues.