Combustion of HAN-based liquid monopropellants near the thermodynamic critical point

Abstract

The high-pressure combustion properties of liquid monopropellants involving mixtures of hydroxyl ammonium nitrate (HAN), triethanol ammonium nitrate (TEAN), and water are considered theoretically. Liquid surface properties and the critical combustion pressure (the pressure required for the propellant surface to exceed its thermodynamic critical point) were found allowing for real-gas phenomena and the presence of dissolved combustion product gases in the liquid. Critical combustion pressures for the HAN-based monopropellants were found to be unusually high, ca. 2500 atm, with an estimated uncertainty of 50%. Predictions were unusually sensitive to the critical temperature of TEAN and the binary interaction parameter between TEAN and water; both must be known more accurately for definitive estimates of the liquid-surface properties of HAN-based monopropellants at high pressures.