Combustion Behavior and Flame Structure of XM46 Liquid Propellant

Abstract

This investigation was focused on the combustion behavior of XM46. The regression rate of XM46 has been characterized up to 207 MPa, displaying a complex burning behavior with both negative pressure exponent and plateaulike behavior. The e ame structure displayed three different stages: 1 ) nearly simultaneous decomposition of both hydroxylammonium nitrate (HAN) and triethanol ammonium nitrate initiating in the liquid to produce gases around 300 ±C, 2) breakdown of heavy opaque intermediate molecules into transparent species, and 3 ) reaction of transparent species to form e nal products in the luminous e ame. The feeding tests showed peculiar e ashback phenomena, believed to be related to the interaction between gas-phase radicals and unburned liquid propellant. Pyrolysis tests of XM46 were conducted in a specially designed pyrolyzer used in conjunction with a gas chromatograph/mass spectrometer. The major pyrolysis products observed were NO, N 2O, N2, CO2, CO, H2O, HCN, and C2H4 when pyrolyzed at temperatures between 130 and 540 ± C. The pressure dependency of the burning rate of the HAN-based liquid propellant is highly nonlinear. Water evaporation has a noticeable effect on combustion characteristics of XM46. Gas dissolution/desorption could also affect the burning rate. The type of fuel ingredient was found to have a signie cant effect on the overall burning characteristics.