Combustion Characteristics of Energetic HAN/Methanol-Based Monopropellants

Abstract

The pressure dependence of burning rate for two HAN/Methanol-based liquid monopropellants is studied between 0.74 and 7.3 MPa. The less energetic formulation, HAN269MEO15, is found to exhibit different combustion characteristics above 1.21 MPa and below 1.14 MPa. Changed characteristics include a sharp increase in the burning rate, and a drastic change in the combustion behavior. HAN284MEO17 also exhibits two distinct combustion behaviors, however the transition occurs around 2.9 MPa. The appearance of a flame, a pronounced increase in the burning rate slope, and a characteristic change of the temperature-time trace of the reaction zone all indicate a change in the burning mechanism at this pressure. Surprisingly, the burning rate of the more energetic formula is lower than the less energetic one. Temperature measurements of the reaction zones of both propellants indicate that the boiling points of water and methanol play an important role in the combustion processes. Since the measured reaction zone temperatures are significantly less than calculated adiabatic flame temperatures, it is likely that the propellants are not reacting to their full potential in the near field.