Analysis of Combusting High-Pressure Monopropellant Sprays

A simplified analysis of monopropellant spray combustion was developed, based on the locally-homogeneous-flow approximation of multiphase flow theory and the thin-flame approximation of turbulent premixed flame theory. The performance of the analysis was evaluated using shadowgraphs of spray flames for a hydroxyl ammonium nitrate (HAN)-hased liquid monopropellant at ambient pressures of 6–8 MPa. Predictions showed that these spray flames are very sensitive to the degree of flow development at the injector exit, with fully-developed turbulent flows requiring significantly smaller combustion volumes than slug flows having low initial turhulence levels. There was encouraging agreement between predictions and measurements; however, uncertainties concerning injector exit conditions for the experiments precluded definitive assessment of the analysis.