Separated-flow considerations for pressure-atomized combusting monopropellant sprays

The drop and spray combustion properties of the hydroxyl-ammonium nitrate (HAN)-based monopropellant LGP 1845 were studied. Drop-burning rates were measured with drops supported in a combustion gas environment at pressures of 0.2-7.0 MPa. Some internal gasification of drops-causing swelling, partial bursting, and microexplosions-was observed throughout this region, but these disturbances decreased with increasing pressure. Effective drop-burning rates (including effects of both surface gasification and bursting) were relatively constant, ca. 10 mm/s, and were consistent with earlier strand-burning-rate measurements of gelled propellant. Pressure-atomized combusting sprays were studied in combustion gas environments at pressures of 3-9 MPa. The liquid-containing region was significantly larger than earlier measurements of Birk and Reeves,19 as well as predictions based on the locally-homogeneous-flow approximation of multiphase flow theory. In conjunction with drop-trajectory calculations, based on present measurements of drop-burning rates, these findings suggest significant effects of separated flow in combusting HAN-based monopropellant sprays.