Gelled propellants behave as non-Newtonian fluids and are promising for future aerospace application because they combine the advantages of solid propellants with those of liquid propellants. Spray formation of gel simulants from swirl injectors was described by carrying out experiments in a spray test facility. A high speed camera was used to record detailed information about the liquid sheet breakup process and spray development. The experiments were performed with injectors of different configurations to test the effect of injector geometry on spray characteristics. Spray patterns were identified and their characteristic features were presented. The spray patterns identified for the gel investigated are swirling jet, twisted ribbon, fluid web and fully developed hollow cone. The fully developed spray field can be divided into four parts: the intact conical liquid sheet, coexistence of liquid sheet and ligaments, turbulent weblike ligaments and coexistence of ligaments and droplets. Regarding the effect of injector geometry, increasing the injector geometry characteristics constant always tends to increase the breakup length of the conical liquid sheet, and decrease the discharge coefficient (except when the geometry characteristics constants of two injectors are close, other flow parameters have greater influence on the flow characteristics than injector geometry characteristics constant). The spray cone angle generally increases as the geometry characteristics constant increases. However, it was difficult to measure the spray cone angle accurately because under some conditions the spray cone pulsates. The pulsation frequency increases as the pressure drop increases, and it decreases as the geometry characteristics constant increases. (C) 2012 Elsevier Ltd. All rights reserved.