Spray characteristics of gel propellants in an open-end swirl injector

Gel propellants have both liquid and solid characteristics, giving them a broad array of application possibilities; because they are a type of power law fluid, high viscosity and difficulty in atomization have restricted their application in the aerospace field. Open-end swirl injectors can be combined with other nozzles to form gas-liquid coaxial nozzles, but at present, there are few studies on the application of gel propellants to open-end swirl injectors. A set of gel simulant spray systems was established to investigate the spray characteristics of gel propellants in an open-end swirl injector. Three types of gel simulants with different rheological parameters were used; and three open-end swirl injectors with different tangential channel diameters were designed to change the geometrical characteristic constant A of the swirl injectors associated with the injector exit radius, number of tangential inlets, radius of tangential inlets, etc. The thickness of the liquid film, and their spray characteristics in the open-end swirl injectors, were experimentally studied. The liquid film thickness of the gel propellant was measured using the conductance method. Details of the liquid film break-up and spray development were recorded with a high-speed camera. The effects of the above rheological and geometrical parameters on liquid film thickness, discharge coefficient, spray cone angle and liquid film breakup length, etc. were obtained, and the empirical equations were summarized.