EFFECT OF AIR INJECTION CONFIGURATION ON THE ATOMIZATION OF GELLED JET A1 FUEL IN AN AIR-ASSIST INTERNALLY MIXED ATOMIZER

Gel propellants are difficult to atomize due to their high viscosity and non-Newtonian, shear-thinning behavior, especially at low gas-to-liquid mass ratio (GLR). Low GLR is prerequisite for volume-limited propulsion systems. The present study explores the possibility of atomizing viscous gel propellant, using the conventional design of an air-assist internally mixed atomizer and offers comparison with a new atomizer design in which the air injection configuration is altered. Spray visualization reveals that the conventional atomizer does not produce a well-atomized spray within the given envelope of operating conditions and the spray is characterized by the presence of unatomized gel jet at the nozzle exit. However, due to its ability to provide large shearing force, the modified design promotes complete atomization of gelled fuel. The shearing effect of air in the modified atomizer configuration is more suitable for providing a well-atomized spray for highly viscous non-Newtonian fluids. Effects of GLR and gellant concentration on spray characteristics are examined in the modified atomizer configuration. Droplet size measurements show that the smallest mean droplet size is achieved at very low GLR and high gellant concentration does not significantly affect the Sauter mean diameter.