Experimental Study Swirl Injector Dynamic Response Using a Hydromechanical Pulsator

Abstract

The dynamic response of a classical (simplex style) swirl injector has been studied experimentally using a superscale transparent model with water as the working fluid. A unique mechanism was developed for imparting controlled perturbations to the injector inlet mass flow by successively blocking and opening tangential inlet flow passages using a rotating cap over the inlet ports. Two vortex chamber designs (long and short) were evaluated to assess the effect of this important design variable. High-speed imaging of the spray cone and air core/liquid interface inside the vortex chamber was used to assess dynamic behavior at frequencies up to 500 Hz. Resonant conditions were detected in both designs, and bothmeasurements gave similar frequencies for the resonant peak. The resonant peak was compared against recent theory due to Ismailov and Heister (“Dynamic Response of Rocket Swirl Injectors, Part I: Wave Reflection and Resonance,” Journal of Propulsion and Power, Vol. 27, No. 2, 2011, pp. 402– 411), and results compare well only when the theory is adjusted to account for potential water hammer effects induced by the rotating cap.