Parametric Evaluation of Swirl Injector Dynamics in the High-Frequency Range

Abstract

This work augments the classical linear swirl injector dynamics theory to evaluate the hydrodynamic frequency response characteristics of a single element as an analysis aid for experimental results from cold flow testing. Specific focus is placed on how surface waves within the swirl injector are modeled. A modified formulation of wave interactions within the vortex chamber includes disturbance origins displaced from the posterior wall of the injector. Differing phase delays in both downstream and upstream directions are accounted for by dispersive calculations valid at all frequencies rather than by the traditional long wave approximation. The model is semiempirically tailored to hydraulic conditions for a study element, and a response function analysis is presented for an example case. Distinct features in the range of 2000–4000 Hz are found to be predominately related to surface wave patterns within the injector’s vortex chamber. Comparisons are made to experimental data, showing qualitative agreement with injector response and detection of computed high-frequency surface wave responses. Calculations are then mapped over steady mass flow conditions that range from 39 to 89% of the injector’s nominal design point. The results show that response features associated with surface wave dynamics consistently manifest across the entire parameter space investigated for the study injector element.