Effect of Acoustic Excitation of Gas Flow in a Gas-Centered Swirl Coaxial Injector

Abstract

We investigate experimentally the effect of periodic perturbations on the gas flow and assess the possible coupling between the chamber acoustics and the atomization process in a recessed gas-centered swirl coaxial (GCSC) injector by studying the liquid sheet breakup dynamics. Experiments are conducted using water and air, and acoustic perturbations are introduced to the gas flow line using a speaker. High-speed imaging is used for flow diagnostics. The steady spray is observed to transform into a pulsating spray by the acoustic excitation of the gas flow. This pulsating spray resulting from the gas flow perturbations occurs at much lower MFR where the self-pulsation of spray is otherwise not observed without acoustic forcing. The characterization of spray pulsation frequency shows that it matches well with the acoustic frequency. The pulsation effect is more severe with an increase in the MFR. It is further noted that the periodic pulsation of spray exists up to a certain excitation frequency of the gas flow, and beyond this frequency, the dominant pulsation frequency disappears. The atomization process is further quantified in terms of the waviness of the liquid sheet (tortuosity) and the spray turnback angle, which show significant changes in the presence of acoustic excitation.