Dynamics of a spray formed by laminar liquid jet in modulated crossflow

Abstract

This paper deals with the study of the spray dynamics inside a turbojet engine injector in the frame work of thermo-acoustic instabilities comprehension and control. For that an experimental setup was developed at laboratory scale. It consists of a laminar water jet transversally injected into an oscillating air crossflow at ambient conditions. Phase Doppler Anemometry was used to determine the characteristics of crossflow and of the spray in terms of droplets velocity and concentration. The phase averaged technique was used to characterize the air velocity field and the spray oscillations during the excitation cycle. The results reveal the existence of velocity and concentration waves travelling behind the liquid jet. Coupling phenomena between the crossflow, the atomization of the liquid jet and the transport of droplets are observed, revealing different wave transport velocities. It was also proved that the spray dynamics is piloted either by the liquid column or by the crossflow oscillations.