Investigation of Spray Behavior Downstream of an Aeroengine Injector with Acoustic Excitation

DO1: 10.251411.22394 An experiment was developed to reproduce the effects on fuel spray behavior of large pressure and velocity fluctuations observed in a gas turbine with combustion instability phenomena. A spray produced by an air-blast atomizer was injected into a chamber closed on both sides by sonic nozzles. The pressure and velocity fluctuations were created by periodic modification of the downstream nozzle area using a cogged wheel. Phase-averaged techniques were used to monitor the air velocity field and spray pattern oscillations during the excitation cycle. The results revealed the existence of low Mach number traveling waves inside the chamber. Convection velocities of these waves were determined. The spray exhibited a droplet density wave formed mainly with smaller droplet sizes. An analysis based on experimental observations and numerical calculations showed that this wave has two origins. The first is linked to the atomization process and the second to the transport of droplets by the oscillating airflow. The existence of this wave plays an important role in the pressure and heat release coupling that is at the origin of the combustion instabilities.