Injection of micro jets to improve hydrodynamic performance of a ducted propeller

Abstract

In this study, micro jets were applied to actively controlling the flow of the international standard ducted propeller model. The detached-eddy simulation (DES) method with the shear stress transport (SST) k‐ω turbulence model was adopted for numerical simulation. Three ways of installing injectors and three jet flow velocities were considered. It was found that for all installation ways, injecting the jets improves the hydrodynamic efficiency when the jets are set at the two lower velocities. The maximum improvement of 3.8% was obtained from the two-injector installation with the medium jet velocity that is two times the freestream velocity. The micro jets disturb vortices developed from the blade tips and hub, and the disturbance aggregates the breakdown of these vortices. The micro jets trigger additional vortices at the duct leading edge, which become secondary vortices aside the helical blade-tip vortices. This effect was also found for the baseline model, but it is much weaker. The angle of attack of the blade is changed accordingly, which leads to the increasing of both thrust and torque. However, the hydrodynamic efficiency is increased, since the power consumed by the torque increment is smaller than that for the thrust increment.