Aerodynamic Performance of a Vibrating Piezoelectric Blade Under Varied Operational and Confinement States

This paper investigates the aerodynamic performance of a piezoelectrically actuated cantilever blade operating in the first mode of vibration. Bulk air-moving capability and local velocity field features have been experimentally measured for different operational conditions and blade confinement states. A testing facility has been developed to determine the pressure-flow rate characteristics of a vibrating blade and simultaneously conduct particle image velocimetry. Under high system resistance, similar to that found in densely packed electronics, flow reversal occurs at the blade outlet region analogous to stall. This is accompanied by increased local unsteadiness in the airflow being emitted. Local turbulence intensity increases by 50% between maximum flow rate and maximum efficiency operating points. The introduction of confinement around a vibrating blade reduces bulk air-moving capability significantly, with pressure rise and volumetric flow rate measured as low as 20% of what can be achieved for an unconfined blade. However, there is an accompanying change in spatial velocity distribution, which focuses the flow normal to the outlet. This has potentially beneficial uses for targeted electronics cooling applications. The findings identify the relationship between local and bulk airflow characteristics that ultimately provides information about the sensitivity of this type of air-moving device in practical installations.