Wells Turbine Stall Control Using Plasma Actuators

Abstract

Dielectric barrier discharge (DBD) plasma actuators were implemented on the leading edges of Wells turbine impeller blades for the purpose of controlling leading-edge separation, and the turbine performance was recorded. Pulse-modulated perturbations at dimensionless frequencies near unity produced remarkable increases in performance. Under massively stalled conditions, with upstream angles of attack exceeding 50°, perturbations produced spin-up and acceleration of the impeller, whereas termination of the pulsations caused the impeller to spin down to uncontrolled conditions. With pulsations active, the impeller was then allowed to accelerate and was subsequently slowed by loading the shaft. Under these loaded conditions the turbine power output exceeded that of the plasma power input by a factor of nearly 30. Given the large changes in angle of attack and reduced frequency across the span of the blades, it is astonishing that plasma actuators produce such a positive net effect. It was hypothesized that the excitation mechanism of separation control observed on airfoils and wings is also active on the rotating impeller blades. Technical challenges associated with the implementation can be overcome, rendering pulsed DBD plasma actuators a potentially game-changing technology.