ACTIVE FLOW CONTROL TECHNIQUES ON A STATOR COMPRESSOR CASCADE: A COMPARISON BETWEEN SYNTHETIC JET AND PLASMA ACTUATORS

In this work it is applied a CFD analysis to study the suppression of the boundary layer separation in to a highly - loaded subsonic compressor stator cascade, by active flow control techniques, as zero net mass flux Synthetic Jet (SJA) actuation and Plasma actuation. Active flow control techniques have the potential to delay separation and to increase the pressure ratio. Several works have investigated the use of synthetic jet and plasma actuators on the airfoil, but only few studies have compared the effect of these two devices. Concerning the synthetic jet actuator, a suction/blowing type boundary condition is used, imposing a prescribed sinusoidal velocity depending on velocity amplitude, jet frequency and jet angle of ejection with respect to the wall. Concerning the plasma actuation, the effect is modeled into numerical flow solvers by adding the paraelectric force that represents the plasma force into the momentum equation. The plasma, generated by Dielectric Barrier Discharge, acts as a momentum source to the boundary layer allowing it to remain attached throughout a larger portion of the airfoil. The timeaveraged body force component, acting on the fluid, depends on the frequency and on the applied voltage, the charge density, the electrical field and the dimensional properties of the actuator, like width of the electrodes and gap between the electrodes. Using this numerical model, the effect of plasma actuators to suppress the flow separation over the blade has been investigated, increasing the turbo-machinery performance too. Finally, the comparison between these two devices shows that, reducing the secondary flow structures, both actuation techniques beneficially affect the performance of the stator compressor cascade, even if in the steady jet the costs are relevant.