Active Turbine Flow Control Using Microelectromechanical Systems (MEMS)

Sponsored by: NASA Glenn STTR Program
Team Members: University of Maryland, College Park

Efficient operation of turbine engines requires that the air is able to cleanly and smoothly flow throughout the engine. To achieve high efficiency, compressor and turbine blades are highly engineered to optimize their performance. Nonetheless, improvements in controlling the airflow around these blades can lead to significant performance improvements and costs savings. One potential technique is to include active flow control devices, such as synthetic jet actuators, on the blades.

AITHER investigated the feasibility of using MEMS (microelectromechanical systems) synthetic jet actuators to affect turbine compressor flow separation and to reduce engine noise. The product of the effort was an experimentally validated fabrication technology and associated analysis tools for active flow control using MEMS-based synthetic microjets.

During the project, AITHER and UMD manufactured and characterized MEMS-scale microjet arrays for the leading edge of the compressor blades of a turbine in order to affect the flow separation characteristics of the compressor stage(s). To help guide this and future designs, the research team developed a compressible, two-dimensional, Reynold's Averaged Navier Stokes CFD analysis to predict the performance of the microjets. Truly MEMS-scale devices were unsuccessful, but highly successful devices on the order of 1”x1”x1/8” were produced.

Particle Image Velocimetry (PIV) testing was used to experimentally evaluate the effectiveness of candidate microjet designs. Results shown below for the final synthetic jet design clearly show the presence of counter-rotating vortices, which are crucial to obtaining useful design.

With a viable microjet design validated and tested individually in static conditions, the team then conducted low-speed wind tunnel tests on a fixed-wing, 2-D airfoil. As shown below, an array of seven synthetic jets were placed along the ¼ chord of a NACA0012 symmetric airfoil section. Test results clearly demonstrated the ability of the microjets to delay the onset of stall and improve the overall performance (L/D ratio) of the airfoil.