Numerical Investigations of the Efficiency of Circulation Control in a Compressor Stator

Airfoil active flow control has been attempted in the past in order to increase the permissible loading of boundary layers in gas turbine components. The present paper presents a stator with active flow control for a high-speed compressor using a Coanda surface near the trailing edge in order to inhibit boundary layer separation. The design intent is to reduce the number of vanes while—in order to ensure a good matching with the downstream rotor—the flow turning angle is kept constant. In a first step, numerical simulations of a linear compressor cascade with circulation control are conducted. The Coanda surface is located behind an injection slot on the airfoil suction side. Small blowing rates lead to a gain in efficiency associated with a rise in static pressure. In a second step, this result is transferred to a four-stage high-speed research compressor, where the circulation control is applied in the first stator. The design method and the first results are based on steady numerical calculations. The analysis of these results shows performance benefits of the concept. For both the cascade and the research compressor, the pressure gain and efficiency are shown as a function of blowing rate and jet power ratio. The comparison is performed based on a dimensionless efficiency, which takes into account the change in power loss.