Endwall Flow Control in Stator Blade Rows

Advances in rotor and fan blade design have produced compressors that generate greater compression ratios with higher efficiencies using fewer stages. A direct result of designing more compact compressors with higher pressure ratios is a more adverse pressure gradient which causes flow separation on the endwalls of both the rotor and stator passageways. Consequently, the performance potential of the compressor is not reached. Technology in Blacksburg is proposing the use of engine casing and hub flow control in the stator blade rows to increase stator performance and efficiency while simultaneously reducing the length and thus overall weight of the engine. Flow control is achieved with miniature ejector pumps, integrally machined into the hub and casing. Ejector pumps provide a simple and efficient way of simultaneously producing suction and a high momentum jet for flow control. Low momentum fluid in boundary layer of the endwalls is removed with suction. The fluid is then re-energized by the ejector pump and injected into the flow as a high momentum jet flowing tangent to the endwall. In this way, the boundary layer along the wall is provided with the energy necessary to remain attached in an adverse pressure gradient.