Compressors with Aspirated Flow Control and Counter-Rotation

Viscous flow control via aspiration enables the design of higher work, compact, and efficient compression systems than are possible without such control. Recent progress to date on the application of this technology to single-stage compressors is first reviewed. Next, design studies are described which extend this concept to multistage compressors. From these studies a counter-rotating fan configuration was selected for detailed design. It consists of a counter-swirl-producing inlet guide vane, followed by a high speed non-aspirated rotor and a counter-rotating low speed aspirated rotor. Both rotors have full-span supersonic relative flow Mach numbers due to the counter-swirl produced by the inlet guide vane and the absence of a stator between the two rotors. The lower speed of the second rotor, while increasing the blade loading above conventional limits, delivers a more optimum balance between the shock loss and viscous boundary layer loss, which can be controlled by aspiration. Aspiration also adds the benefit of stabilizing the passage shock position, which improves the compressor performance. The design aspiration requirement for the configuration is 1% of the inlet mass flow. Aspiration is applied through a single slot on the rotor suction surface, and the aspirated flow is transported radially inward through a passage in the rotor. The tip speeds of the two rotors are 1450 and 1200 feet per second, respectively, and both rotors have nominal tip clearances of 0.5% of the tip chord. The fan is predicted to produce an overall pressure ratio of 3 at an adiabatic efficiency of 0.9. The experimental performance of the fan is to be evaluated in a short duration blowdown facility. Applications for such fans may be found in engines for multi-mission aircraft, for high-supersonic cruise aircraft, and for first stage earth-to-orbit vehicles.