Separation Control for Rotorcraft
Final rept. 1 Sep 1998-31 Aug 2002
UNITED TECHNOLOGIES RESEARCH CENTER EAST HARTFORD CT
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Active flow control can play a significant role in improving rotorcraft performance by delaying flow separation. Retreating blade stall RBS limits rotor capability to generate lift and transmits large pitching moments to the flight control system. This project developed compact, high-power flow control actuators for RBS and evaluated them using a combination of computation and a wind tunnel test on a full scale helicopter blade section. A set of electromechanical Directed Synthetic Jet DSJ actuator modules were designed, fabricated, and installed. The actuators produced the intended unsteady momentum coefficient of 0.1 at Mach 0.4 at 260 Hz. Flow control improved airfoil steady and dynamic stall characteristics, but the improvements were not as large as desired, especially for dynamic stall at higher Mach number. Additional computations of the coupled flow fields showed that moving the DSJ exit slot further aft could increase recovery of post-stall lift, but could not further increase unsteady peak lift or stall delay at momentum coefficients less than 0.5. A 2nd generation DSJ actuator was designed and bench tested. By operating two slots, inboard and outboard of the piston, this actuator avoids back acoustic losses and can tolerate the centrifugal loads of a rotating blade.
- Flight Control and Instrumentation