Abstract:
Installation effects of the lateral rotors for a compound helicopter were investigated by means of unsteady CFD simulations. The helicopter featured a box-wing design for additional lift in cruise and wingtip-mounted lateral rotors in pusher configuration for additional thrust in cruise and counter-torque in hover. It was found that propeller performance installation effects for a compound helicopter are highly beneficial in cruise, while some penalties exist in extreme and specific cases in hover and autorotation. In cruise the main interaction was between the wing and lateral rotors, resulting in a propulsive efficiency increase up to 10.6% due to wingtip vortex energy recovery. In hover the main rotor slipstream resulted in a near perpendicular inflow to the lateral rotors, with a disturbance from the wings due to the deflection of the main rotor slipstream. For higher than nominal lateral rotor thrust settings, this resulted in a performance penalty. In autorotation a small power installation penalty was present due to inflow disturbances.