Aerodynamic Interference between Main Rotor and Side Propellers of a Winged-type Compound Helicopter in Hover

Abstract

Performance changes due to aerodynamic interference between the main rotor and propeller are investigated using Computational Fluid Dynamics (CFD) for a winged high-speed compound helicopter proposed by JAXA. The study focused on hovering conditions and confirmed that the propeller exposed to the downwash and swirl of the main rotor wake tended to increase the generated thrust and propeller efficiency. On the other hand, periodic thrust fluctuations occur in the propeller and, the shift of the thrust center changes the moment arm length of side propellers, which compensates for the aircraft’s anti-torque, changing the magnitude of thrust required to maintain the aircraft’s attitude. These facts provide important insights for the future design of compound helicopters with side propellers.