동축반전 로터 간의 간격이 전진 비행하는 전기체 헬리콥터의 공력 및 소음에 미치는 영향

초록

High-speed and long-range compound helicopter utilizes a coaxial rotor as the main rotor system, eliminating the torque and the requirement for a tail rotor. The coaxial rotor system induces significant aerodynamic interaction phenomena that could affect the aerodynamic performance and the noise levels of helicopter. A distance between the upper and lower rotors, which is called inter-rotor spacing(IRS), is a crucial parameter that determines the interactional aerodynamics and acoustics. Moreover, the flight speed directly affect the evolution of the wake structure and rotor-wake interference. This study investigated the IRS effects on the aerodynamics and acoustics of the coaxial rotor in low and high speed forward flight conditions using the Spalart-Allmaras improved delayed detached eddy simulation(SA-IDDES) and Ffowcs Williams-Hawkings(FW-H) acoustic analogy based on impermeable surface method. In this study, X2TD in full configuration without the pusher propeller is used with IRS values for 1.5 and 2 times the original value. The sectional normal forces on the azimuth angle of the X2TD rotor at various advance ratios were compared with the other computational results for solver validation. As IRS increased, the additional thrust generated in low-speed flight condition was significant than that in high-speed flight condition. In both conditions, noise levels decreased.

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