IntroductionĬoaxial rigid rotor helicopters with auxiliary propulsion are able to attain better performance at high forward speed compared with conventional single-rotor helicopters. The optimized coaxial rotor increases lift-to-drag ratio by 30% under the design conditions. A kind of blade planform combining swept-back tapered tip and nonlinear chord distribution was optimized to improve the rotor efficiency for a given high-speed level flight based on geometric parameter studies. Results show that swept-back tip could reduce the advancing side compressibility drag and elliptic shape of blade planform could optimize the airload distribution at high advance ratio flights. Then, the influence of geometrical parameters of the coaxial rigid rotor on forward performance was investigated. Shock-induced separation occurs at the advancing side blade tip and severe reverse flow occurs at the retreating side blade root. Firstly, the forward flow field characteristics of the coaxial rotor were analyzed. The aerodynamic performance analysis and blade planform design of a coaxial rigid rotor in forward flight were carried out utilizing CFD solver CLORNS.
