Research on aerodynamic characteristics of autorotating coaxial twin-rotor

In order to investigate the aerodynamic characteristics of autorotating coaxial twin-rotor,the wind-tunnel test of an autorotating coaxial twin-rotor was performed with the theorical investigation.The blade element theory is adopted to calculate aerodynamic force and moment.The aerodynamic interaction model and the dynamic inflow model were used to investigate the inflow of the autorotating coaxial twin-rotor.The comparison between experiment and calculation shows that the error is less than 5% when the rotor speed is greater than 300 r/min.Thus,the model of the aerodynamic characteristics of autorotating coaxial twin-rotor was verified.The relationship of speed and lift of the twin-rotor and the design parameters which included pitch angle,shaft angle,the distance between the upper rotor and the lower rotor,and wind speed of the wind tunnel was obtained.The aerodynamic interaction between the rotors was analyzed.The method of calculation for the thrust ratio of the upper rotor and the lower rotor was derived.