Analysis On Aerodynamic Characteristics Of Helicopter Ducted Tail Rotor Using CFD

The analysis on the ducted tail rotor's flowfield and aerodynamic characteristics is a challenging subject in the field of helicopter aerodynamics. In this thesis, a numerical simulation method is established by solving the Euler equations coupled with the momentum source model. Based on this method, the effects of different design parameters of ducted tail rotor on its flowfield and aerodynamic characteristics in hover are investigated emphatically. Then, further investigations are conducted to simulate the flowfield of ducted tail rotor at different forward-flight speed conditions. The major research work in the thesis is as follows:As the background of the current work, the domestic and overseas research results on the aerodynamic characteristics of ducted tail rotors have been introduced briefly, and it is pointed out that the CFD method based on the momentum source model is important for the research of helicopter shroud tail rotor aerodynamic characteristics.In Chapter 2, based on the Jameson finite volume method and the momentum source model which is used to consider the effect of rotor blades on its flow field, a numerical method suitable to solve the flowfield of helicopter ducted tail rotor has been developed. In the method, the far boundary model for solving rotor flow field is improved to be suitable for solving the flow field of ducted tail rotor both in hover and in forward flight.In Chapter 3, an unstructured mesh generation method around the flowfield of ducted tail rotor has been established by considering the geometry characters of ducted tail rotor and the momentum source model.In Chapter 4, the TsAGI ducted tail rotor is taken as numerical examples and the spanwise distributions of the blade section thrust and axial induced velocity are calculated. The validity of the present method is demonstrated by comparing the calculated results with available experimental data. Then, the flowfield and aerodynamic characteristics of the helicopter ducted tail rotor with different design parameter (tip gap, shroud angle of contraction, the distance of the rotor plan from the inlet, and shroud lip radii) have been investigated respectively. Based on the above investigation, some meaningful conclusions are given.In Chapter 5, applying the above model, the flowfield and aerodynamic characteristics of the ducted tail rotor in forward flight are calculated and analyzed for different advanced ratios. The preliminary relationships of the blade thrust, shroud thrust and shroud drag at different forward-flight speed conditions are obtained.