Researches On Aerodynamic Design And Analyses On Aerodynamic Characteristics Of A Quad Tilt Rotor Aircraft

As a special type of aircraft,quad tilt rotor aircraft has the abilities of high-speed cruise as a fixedwing aircraft and the abilities of vertical taking-off and landing as a helicopter.However,with these advantages,its unique aerodynamic configuration and complex working conditions also lead to more aerodynamic interference problems such as wing download during hovering,influence of rotor slip at cruise,and adaptation different working conditions of the rotor aerodynamic design issues.In this paper,the aerodynamic characteristics under different flight states are calculated and the aerodynamic configuration is improved based on the CFD method for a quad tilt rotor aircraft.The blade shape is optimized by considering hovering and cruising efficiency.Firstly,a numerical simulation model of aerodynamic characteristics of a quad tilt rotor aircraft based on a momentum source method is established.The numerical results is given to demonstrate the effectiveness of the model in calculating the performance of the rotor and in simulating the disturbing effect of the rotor on the flow fieldThen based on this aerodynamic model,the aerodynamic interference characteristics of the quad tilt rotor aircraft in hover,forward flight and conversion states are analyzed.Analysis indicated that in the hover state,the rotor has a large download on the wing,which can effectively reduce the downward load by inclining a wing together with the nacelle.In the forward flight state,the aerodynamic interference can be effectively reduced by staggering the front wing and the rear wing,the front rotor and the rear rotor,the front rotor mainly increases drag of the front wing,the rear rotor mainly enhances the lift of the rear wing,the lift-drag ratio of the whole aircraft has decreased and the efficiency of the rotor has been improved.The interference of the rotor during the conversion has increased the lift and drag of the aircraft,and the aircraft can complete the conversion at the hover rotating speed of the rotor.Finally,based on the standard strip analysis and genetic algorithm,taking the rotor hover efficiency and cruise efficiency as the objective function and the chord length distribution and torsion of blade as the design variables,an optimized design model of tilt rotor blade profile is established.The optimized tilt rotor has an increase of 1.9% in hover efficiency and an increase of 1.5% in cruise efficiency.