Aerodynamic Interaction Analysis And Wing Optimization Of Tiltrotor Aircraft

Tiltrotor aircraft creatively combines the excellent performance of helicopter and fixed-wing aircraft,which is one of the promising directions of future air transport.However,the strong aerodynamic interference of the rotor/wing in the hover state restricts the load-carrying capacity,and the concept of tiltwing has been clearly proposed in foreign studies.In view of the current common aerodynamic layout of tiltrotor aircraft,in order to further explore the download reduction effect of tiltwing layout and the influence of rotor on aerodynamic performance of the wing,a comparative study on the aerodynamic interference characteristics and the force acting on the wing of two layouts in hover and transition states is carried out.As the core component of aircraft,wing design largely determines the performance of aircraft.Aerodynamic optimization design of wing is of great significance to improve the flight performance of tiltrotor aircraft.The main work of this paper is divided into two parts: one is the analysis of aerodynamic interaction between rotor and wing;the other is the optimization of wing.Based on embedded grid and momentum source method,the interaction flow fields of tiltrotor layout and tiltwing layout in hover and transition states are numerically simulated,and the interaction flow fields and the wing aerodynamic forces of the two layouts were compared,and characteristics of the rotor interaction on the wing in different states is analyzed.The results indicate that when tiltwing layout is adopted,the downward load of the wing in hovering state is about 1% of the thrust of the rotor,and the aerodynamic interaction between the rotor and the wing is reduced.The interaction airflow is not enough to form a "fountain effect" on the symmetrical plane.In the transition state,the tiltrotor layout is affected by the downwash flow of the rotor,and the wing will generate downward loads;when the tiltwing layout is adopted,the lift of the wing is greater than its tiltrotor layout counterpart,which improves the lift performance of the wing,but the drag is also greater.In order to improve lift/drag of the tiltrotor aircraft in forward flight mode,the airfoil is optimized according to the flow velocity in front of the wing.Using NACA2412 as the original airfoil.Firstly,the airfoil parameterization is carried out by Hicks-Henne method and the design variables are determined;Isight which integrated airfoilgeneration,mesh generation and flow field solver are used to build airfoil automatic optimization platform.Then,in order to improve the efficiency of optimization,a surrogate model based on Optimal Latin Hypercube Design(Opt LHD)and Radial Basis Function(RBF)are adopted,and multi-island genetic algorithm(MIGA)is used to optimize the airfoil.Finally,the optimized airfoil is used to generate wing and the aerodynamic characteristics are calculated.In order to illustrate the effectiveness of the optimization method used in this paper,two optimization results are compared according to the different boundary conditions.In order to reduce the computational complexity,the rotor is replaced by actuator disk with the use of momentum source method.The results show that the lift/drag of the wing is increased by 66.03% in the forward flight mode.