Research On The Rules Of Pylon Outboard Wing Extensions Suppressing On Tiltrotor Aircraft Whirl Flutter

Tiltrotor aircraft whirl flutter is one of the main reasons that limit the maximum flight speed of tiltrotor,which is the vibration divergence coupled with the aerodynamic force in the plane of rotation and the bending and twisting of the elastic wing caused by the blade waving.In the later stage,in order to increase the whirl flutter boundary and increase the maximum flight speed,the V22 wing adopts the design scheme of thick airfoil and small aspect ratio,and uses the method of increasing the wing stiffness to weaken the aeroelastic coupling between the tilting rotor and the wing.The purpose of increasing the critical speed of the front whirl flutter.The V22 sacrifices cruise efficiency and adds a significant structural weight penalty to increasing the critical speed of the whirl chatter.This paper is based on the Hamilton principle and uses the elastic wing finite element model,Full consideration of the contribution of the aerodynamic,inertial and damping forces of the outboard wing extensions to the system,established an aeroelastic coupling analysis model for tilting rotors,pylon,outboard wing extensions and wings.Through the analysis of whirl flutter stability,the critical speed and boundary velocity of the whirl flutter of the analytical model are estimated.At the same time,CFD software is used to study the air medium flow between the rotor and pylon outboard wing extensions in detail and to provide theoretical basis and guidance for the extensor wing design.Since the symmetrical modal whirl flutter occurs prior to the antisymmetric mode,this paper designs a wind tunnel experimental scaling model with half-spanned wings.The specially designed wing girder ensures a low torsional stiffness of the wing while maintaining the vertical stiffness and deflection of the wing,enabling it to achieve whirl flutter at lower wind speeds.Using the 3D printing technology to design and manufacture the pylon with different geometrical parameters,wind tunnel test was conducted to study the effect of outboard wing extensions on the suppression of whirl flutter and the influence of design parameters.The results of the study indicate that the use of pylon outboard wing extensions has the potential to suppress the whirl flutter of rotors and improve the cruising efficiency.