报告题目：Studies of Wing Extension on Tiltrotor Whirl Flutter Stability
报告人： Dr. Jianhua Zhang (The Pennsylvania State University)
Whirl flutter stability has always been a challenge in the development of tiltrotor aircraft. To meet the stability requirement, the tiltrotor wing has to be designed with enough stiffness, which usually results a bulky and heavy wing with reduced aerodynamic performance. This study focuses on the influences of wing tip devices (wing extension and winglets) on tiltrotor whirl flutter speed. The work was first based on the XV-15 tiltrotor aircraft. The results indicated that adding a wing extension outboard of the pylon, could significantly increase the wing beam mode damping. Tuning the wing extension beam stiffness had the potential to amplify the aerodynamic damping contribution of wing extensions. Furthermore, wing torsion mode damping could also be increased due to the coupling between wing beam bending mode and torsion mode. With US Army's present interest in high speed tiltrotor technologies, NASA and Army researchers are proposing a new wind tunnel model for high speed tiltrotor research. The purpose is to replace WRATS testbed to eliminate the restrictions due to the proprietary WRATS test data. The newly developed US Army/NASA Tiltrotor aeroelastic Stability Testbed (TRAST) has been designed such that it can be used to explore new tiltrotor technologies. The wing and nacelle structural design allow a wing extension or winglet mounted on the outboard of nacelle to investigate impact of wing extension or winglet on stability and performance. The whirl flutter stability of the TRAST model has been studied. A detailed wing-pylon structure model has been implemented, and integrated with a wing extension. Sizing studies of wing extensions are conducted based on stiffness required. The integrated rotor, wing-pylon and wing extension model represents all inertia, stiffness, and load path details which provide more accurate prediction of wing mode damping of the system.
Jianhua Zhang currently is a research faculty at Rotorcraft Center, Department of Aerospace Engineering at Pennsylvania State University. He received B.E. and M.E. in Aeronautical Engineering in 1987 and 1990 from NUAA. Between 1990 and 1966, he was an aeronautical engineer at China Helicopter Corp. of AVIC. He graduated from Penn State University in 2001 with Ph.D.in Aerospace Engineering. He has more than fifteen years of extensive experience on Rotorcraft Dynamics, Aerodynamics and Aeromechanics, and has been working on many rotorcraft related projects with NASA, Army Research Lab, ONR, and rotorcraft industries. He has won NASA Group Achievement Award for his work on composite rotor blade design and analysis in NASA Heavy Lift Rotorcraft Systems Investigation in 2007.