报告人：Dr. Jianhua Zhang (The Pennsylvania State University)

报告时间：2019年6月19日（周三）上午10:00

报告地点：明故宫校区5号楼201报告厅

主办单位：直升机旋翼动力学国家级重点实验室、航空学院

报告题目1：Analysis of Start-up and Shutdown of Rotor in Complex Wind Conditions on Sea-based Oil Rig

报告内容简介：

A combined rotor transient responses and analysis tools/computational fluid dynamics effort was completed to assess the rotor response in a complex flowfield. A generic helicopter on a oil-rig platform was chosen because the bluff nature of the rig presents unique challenges to rotorcraft operations. The rotor start-up and shutdown simulation model was validated with the test data. Comprehensive studies of rotor transient responses under various wind directions and wind speeds were conducted to establish the safe-operation envelope. The study found that horizontal wind velocities may be accelerated by the oil-rig building corner, and cause significant rotor flap motions. The upwash and downwash flow due to the blockage of the helicopter fuselage to the crosswind had great impact on rotor transient responses, and the peak blade flap responses can be 2.5 times higher than the simulation results when the effect of airframe on air wake was ignored. The influence of unsteady air wake on rotor transient responses was also investigated, and the results showed that it could increase the blade tip deflections by 70% if the unsteady-flow components were included. The sensitivity of the rotor-blade initial azimuth positions for rotor start-up operations was also examined.

报告题目2：Autorotation Performance of Multi-Rotor Aircraft with Partial Power Loss

报告人： Dr. Jianhua Zhang (The Pennsylvania State University)

报告时间：2019年6月20日（周四）上午10:00

报告地点：明故宫校区5号楼201报告厅

报告内容简介：

Autorotation and one engine inoperative (OEI) performance of any rotary-wing aircraft is very important for safe landing or continued flight in case of engine failure. Although the initial kinetic energy stored in the main rotor is essential, a good choice of control schedule is vital to wisely use the available energy (both kinetic and potential) to achieve a successful landing or fly-away. Therefore, various studies have been conducted in the past to evaluate helicopter autorotation characteristics using optimal control techniques, This study is to extend the Army DESCENT simulation program of single main rotor to multi-rotor aircraft. The X-15 tiltrotor aircraft, CH-47 type tandem rotor helicopter, and X-2 compound helicopter with a pusher propeller are the three multi-rotor configurations studied. An analytic model has been developed and integrated with a path optimization program, which is capable of predicting the autorotational performance of multi-rotor aircraft after partial power loss. Both partial power forced landing and recovery to fly away are investigated at different initial altitude and forward speed conditions. The characteristics of optimized flight path and controls are identified and discussed for each type of aircraft. High resolution height-velocity diagrams are generated to illustrate safe flight profiles of the aircraft after partial power loss.

报告题目3：Studies of Wing Extension on Tiltrotor Whirl Flutter Stability

报告人： Dr. Jianhua Zhang (The Pennsylvania State University)

报告时间：2019年6月26日（周三）上午10:00

报告地点：明故宫校区5号楼201报告厅

报告内容简介：

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.

报告人简介：

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 1996, 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.