桨尖后掠对旋翼流场和气动特性的影响

摘要

推导了后掠桨尖剖面法向马赫数和等效迎角与矩形桨尖的关系,指出前飞状态下旋翼后掠桨尖上的法向来流并不一定总比矩形桨叶小的新结论,进一步得出了在后掠桨尖上出现较大法向来流马赫数的解析区间,并给出了克服这种情况出现的解决办法；提出了保持前缘法向来流速度为常数的桨尖设计方案.然后,采用CFD方法,针对后掠新型桨尖旋翼的悬停和前飞跨声速流场进行了数值模拟,并结合理论分析的结果,深入地分析了桨叶后掠对旋翼流场、气动特性的影响,得出了后掠桨尖流场的细节特征,尤其是桨尖附近的激波位置、范围和强度的变化规律.%The relationships between the section normal mach number and the equivalent angle of attack of the rotor with a swept tip and the mach number and angle of attack of the rotor with a rectangular tip are derived, and a new conclusion that the normal incoming flow on a swept blade tip are not always less than that on a rectangular tip in forward flight is presented and proved. As a result, an analytic az-imuthal interval where the normal incoming mach number on a swept tip is bigger than that on a rectangular tip is given. On the contrary, in order to avoid the emergence of the analytic azimuthal interval, a sweepback angle distribute regulation is presented. A design program of the rotor with a curvilinear swept tip for keeping the velocity of leading-edge normal incoming flow constant is raised. Then, numerical simulations of transonic flowfield for a helicopter rotor -with a swept tip in both hover and forward flight are performed by using CFD. Based upon the theoretical analysis results and numerical simulated results, the effects of a swept blade tip on the flowfield and aerodynamic characteristic of the rotor, especially the changing of shock wave location, scope and strength nearby the blade tip are analyzed thoroughly.