新型桨尖抑制旋翼跨声速特性的影响分析

为研究不同形式的新型桨尖在抑制旋翼跨声速特性方面的作用,开展了多种桨尖对旋翼局部流动及气动特性影响的数值分析研究.发展了基于高效嵌套网格方法的旋翼流场高精度CFD求解方法.在此基础上,详细分析了桨尖外形对旋翼桨叶跨声速区域激波强度、激波诱导气流分离、桨尖涡尾迹及气动性能的影响.数值结果表明:桨尖的后掠和上反在缓解旋翼跨声速特性方面的作用相对较小;桨尖前掠和下反能更有效地减少桨尖外端跨声速区域,降低该位置激波强度并缓解激波-附面层干扰诱导的气流分离;后掠桨尖在减小旋翼反扭矩方面的整体效果良好,直线前掠桨尖在大桨盘拉力状态能够更有效降低旋翼扭矩(直线前掠30°时,扭矩降低达12.3%),桨尖下反可以有效抑制桨尖涡强度(抛物下反30°时,桨尖涡强度降低50%),并加快桨尖涡尾迹的耗散. 

Analyses on inhibiting of transonic characteristics of rotor with new type blade-tip

To investigate effects of different new type blade tips on transonic characteristics of helicopter rotor, numerical analyses about the impacts of blade tips on the local flow details and aerodynamic characteristics near blade-tip were carried out. A high-precision CFD method was developed with a highly-efficient embedded grid method for the simulation of the rotor flowfield. Based on these methods, the influences of shape of blade tip on the intensity of shock wave, shock-boundary layer interference, blade tip wake and aerodynamic performance of rotor were analyzed at a transonic state respectively. The numerical results indicate that backward sweep and dihedral shape of blade tip have a smaller effect on reducing the transonic characteristics of rotor, but forward sweep and anhedral shape of blade tip can effectively reduce the transonic region, the intensity of shock wave and flow separation induced by the shock-boundary layer interference. Furthermore, sweepback blade-tip has a remarkable effect in reducing rotor torque, and straight forward sweep blade-tip can effectively reduce rotor torque (12.3% reduction of rotor torque for the case of straight forward sweep 30°) at larger rotor disc loading state, and anhedral blade-tip can effectively inhibit the blade tip vortex intensity (50% reduction of vorticity magnitude of blade-tip vortex for the case of anhedral 30°) and accelerate the dissipation of blade-tip vortex wake.