剪刀式尾桨涡流干扰机理和气动特性研究

采用非常规剪刀式尾桨对直升机整体性能有着重要影响,关于其复杂流动干扰机理的研究尚处在发展之中.为了掌握剪刀式尾桨的流动干扰机理和参数影响规律,建立了适合于悬停状态下剪刀式尾桨干扰涡流场分析的计算流体力学(computational fluid dynamics,CFD)数值模拟方法.采用积分形式的Reynolds-averaged Navier-Stokes(RANS)方程作为旋翼流场求解控制方程,围绕旋翼流场的结构网格采用嵌套网格方法生成.在CFD方法验证基础之上,对悬停状态下两种不同构型剪刀式尾桨桨尖涡的涡核位置和强度的演变规律进行了定量分析,并对流场中桨尖涡与桨叶的贴近干扰、碰撞、破碎运动,同时准确捕捉了不同尺度涡之间的相互干扰、融合的过程进行了分析.进一步研究了剪刀角和轴间距参数对不同构型剪刀式尾桨气动特性的影响规律.计算结果表明,剪刀式尾桨流场中存在复杂的桨-涡干扰和涡-涡干扰现象,剪刀角和轴间距对剪刀式尾桨的气动特性有重要影响,L构型剪刀式尾桨气动性能整体优于U构型剪刀式尾桨.

STUDIES ON VORTEX INTERACTION MECHANISM AND AERODYNAMIC CHARACTERISTIC OF SCISSORS TAIL ROTOR

The design of the unconventional scissors tail rotor has a powerful influence on the overall aerodynamic performance of helicopter, and the aerodynamic interaction mechanism of the unconventional tail rotor has been inves-tigated due to its complexity. To get the interaction mechanism and aerodynamic characteristic of scissors tail rotor, a numerical method based on computational fluid dynamics (CFD) technique is established to simulate the vortex flowfield of scissors tail rotor in hover. Based on the embedded grid system, a CFD simulation method is developed by solving the compressible Reynolds-averaged Navier-Stokes (RANS) equations. Based on the validation of the CFD method, the evolution laws of position and strength of blade-tip vortex for two different scissors tail rotors are obtained by quantitative analysis in hover. Thus, close vortex-surface interactions, impingement and burst motions in the process of blade-vortex interaction are analyzed in detail, also the interaction and mergence process among the different scales vortex has been captured accurately. Furthermore, the influences of the two configuration parameters (scissors angle and vertical space) on their aerodynamic characteristics have been analyzed in hover. The simulated results demonstrate that the flowfield of the scissors tail rotor is very complicated due to various blade-vortex and vortex-vortex interaction. In addition, the configuration parameters of scissors tail rotor have important effects on its aerodynamic characteristics, and configuration L shows more advantages of improving the aerodynamic performance than configuration U has.