无轴涵道旋翼气动特性数值研究

Numerical Study on Influence of Key Parameters of Aerodynamic Characteristics of Shaftless Ducted Rotor

无轴涵道旋翼(Shaftless ducted rotor,SDR)是一种采用涵道-旋翼-电机一体化设计的新型涵道旋翼系统,其与传统涵道旋翼(Ducted rotor,DR)气动特性有较大差异。基于非结构网格的滑移网格技术,首先分析了SDR与DR气动特性差异,然后分别考察了桨盘高度、桨叶片数、涵道扩散角、中心孔径及涵道唇口半径5个关键参数对SDR气动特性的影响。研究发现:相同尺寸SDR比DR在悬停状态能够产生更大的总拉力,但其涵道拉力占比减小。前飞状态下SDR涵道后方产生较大的低速区,前行桨叶上方涡环有向内扩散趋势。桨盘高度对SDR与DR的影响机理相似。增加桨叶片数能够有效提高SDR的总拉力值,也能提高涵道拉力占比。增大涵道扩散角将导致SDR旋翼拉力系数下降。减小中心孔径能提高总拉力,但各部分拉力系数在下降。适当增加涵道唇口半径能够提高总拉力大小,超过一定值后总拉力开始下降。

Shaftless ducted rotor(SDR)is a new type of ducted rotor system designed with ducted-rotor-motor integration,which is quite different from traditional ducted rotor(DR)in aerodynamic characteristics.The sliding mesh based on unstructured grid is used to simulate the aerodynamic characteristics of SDR and DR.Then,the effects of five key parameters,namely,the rotor disk height,the number of blades,the spread angle of the duct,the central hole radius and the ducted lip radius on the aerodynamic characteristics of the SDR are investigated.It is found that the same-sized SDR produces a larger total lift than the DR in hovering,but the lift proportion of its duct is reduced.In the forward flight,a large low-speed region is generated behind the SDR duct,and the reflux vortex in blade root above the advancing blade has the trend for inward diffusion.The rotor disk height has similar effects on SDR and DR.Increasing the number of blades can effectively increase the total lift of SDR,which also increases the lift proportion of duct.Increasing the spread angle of the duct will lead to the rotor lift coefficient decrease,reducing the central hole radius can increase the total lift,but the component lift coefficient decreases.Appropriately increasing the ducted lip radius can increase the total lift,which begins to decrease after reaching a certain value.