悬停涵道共轴双旋翼干扰流动数值模拟

Numerical Simulation of Interaction Unsteady flows around Ducted Co-axial Rotors in Hover

采用非结构网格法对共轴式涵道双旋翼和涵道单旋翼的气动特性进行了定常Navier-Stokes(N-S)方程数值模拟对比研究和分析。将计算域分别为旋转区与静止区两个子域,涵道入口前缘形成负压区是涵道产生附加拉力的原因所在。对比计算结果表明:双旋翼及涵道间的相互干扰使得上下旋翼的拉力性能下降,上旋翼对下旋翼的干扰程度大于下旋翼对上旋翼的影响程度;桨叶总距角增加,则下洗速度大幅度增加,拉力系数增加;涵道双旋翼之间距离增加,上、下旋翼拉力系数均增大,总拉力系数增大,上、下旋翼间的干扰减弱,总拉力性能提升;随着总距角的增加,涵道双旋翼和涵道单旋翼涵道产生的附加拉力均增加,涵道附加拉力在总拉力中所占的比重有所减少;增大桨涵间隙可使涵道双旋翼增升效益降低,在设计中要尽可能减小桨涵间隙。

The complicated flows around the ducted co-axial rotors and the ducted isolated rotor were numerically simulated by steady Navier-Stokes（N-S）equations based no unstructured grid,and the aerodynamic characteristics between them were compared.The computational domain was decomposed into subzones.The lower-pressure area at the leading duct leads to the generation of additional thrust on the duct.The thrust performances of two rotors became worse because of the interaction between them,and the influence of the upper rotor on the lower rotor was greater than that of the lower rotor on the upper rotor.The downwash velocity and thrust coefficient became larger when the collective angle of blades was added.With the increase of distance between the co-axial rotors,the thrust coefficient of the upper rotor and the lower rotor increased,the total thrust coefficient increased,and the thrust performances of two rotors became better because of the interaction between them.With the increase of the collective angle of blades,the additional thrust increased which generated on the duct of ducted co-axial rotors and single rotor,the additional thrust on the duct in the total of the proportion of thrust reduced.With the increase of the distance between duct and rotor,the total thrust of ducted co-axial rotors will reduce.Hence,we should reduce the distance between duct and rotor as much as possible during the process of our design.