涵道螺旋桨设计变量的影响及其流动机理

The ducted propeller is considered to have the advantages of high propulsion efficiency, compact structure, high safety, and low noise level, so it has high application potential in aircraft design. The influences of several important design variables on the aerodynamic characteristics and flow mechanism of the ducted propeller are explored in this paper. A typical push ducted propeller is selected for the study. The quasi-steady method based on the Reynolds Averaged Navier-Stokes (RANS) equation and the Multiple Reference Frame(MRF) is used. Both static and rotational domains are divided into structural meshes, and coupled by the surface overlapping strategy. The influences of different rotation speeds, freestream speeds, aspect ratios of the duct and duct lip deflection angles are studied. The result shows that with the increase of the rotation speed, the proportion of duct thrust to total thrust increases first and then decrease. Within a certain range of the freestream speed, the duct and the propeller show different flow characteristics at different forward speeds. With the increase of the forward speed, the total thrust first increases and then decreases, but the propulsion efficiency monotonically increases. The non-monotonic variation of thrust is mainly affected by the local working conditions of the duct and propeller parts and the separation of the duct lip and propeller parts. In the configuration with the duct, the aspect ratio of the duct has an important effect on the thrust characteristic of the propeller, and the propulsion efficiency of the ducted propeller is higher than that of the isolated propeller in the cruising condition. The outward expanding duct lip has better aerodynamic characteristics at high angle of attack, which are mainly reflected in large thrust and better stall characteristics. The differences between the ducted propeller and the isolated propeller and the interaction mechanism between the duct and propeller are also analyzed.