内外流耦合对分布式涵道风扇影响的机理

内外流耦合效应对分布式涵道风扇的气动性能有显著影响。为了进一步揭示分布式涵道风扇部件在爬升、巡航过程中内外流耦合效应对气动性能和流动机理的影响规律,通过三维RANS(Reynolds-averaged Navier-Stokes)数值、试验方法对该问题进行详细探讨。结果表明:不同飞行状态中转子叶片和唇口壁面对风扇推力影响显著。随着无量纲质量流量率的提高,转子进气方向由负迎角往正迎角改变,推力系数增加。爬升时存在最佳进气迎角,气动效率最高。巡航状态的唇口摩擦阻力最小,推进效率最高。过大或过小的无量纲质量流量率会使得唇口的摩擦阻力和压差阻力增大,从而降低推进效率。 

Mechanism of internal/external flow coupling effects on the performance of distributed ducted fan

The coupling effects of internal/external flow has a significant impact on the aerodynamic performance of the distributed ducted fan.In order to further reveal the aerodynamic performance and mechanism of the internal/external flow coupling effect during the climbing and cruising of the distributed ducted fan, this problem was discussed in detail through three-dimensional RANS (Reynolds-averaged Navier-Stokes) numerical simulation and experimental methods. Results showed that the rotor blades and lip affected the thrust significantly in different flight conditions. With the increase of dimensionless mass flow rate, the rotor inlet flow direction changed from negative angle of attack to positive angle of attack, and the thrust coefficient increased. There was an optimal air angle of attack, resulting in highest aerodynamic efficiency in the climbing condition. At cruising condition state, the lip friction resistance was the least and the propulsion efficiency was the highest. Either larger or smaller dimensionless mass flow rate could increase the frictional resistance and differential pressure resistance of the lip wall, thereby reducing the propulsive efficiency.