定常吹气对倾转旋翼机向下载荷的影响

为进一步提高倾转旋翼机悬停状态下的有效载重,开展了定常吹气流动控制对向下载荷的影响研究。首先应用延迟脱体涡模拟(DDES)方法对翼型-90°迎角下非定常大范围分离流动结构进行了数值分析;然后分别开展了前缘吹气、后缘吹气降载措施研究,揭示了吹气降载的机理,并对不同吹气口位置和吹气动量系数的影响进行了定量分析,最后开展了前、后缘同时吹气作用下降载数值模拟研究。计算结果表明:前缘最佳吹气位置在翼型的前缘点,而后缘吹气最佳位置位于襟翼弦长的15%处;前缘吹气的降载效果要优于后缘吹气,而且吹气动量系数对向下载荷的影响较小;相对于初始未施加流动控制构型,阻力系数减小量可达到32.72%。

Tiltrotor download reduction using steady blowing control

Flow control using steady blowing has been computationally investigated to further increase net vertical lift of tiltrotor aircraft in hover. Firstly, a numerical study solving the Navier-Stokes equations for the unsteady massively separated flows around an airfoil section at-90°angle of attack is performed based on the SA-DDES approach. Based on the observed flow structures, flow control using synthetic jets are applied to the leading and trailing edges. The influence of jet location and nondimensional momentum coefficient are also discussed. The results indicate the optimal leading-edge jet locates directly on the leading edge, 0 percent of the chord;while the optimal trailing-edge jet locates at 15% flap chord. In general, the airfoil download is more susceptible to the leading-edge vortex than the flap trailing-edge vortex. Moreover, the influence of blowing momentum coefficient on the section drag is small. Finally, detailed computations reveal that the download can be efficiently reduced by using both the leading-edge and trailing-edge jets. Results show that a drag reduction by 32.72% is achieved with respect to the basic airfoil value without active flow control.