Abstract
Focusing on the aerodynamic characteristics of the blended wing body (BWB) aircraft with boundary layer ingestion(BLI) distributed propulsion system; the influences of propulsion system parameters under the condition of cruise and takeoff are studied. Firstly, based on the momentum source method (MSM), the NASA ducted propeller model is simulated, which verifies the reliability of the numerical method in this paper. Then, by using the method of structural grid and S-A turbulence model to solve the Reynolds averaged Navier-Stokes (RANS) equation, the aerodynamic characteristics of the BLI UAV model with D80 ducted fan in cruise state are numerically calculated. It is proved that the advantage of the BLI distributed propulsion system is superior in increasing lift. And the aerodynamic characteristics of the BLI UAV with different propulsion system parameters are compared. At last, the aerodynamic effect of ducted fan thrust on the BLI UAV is carried out. The results show that, due to the suction function of the BLI distributed propulsion system, the air flow velocity near the BWB fuselage is effectively accelerated, and the flow along the spanwise is restrained, which improves the lift coefficient about 16% and lift-to-drag ratio about 10%. Under the condition of equal thrust, the D80 ducted fan brings larger load of the propeller, which makes the static pressure at the inlet and outlet smaller. Compared with D150 ducted fan, the lift-to-drag ratio is increased by 15%. When aircraft takes off, increasing the thrust of the ducted fan can reduce the possibility of flow separation on the upper surface of the fuselage, which is conducive to the safety.
Highlights
Based on the momentum source method ( MSM), the NASA ducted propeller model is simulated, which verifies the reliability of the numerical method in this paper
It is proved that the advantage of the BLI distributed propulsion system is superior in increasing lift
The results show that, due to the suction function of the BLI distributed propulsion system, the air flow velocity near the BWB fuselage is effectively acceler⁃ ated, and the flow along the spanwise is restrained, which improves the lift coefficient about 16% and lift⁃to⁃drag ratio about 10%
Summary
通过 WPN / TFN 2 种构型的对比,可以看到 BLI 翼身融合布局在分布式动力系统影响下具有一定的 增升优势,中心体的气动特性有所改善。 下面研究 不同动力系统尺寸参数对全机气动特性的影响。 本文针对耦合分布式动力系统的 BWB 布局无 人机动力系统参数为研究对象,首先研究了 WPN / TFN 全机构型气动特性的差异,然后在动力系统同 等推力的前提下,通过对巡航状态下全机的气动特 性研究,探究了动力系统尺寸参数对全机的影响,最 后研究了起飞状态下动力系统推力参数对全机起飞 性能的影响,得到以下结论: 1) BWB 布局飞行器在分布式动力系统的作用 下具有良好的气动特性,相比于 TFN 构型,WPN 构 型有效提高了机身附近的流速,同时一定程度上抑 制了气 流的展向流动, 全机的升力系数提高了约 16%,升阻比提高了约 10%; 2) 动力系统尺寸参数对全机的气动影响主要 体现在涵道风扇桨盘载荷的差异,其尺寸越小,桨盘 载荷越大,进出口静压越小,引起流速、进出口速度 差越大;对全机气动特性来说,涵道风扇尺寸越小, 全机压差阻力越小。 相比于 D150 构型,D80 构型的 升阻比达到 11,提高了约 15%; 3) 起飞时全机迎角较大而速度较小,动力大小 成为影响全机气动特性的关键因素。 增大动力系统 推力可以降低机身上表面气流分离的可能性,全机 升力进一步增大,具备提高起飞质量的能力,同时阻 力随着前后压差的增大而增大。
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