Influences of distributed propulsion system parameters on aerodynamic characteristics of a BLI-BWB UAV

分布式动力系统参数对翼身融合布局无人机气动特性的影响

School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China

Received: 12 September 2019

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.

摘要

以耦合分布式动力系统的边界层吸入（BLI）翼身融合（BWB）布局无人机为研究对象，研究了动力系统参数对全机在巡航/起飞条件下的气动影响。使用动量源方法（MSM）对NASA涵道螺旋桨模型进行了数值计算，验证了文中数值计算方法的可靠性。采用结构网格及S-A湍流模型求解雷诺平均Navier-Stokes（RANS）方程的方法，对装配D80涵道风扇的全机构型在巡航状态下的气动特性进行了数值计算，验证了BWB布局飞行器在分布式动力系统影响下具有增升的气动效果，并与不同动力系统尺寸参数的构型进行了对比。研究了动力系统推力大小对起飞状态下全机的气动影响。研究表明，由于分布式动力系统的抽吸作用，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，使得全机的升力系数提高了16%，升阻比提高了10%；在同等推力的条件下，D80涵道风扇桨盘载荷更大，使得进出口静压较小，气流流速较大，相比于D150涵道风扇，全机升阻比提高了15%；起飞时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，具备提高起飞质量的能力。