STUDY OF IMPROVING METHOD OF AERODYNAMIC PERFORMANCE FOR AN AIRCRAFT AT HIGH ANGLES OF ATTACK BASED ON BLOWING AND SUCTION CONTROL

Flow control is an important approach to improve the aerodynamic performance of aircraft and expand flight envelope. Previous flow control designs rarely considered actual flow conditions, leading to problems such as difficulty in implementing control methods and parameter designs. This paper proposes a control principle based on vortex disturbance that improves aerodynamic performance by regulating leading-edge vortex through blowing and suction at high angles of attack. Taking a flying-wing configuration aircraft as an example, it elaborates on how to design control parameters based on the pressure information of the flow over an uncontrolled aircraft, and further verifies the control effect and operability. First, the longitudinal aerodynamic characteristics of a low-aspect-ratio flying-wing aircraft with a sweep angle of 65° are studied, and it was found that the aircraft would experience lift stall and moment stall at an angle of attack of 38°. Second, under the guidance of the control principle based on vortex disturbance, four blowing and suction slots distributed along the leading edge of the aircraft are designed, and the control effect of applying blowing and suction at different positions of the wing is studied. Furthermore, a combined control method of blowing from the front slots and suction from the rear slots is proposed. The pressure distribution on the wing surface and the design of control parameters show that this method can blow out the gas sucked in by the suction ports through the blowing ports, thus realizing control without relying on external air source. Analysis of the control effect shows that the combined blowing and suction control can enhance the intensity and negative pressure of the leading-edge vortex while delaying vortex breakdown, thereby significantly increasing the lift coefficient in the post-stall phase, delaying the drop of the lift coefficient and pitching moment coefficient after stall, and expanding the flight envelope. In summary, the control principle and method proposed in this study are designed based on the actual flow conditions on the aircraft wing surface, which are effective, highly operable, and of great value.