Studies on increasing the aerodynamic lift performance of a laminar wing with a Kruger flap

DOI: 10.34759/vst-2023-2-17-23

Аuthors

Kurilov V. B.

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

Abstract

Airframe elements laminarization is considered to be one of the further aviation development paths. Airframe elements laminar flow can be provided passively (by Natural Flow Laminarization, NFL), as well as by means of boundary layer suction through the perforated aircraft skin. The NFL utilization proves to be rational as small regional aviation regards. A regional aircraft with its wing to be laminar and its engines to be arranged over the upper surface of the wing trailing edge is one of the most promising layouts for the NFL positive effects to be realized and for the engine noise to be shielded by airframe elements. This paper presents experimental studies which were conducted on a laminar wing supplied with Krueger flap and for the wing lift performance to be improved.

The large-scale semi-span model of a regional aircraft with a small-swept wing in landing configuration was tested in TsAGI T‑128 wind tunnel in the wide range of the Reynolds number. The Krueger flap had eight different root inserts which covered a gap between the flap root and the fuselage; and the fuselage had one vortex generator.

The test results revealed that the root inserts & vortex generator application leads to flow separation diminishing in the wing root region, flow pattern improving and the layout lift performance increasing. The root inserts proved to be more efficient than the vortex generator, and the most effective of the former ones significantly augmented the magnitude of stalling incidence, reduced C_D and increased the maximum lift of the layout by ΔС_Lmax = 0.21. With this Krueger flap root insert being applied to the layout configuration the resulting lift magnitude (ΔС_Lmax = 2.78) proved to be not worse than the ones achieved on layouts with a common slat, though a Krueger flap used as high-lift device for wing leading edge is characterized by its lower efficiency.

Keywords:

laminar wing aircraft, Kruger Flap, Kruger Flap insert, vortex generator, separation in the wing root region

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