RU2495787C1 - Aircraft wing tip - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to aircraft engineering. Aircraft wing tip has root profile with S-shape mid line and section of negative concavity of length making 20-70% of the chord. Tip curved and end profiles feature positive concavity. Wing tip has bulge at root section and bend in leading edge.

EFFECT: better aerodynamics.

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Description

The present invention relates to aircraft and can be used on civilian aircraft with subsonic and transonic speeds.

It is known that the installation of wingtips is one of the means to increase the aerodynamic quality of an aircraft. The use of endings leads to a weakening of the intensity of the end vortices, an increase in the effective elongation of the wing, and a corresponding decrease in the inductive drag.

Known wingtip installed in the wing plane and having a step along the leading edge (RF Patent No. 2063365. Cl. B64C 3/10, 1993). The aerodynamic quality loss of the aircraft in this technical solution is reduced by creating additional suction force at the leading edge of the ledge streamlined by the end vortex.

However, on the swept wing, at high transonic speeds of flight, the loss of aerodynamic quality becomes significant, and such a tip becomes ineffective.

Known wingtips in the form of end "wings" (Zhitomirsky GI Aircraft Design. - M. Engineering 1991, p.94, Fig.2.68), which through the use of bevels on the outside of the end vortices reduce the loss of aerodynamic quality the plane.

However, such devices are complex in shape, have large dimensions and weight, require an increase in the stiffness of the wing, which leads to a heavy structure.

A prototype of the proposed technical solution is the wingtip made with profiles increased in curvature and twist angles compared to the wing, while the end edge of the tip before the ledge is made sharp, smoothly turning into the blunt front edge of the tip behind the ledge, and the line of maximum thicknesses of the suprachordinal part of the ending profiles for the ledge is shifted back along the upper contour and is located in the range (60-80)% of the local ending chord. (RF patent No. 2086467, class B64C 3/10, 08/10/1997).

As the disadvantages of the prototype, you can specify the occurrence of an early stall of the flow from the tail end of the tip from the excessive diffusivity of the descent of the profiles on the upper surface, as a result of which, only a slight positive effect was obtained.

The objective and technical result of the invention is the creation of a wingtip providing a continuous flow around the tip, an increase in the effective elongation of the wing and a decrease in drag of the wing and the aircraft as a whole and, as a result, an increase in the aerodynamic quality of the aircraft both at subsonic and near-sonic flight speeds.

The solution of the problem and the technical result are achieved by the fact that the wing tip of the aircraft, made with profiles increased in comparison with the wing curvature, has a root profile made with an S-shaped middle line and a section of negative concavity with a length of 20-70% of the chord, kink and end profiles of the tip made with positive concavity, the tip has an influx in the root part and a kink along the leading edge.

Figure 1 shows a diagram of the wingtip in the plan;

figure 2 presents a flow diagram of the proposed ending and prototype (top view, section AA);

figure 3 presents the middle line of the root profile of the ending,

figure 4 presents the flow diagram of the proposed ending (view in plan);

figure 5 distribution of pressure at the tip;

figure 6 presents a picture of isobars and surface streamlines;

Fig.7 shows the experimental dependence of the increase in maximum aerodynamic quality of the model of the aircraft in speed for ending the prototype and the proposed ending.

The wing of the aircraft 1 has a tip 2, made of complex shape with a kink 3 along the front edge 4, an influx in its root part 5 of FIG. 1, the tip profiles increased in comparison with the wing of curvature 6, (FIG. 2). The root profile of the ending has an S-shaped middle line with a section of negative concavity 7 (Fig. 3), the kink and end profiles are made with positive concavity, providing an inseparable descent of stream 8 instead of disruption from the tail portion 10 of stream 9 in the prototype. The first vortex 11 (figure 4), causing the bevels of the flow from the outside to kink 3, as well as vortices 12 (figure 4), the suction of the stream 13 from the end part of the wing 14, arising from the vortex 11.

According to figure 4, the device operates as follows. When flowing around the wing, a vortex 11 is formed in its end part, which, prior to kink 3, causes a favorable upward bevel on the outside of kink 3. This creates an additional suction force at the leading edge of the wing tip 4, and the passage of the vortex 11 above the upper surface of the wing creates a suction flow 13 and additional discharge. The efficiency of the suction flow 13 is enhanced by the appearance of vortices 12, escaping from the upper edge 15 of the tail portion 10 of the tip 2.

In addition, the use of the root profile of the tip having an S-shaped midline with a negative concavity section of 20-70% chord length reduces the relative thickness of the tip. This allows you to delay the occurrence of supersonic zones and provide continuous flow past the tip (Fig.5, 6) to high flight speeds M = 0.82. As a result, the invention can be used at transonic flight speeds.

Research was carried out in a wind tunnel on a model of an airplane with a large elongation wing. The test results showed that the proposed ending in comparison with the prototype allows to increase the maximum aerodynamic quality at both low and transonic speeds. At a flow rate corresponding to the number M = 0.7-0.84, the transition from the tip - the prototype to the proposed one made it possible to increase the maximum aerodynamic quality of the model by ΔKmakh≈0.2 ÷ 0.6 (Fig. 7).

The installation of the tip allowed eliminating the adverse effects caused by the end vortex on the flow around the end part of the wing.

Using the proposed invention will reduce the resistance of the wing and the aircraft as a whole and, as a result, increase the aerodynamic quality of the aircraft both at subsonic and transonic speeds, which will allow significant savings in aviation fuel.

Claims (1)

The wingtip of the aircraft, made with profiles increased in curvature compared to the wing, characterized in that the root profile of the tip is made with an S-shaped middle line and a section of negative concavity with a length of 20-70% of the chord, the kink and end profiles of the tip are made with positive concavity, the tip has an influx in the root part and a kink along the leading edge.

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