AERODYNAMIC SURFACE OF AN AIRCRAFT

Abstract

An aerodynamic surface of an aircraft comprises a main part having a leading and a trailing edges and having an airfoil section. The aerodynamic surface also having at least two vortex generators in the form of teeth having edges along the length thereof. The teeth are mounted on the leading edge of the main part so as to be capable of generating two vortex cores on one tooth. The edges of a tooth adjoin the leading edge of the main part of the aerodynamic surface. The radius of an edge of each tooth along the length of the vortex generator is five times less than the radius of the leading edge of the main part. The main part of the aerodynamic surface has a cambered airfoil section, wherein the teeth are mounted with a deflection towards the smallest degree of curvature of the airfoil section of the main part. The invention is intended for reducing an aerodynamic drag at low angles of attack while maintaining an increased load hearing capacity of the aerodynamic surface by generating vortex cores adjoining one of the sides thereof.

Claims

1. An aerodynamic surface of an aircraft, comprising a main part having a leading edge and a trailing edge and having an airfoil section; at least two vortex generators in the form of teeth having edges along the length thereof, wherein the teeth are mounted on the leading edge of the main part so as to be capable of generating two vortex cores on one tooth, the edges of a tooth adjoin the leading edge of the main part of the aerodynamic surface, and the radius of an edge of each tooth along the length of the vortex generator is at least five times less than the radius of the leading edge of the main part, characterized in that the main part of the aerodynamic surface has a cambered airfoil section, and the teeth are mounted with a deflection towards the smallest degree of curvature of the airfoil section of the main part.

2. The aerodynamic surface according to claim 1, characterized in that a ratio of the width of the tooth base to the height thereof is from 0.8 to 3; a ratio of the width of the tooth base to the distance between the teeth is from 1.6 to 3.5; and the height of the tooth is equal to 10-45% of a local chord of the main part of the aerodynamic surface.

3. The aerodynamic surface according to claim 1, characterized in that the edges of the teeth are made sharpened by at least 50% of the length thereof.

4. The aerodynamic surface according to claim 1, characterized in that the leading edge of the main part of the aerodynamic surface is made wavy; the teeth are disposed on the protrusions of the wavy surface of the leading edge; and the maximum foil difference of the wavy surface is from one twentieth to one third of the distance between the teeth.

5. The aerodynamic surface according to claim 1, characterized in that it further comprises at least one deflectable trailing edge assembly hingedly mounted on the trailing edge of the main part of the aerodynamic surface, and at least one of the teeth is configured to be deflected relative to the main part of the aerodynamic surface and is kinematically connected to the deflectable trailing edge assembly of the aerodynamic surface so as to be capable of being synchronously deflected relative to the main part of the aerodynamic surface, providing the creation of a total aerodynamic force or moment with the simultaneous aerodynamic compensation of a hinge moment of the movable trailing edge assembly owing to the hinge moment of said at least one of the teeth that is opposite in sign.

6. The aerodynamic surface according to claim I, characterized in that the main part of the aerodynamic surface is made in the form of a leading and a trailing aerodynamic member mounted one after another, and the teeth are mounted between the leading and trailing aerodynamic members, forming trapezoidal windows tapering in the air flow direction so as to be capable of generating vortex cores adjoining the surface of the trailing aerodynamic member.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0048] FIG. 1 schematically shows a behavior of the flow around the aerodynamic surface according to the invention at a low positive angle of attack, a lateral view;

[0049] FIG. 2 schematically shows a roll damping moment formation pattern in the known aerodynamic surface, a front view;

[0050] FIG. 3 schematically shows a behavior of the flow around the known aerodynamic surface at a considerable positive angle of attack, a top view;

[0051] FIG. 4 schematically shows a behavior of the flow around the known aerodynamic surface at a considerable positive angle of attack, a lateral view;

[0052] FIG. 5 schematically shows a suction distribution on the known aerodynamic surface at a considerable positive angle of attack, a lateral view;

[0053] FIG. 6 schematically shows a suction distribution on the known aerodynamic surface at a critically high positive angle of attack, a lateral view;

[0054] FIG. 7 shows a skeleton diagram of aerodynamic force control according to a second embodiment of the invention by means of joint deflection of the tooth and deflectable trailing edge assembly, a lateral view;

[0055] FIG. 8 schematically shows a behavior of the flow around the aerodynamic surface according to a third embodiment of the invention at a considerable positive angle of attack, a top view;

[0056] FIG. 9 schematically shows a behavior of the flow around the aerodynamic surface according to the third embodiment of the invention at a considerable positive angle of attack, a lateral view.

EMBODIMENTS OF THE INVENTION

[0057] An aerodynamic surface of an aircraft according to the first embodiment of the invention shown in FIG. 1 is made in the form of a console and comprises a main part 1 having a cambered airfoil section, and having a leading edge 2, a trailing edge 3, an upper side 4, a lower side 5 and a tip 6. Vortex generators made in the form of teeth 7 having edges 8 disposed along the length of the teeth 7 are arranged on the leading edge 2. The teeth 7 are deflected towards the smallest degree of curvature of the airfoil section of the main part 1.

[0058] It is also possible to make the main part 1 with a wavy leading edge 2 (FIG. 3), which includes cyclically repeating protrusions 9 and recesses 10, wherein the teeth 7 are disposed on the protrusions 9.

[0059] An aerodynamic surface of an aircraft according to the second embodiment of the invention shown in FIG. 7 is characterized by a movable mounting of the tooth or teeth 7 and the presence of a deflectable trailing edge assembly 11, wherein the tooth 7 and the deflectable trailing edge assembly 11 are mounted on the main part 1 by means of hinges 12 and are provided with pylons 13. The pylons 13 mounted on the teeth 7 are kinematically connected to the pylons 13 of the deflectable trailing edge assembly 11 by means of at least one linkage 14, wherein the main part 1, the pylons 13 and the linkage 14 form a parallel-link motion.

[0060] An aerodynamic surface of an aircraft according to the third embodiment of the invention is characterized by the implementation of the main part 1 in the form of a leading aerodynamic member 15 and a trailing aerodynamic member 16 disposed one after another. The teeth 7 are disposed in the gap between these aerodynamic members, forming trapezoidal windows 17 tapering in the flight direction. The side walls of the trapezoidal windows are the incoming edges 8.

[0061] The aerodynamic surface of the aircraft according to the first embodiment of the invention operates as follows.

[0062] At low positive angles of attack of the main part 1 of the aerodynamic surface 15, the teeth 7, due to their deflection towards the smallest degree of curvature of the airfoil section of the main part 1, are strictly streamwise and have a near-zero angle of attack (see FIG. 1), which reduces a drag and increases a lift over drag ratio, which is especially important with the laminar foil of the main part 1, the foil having a C.sub.ymax shifted backwards. Furthermore, at near-zero angles of attack, the drag of the aerodynamic surface is further reduced owing to the disposition of the points of the edges 8 of the teeth 7 adjoining the leading edge 2 of the main part 1 in the stagnation zone of the flow 18 and owing to the sharpening of the edges 8 of the teeth 7.

[0063] In addition, the drag can be further reduced owing to the wavy foil of the leading edge 2, which reduces the flow deceleration in the area where the edge 8 adjoins the leading edge 2.

[0064] When the aerodynamic surface reaches high positive angles of attack, the pressure drop at the edges 8 creates conditions for the generation of vortex cores, the stability of which is increased with an increase in the Reynolds number, wherein the incoming flow energy spent for the generation of vortices is partially imparted to the boundary layer on the upper side 4 of the main part 1, which raises a C.sub.y of the aerodynamic surface and increases an crit. (see FIGS. 3 and 4).

[0065] In this case, a fraction of the vortex energy that has not been spent for maintaining the energy of the boundary layer and being lost during the shedding of the vortices from the upper side 4 of the main part 1 will be the greater, the greater the ratio of the height and the width of the tooth base 7 to the local chord of the main part 1 is, which determines the direction of optimization of this technical solution.

[0066] In experiments on models of aerodynamic surfaces, an crit. for a wing having a relative height of the teeth of 5-25% of the local chord of the main part 1 has ranged from 35 to 40 degrees with a relative thickness of the foil of the main part 1 equal to 12% with an expressed backward movement of the center of pressure as the angle of attack is increased, which allows preliminary asserting the applicability of the proposed aerodynamic surface for use, for example, for the tail rotors of helicopters, whose operation often takes place under conditions of a small stall margin due to the summation of the control and compensating moments produced by the antitorque rotor.

[0067] In this case, the backward movement of the center of pressure in the aerodynamic surface according to the invention is achieved due to the fact that as the angle of attack a is increased, the main part of the vortex suction increment falls at the middle and rear thirds of the upper side 4 of the main part 1, which compensates for the forward pressure redistribution on the lower side 5 of the main part 1 (see FIGS. 5 and 6).

[0068] The operation of the aerodynamic surface having a wavy leading edge 2, in the vortex generation mode, is characterized by a smaller C.sub.x at high angles of attack due to the lower drag occurring when the vortex-type flow passes from the edge 8 to the upper side 4 of the main part 1, since the mounting of the teeth 7 on the protrusions 9 gives a local sweep angle to the leading edge 2 at the point of adjoining the edge 8.

[0069] The operation of the aerodynamic surface according to the second embodiment of the invention, the surface provided with the tooth 7 mounted on the hinge 12 and kinematically connected to the deflectable trailing edge assembly 11 by means of the linkage 14 and the pylons 13, is characterized by the possibility of highly efficient control over the aerodynamic force created by such surface, since, simultaneously with subtracting the hinge moments of the deflectable trailing edge assembly 11 and the tooth 7, which is equivalent to a conventional horn balance of the flight control surface, the control moments produced by the deflectable trailing edge assembly 11 and the tooth 7 are added to the vortex aerodynamic force generated on the main part 1 by the vortices generated by the tooth 7, which increases a gain of a control system (see FIG. 7).

[0070] The operation of the aerodynamic surface according to the third embodiment of the invention, the main part of which is made in the form of leading and trailing aerodynamic members 15 and 16, is characterized in that the absence of a vortex-lift increment on the leading aerodynamic member 15 additionally increases the marginal angle-of-attack stability of the aircraft. Furthermore, when using such aerodynamic surface as a wing and a horizontal empennage, the probability of injuring people due to an accidental contact with the sharpened edges 8 is reduced (see FIGS. 8 and 9).

[0071] Thus, owing to the structural changes introduced into the known design of the aerodynamic surface having teeth on the leading edge, the following problems have been successfully solved: [0072] reducing a drag at low angles of attack; [0073] improving a resistance and sensitivity of an aircraft as well as increasing a gain in a control system of the aircraft; [0074] reducing an injury risk; [0075] improving an angle-of-attack stability.

[0076] Furthermore, owing to an increase in the energy of the boundary layer near the trailing edge, a forward movement of the center of pressure with an increase in an angle of attack has been excluded, which has improved the angle-of-attack and rate stability of the aircraft.