CN110920870A

CN110920870A - Method for restraining rock motion of sharp-edge fuselage layout through leading edge flap

Info

Publication number: CN110920870A
Application number: CN201911125405.7A
Authority: CN
Inventors: 李乾; 王延奎; 齐中阳; 贾玉红; 宗思宇
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2020-03-27

Abstract

The invention relates to a method for controlling the rock motion of a plane with a sharp-edge fuselage layout, which weakens the strong induction action of asymmetric vortexes of a fuselage on a wing flow field by deviating a certain angle on a wing leading edge flap with a proper size, thereby inhibiting the rock motion of the plane with the sharp-edge fuselage layout. The method can be realized easily by means of the conventional aerodynamic control surface of the airplane without adding a mechanism, and is a new technology for inhibiting rock motion. The experimental results show that: the method is simple and convenient, has obvious control effect and has strong engineering application prospect.

Description

Method for restraining rock motion of sharp-edge fuselage layout through leading edge flap

Technical Field

The invention discloses a method for restraining rock motion of a airplane with a sharp-edge fuselage layout through a leading-edge flap, which is mainly used for airplane flight control research and belongs to the technical field of aerospace.

Background

The novel fighter plane is mainly characterized by a sharp-edged fuselage layout, such as the American F-22 fighter plane and the Russian T-50 fighter plane. Different from the conventional rotating body, the sharp-edge fuselage is also called a ridge fuselage, the cross section of the sharp-edge fuselage is formed by an upper parabola and a lower parabola, the intersection point of the parabolas is a side edge point, the cross section is formed by fusing the rotating body fuselage and an edge strip, the airplane layout can have good pneumatic and stealth performances, and a typical sharp-edge fuselage layout model adopted by the novel fighter is shown in figure 1. The requirement of the novel fighter plane is high maneuverability and high agility, which are often reflected by large attack angle and stall maneuver. However, in a large-attack-angle aircraft, a complex vortex and flow separation phenomenon occurs on the leeward side of the tip-edge fuselage layout, and various types of non-command motions are induced, wherein the more typical wing rock motions are mainly represented by uncontrollable limit ring oscillation around the body axis of the aircraft, and fig. 2 shows the limit ring rock motions generated by the tip-edge fuselage layout at a large attack angle of 30 degrees, and the rock motions seriously affect the operating characteristics and flight safety of the fighter. Therefore, researchers at home and abroad develop research for nearly thirty years, try to find out a flow mechanism generated by the rock motion, and provide a method for inhibiting the rock motion of the wings.

The large angle of attack wing rock motion may occur in various configurations of fighter aircraft, such as delta wings, rectangular wings, flying wings, wing body combinations, etc. Research shows that the flow mechanism of the rock motion is different due to different layouts, and a universal general flow mechanism does not exist. Therefore, the method for suppressing the rock motion is different according to different layouts, which brings certain difficulty to the method for suppressing the rock motion based on the flow mechanism. The existing restraining method mainly aims at the layout of a wing body assembly of a slender delta wing and a rotary body, and the layout of a sharp-edge body is less involved. For the triangular wing layout, the asymmetric vortex of the front edge induces an initial rolling torque at a large attack angle to form a rock motion triggering mechanism, and the normal vortex position hysteresis of the vortex of the front edge promotes the rock motion to form a rock motion maintaining mechanism, so the rock motion inhibiting thought of the triangular wing layout is mainly to reasonably and effectively control the asymmetric front edge vortex. For the layout of the rotating body, the asymmetric vortex of the rotating body, which appears at a large attack angle, induces the initial rolling torque to form a trigger mechanism, and the vortex position switching of the asymmetric body vortex forms a maintenance mechanism of the rock motion, so that the suppression idea is to control the asymmetric vortex of the body. Based on the above-mentioned suppression concept, the existing suppression methods include rotating head artificial particles, head blowing, head strake, etc., because the asymmetric vortex of the delta wing leading edge and the asymmetric vortex of the rotating body fuselage are controlled by the head artificial particles, the head blowing, or the head strake. However, experiments have demonstrated that the slightly modified method of the head cannot be used to suppress the tip-edge fuselage layout rock motion. This is because: on the one hand, the prior literature finds that minor modifications (such as artificial particles) near the nose of the sharp-edged fuselage hardly affect the development of the fuselage vortex motion; on the other hand, the asymmetric vortex of the lower sharp-edge fuselage with a large attack angle is greatly different from the asymmetric vortex of the rotating fuselage, and is represented by the fact that when the model rolls, the asymmetric vortex of the rotating fuselage is always controlled by small changes (such as artificial particles) of the head, the asymmetric vortex of the sharp-edge fuselage is only controlled by small changes (such as artificial particles) of the head near a roll angle of 0 degrees, and the asymmetric vortex of the lower sharp-edge fuselage with a non-zero roll angle is controlled by a lateral slip angle of the lateral edge of the model. Therefore, the concept of suppressing the sharp-edged fuselage vortex cannot suppress the rock motion well, and a new flow control method needs to be proposed.

There have been few studies relating to the suppression of rock motions in a tip-edge fuselage layout. Preliminary studies have found that the key flow of the rock motion for a tip-skirt fuselage layout is the strong interaction between the asymmetric vortices of the fuselage and the flow of the wing. Therefore, the main idea of the invention is to influence the strong interaction between the asymmetric vortexes of the fuselage and the flow of the wing by controlling the flow of the wing, thereby inhibiting the rock motion.

Aiming at the rock motion generated by the sharp-edge fuselage layout under a large attack angle, once the aircraft has the rock phenomenon, the wing flaps of the leading edges at two sides are only required to be simultaneously deflected by a certain angle, so that the induction of asymmetric vortices of the fuselage to the flow of the wing can be weakened, and then the rock can be inhibited without applying any means. The control method is simple, has obvious control effect, and is a new technology for inhibiting wing rock of sharp-edge fuselage layout.

Disclosure of Invention

The invention provides a method for inhibiting rock motion of a tip-edge fuselage layout through a leading edge flap, which aims to inhibit rock motion generated by strong interaction of a tip-edge fuselage vortex and wing flow and provide an important technical means for the research of safe flight of an airplane. The invention will be described in detail below by way of an overview of the model, the characteristics of the free rock motion without applied control, and the specific process of applying control:

1. overview of the model

FIG. 1 shows an experimental model used in the present invention. The layout is a combined model consisting of a sharp-edged fuselage 1 and a medium swept wing 3. The cross section of the sharp-edge fuselage adopts a design mode with similar cross section, the fuselage can be divided into a front body part and a rear body part, the side edge line of the front body part is a curve, the front body part is 240mm long, the side edge line of the rear body part is a straight line, and the rear body part is 440mm long. The width of the rear body of the fuselage is 80mm, and the height of the rear body of the fuselage is 70 mm. The medium sweepback wing is a flat-plate wing type, the front edge sweepback angle is 48 degrees, the rear edge sweepback angle is 15 degrees, and the front edge point of the wing root is 360mm away from the nose. In order to be able to suppress the rocking motion of the wing, a flap 2 is mounted on the leading edge of the model wing, the leading edge flap being angled upwards.

2. Free rock motion characteristic of model without leading edge flap

When the leading edge flap is not installed, the single-degree-of-freedom rock experiment of the model shows that: when the incidence angle is 30-40 degrees, the model generates complex wing rock motion. Fig. 2, 3 and 4 are graphs of the time history of the rock movement of the model at angles of attack of 30 °, 35 ° and 40 °, respectively. When the attack angle is 30 degrees, the model has the limit ring rock motion deviating to one side; when the attack angle is 35 degrees, the model has large-amplitude limit ring rock motion around the zero roll angle; when the attack angle is 40 degrees, the model has chaotic rock motion.

3. Free rock motion characteristic of model when installing leading edge flap

The invention utilizes the upward deviation of the leading edge flap to inhibit the rock motion of the fuselage layout of the sharp-edge, and the leading edge flap needs to be installed, so the size, the position and the upward deviation angle of the flap are main parameters. The flap is 195mm long and 15mm wide, is mounted along the leading edge of the wing, starts at the root of the leading edge of the wing, and has an upward deflection angle of 45 degrees.

Fig. 5, 6 and 7 show the curves of the time course of the model's rock movement at angles of attack of 30 °, 35 ° and 40 °, respectively, after installation of a leading-edge flap offset by 45 °. It can be seen that the sharp-edged fuselage layout aircraft did not rock at angles of attack of 30 °, 35 ° and 40 ° after application of the leading-edge flap control, and the model stabilized near zero roll angle.

By combining the experimental results, the invention inhibits the rock movement of the fuselage layout of the sharp-edge side edge through the upward deviation of the leading edge flap, has obvious control effect and simple and convenient method, and is a method for inhibiting the rock movement of the wing.

Drawings

FIG. 1 tip-edge fuselage layout model and leading-edge flap installation schematic

FIG. 2 is a graph of the time history of the rock and roll movements of a sharp-edged fuselage layout aircraft at an angle of attack of 30 °

FIG. 3 is a graph of the time history of the rock and roll movements of a sharp-edged fuselage layout aircraft at an angle of attack of 35 °

FIG. 4 is a graph of the time history of the rock and roll movements of a sharp flank fuselage layout aircraft at an angle of attack of 40 °

FIG. 5 shows a time history of the rock movement of a sharp flank fuselage layout aircraft with a leading edge flap mounted at a 30 DEG rear angle of attack

FIG. 6 shows a time history of the rock-roll movement of a sharp-edged fuselage layout aircraft with a leading-edge flap mounted at a 35 ° rear angle of attack

FIG. 7 is a graph of the time history of the rock and roll motion of a sharp-edged fuselage layout aircraft with a leading-edge flap mounted at a rear angle of attack of 40 °

The numbers in the figures are as follows:

1 tip-side edge fuselage 2 leading edge flap 3 sweepback wing (leading edge sweepback angle 48 degree, trailing edge sweepback angle 15 degree)

Detailed Description

The invention may be carried out in accordance with the following embodiments:

1) selecting leading edge flaps with proper sizes, wherein the leading edge flaps with the lengths of 195mm and the widths of 15mm are selected in the example, and the upward deflection angles of the leading edge flaps are 45 degrees;

2) setting the position of the leading-edge flap: the leading edge flap is arranged along the leading edge of the wing, and the starting point of the leading edge flap is positioned at the root of the leading edge of the wing;

3) after the leading edge flap is set to deviate a certain angle, if the aircraft rolls, the aircraft converges to be close to the balance position of the roll angle of 0 degree, and the rolling motion is effectively controlled.

Claims

1. The method for inhibiting rock motion of the layout of the sharp-edged fuselage by the leading-edge flap is mainly characterized in that: the method adopts leading edge flaps on two sides, and the leading edge flaps have a certain upward deflection angle.

2. The method of claim 1 wherein the leading edge flap plan shape is rectangular.

3. The method of claim 1, wherein the leading-edge flap tip-up angle is 45 °.

4. The method of claim 1, wherein the leading edge flap is mounted to the leading edge of the wing with the spanwise origin at the root of the leading edge of the wing.