A grid blended wing for low speed high angle of attack flow characteristics improvement

Abstract

This invention discloses a grid-integrated wing for improving low-speed, high angle-of-attack flow characteristics. The grid-integrated wing includes a base wing, a grid frame arranged on the base wing to form a hollowed-out wing structure, transverse grid partitions and longitudinal grid partitions, both arranged inside the grid frame. The transverse grid partitions are arranged parallel to the upper and lower surfaces of the grid frame, and the longitudinal grid partitions are arranged perpendicular to the upper and lower surfaces of the grid frame and intersect with the transverse grid partitions, dividing the grid frame into multiple hollowed-out grid holes. A grid air inlet is arranged in the leading edge region of the lower surface of the base wing, forming a cavity between the upper surface of the transverse grid partition and the upper surface of the grid frame. A grid air outlet is arranged on the upper surface of the base wing, forming a cavity between the lower surface of the transverse grid partition and the lower surface of the grid frame. The grid-blended wing designed in this invention can effectively suppress airflow separation at high angles of attack, increase the wing's stall angle of attack, and improve the wing's maximum lift coefficient without consuming additional energy or generating additional drag.

Description

Technical Field

[0001] This invention relates to the field of aviation equipment technology, and more specifically to a grid-blended wing for improving low-speed, high angle-of-attack flow characteristics. Background Technology

[0002] When an aircraft wing reaches the critical stall angle of attack, its lift decreases as the angle of attack increases. In a stall state, the aircraft will experience uncontrolled diving and turbulent motions as well as uncontrolled rotations. The main cause of stall is the asymmetric airflow separation phenomenon that occurs on the wing at high angles of attack. Many aviation accidents are caused by wing stall, therefore, increasing the stall angle of attack of the aircraft wing is of great significance to the safety and maneuverability of the aircraft.

[0003] At present, the main method for suppressing airflow separation and delaying wing stall is flow control technology. Flow control technology is further divided into passive flow control and active flow control according to the control method. The most typical engineering application of passive flow control technology is the vortex generator. Its main control mechanism is to generate vortices through the vortex generator to transfer energy to the low-energy boundary layer, thereby overcoming the adverse pressure gradient and delaying airflow separation. This can increase the wing's stall angle of attack and maximum lift coefficient. The cost of this lift increase is increased drag and a decreased lift-to-drag ratio. In addition to vortex generators, slotted airfoils, biomimetic nodules, and grooved technology all fall under the category of passive flow control. Active flow control directly applies appropriate disturbance modes to the flow field and couples them with the inherent flow characteristics to control the flow. Its main methods for suppressing airflow separation include jetting, blowing and sucking, and releasing plasma.

[0004] The main drawback of active flow control is the need for additional energy to control the flow around the wing. Furthermore, the addition of active flow control equipment increases the aircraft's weight, impacting its fuel economy. Passive flow control methods, such as vortex generators, while suppressing airflow separation around the wing, can increase drag to some extent. Moreover, because passive flow control is pre-designed, it cannot achieve the desired control effect when the flow field deviates from the design conditions, and may even adversely affect the flow around the wing. Summary of the Invention

[0005] The purpose of this invention is to provide a grid-blended wing for improving low-speed, high angle-of-attack flow characteristics, aiming to enhance the anti-separation and stall characteristics of aircraft at low speeds and high angles of attack.

[0006] The technical solution adopted in this invention is:

[0007] A grid-blended airfoil for improving low-speed, high angle-of-attack flow characteristics, the grid-blended airfoil comprising:

[0008] Basic monoplane,

[0009] A grid frame is arranged on the basic monoplane to form a hollowed-out wing structure.

[0010] Both horizontal and vertical grid partitions are arranged inside the grid frame. The horizontal grid partitions are arranged parallel to the upper and lower surfaces of the grid frame, while the vertical grid partitions are arranged perpendicular to the upper and lower surfaces of the grid frame and intersect with the horizontal grid partitions, dividing the grid frame into multiple perforated grid holes.

[0011] The grille air intake is located on the leading edge of the lower surface of the basic single wing, and is formed by the cavity between the upper surface of the transverse grille partition and the upper surface of the grille frame.

[0012] The air vent is located on the upper surface of the single wing of the foundation and is formed by the cavity between the lower end face of the transverse grid partition and the lower plate face of the grid frame.

[0013] Preferably, the guide angle of the grid frame is -10° to -20°.

[0014] Preferably, the overall grid width of the grid frame is 10% of the length of the basic single-wing chord.

[0015] Preferably, the thickness of the transverse grid partition and the longitudinal grid partition is 1% to 2% of the length of the basic single-wing chord.

[0016] Preferably, the width-to-chord ratio of the perforated grid holes is 0.14.

[0017] Preferably, the number of horizontal grid partitions is 1, and the number of vertical grid partitions is 2.

[0018] The beneficial effects of this invention are:

[0019] This invention relates to a grid-blended wing designed to improve the flow characteristics of airfoils at high angles of attack. Suitable for low-speed and subsonic high angle-of-attack conditions, it consists of three parts: a base wing, a grid frame, and grid partitions. The grid is arranged in a perforated wing (wing opening) configuration. The grid air inlets are located in the area below the leading edge of the base wing, while the grid exhaust outlets are located on the upper surface of the base wing. This grid-blended wing effectively suppresses airflow separation at high angles of attack without consuming additional energy or generating additional drag, thereby increasing the wing's stall angle of attack and improving its maximum lift coefficient. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a global view of a grid-blended airfoil for improving low-speed, high angle-of-attack flow characteristics according to the present invention;

[0022] Figure 2 This is a top surface view of a grid-blended airfoil for improving low-speed, high angle-of-attack flow characteristics according to the present invention.

[0023] Figure 3 This is a lower surface view of a grid-blended airfoil for improving low-speed, high angle-of-attack flow characteristics according to the present invention.

[0024] Figure 4 This is a cross-sectional view of the grid fusion wing;

[0025] Figure 5 For the guide angle of the grid fusion wing;

[0026] Figure 6 Mach number cloud images of a monoplane and a grid-blended wing; (a) monoplane; (b) grid-blended wing;

[0027] Figure 7 Flow field streamline diagrams for a single-wing and a grid-blended wing; (a) Single-wing; (b) Grid-blended wing;

[0028] Figure 8 The curves showing the lift coefficient and drag coefficient of a single-wing and grid-blended wing with different guide angles as a function of angle of attack (Ma=0.6); (a) Curve showing the lift coefficient as a function of angle of attack; (b) Curve showing the drag coefficient as a function of angle of attack.

[0029] Among them, 1-grid frame; 2-basic single wing; 3-transverse grid partition; 4-longitudinal grid partition; 5-grid exhaust port; 6-grid air inlet; 7-guide angle. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0032] Specifically, this invention provides a grid-blended airfoil for improving low-speed, high angle-of-attack flow characteristics, such as... Figure 1-5 As shown, the grid fusion wing includes

[0033] Basic monoplane,

[0034] A grid frame is arranged on the basic monoplane to form a hollowed-out wing structure.

[0035] Both horizontal and vertical grid partitions are arranged inside the grid frame. The horizontal grid partitions are arranged parallel to the upper and lower surfaces of the grid frame, while the vertical grid partitions are arranged perpendicular to the upper and lower surfaces of the grid frame and intersect with the horizontal grid partitions, thus dividing the grid frame into multiple perforated grid holes.

[0036] The grille air intake is located on the leading edge of the lower surface of the basic single wing, and is formed by the cavity between the upper surface of the transverse grille partition and the upper surface of the grille frame.

[0037] The air vent is located on the upper surface of the single wing of the foundation and is formed by the cavity between the lower end face of the transverse grid partition and the lower plate face of the grid frame.

[0038] The geometric features of the grid fusion wing device of the present invention are described as follows:

[0039] 1) The guide angle of the grid frame is -10° to -20°, which can be adjusted according to actual needs. The guide angle is defined as the angle between the grid chord and the chord of the basic single wing. When the grid structure air inlet is on the lower surface of the basic single wing, the guide angle is negative.

[0040] 2) The basic monoplane airfoil is the NACA2214 airfoil, and other airfoils can be selected according to the actual needs of the aircraft.

[0041] 3) The overall width of the grid frame is about 10% of the length of the basic single-wing chord.

[0042] 4) The thickness of the grid partition (including transverse grid partition and longitudinal grid partition) is 1% to 2% of the length of the basic single-wing chord.

[0043] 5) The width-to-chord ratio of the perforated grid holes is approximately 0.14. Changes in the number of grids affect this dimensionless value. Here, the width-to-chord ratio refers to the ratio of the width (longitudinal length) of each perforated grid hole to the chord length of the grid partition.

[0044] 6) The number of horizontal grid partitions is 1, and the number of vertical grid partitions is 2. The number of grid partitions can be adjusted according to the structural strength requirements.

[0045] The guide angle and the number of transverse grid baffles in the above geometric parameters were obtained through numerical experiments. Tables 1 and 2 show the numerical experimental data of the aerodynamic characteristics of the grid-blended airfoil at different guide angles under low-speed and subsonic conditions. It can be seen that at low speed (Ma=0.3), the stall angle of attack of the grid-blended airfoil is significantly greater than that of a conventional single wing in the range of -10° to -20°. The grid-blended airfoil has a relatively larger maximum lift coefficient when the guide angle is -10°, and a larger stall angle of attack when the guide angle is -20°. At subsonic speed (Ma=0.6), the grid-blended airfoil has both a larger stall angle of attack and a larger maximum lift coefficient when the guide angle is -20°. Therefore, the guide angle range of the grid-blended airfoil designed in this invention is selected as -10° to -20°.

[0046] Table 1. Effect of guide angle on the aerodynamic characteristics of the blended lattice airfoil at high angle of attack (Ma=0.3)

[0047] Guide angle / ° -10 -15 -20 conventional monoplane Stall angle of attack / ° 28 30 32 20 Maximum lift coefficient 1.60 1.54 1.52 1.47

[0048] Table 2. Effect of guide angle on the aerodynamic characteristics of the blended lattice airfoil at high angle of attack (Ma=0.6)

[0049] Guide angle / ° -10 -15 -20 conventional monoplane Stall angle of attack / ° 20 25 28 16 Maximum lift coefficient 1.11 1.16 1.22 1.01

[0050] Table 3 shows the numerical experimental data of the aerodynamic characteristics of the grid-blended airfoil with different numbers of transverse grid slats in the subsonic (Ma=0.6) state. It can be found that the stall angle of attack of the grid-blended airfoil is basically independent of the number of transverse grid slats. The maximum lift coefficient of the grid-blended airfoil without transverse grid slats is relatively smaller than that of the grid-blended airfoil with transverse grid slats. After the number of transverse grid slats exceeds 1, the change in the maximum lift coefficient with the increase of the number of slats is not obvious. Using more transverse grid slats will lead to an increase in drag. Therefore, the number of transverse grid slats in the grid-blended airfoil designed in this invention is taken as 1.

[0051] The number of longitudinal grid baffles in the grid fusion wing has little impact on the aerodynamic characteristics of the grid fusion wing designed in this invention. The main reason for arranging longitudinal grid baffles is to enhance the structural strength of the grid fusion wing, and the number of baffles is selected based on experience in arranging conventional grid wing baffles.

[0052] Table 3. Effect of the number of transverse grid slats on the aerodynamic characteristics of the blended fin at high angle of attack (Ma=0.6)

[0053] Number of horizontal grid partitions 0 1 2 3 conventional monoplane Stall angle of attack / ° 28 28 28 28 16 Maximum lift coefficient 1.14 1.21 1.19 1.20 1.01

[0054] The remaining geometric parameters mainly include the thickness of the longitudinal grid partition, the thickness of the transverse grid partition, the overall grid width, and the grid width-to-wing ratio. Most of these parameters are set based on engineering practice experience.

[0055] From an aerodynamic perspective, the smaller the thickness of the longitudinal and transverse grid slats, the better the aerodynamic characteristics of the blended grid wing. However, to ensure the structural strength of the longitudinal and transverse grid slats and the reliability and safety of the blended grid wing, their thickness is set to 1%-2% of the wing chord length after comprehensive consideration based on existing grid wing design data.

[0056] The overall grid width of the grid frame is affected by the maximum thickness of the wing and the guide angle of the grid frame. Taking its width as about 10% of the wing chord length can reserve design space for the grid-blended wing under other guide angle conditions while ensuring the high angle of attack aerodynamic performance of the grid-blended wing.

[0057] The chord ratio of a single grid hole, which is divided into a grid frame by longitudinal and transverse grid partitions, is determined by the overall width of the grid frame, the guide angle, and the airfoil. Any change in these parameters will cause fluctuations in the chord ratio. Since the overall width of the grid frame, the guide angle, and the airfoil of the grid fusion wing designed in this invention are all optimized, the chord ratio determined by these three factors is significantly different from that of a conventional grid wing, but is more suitable for the grid fusion wing designed in this invention.

[0058] The grid-blended wing designed in this invention can effectively suppress airflow separation at high angles of attack, increase the wing's stall angle of attack, and improve the wing's maximum lift coefficient without consuming additional energy or generating additional drag. The main mechanism by which the grid-blended wing suppresses airflow separation and improves the wing's lift performance at high angles of attack is that the grid structure guides the high-energy airflow on the lower surface of the wing to the low-energy separation zone on the upper surface, thus suppressing airflow separation on the upper surface. Simultaneously, due to the rearward shift of the stagnation point at the rear of the lifting surface, the pressure on the lower surface of the grid-blended wing is higher than that of a basic monoplane, resulting in superior aerodynamic characteristics at high angles of attack for the grid-blended wing.

[0059] Simulation Example

[0060] This embodiment uses a numerical simulation method based on the three-dimensional Reynolds-averaged Navier-Stokes equations to numerically simulate the aerodynamic characteristics of the grid-blended wing at high angles of attack. This verifies the ability of the grid-blended wing of the present invention to suppress airflow separation, increase the wing stall angle of attack and maximum lift coefficient in subsonic conditions, and proves the practicality of the grid-blended wing designed in this invention at high angles of attack.

[0061] The simulation object is a grid-blended wing with a base monoplane and grid guide angles of -10° and -20°. The base monoplane airfoil is NACA2214. The overall grid width is 10% of the base monoplane chord length, the thickness of the transverse and longitudinal grid septa is 1% of the base monoplane chord length, the grid width-to-chord ratio of a single open grid hole is 0.14, the number of transverse grid septa is 1, and the number of longitudinal grid septa is 2. The simulated incoming flow Mach number is 0.6, and the wing angle of attack ranges from 0 to 36°.

[0062] Figure 6 Mach number contour maps for a monoplane (a) and a blended wing (b) at Mach number 0.6 and angle of attack 28°. Figure 7 The streamline diagrams of the monoplane (a) and the grid-blended wing (b) at a Mach number of 0.6 and an angle of attack of 28° show that the grid-blended wing designed in this invention can effectively suppress airflow separation on the upper surface of the wing. Under the action of the grid exhaust airflow, the dead zone of flow on the upper surface of the wing is significantly reduced, which is of great significance for improving the wing's stall angle of attack and lift performance at high angles of attack.

[0063] Figure 8 The graphs show the lift and drag coefficients of a single-wing and a blended grid wing with different guide angles as a function of angle of attack. Compared to a single-wing, the blended grid wing with a guide angle of -10° has an increased stall angle of attack of approximately 8° and a maximum lift coefficient of approximately 10%. The blended grid wing with a guide angle of -20° has an increased stall angle of attack of approximately 16° and a maximum lift coefficient of approximately 20%. The drag coefficient of the blended grid wing with a guide angle of -20° is close to that of a single-wing at larger angles of attack, while the drag coefficient of the blended grid wing with a guide angle of -10° is slightly lower than that of a single-wing at larger angles of attack.

[0064] Numerical simulations have verified that the grid-blended wing device designed in this example can effectively suppress airflow separation at high angles of attack, improve the high angle-of-attack flow characteristics of the wing without consuming additional energy or generating additional drag, and significantly enhance the wing's stall angle of attack and maximum lift coefficient.

[0065] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A grid-blended airfoil for improving low-speed, high angle-of-attack flow characteristics, characterized in that, The grid fusion wing includes Basic monoplane, A grid frame is arranged on the basic monoplane to form a hollowed-out wing structure. Both horizontal and vertical grid partitions are arranged inside the grid frame. The horizontal grid partitions are arranged parallel to the upper and lower surfaces of the grid frame, while the vertical grid partitions are arranged perpendicular to the upper and lower surfaces of the grid frame and intersect with the horizontal grid partitions, dividing the grid frame into multiple perforated grid holes. The grille air intake is located on the leading edge of the lower surface of the basic single wing, and is formed by the cavity between the upper surface of the transverse grille partition and the upper surface of the grille frame. The grid air outlet is located on the upper surface of the single wing of the foundation and is formed by the cavity between the lower end face of the transverse grid partition and the lower plate face of the grid frame. The guide angle of the grid frame is -10° to -20°; The overall width of the grid frame is 10% of the length of the basic single-wing chord. The thickness of the transverse and longitudinal grid partitions is 1% to 2% of the length of the basic single-wing chord. The width-to-chord ratio of the perforated grid holes is 0.14; The number of horizontal grid partitions is 1, and the number of vertical grid partitions is 2.

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