Biplane wing with improved aerodynamic characteristics

Abstract

The invention relates to aviation technology, primarily for improving aerodynamics in the case of a wing having a biplane configuration. A biplane wing consists of a bottom plane and a top plane, the tips of which are connected by strengthening plates. The bottom plane has a profile with a thickness of 17-21% and a camber of 4% at 35-40% of the chord, the top chord being twice as short and the angle between the chord lines of the top and bottom wing being in the order of from -6° to -8°. The planes form a tapered channel, in which the distance between the planes is selected so that their boundary layers do not interact. The top plane is offset forwards so that the trailing edge thereof is situated above the point of maximum thickness of the bottom plane. The invention provides a simpler structure having a lower weight and cost but high aerodynamic and flight characteristics.

Description

[0001] Biplane wing with improved aerodynamic characteristics

[0002] Description

[0003] The invention relates to aviation technology, in particular to the sections of aerodynamics and aircraft construction, and can be primarily used on aircraft to improve aerodynamic characteristics when using a biplane wing.

[0004] The closest patents to the claimed biplane wing are Patent No. 59180, Class 62 B, 5, author R.Z. Kavtaradze "Biplane-type aircraft", publication date 02 / 28 / 1941, and Russian Federation Patent No. 2060912 C1 "Method for improving the aerodynamic characteristics of a biplane wing", authors: Shirokov I.A., Tatarnikov A.P., Ermolaev V.A. and Chichikaylo V.V., 05 / 27 / 1996. This patent is accepted as a prototype. Structurally, the biplane wing prototype is a mechanism that continuously monitors the most advantageous position of the upper plane relative to the lower one in accordance with the trim position of the aircraft control stick in order to expand the operating range of angles of attack due to an increase in aerodynamic quality. A technical review and engineering analysis of the biplane wing prototype according to Russian patent No. 2060912 C1 showed that the biplane wing prototype has a number of disadvantages, including:

[0005] - complexity, and therefore reduced reliability of the design of the upper wing movement mechanism, the main requirement for which is the synchronous operation and increased service life of at least three (one in the center of the biplane wing and two at its ends) drive mechanisms (MP-100 type), installed on the lower wing, telescopic rods and rods of constant length;

[0006] - an increase in the mass of the biplane wing due to the use of drive mechanisms (such as MP-100) and rods in the design; - an increase in labor costs during the construction of an aircraft with such a biplane wing and, as a consequence, an increase in its cost;

[0007] - the presence of at least three drive mechanisms (such as MP-100) in the design will require additional power sources, which will also affect the weight of the aircraft and its cost.

[0008] The proposed biplane wing is illustrated by figures, where Fig. 1 depicts the profiles (their relative dimensions) of the lower, designated by the number 1, and upper, designated by the number 2, planes of the biplane wing, as well as their relative positions relative to each other, which are fixed over the entire span. For the lower plane, an airfoil with a large relative thickness (17-21%) and a curvature of its centerline of approximately 4% at 35-40% of the mean aerodynamic chord is selected. For the upper plane, an airfoil with a chord approximately half that of the lower plane is selected, with low effective Reynolds numbers and a high value of the maximum operating angles of attack. The location of the upper plane relative to the lower plane is selected so as to ensure the most favorable angle of attack to the velocity vector of the local oncoming airflow, while the lower plane is located at the most favorable angle of attack to the velocity vector of the undisturbed airflow.In this case, the lower surface of the upper plane and the upper surface of the lower plane form a converging channel between them, and the distance between them is chosen so that their boundary layers do not interact. The forward offset of the upper plane relative to the lower plane is chosen so that the tail of the upper plane's profile is located above the point of maximum thickness of the lower plane's profile.

[0009] Fig. 2 shows a front view and a side view of the biplane wing, where the number 3 indicates the end load-bearing elements, made in the form of washers connecting the tips of the upper and lower consoles. The number 4 designates the pyramidal struts rigidly connecting the middle of the upper plane with the lower one or with the fuselage 5, as shown in the front view. In addition, Fig. 1 and Fig. 2 contain the following designations: НП – flight direction, Woo – the vector of the impact of the oncoming undisturbed flow on the biplane wing.

[0010] The essence of the invention and its main difference from the prototype biplane wing lies in the fixed position of the biplane wing's upper plane relative to the lower plane. This ensures mutually positive interference between the planes by selecting their shapes, sizes, and the installation angle between the chords of these planes. The forward extension of the upper plane relative to the lower plane improves its aerodynamic characteristics, simplifies and reduces the cost of the wing design, and reduces its weight. The proposed biplane wing configuration increases the operating range of angles of attack to α = 19° - 20° due to continuous flow caused by flow acceleration in the narrowing channel between the upper and lower planes. This also results in an increase in the maximum angle of attack (SU) to SU = 2.6-2.9 during takeoff and landing without the use of wing high-lift devices. These SU values ​​were confirmed during flights on an aircraft with a wing of a similar configuration.The presence of such obtained aerodynamic characteristics, the simplification of the wing design, and the reduction of its weight suggest a reduction in takeoff and landing speeds and a reduction in the takeoff and landing roll, or an increase in payload. The angle between the chord lines of the upper and lower wings is approximately -6° to -8°. This angle is selected during wind tunnel tests of a biplane wing model or during a flight experiment. In this case, the main criterion will be an increase in the maximum lift-to-drag ratio of the biplane wing. From Fig. 1 it is evident that, due to the flow around the upper wing by a flow whose velocity vector has a certain angle to the vector of the undisturbed incoming flow, the projection of the horizontal component X of the total aerodynamic force Yaverhn.The effect of the undisturbed incoming flow vector Woo is significantly reduced, reducing the drag of the biplane wing compared to the sum of these isolated wings, resulting in a 10-15% increase in maximum lift-to-drag ratio. Furthermore, the force washers 4, connecting the tips of the upper and lower surfaces, limit the flow of air from beneath their lower surfaces to the upper ones, preventing vortex formation and reducing the induced drag of the biplane wing.

[0011] The proposed biplane wing represents a simpler design, with lower weight and cost, while maintaining the same high aerodynamic and flight characteristics, due to the selection of aerodynamic profiles for the upper and lower planes, connected by endplates, as well as the choice of their chord sizes and mutually beneficial layout.

Claims

Formula 1. A biplane wing consisting of a lower and upper planes having tips connected by end force washers, wherein said planes have a fixed mutual arrangement relative to each other, wherein the lower plane has an airfoil with a relative thickness (17-21%) and a curvature of its midline of about 4% by 35-40% of its average aerodynamic chord, and the upper plane has an airfoil, the chord of which is approximately two times smaller than the chord of the lower plane, and the angle between the chord lines of the upper and lower wing is about -6° to -8°, wherein the lower surface of the upper plane and the upper surface of the lower plane form a tapering channel between themselves, in which the distance between the planes is selected from the condition of the absence of interaction of their boundary layers, wherein the upper plane is moved forward relative to the lower one so that the tail of the upper plane profile is located above the point of maximum thickness of the lower plane profile.

2. A biplane wing according to claim 1, in which the end force washers connecting the tips of the upper and lower wings have an angle between their plane and the upper surface of the lower wing of about 130° - 140°.

Images