Airfoil for lifting element of aircraft

Abstract

The invention relates to an airfoil for a lifting element of an aircraft. The airfoil includes upper and lower contours formed by convex curves and intersection points of the convex curves, the upper and lower contours having given coordinates relative to a chord, the airfoil having a rounded leading edge. For the given chord length and maximum relative thickness of the airfoil, the relative coordinates # imgabs1 # # imgabs2 # of the convex curve of the airfoil are calculated from the midline of the airfoil at a position up to a relative distance # imgabs0 # from the leading edge. The maximum relative thickness of the airfoil is 8% to 15%. The airfoil of a lifting element of an aircraft allows a tail tab to be mounted behind the trailing edge of the airfoil, the tail tab having a rectangular or trapezoidal cross-sectional shape, including a curvilinear shape. The main aerodynamic characteristics of the airfoils are improved for the ends and middle of the rotor blades, the flight data of the aircraft in hovering mode and translational flight, acceptable low levels of variable and constant loads in the carrier system, aeroelastic stability over a wide range of flight speeds.

Description

Technical Field

[0001] The invention relates to the field of aviation engineering, and in particular to an airfoil used for the middle and root parts of a main rotor blade and a tail rotor of an aircraft.

[0002] The airfoil of the NCV-3 lifting element of an aircraft, like other known airfoils having a similar purpose, consists of the profiles of an upper surface and a lower surface described by a set of geometrical coordinates of the upper surface and the lower surface.

[0003] The geometry of the upper and lower surfaces of the airfoil (i.e. the shape of the profile) determines the flow properties of the airfoil (i.e. the distribution of air pressure and velocity over these surfaces), and therefore the distribution of aerodynamic forces and moments that occur on the airfoil as air flows around it. Therefore, the shape of the airfoil profile determines the aerodynamic properties of the airfoil as air flows around it.

[0004] The main aerodynamic characteristics of the airfoil (i.e., maximum lift coefficient, minimum drag coefficient, maximum aerodynamic mass value, pitching moment coefficient at zero lift, position of the aerodynamic focus) have a significant influence on the maximum lifting capacity of the rotor, the power consumed by the rotor in various flight modes, the load level in the control system and the stable movement of the blades during rotor operation. Background Art

[0005] Known rotorcraft blade airfoils (CN106314791A, B64C27 / 467, published on January 11, 2017) have a maximum relative thickness of 8%, 9%, 12%. These airfoils have a modified centerline, the concavity of which increases the laminar part of the flow around the airfoil, which makes it possible to reduce aerodynamic drag.

[0006] The airfoil of the middle part of the main rotor blade is known (KR20090069064A, B64C27 / 467; B64C27 / 54, published on June 29, 2009), which consists of a convex lower surface and an upper surface connecting the leading edge and the trailing edge of the airfoil. The geometry of the airfoil provides a high lift coefficient and angle of attack of the blade part during stall, thereby achieving the advantages of increasing the maneuverability of the helicopter, increasing the airspeed and the permissible blade thrust.

[0007] A known helicopter blade (JP2001239997A, B64C11 / 18; B64C27 / 467, published on September 4, 2001) includes an airfoil having a rounded leading edge with a large radius, a center line with a large curvature, and a flat shape of the upper and lower surfaces of the central portion of the airfoil surface. The geometric shape of this airfoil provides a low pitch moment coefficient, a high maximum lift coefficient, and a high critical Mach number, which reduces structural loads, increases flight speed, and increases effective load.

[0008] The mentioned airfoils do not offer an optimal combination of aerodynamic properties and have specific application within the model range of aircraft for solving a limited range of tasks.

[0009] Unbalanced airfoils of the NACA 230XX series with five-digit designations are known, where the last two digits XX are the maximum relative thickness of the airfoil as a percentage of its chord (see, for example, NACA Report No. 586, 1937, p. 236; Kravets AS, Characteristics of aircraft airfoils, M.-L.: Oborongiz, 1939, pp. 206-217; Ushakov BA et al., Atlas of aerodynamic characteristics of wing airfoils, Moscow: BNT NKAP at TsAGI, 1940, pp. 165-196; NACA Report No. 824, 1945, pp. 101, 146-150). These airfoils are widely used in the design of helicopter blades.

[0010] The NACA230XX series of airfoils have an elongated teardrop shape with a rounded leading edge and a pointed or blunt trailing edge, the leading and trailing edges being connected by contoured portions of the upper and lower airfoil surfaces. The contours of these airfoils are formed by a continuous smooth line with a smoothly varying curvature, by superimposing the contours of symmetrical airfoils (with corresponding thicknesses) on a median line (perpendicular to the median line), which median line does not change for the entire series of airfoils. The maximum relative thickness of the airfoil series is located at 30% of the airfoil chord length, and the median line has a maximum relative concavity of 2% (along the axial arc) and is located at 15% of the airfoil chord length. The contour shape of the NACA23012 prototype airfoil obtained in this way determines the aerodynamic characteristics of the airfoil when the airflow flows around the airfoil.

[0011] The disadvantages of NACA23012 airfoil are:

[0012] - In the Mach number range of 0.3 to 0.6, the maximum lift coefficient of the airfoil is relatively low;

[0013] - the minimum drag coefficient of the airfoil has relatively high values ​​in the Mach number range from 0.3 to 0.76;

[0014] - relatively small values ​​of aerodynamic mass in the Mach number range of 0.3 to 0.9;

[0015] - In the Mach number range of 0.3 to 0.65, the proposed airfoil has a pitching moment coefficient С at zero lift mo lower value. Summary of the invention

[0016] The technical problem solved by the present invention is to develop the geometry of the upper and lower surfaces of the profile of the NCV-3 airfoil (hereinafter referred to as airfoil) of an aircraft lifting element for the ends and the middle of the blade, wherein:

[0017] - compared to the prototype, in the range of Mach numbers from 0.3 to 0.6 it has the maximum lift coefficient С ya max The larger value of

[0018] - Compared to the prototype, it has the lowest drag coefficient C in the Mach number range from 0.3 to 0.76 xa min The lower value of

[0019] - Compared to the prototype, it has the maximum lift coefficient K in the range of Mach numbers 0.3 to 0.9 max The larger value of

[0020] - compared to the prototype, in the range of Mach numbers from 0.3 to 0.65, it has a pitch moment coefficient at zero lift of С mo The smaller value of

[0021] - Compared to the prototype, it has the location of the aerodynamic focus in the Mach number range of 0.3 to 0.8 Further back.

[0022] The specific aerodynamic characteristics of the airfoil have a significant influence on the power consumed by the main and tail rotors, the level of loads on structural elements in the thruster control components, the efficiency of the parameters of the blades, main rotor, tail rotor and other lifting surfaces of the aircraft.

[0023] The technical result of the application of the invention is the improvement of the basic aerodynamic characteristics of the airfoils for the end and middle parts of the tail rotor blades by using the developed airfoil profiles which ensure the highest possible quality of the blade and the rotor as a whole in the hover mode and in forward flight, an acceptable low level of variable and constant loads in the system, and aeroelastic stability over the entire flight speed range.

[0024] In order to achieve the technical effect, an airfoil of a lifting element of an aircraft is proposed, the airfoil comprising an upper contour and a lower contour formed by a convex curve and an intersection of the convex curve, the upper contour and the lower contour having given coordinates relative to the chord, the airfoil having a circular leading edge, and further, for a given chord length and a maximum relative thickness of the airfoil, at a relative distance from the leading edge The relative coordinates of the contour line at the position Determined by equations (1) and (2):

[0025]

[0026]

[0027] in:

[0028] -Relative abscissa of the airfoil contour point, %;

[0029] -Relative ordinate of the point on the upper contour line of the airfoil, %;

[0030] -Relative ordinate of the point on the lower contour line of the airfoil, %;

[0031] - Relative ordinate of the point on the midline of the airfoil, %;

[0032] - relative ordinate of the points in the symmetric components of the upper and lower profiles of the airfoil, %;

[0033] - Maximum relative thickness of airfoil, %;

[0034] c MAX - Maximum thickness of airfoil, m;

[0035] X - the horizontal coordinate of the contour point of the airfoil, m;

[0036] Y B - the ordinate of the point on the upper contour of the airfoil, m;

[0037] Y Н - the ordinate of the point on the lower contour of the airfoil, m;

[0038] В-chord length of airfoil, m,

[0039] At the same time, the following lists the distance from the leading edge The ordinate of the airfoil at the position The value associated with the chord length B: For the maximum relative thickness Defines the vertical axis Range:

[0040]

[0041]

[0042] Furthermore, the maximum relative thickness of the airfoil is 8% to 15%.

[0043] In this case, the airfoil of the lifting element of the aircraft may have a pointed, blunt or rounded trailing edge.

[0044] Furthermore, the airfoil of the lifting element of the aircraft allows the installation of a tail tab behind the trailing edge of the airfoil, said tail tab having a rectangular or trapezoidal cross-sectional shape, including a curved shape, a length not exceeding 15% of the chord without the tab, a thickness not exceeding 1.5% of the chord, the deflection angle of the tail tab relative to the chord being in the range of -5° to +10°.

[0045] Thus, the technical result of the application of the invention is achieved - the goal is to improve the basic aerodynamic characteristics of the airfoil of the end and middle part of the tail rotor blade by using the developed airfoil profile, which ensures the highest possible quality of the blade and the rotor as a whole in hover mode and forward flight, promotes an acceptable low level of variable and constant loads in the system, and aeroelastic stability over the entire flight speed range. The use of the proposed airfoil allows to improve flight performance and economic characteristics, extend range and increase the competitiveness of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention is explained by the following drawings:

[0047] Figure 1 - For maximum thickness Plot of the variation of the airfoil profile and the dependence of the geometrical characteristics of the airfoil on the percentage of the airfoil chord length.

[0048] Figure 2 - Maximum lift coefficient С of the compared airfoils ya max Plot of the dependence on Mach number.

[0049] Figure 3 - Minimum drag coefficient С of the compared airfoils xa min Plot of the dependence on Mach number.

[0050] Figure 4 - Maximum aerodynamic quality coefficient K of the compared airfoils max Plot of the dependence on Mach number.

[0051] Figure 5- The pitching moment coefficient C determined for the compared airfoil relative to the leading edge of the airfoil at zero lift m0 Plot of the dependence on Mach number.

[0052] Figure 6 - Relative coordinates of the aerodynamic focus of the compared airfoils Plot of the dependence on Mach number. DETAILED DESCRIPTION

[0053] The proposed airfoil has a rounded leading edge and a pointed, blunt or rounded trailing edge, the leading edge and the trailing edge being interconnected by smooth profiles of the upper and lower surfaces of the airfoil, the leading edge being made with a rounded radius which increases smoothly along the chord length B of the airfoil so that the distance Y from the chord perpendicular to the chord upward to the upper part of the profile is B The upper part of the profile changes smoothly from convex to concave, increasing smoothly from the leading edge of the airfoil and reaching its maximum value in the coordinate range X=0.25B to 0.35B along the chord. The leading edge of the lower surface of the airfoil is rounded with a radius of curvature along the lower part of the profile. The distance Y from the chord to its lower surface is H It gradually increases from the leading edge and reaches its maximum value at X=0.3B to 0.45B.

[0054] The proposed airfoil refers to the ends and the middle of the blade and comprises an upper and a lower profile formed by convex curves and their intersections, with given coordinates relative to the chord. The coordinates of the convex curves are measured from the airfoil centerline: the upper ones are plus, the lower ones are minus.

[0055] For a given chord length and maximum relative thickness of the airfoil, at a relative distance from the leading edge The relative coordinates of the contour line at the position Determined by equations (1) and (2):

[0056]

[0057]

[0058] in:

[0059] -Relative abscissa of the airfoil contour point, %;

[0060] -Relative ordinate of the point on the upper contour line of the airfoil, %;

[0061] -Relative ordinate of the point on the lower contour line of the airfoil, %;

[0062] - Relative ordinate of the point on the midline of the airfoil, %;

[0063] - Relative ordinate of the points in the symmetrical components of the upper and lower profiles of the airfoil, %.

[0064] - Maximum relative thickness of airfoil, %;

[0065] c MAX - Maximum thickness of airfoil, m;

[0066] X - the horizontal coordinate of the contour point of the airfoil, m;

[0067] Y B - the ordinate of the point on the upper contour of the airfoil, m;

[0068] Y Н - the ordinate of the point on the lower contour of the airfoil, m;

[0069] В-chord length of airfoil, m,

[0070] Table 1 (columns 1, 2, and 3) lists the values ​​of the following items: Relative abscissas of points of the airfoil profile The corresponding relative ordinate of the airfoil centerline point And the ordinate range of the points of the symmetric components of the upper and lower profiles of the airfoil The maximum relative thickness for a given airfoil is given in Table 1. The relative ordinates of the points on the upper and lower lines of the airfoil Calculation of the range (see columns 4 and 5).

[0071] Table 1 Geometric characteristics of airfoil:

[0072]

[0073]

[0074] When designing an airfoil, the value c MAX , X, Y В , Y Н ,В's dimensions can be selected not only in meters, but also in other units.

[0075] The coordinates of a series of airfoils of different thicknesses can be plotted.

[0076] in this case, The values ​​of remain the same as in Table 1, and The values ​​of are based on the relations (1), (2) correspondingly for the maximum relative thickness of the airfoil in the range of 8 to 15% calculate.

[0077] By adding the relative value Multiply the given dimension value В by the airfoil chord length to obtain the dimension value Х, Y CP , Y CИМ , Y В , Y Н .

[0078] The geometry of the airfoil profile ( Figure 1 ) defines the aerodynamics of the airfoil when air flows around it. The aerodynamic characteristics of the proposed airfoil obtained by computational fluid dynamics are Figures 2 to 6 The proposed airfoil is shown in FIG. 1 and compared with the characteristics of the NACA23012 prototype airfoil. In the graph, the dotted line represents the characteristics of the NACA23012 prototype airfoil, and the solid line represents the characteristics of the proposed airfoil.

[0079] Figure 1 Shown for the maximum thickness Dependence of the airfoil profile variation and the airfoil geometrical characteristics as a percentage of the airfoil chord length, where:

[0080] Y CP - the ordinate of the midline point of the airfoil;

[0081] Y CИМ - ordinates of the points of symmetry of the upper and lower profiles of the airfoil;

[0082] Y В - ordinate of the upper contour point;

[0083] Y Н - ordinate of the lower contour point;

[0084] В – chord length of the airfoil;

[0085] - Maximum relative thickness of airfoil, %;

[0086] -Relative abscissa of the airfoil contour point, %;

[0087] -Relative ordinate of the contour point of the airfoil, %;

[0088] -Relative ordinate of the midline point of the airfoil, %;

[0089] - Relative ordinates of the points of symmetry components of the upper and lower profiles of the airfoil, %.

[0090] Figure 2 is the maximum lift of the compared airfoil yamax Plot of the dependence of the coefficients on the Mach number. In terms of maximum lift, the proposed airfoil exceeds NACA 23012 in the range of Mach numbers 0.3 to 0.6 by 8% at Mach 0.6.

[0091] Figure 3 is the minimum drag coefficient of the compared airfoil xa min Plot of the dependence on Mach number. The minimum drag of the proposed airfoil is on average 17% lower than the minimum drag of the NACA23012 airfoil in the range of Mach numbers from 0.3 to 0.76.

[0092] Figure 4 The maximum aerodynamic mass K of the compared airfoils max Plot of dependence on Mach number. The maximum aerodynamic values ​​of the proposed airfoil are higher than those of the NACA 23012 airfoil in the Mach number range of 0.3 to 0.9 and are 64% higher for Mach number 0.7.

[0093] Figure 5 The pitching moment coefficient C of the compared airfoil determined relative to the leading edge of the airfoil at zero lift m0 The results of the plot of the dependence on the Mach number are shown in Figure 2. The pitching moment coefficient values ​​of the proposed airfoil are lower than those of the NACA 23012 airfoil in the Mach number range of 0.3 to 0.65.

[0094] Figure 6 Relative coordinates of the aerodynamic focus of the airfoils with comparison The aerodynamic focus position of the proposed airfoil is further aft than that of the NACA23012 airfoil in the Mach number range from 0.3 to 0.8, which helps to increase the aeroelastic stability of the blade motion in a wide flight speed range.

[0095] Therefore, the proposed aerodynamic airfoil NCV-3 of the lifting element of an aircraft designed according to the essence of the present invention has advantages over the prototype airfoil NACA23012 in terms of the main aerodynamic characteristics within a certain range of Mach numbers, namely, it is superior in terms of maximum lift, the drag is reduced, the value of the maximum aerodynamic mass is increased, a smaller pitching moment value is achieved at zero lift, the aerodynamic position is improved, and the maximum aerodynamic mass is increased.

[0096] The proposed aerodynamic airfoil of the aircraft carrier allows the installation of an airfoil tail trim tab behind the rear edge, said airfoil tail trim tab having a rectangular or trapezoidal cross-sectional shape, including curves, a length not exceeding 15% of the chord without the tab, a thickness not exceeding 1.5% of the chord, and a deflection angle relative to the chord in the range of -5° to +10°.

[0097] When manufacturing blades using the developed family of aerodynamic airfoils, it is planned to use modern materials and technologies.

Claims

1. An airfoil of a lifting element of an aircraft, the airfoil comprising an upper profile and a lower profile formed by a convex curve and the intersection of the convex curve, the upper profile and the lower profile having given coordinates relative to the chord, the airfoil having a rounded leading edge, characterized in that At a relative distance from the leading edge The relative coordinates of the convex curve of the airfoil at the position is measured from the airfoil centerline. For a given chord length and maximum relative thickness of the airfoil, the relative coordinate It is determined by the relations (1) and (2): in: -Relative abscissa of the airfoil contour point, %; -Relative ordinate of the point on the upper contour line of the airfoil, %; -Relative ordinate of the point on the lower contour line of the airfoil, %; - Relative ordinate of the point on the midline of the airfoil, %; - relative ordinate of the points in the symmetric components of the upper and lower profiles of the airfoil, %; - Maximum relative thickness of airfoil, %; c MAX - Maximum thickness of airfoil, m; X - the horizontal coordinate of the contour point of the airfoil, m; Y B - the ordinate of the point on the upper contour of the airfoil, m; Y Η - the ordinate of the point on the lower contour of the airfoil, m; Β - chord length of airfoil, m, At the same time, the following lists the distances from the leading edge The ordinate of the airfoil at the location The value associated with the chord length B, the distance For the maximum relative thickness Defines the vertical axis Range:

2. The airfoil of a lifting element of an aircraft according to claim 1, characterized in that The maximum relative thickness of the airfoil is between 8% and 15%.

3. The airfoil of a lifting element of an aircraft according to any one of claims 1 and 2, characterized in that The airfoil has a pointed, blunt or rounded trailing edge.

4. The airfoil of a lifting element of an aircraft according to any one of claims 1 to 3, characterized in that The airfoil allows a tail tab to be installed behind the trailing edge of the airfoil, the tail tab having a rectangular or trapezoidal cross-sectional shape, including a curved shape, a length not exceeding 15% of the chord without the tail tab, a thickness not exceeding 1.5% of the chord, and a deflection angle of the tail tab relative to the chord in the range of -5° to +10°.

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