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 a specific chord length and a maximum relative thickness of the airfoil, relative coordinates # imgabs1 # # imgabs2 # of a convex curve of the airfoil are calculated from a 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%. An aerodynamic 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 root and middle of the rotor blades, flight data of the aircraft in hovering mode and translational flight are improved, low levels of variable and constant loads acceptable 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 tail parts of a main rotor blade and a tail rotor of an aircraft.

[0002] The airfoil of the NCV-1 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 an 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 lift 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] The aerodynamic layout of rotorcraft blades with high quality and low noise is known (CN101541634B, B64C27 / 467, published on July 17, 2013). The cross section of the blade includes a rear bulge. The difference between the cross-sectional chord line and the cross-sectional bulge line increases from the leading edge of the cross section to the maximum value between the trailing edge of the cross section and the midpoint of the chord line, and decreases toward the trailing edge, thereby forming a rear bulge of the blade. The rear curvature produces greater lift and less drag, and slows down flow stall at high Mach numbers.

[0006] Helicopter tail rotor blades are known (CN101585413A, B64C27 / 32, B64C27 / 467, B64C27 / 473, published on November 25, 2009), which have a leading edge and a trailing edge positioned relative to each other and extending along the longitudinal axis of the blade; when the propeller rotates, the specially shaped trailing edge interacts with the airflow; the blade also has a chord end, which radially decreases from an initial cross-section to an outer cross-section at the end.

[0007] A rotorcraft main rotor blade airfoil and a main rotor blade having such an airfoil are known (CN1253532A, B64C11 / 18; B64C27 / 467, published on May 17, 2000). The airfoil of the blade comprises an upper surface and a lower surface between a leading edge and a trailing edge, wherein the geometric position of a point equidistant from the upper surface and the lower surface determines the center line of the airfoil. In this case, the ratio of the maximum concavity of the center line to the maximum thickness varies linearly with the relative thickness of the airfoil, and is 0.13-0.19 for a 7% airfoil relative thickness (from the chord), and 0.18-0.24 for a 15% airfoil relative thickness (from the chord). The resulting airfoil provides increased main rotor performance at low lift values ​​and high Mach numbers.

[0008] Well-known airfoil series for blades and rotors of rotary-wing aircraft (such as helicopters) (US4412664A, B64C27 / 467, published on November 1, 1983). The distribution of thickness and curvature along the chord of these airfoils provides a pitch moment coefficient close to zero in a wide range of lift coefficients, and a zero pitch moment coefficient at a Mach number of about 0.80. This leads to an improvement in the aeroelastic stability characteristics of the aircraft.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] The disadvantages of NACA23012 airfoil are:

[0013] - the value of the minimum drag coefficient of the airfoil is relatively high;

[0014] - low aerodynamic mass values ​​in the Mach number range of 0.4 to 0.7;

[0015] - the value of the pitching moment coefficient of the airfoil at zero lift is relatively high;

[0016] -The aerodynamic Mach number position of the airfoil varies. Summary of the invention

[0017] 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-1 aerodynamic airfoil (hereinafter referred to as airfoil) of an aircraft lifting element for the middle and tail parts of the blade, while:

[0018] - compared to the prototype, in the range of Mach numbers from 0.45 to 0.7 it has the maximum lift coefficient С ya max The larger value of

[0019] - Compared to the prototype, it has the smallest drag coefficient C in the Mach number range from 0.3 to 0.7 xa min The lower value of

[0020] - Compared to the prototype, it has the maximum lift coefficient K in the range of Mach 0.4 to 0.7 max The larger value of

[0021] - Compared to the prototype, it has a zero lift pitching moment coefficient C in the range of Mach 0.3 to 0.65 mo The smaller modulus value of

[0022] - 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.

[0023] The specific aerodynamic characteristics of the airfoil have a significant influence on the power consumed by the main rotor and tail rotor, the load levels on the structural elements in the actuation system, the maximum lifting capacity, the efficiency and the kinematic parameters of the main rotor blades, tail rotor and other lifting surfaces of the aircraft.

[0024] The technical result of applying the present invention is the improvement of the main aerodynamic characteristics of the airfoils of the middle and tail parts of the propeller blades by using the developed airfoil profile, which ensures the maximum possible mass of the blade and the propeller as a whole in hover mode and translational flight mode, an acceptable low level of variable and constant loads in the lifting system, and aeroelastic stability over a wide range of flight speeds.

[0025] In order to achieve the technical effect, an aerodynamic airfoil of a lifting element of an aircraft is proposed, the airfoil comprising an upper profile and a lower profile formed by a convex curve and an intersection of the convex curve, the upper profile and the lower profile having given coordinates relative to the chord, the airfoil having a circular leading edge, and 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 airfoil contour line at the position Determined by equations (1) and (2):

[0026]

[0027]

[0028] in:

[0029] -Relative abscissa of the airfoil contour point, %;

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

[0031] -Relative ordinate of the point on the lower contour line of the airfoil, %;

[0032] - Relative ordinate of the point on the midline of the airfoil, %;

[0033] - relative ordinate of the points in the symmetric components of the upper and lower profiles of the airfoil, %;

[0034] - Maximum relative thickness of airfoil, %;

[0035] c MAX - Maximum thickness of airfoil, m;

[0036] X - the horizontal coordinate of the contour point of the airfoil, m;

[0037] Y B - the ordinate of the point on the upper contour of the airfoil, m;

[0038] Y H - the ordinate of the point on the lower contour of the airfoil, m;

[0039] Β - chord length of airfoil, m,

[0040] At the same time, the following gives the distance from the leading edge The ordinate of the airfoil at the position The ordinate value associated with the chord length B, the distance For the maximum relative thickness Defines the vertical axis scope;

[0041]

[0042] Furthermore, the maximum relative thickness of the airfoil is between 8% and 20%.In this case, the aerodynamic airfoil of the lifting element of the aircraft may have a pointed, blunt or rounded trailing edge.

[0043] Furthermore, the aerodynamic profile 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 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°.

[0044] Thus, the technical result of the application of the invention is achieved - the main aerodynamic characteristics of the airfoil in the middle and end parts of the propeller blade are improved due to the application of the developed airfoil profile, which ensures the highest possible quality of the blade and the propeller as a whole in hovering mode and translational flight mode, promotes an acceptable low level of variable and constant loads in the system, as well as aeroelastic stability in a wide range of flight speeds.

[0045] The use of the proposed airfoil allows improving flight performance and economic characteristics, extending the range of applications and increasing the competitiveness of 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 mass 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 connected by smooth profiles of the upper and lower surfaces of the airfoil, the leading edge being made with a rounded radius which gradually increases along the chord length B of the airfoil so that the distance Y from the chord perpendicular to the chord to the upper part of the profile is B It increases smoothly from the leading edge of the airfoil and reaches its maximum value in the coordinate range X=0.3B to 0.4B along the chord, with the upper part of the profile smoothly transitioning from convex to concave. 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=0.6B to 0.8B.

[0054] The proposed airfoil refers to the middle and annular parts of the blade and comprises an upper and a lower profile formed by the convex curve and the intersection of the convex curve, with specific coordinates relative to the chord. The coordinates of the convex curve are calculated from the airfoil centerline: the upper one is plus, the lower one is 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 airfoil 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 symmetric components of the upper and lower profiles of the airfoil, %; - Maximum relative thickness of airfoil, %;

[0064] c MAX - Maximum thickness of airfoil, m;

[0065] X - the horizontal coordinate of the contour point of the airfoil, m;

[0066] Y B - the ordinate of the point on the upper contour of the airfoil, m;

[0067] Y H - the ordinate of the point on the lower contour of the airfoil, m;

[0068] Β - chord length of airfoil, m,

[0069] Table 1 (columns 1, 2, and 3) lists the values ​​of the following items: Relative abscissas of points of the airfoil profile Corresponding relative ordinate of the airfoil midline point and the ordinates of the points of symmetry of the upper and lower contours of the airfoil The range of the maximum relative thickness for a given airfoil is given in Table 1. The relative ordinates of the points on the upper and lower contours of the airfoil Calculation of the range (see columns 4 and 5).

[0070] Table 1 Geometric characteristics of airfoil:

[0071]

[0072] When designing an airfoil, the value c MAX , X, Y Β , Y Η, the size of Β can be selected not only in meters, but also in other units.

[0073] The coordinates of a series of airfoils of different thicknesses can be plotted. In this case, The values ​​of remain the same in Table 1 and for the maximum relative thickness of the airfoil in the range of 8% to 20% Based on equations (1) and (2), we calculate The value of .

[0074] By adding the relative value Multiply the given dimension value Β by the airfoil chord length to obtain the dimension values ​​X, Y CP , Y CИΜ , Y Β , Y Η .

[0075] The geometry of the airfoil profile ( Figure 1 ) determines the aerodynamics of the airfoil when the 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.

[0076] Figure 1 Shown for the 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, where:

[0077] Y CP - the ordinate of the midline point of the airfoil;

[0078] Y CИΜ - ordinates of the points of symmetry of the upper and lower profiles of the airfoil;

[0079] Y Β - ordinate of the point on the upper contour of the airfoil;

[0080] Y Η - ordinate of the point of the lower contour of the airfoil;

[0081] Β – chord length of the airfoil;

[0082] - Maximum relative thickness of airfoil, %;

[0083] -Relative abscissa of the airfoil contour point, %;

[0084] - Relative ordinate of the contour point of the airfoil, %;

[0085] -Relative ordinate of the midline point of the airfoil, %;

[0086] - Relative ordinates of the points of symmetry components of the upper and lower profiles of the airfoil, %.

[0087] Figure 2 is the maximum lift of the compared airfoil ya max Plot of the dependence of the coefficients on the Mach number. In terms of maximum lift, the proposed airfoil exceeds NACA 23012 at Mach numbers greater than 0.45.

[0088] Figure 3 Minimum drag coefficient С of the compared airfoils xa min Plot of the dependence on Mach number. The minimum drag values ​​of the proposed airfoil are on average 12% lower than the minimum drag of the NACA 23012 airfoil in the range of Mach numbers from 0.3 to 0.7.

[0089] 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 on average 24% higher than those of the NACA 23012 airfoil in the Mach number range of 0.4 to 0.7.

[0090] Figure 5 The pitching moment coefficient C of the compared airfoil determined relative to the leading edge of the airfoil at zero lift m0 Graph of the results of the dependence on Mach number. The pitching moment values ​​of the proposed airfoil at zero lift are lower than those of the NACA 23012 airfoil in the Mach number range of 0.3 to 0.65.

[0091] Figure 6 Relative coordinates of the aerodynamic focus of the airfoils with comparison The results of the dependence on Mach number are plotted. The focal 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 range of flight speeds.

[0092] Thus, the proposed aerodynamic airfoil NCV-1 of the lifting element of an aircraft designed according to the essence of the 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 head-on drag is reduced, the value of the maximum aerodynamic mass is increased, a smaller pitching moment value is achieved at zero lift, the aeroelastic stability of the movement of the blade within a wide range of flight speeds is increased.

[0093] When manufacturing the blades using the developed family of airfoils, it is planned to use state-of-the-art materials and techniques.

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 H - 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 gives the distance from the leading edge The ordinate of the airfoil at the location The ordinate 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 20%.

3. A wing of a lifting element for an aircraft according to any one of claims 1 and 2, characterized in that The airfoil can have 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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