RU2789094C1 - Airfoil of the carrier element of an aerial vehicle - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: invention relates to aviation and can be used in designing main and tail rotor blades of rotary-wing aerial vehicles. Airfoil of the carrier element of an aerial vehicle, formed by the upper and lower parts of the contour thereof, provided with a rounded leading edge, a pointed or blunted trailing edge, interconnected by the smooth upper and lower sections of the airfoil contour. Herewith, the distance Yv measured from the airfoil chord along the normal thereto up to the upper part of the contour gradually increases from the leading edge of the airfoil to the maximum value thereof Yv_max 0.0778B in the range X 0.36B…0.37B. The rounded leading edge of the airfoil is made with a radius of curvature Rv along the upper part of the contour equal to Rv=0.019B, wherein said radius then gradually increases along the airfoil chord up to values Rv=1.9B, at the point of the contour farthermost from the airfoil chord, wherein X is the distance counted from the leading edge along the airfoil chord, B is the airfoil chord. The distance from the airfoil chord to the contour thereof decreases monotonously in the direction of the trailing edge, and the radius of curvature of the upper part of the contour continues to increase up to the value of 0.85B, wherein the convex front part of the contour of the upper airfoil surface is smoothly mated with the rectilinear tail section. The angle between the tangent to the upper part of the contour and the airfoil chord at X=B is 10.35°. The distance Yn measured from the airfoil chord along the normal thereto down to the lower part of the contour gradually increases from the leading edge of the airfoil up to the maximum value thereof Yn_max 0.0366B at X=0.26B and then decreases monotonously to the trailing edge of the airfoil. The rounded leading edge of the lower airfoil surface is made with a radius of curvature Rn=0.0127 B along the lower part of the contour, increasing non-monotonously along the airfoil chord, reaching the maximum at X=0.675B, and then decreases down to values of 1.0B…1.2B at the trailing edge at X=B; the angle between the tangent to the lower part of the airfoil contour by the trailing edge and the airfoil chord is 5.4°, and the thickness of the trailing edge of the airfoil is 0.005B.

EFFECT: higher aerodynamic quality as compared with the prototype NACA 23012 at higher values of the lift coefficient Cya at Mach numbers M=0.5 to 0.8.

4 cl, 12 dwg, 2 tbl

Description

The invention relates to aviation and can be used in the design of the blades of the main and tail propellers of rotary-wing aircraft.

A sufficiently large number of aerodynamic profiles are known, similar to the proposed structure and purpose [see. TsAGI patents RU 2098321, publ. December 10, 1997, RU 2123453, publ. December 20, 1998, RU 2145293, publ. 02/10/2000., 10385 publ. July 16, 1999].

The disadvantages of most of the known helicopter airfoils is the absence of a mathematically smooth analytical generatrix, which is a consequence of the experimental method of their design. In this regard, within the framework of this invention, an attempt was made to construct all elements of the helicopter profile based on the use of a single complex mathematical algorithm. Such an approach to airfoil design made it possible to achieve mathematical smoothness of its generatrix and, as a result, unseparated flow over a wide range of angles of attack in the range of actual for rotorcraft Mach numbers 0.3<=M<=0.8. The possibility of using an airfoil in a wide range of angles of attack will make it possible to achieve high values of helicopter main rotor thrust with its relatively small dimensions, which is especially important when designing light helicopters.

The closest to the invention (prototype) is the well-known airfoil NACA 23012 (4.3 of the book "Helicopters. Calculation and design". - M.: Mashinostroenie, 1966), the contour of which is formed by imposing a smooth contour of the symmetrical profile NACA-0012, described by a fractional-power polynomial, to the midline (along the normal to it), composed of the nose - a cubic parabola and the tail of a rectilinear part, docked without a break and a break in the curvature of the contour (NACA Report, N 824, 1945, pp. 101, 146). The contour shape of the prototype profile obtained in this way determines its aerodynamic characteristics when flowing around with air flow.

The reason that prevents obtaining the technical result indicated below when using the known NACA 23012 airfoil is the relatively small values of the aerodynamic quality at the Mach number of the oncoming flow M=0.5-0.65, insufficiently high bearing capacity Cymax at M=0.3-0, 5; relatively low values of critical values of numbers M of the beginning of the growth of profile resistance in the operating range of its loading 0.2<C _Y (M)<C _Ymax (for the average sections of the rotor blades of helicopters) in cruising flight; variable according to the values of the number M, the position of the aerodynamic focus X _f . These features greatly limit the possibility of using this profile in the design of rotors of modern helicopters.

The essence of the invention is as follows.

The objective of the invention is to create a helicopter airfoil with a mathematically smooth generatrix, allowing to provide high bearing properties and lift-to-drag ratio in a wide range of angles of attack at Mach numbers M=0.5-0.8. The technical result obtained in the implementation of the invention is expressed in a higher, compared with the prototype NACA 23012, aerodynamic quality with higher values of the lift coefficient Sua at Mach numbers M=0.5-0.8.

This technical result is achieved by the fact that in the known profile NACA 23012, containing the upper surface, the lower surface and the blunt rear edge, according to the invention, the shape of the upper and lower surfaces is modified and, in addition, the blunt rear edge is replaced by a thin tail part in the form of a plate with a thickness equal to the thickness the trailing edge of the profile, which protrudes beyond the chord by 0.06V, and the angle that the plate makes with the profile chord is in the range from -3° to 6°.

The causal relationships of the features of the invention with the technical result are expressed as follows: the new shape of the lower and upper surfaces changes the flow around the profile compared to the prototype, improving its ADC. A thin tail section in the form of a plate contributes to an increase in the carrying properties of the airfoil not only due to the flow near the plate itself, but also due to the redistribution of the pressure coefficient over the entire surface of the airfoil, which is typical for subsonic flow around airfoils.

The following drawings and tables illustrate the essence of this invention and its comparative effectiveness:

Table 1 - Initial profile (one of the possible profile options with a maximum thickness of about 11.4%, located at X / B = 0.335).

Table 2 - Ranges of profile coordinates (a family of profiles built on the basis of the original profile of Table 1 according to the general principle and differing in relative thickness).

Fig. 1 - illustrates the main elements of the profile according to this invention. The contours of this profile are compared with the contours of the NACA 23012 prototype profile.

Fig. 2 illustrates the shape of a family of airfoils constructed using the general mathematical approach from the original airfoil of FIG. 1. Profiles differ from each other in relative thickness, which is determined by proportionality factors used to change the curvature of the upper and lower surfaces.

Fig. 3 - illustrates the comparison of the profile shape according to this invention with the family of profiles according to the patent RU 2123453 C1.

Fig. 4 illustrates a comparison of the profile shape according to this invention with the family of profiles according to patent RU 2098321 C1.

Fig. 5 - illustrates a comparison of the profile shape according to this invention with the family of profiles according to patent RU 10385 U1.

In FIG. 6-11 shows the characteristics of the maximum lift-to-drag ratio K _max of this airfoil in comparison with the NACA 23012 prototype at Mach numbers of the oncoming flow M=0.3-0.8.

In FIG. 12 shows the dependence of the pitching moment coefficient on the Mach number at zero value of the lift coefficient.

Thus, the aerodynamic profile of the propeller blade, designed in accordance with the essence of this invention, has significant advantages in comparison with the known profiles for helicopter propeller blades in the main aerodynamic characteristics that determine the characteristics of the propellers in various flight modes of the rotorcraft.

Device Description

1. The aerodynamic profile of the carrier element of the aircraft, formed by the upper and lower parts of the line of its contour, having a rounded leading edge, a pointed or blunted trailing edge, interconnected by smooth upper and lower sections of the profile contour, characterized in that the distance Yv, counted from the chord profile along the normal to it upwards to the upper part of the contour, gradually increases from the leading edge of the profile to its maximum value Yv _max 0.0778V, located in the range X = 0.36V-0.37V, the rounded front edge of the profile is made with a radius of curvature Rv along the upper part of the contour, equal to Rv = 0.019V, which then gradually increases along the profile chord to Rv = 1.9V, at the contour point, as far as possible from the profile chord, where X is the distance counted from the leading edge along the profile chord, V profile chord , further towards the trailing edge, the distance from the profile chord to its contour decreases monotonically, and the radius of curvature of the upper h part of the contour continues to increase up to values of 0.85V, where the convex front part of the contour of the upper surface of the profile is smoothly connected to the straight tail part, the angle between the tangent to the upper part of the contour and the chord of the profile at X=B is 10.35°, the distance Yn, counted from the profile chord along the normal to it down to the bottom of the contour, smoothly increases from the leading edge of the profile to its maximum value Yn _max 0.0366V at X=0.26V and then monotonously decreases towards the rear edge of the profile, the rounded front edge of the lower surface of the profile is made with a radius of curvature along the lower part of the contour Rn=0.0127V, which nonmonotonically increases along the profile chord, reaching a maximum at X=0.675V, and then decreases to values of 1.0V…1.2V at the trailing edge at X=B, the angle between the tangent to the lower part of the profile contour at the trailing edge and the profile chord is 5.4°, and the thickness of the trailing edge of the profile is 0.005V. The profile coordinates are given in Table 1.

2. Profile according to claim 1, characterized in that the distance from the chord to the top of the contour is proportional to the distance from the chord to the top of the contour for the profile according to claim 1, the distance from the chord to the bottom of the contour is proportional to the distance from the chord to the bottom of the contour for profile according to claim 1, the proportionality coefficients are in the range of 0.90 ... 1.10 and may differ for the upper and lower surfaces of the profile.

3. Profile according to paragraphs. 1 and 2, characterized in that on its trailing edge there is an additional thin tail in the form of a plate with a thickness equal to the thickness of the trailing edge of the profile, protruding beyond the chord by 0.06V, and the angle that the plate makes with the chord of the profile is in the range from -3° to 6°.

4. Profile according to claim 1, characterized in that it has dimensionless Y / B coordinates located in the ranges shown in table 2.

Table 1 - Coordinates of the original profile (one of the possible options for a profile with a maximum thickness of about 11.4%, located at X / B = 0.335).

Table 2 - Ranges of profile coordinates (a family of profiles built on the basis of the original profile of Table 1 according to the general principle and differing in relative thickness).

Claims (9)

1. The aerodynamic profile of the carrier element of the aircraft, formed by the upper and lower parts of the line of its contour, having a rounded leading edge, a pointed or blunted trailing edge, interconnected by smooth upper and lower sections of the profile contour, characterized in that the distance Yv, counted from the chord profile along the normal to it upwards to the upper part of the contour, gradually increases from the leading edge of the profile to its maximum value Yv _max 0.0778V, located in the range X 0.36V ... 0.37V, the rounded front edge of the profile is made with a radius of curvature Rv along the upper part of the contour, equal to Rv = 0.019V, which then gradually increases along the profile chord to Rv = 1.9V, at the contour point, as far as possible from the profile chord, where X is the distance counted from the leading edge along the profile chord, B is the chord profile, further towards the trailing edge, the distance from the profile chord to its contour decreases monotonically, and the radius of curvature of the upper its part of the contour continues to increase up to values of 0.85V, where the convex front part of the contour of the upper surface of the profile is smoothly connected to the straight tail part, the angle between the tangent to the upper part of the contour and the chord of the profile at X=B is 10.35°, the distance Yn, measured from the chord of the profile along the normal to it down to the bottom of the contour, smoothly increases from the leading edge of the profile to its maximum value Yn _max 0.0366V at X=0.26V and then monotonously decreases towards the trailing edge of the profile, rounded front edge of the lower surface of the profile made with a radius of curvature along the lower part of the contour Rn=0.0127V, which nonmonotonically increases along the profile chord, reaching a maximum at X=0.675V, and then decreases to values of 1.0V...1.2V at the trailing edge at X=B, angle between the tangent to the lower part of the profile contour at the trailing edge and the profile chord is 5.4°, and the thickness of the trailing edge of the profile is 0.005V. 2. Profile according to claim 1, characterized in that the distance from the chord to the top of the contour is proportional to the distance from the chord to the top of the contour for the profile according to claim 1, the distance from the chord to the bottom of the contour is proportional to the distance from the chord to the bottom of the contour for profile according to claim 1, the proportionality coefficients are in the range of 0.90 ... 1.10 and may differ for the upper and lower surfaces of the profile. 3. Profile according to paragraphs. 1 and 2, characterized in that on its trailing edge there is an additional thin tail in the form of a plate with a thickness equal to the thickness of the trailing edge of the profile, protruding beyond the chord by 0.06V, and the angle that the plate makes with the chord of the profile is in range from -3° to 6°. 4. Profile according to claim 1, characterized in that it has dimensionless Y/B coordinates located in the ranges shown in the following table: 2 Table 1 - Initial profile (one of the possible profile options with a maximum thickness of about 11.4%, located at X / B = 0.335). Table 2 - Ranges of profile coordinates (a family of profiles built on the basis of the original profile according to a general principle and differing in relative thickness).

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