RU2539278C1 - Helicopter rotor blade - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: blade comprises root part, aerodynamically shaped parts and tip. In the range of relative radii from 0.5R to (0.95-0.98)R aerofoils feature permanent relative depth making 0.10-0.095 of chord profile. Radii of rounding of top and bottom parts of profile tip feature the ratios of about 1:3. Aerofoils at relative radii 0.4, 0.3 and 0.2 feature variable relative depth consecutively increasing at every said relative radius by about 1/4 of profile relative depth at relative radius 0.5. Tip in plan is composed of elliptic curve while its aerofoil is composed by arcs of ellipses tangentially inscribed in outline of adjacent aerofoil cross-sections. Blade geometrical twist makes approximately 7 degrees while blade finned part starts from relative radius 0.13-0.15R.

EFFECT: better aerodynamics, higher safety at rotor spinup and stoppage.

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Description

The invention relates to the field of aviation, in particular to the aerodynamic layout of the rotor blade of a rotorcraft.

Known rotor blade (patent RU No. 2191717 from 05.06.1998, B64C 11/18, B64C 27/46), the aerodynamic layout of which is designed to operate the rotor in the transonic range of speeds at a low level of lift.

Known rotor blade (patent RU No. 2123453 dated 12/15/1996, B64C 11/16, B64C 11/18) with the aerodynamic profile of the same blade span. The well-known aerodynamic profile, as an isolated object, has relatively high aerodynamic qualities, but when forming a blade, as a supporting object, only from one type of profile does not allow providing the blade with the necessary aerodynamic qualities due to:

- unsatisfactory in sign (clearly positive, see Fig.6) coefficient of aerodynamic moment m _zo at zero lifting force (C _y = 0) due to excessive S-shape of the midline of the profile;

- the absence of the law of changing the thickness of the cross section of the profile for the span of the blade, which makes it difficult to meet the strength conditions and ensure the necessary balancing of the blade along the chord;

- the lack of twist of the blade - as an essential parameter affecting the aerodynamic quality of the rotor as a whole.

A known rotor blade of a helicopter (patent RU No. 2314230 dated 06/14/2006, B64C 27/46), the aerodynamic layout of which includes several types of aerodynamic profiles in the range of the blade, shows the shape of the blade in plan with a constant chord B along the length of the blade and the tip, given changes in the thickness of the cross-section of the profiles along the length of the blade, the law of twist of the blade, a table of coordinates of a typical section of the blade is presented in the range of current relative radii from (0.5-0.6) R to 1.0R. The combination of distinctive features mentioned patent adopted as a prototype.

The analysis of the distinguishing features of the known blade showed that the distribution of the relative thicknesses of the C / B profiles according to the blade span as claimed in the patent RU No. 2314230 is specified only for the typical part of the blade, the value of which, as follows from the formula, is 0.109-0.121 profile chords. And for the transitional part of the blade - from 0.25R to 0.55R, which is up to 45% of the bearing part of the blade, the distribution of the relative thicknesses of C / B profiles is presented in the form of a theoretical field (see figure 4). Moreover, the spread in the values of the relative thicknesses of C / B in each of the mentioned sections of the transitional part of the blade is at least 33%. Thus, it is not entirely correct, as follows from the description of the patent, to transfer the concept of optimality to solutions for changing the relative thickness of the profiles on the transitional part of the blade.

As for the tip of the blade, the patent materials do not reflect:

- ending form in plan;

- aerodynamic profiling of the ending surface;

those. not reflected the entire set of characteristics of the aerodynamic layout of the blade, which claims the prototype.

The beginning of the feathered part of the blade in the prototype is indicated with relative radii of 0.20-0.35, which indirectly indicates a large deflection of the blade under the influence of its own weight and, as a necessary consequence, difficulties in the layout compatibility of the rotor with the fuselage structure bordering the area of dynamic mobility of the blade .

Reference. In accordance with the Appendix to the patent No. 2314230 on the registration of the license agreement for the use of the invention, it follows that the License Agreement No. RD0045296 dated December 20, 2008 was concluded with OJSC Kumertau Aviation Production Enterprise for the manufacture of the Ka-226 helicopter. In the “Ka226 Technical Operation Manual”, book 0. Helicopter, section 006.00.00 p. 3/4 June 10/05 in Fig. 1 “General view of the helicopter and its main dimensions”, the value of the static deflection of the blade, equal to 550 mm, which amounts to 9% of the length of the blade and confirms the reason for the solution of the feathered part of the blade of the prototype.

Another negative consequence of the large static deflection of the blade is the critical overhang of the blade from the ground (in the case of the Ka226 helicopter, it is 1630 mm), which makes it unsafe to keep service personnel near the helicopter when the main rotor is unscrewed and stopped.

When developing the inventive rotor blade of a helicopter, the aim was to create a blade for a light helicopter (including a coaxial rotor), which provides:

- high aerodynamic quality in a wide range of helicopter flight speeds;

- solving the problem of low loads in the blade control system by reducing the hinge moment;

- small values of the static deflection of the blade, ensuring safety during the promotion and shutdown of the rotor.

Achieving this goal allows you to create a blade with parameters, the combination of which affects the key operational criterion of consumer demand for the helicopter.

The result of the proposed technical solution is achieved by the fact that on the rotor blades of the helicopter containing butt and aerodynamic profiled parts, consisting of several types of aerodynamic profiles with chord B, joined along the front and rear edges, and along the upper and lower parts of the profile profile section are connected by a ruler family surfaces stretched over the contours of adjacent aerodynamic profiles, so that they form a twist of the blade close to linear, and an aerodynamic shaped tip moreover, the aerodynamically profiled part of the blade in the range of relative radii from 0.5R to (0.95-0.98) R, where R is the radius of the rotor, is made with a constant relative thickness of the profile in the range of values 0.10V-0.095V, except Moreover, the rounding radii of the lower and upper parts of the profile nose are in a ratio of approximately 1: 3, and their values are correlated with the relative thickness of the profile to the chord, and the contours of the upper part of the profile contour in the range of 0.30-1.0 chords are formed by convex and concave parts contour in the form of radii, approximately equal to 2.5 V each, which are connected by a spline in a section from 0.62 V to 0.72 V, the lower section of the said profile has a convex contour shape with a blurred maximum in the spline range, while the ordinates of the points of the upper part of the Y contour _in / B and the lower part of the contour Y _n / b, located at relative distances X / V from the front edge of the profile, are shown in the table and the ordinate range of the upper (Y _in / B) and lower (Y _n / b) parts of the contour at relative distances X / B from 0.03 to 0.5 allow changes in the range up to + 5%, and on large Х / В - from 0.5 to 0.98 - up to + 10%, aerodynamic profiles at relative radii of 0.4R, 0.3R and 0.2R are made with a variable relative thickness of the profile to the chord, the values of which are changed sequentially increase at each of the mentioned relative radii by about 1/4 of the relative thickness of the profile at a relative radius of 0.5R, and in the section of relative radii from (0.95-0.98) R to R, the shape of the blade in plan is formed by an elliptic curve with a relative value semiaxes, respectively equal to 0.34 and 0.68 chords, forming the law a piece whose surface is formed by arcs of ellipses lying in a plane perpendicular to the plane of the cross sections of this section of the blade and tangentially inscribed in the contour of the corresponding sections, the feathered part of the blade begins with a relative radius (0.13-0.15) R, a geometric twist sections of the blade in the range of relative radii from 0.2R to (0.95-0.98) R is ≈7 °.

The proposed technical solution of the blade is illustrated by drawings, where:

- figure 1 shows a General view of the blade;

- figure 2 shows the shaping of the toe profile;

- figure 3 shows the formation of the upper rear part of the profile contour, integrated with the lower rear part of the profile contour of the prototype;

- figure 4 shows the shape of the aerodynamic profile for a range of relative radii from 0.5R to 0.98R in accordance with the coordinate table;

- figure 5 shows an example of the formation of the nose of the transitional part of the blade at a relative radius of 0.2R;

- figure 6 shows the shape of the tip of the blade in the plan (place A, figure 1);

- Fig.7 shows a longitudinal section of the ending according to EE of Fig.6;

- in Fig.8 - combined longitudinal section of the ending (type D, Fig.5);

- figure 9 shows the change in relative thickness C / B aerodynamic profiles along the length of the blade;

- figure 10 shows an example of the distribution of moments of bending resistance W _{x the} blade along its length;

- figure 11 shows an example of the layout of the rotor with the proposed blade on a helicopter with a take-off weight of 1.5-2.0 tons, providing safe deflection of the blade when the rotor is untwisted and stopped.

The blade 1 of the rotor of the helicopter in accordance with its proposed technical solution is made rectangular in plan with a constant radius R of the rotor of the chord B.

The blade 1 consists of a butt part 2, aerodynamically shaped parts - a transition part 3 in the range of relative radii from 0.2R to 0.5R, typical part 4 in the range of relative radii from 0.5R to (0.95-0.98) R and ending 5.

.The blade rotates on axis 6 with angular velocity $${}^{‵}\Omega$$

.

The feathered part of the blade 1 begins with the relative radii (0.13-0.15) R of the butt part 2 and in the range of relative radii from 0.2R to (0.95-0.98) R has a geometric twist close to linear Δφ≈7 °.

The adopted twist Δφ of the blade allows, as the results of computational studies show, to obtain an efficiency of at least 0.70-0.73 on the rotor and to ensure, in comparison with the prototype, a more uniform distribution of the aerodynamic load on the blade (see M.L. Mil and other Helicopters, calculation and design, Volume 2. M., Engineering, 1967, pp. 81-83, formulas: 7.35; 7.37; .7.39, in which the geometric twist Δφ is an essential component of the aerodynamic load p _о ).

Aerodynamic profiling of the transitional part 3 of the blade 1 is made of at least two types of aerodynamic profiles with a variable relative thickness of the profile to the chord (C / B), where C is the thickness of the profile (the types of profiles used are not shown conditionally).

A typical part 4 of the blade 1 is made of the same aerodynamic profiles with a constant relative profile thickness in the range of values 0.10V-0.095V.

This provides a lower profile resistance of the blade compared to the prototype and the possibility of stable advancement of the operating modes of the rotor to Mach numbers ≈0.6-0.8 with a lifting coefficient C _{ymax of} at least 0.7 (see P.R. Payne “Dynamics and aerodynamics of a helicopter ”, M., Oborongiz, 1963, p. 17, FIG. 1.4).

In contrast to the prototype, the nose contour 7 of type 4 of the aerodynamic profile is formed by the radii of fillet r _n - 8 and r _in - 9 of the lower 10 and upper 11 forming the profile contour in a ratio of approximately 1: 3, respectively, with the point 12 of smooth conjugation of the mentioned radii on the profile chord.

The values of the radii 8 and 9 are correlated with the thickness of the profile C to ensure a smooth transition to the contours of the socks of the transitional part 3 of the blade 1 and are determined from the ratio:

r _{in / n} ≈k _{in / n} * C,

Where

k _at ≈0.266-0.272; k _n = 0,090-0,093.

Contours of the upper part 13 of the contour of the airfoil model portion 4 of the blade 1 in the range of 0,30-1,0 chord formed by the radii r and r _{MY wog} approximately equal to 2.5V, respectively forming convex 14 and concave 15 portion of the contour.

In the range section from 0,62V to 0,72V _MY radii r and r _wog conjugate spline 16. Contours of the bottom of the contour of the airfoil 17 have a convex curvature with a diffuse maximum at portion 18 within the range of accommodation of the spline 16.

Figure 4 shows the aerodynamic profile of a typical part 4 of the blade 1, the contour of which is made in accordance with the table of coordinates and the laws of constructing the contour of the toe 7 of the profile (see figure 2) and the contours of parts 13 and 17 (see figure 3).

Table of coordinates of the aerodynamic profile of type 4 X / B Y _in / in -Y _n / b 0.00 0.00 0.00 0,03 0,032 0.013 0.05 0,041 0.015 0.06 0,044 0.016 0.08 0,050 0.017 0.10 0,055 0.019 0.20 0,069 0,023 0.30 0,073 0,025 0.40 0,071 0,028 0.50 0,064 0,029 0.60 0,054 0,032 0.70 0,041 0,032 0.80 0,025 0,027 0.87 0.015 0.019 0.98 0.006 0.010

The range of relative ordinates of the upper (Y _in / V) and lower (Y _n / V) parts of the contour at relative X / B distances from 0.03 to 0.5 allows changes up to + 5%, and for large X / B - from 0.5 to 0.98 - up to + 10%.

The concavity of the profile f does not exceed 0.024V, which minimizes the displacement of the center of pressure of the profile when its angle of attack changes.

Figure 5 shows an example of a fragment of one of the types of aerodynamic profiles 19 of the transition part 3 at a relative radius of 0.2R.

, значения которого лежат в диапазоне 2,43-2,46.The values of the radii 20 and 21, forming the contour of the nose 22 of the aerodynamic profile 19, are correlated with the values of the same radii 8 and 9 of the typical part 4 of the blade 1 through the coefficient $$k_t^P$$

whose values are in the range of 2.43-2.46.

So, the radius 21, forming the upper part of the contour of the sock 22, corresponds with the same radius 9 of the contour of the sock 7 of the typical part 4 by the ratio:

$$k_{\mathrm{at}}*k_t^P*C_{0,2}$$

where C _0.2 is the thickness of the profile by 0.2R.

On the plot of relative radii from (0.95-0.98) R to R, the shape of the blade 1 in plan is formed by an elliptic curve 23 with a relative size of the axes a and b, respectively equal to 0.34 and 0.68 chords B in the profile, forming the tip 5 blades 1.

The surface of the tip 5, as shown in Fig.7, is formed by arcs of ellipses 24 and 25 lying in a plane perpendicular to the plane of the cross sections of the tip 5, and the corresponding sections of the blade 1 inscribed in a tangent into the contour.

The current values of the semiaxes a _i , b _i and b _j - ellipses 24 and 25 along the chord B are determined by the boundary of the intersection of the ellipses with the transverse profile contour. Moreover, the values of the current semi-axes b _i corresponds to the value Y _{in the} corresponding current profile at the tip 5, ab _j - respectively, to the value Y _{n of the} mentioned profile.

In the example of FIG. 7, b _i and b _j correspond to the tip 5 profile at a relative radius of 0.98R.

On Fig shows the aerodynamic surface of the tip 5, made according to the proposed technical solution, which shows that the upper surface 26 is as if (conditionally) oriented downward at an angle γ from the plane of the chords 27.

The average value of the angle γ lies within 7 deg. -10 deg. And as experimental aerodynamic studies show (see Gubarev B.A. Ignatkin YM "Aerodynamic research connected with blade selection for Kamov 115 helicopter", Proceedings of 26 ^th European Rotorcr Forum, Netherlands, Hague, 26-29 Sept. 2000. p. p. 18.1-18.5), endings with a similar angle of deviation of the upper aerodynamic surface down from the plane of the chords provide:

- an increase in the critical Mach number to ≈0.8, which pushes the “wave crisis” onto the blades in terms of helicopter flight speed;

- reduction of the hinge moment of the blade;

- increase the relative efficiency of the rotor within at least 3%.

The distribution of the relative thicknesses C / B profiles of the blade 1 is shown in Fig.9. On the transitional part 3 of the blade 1 at a relative radius of 0.4R; 0.3R and 0.2R the change in the relative thickness of the C / B profile sequentially increases on each of the mentioned relative radii by approximately 1/4 of the relative thickness of the profile on the relative radius 0.5R of the typical part 4 of the blade 4.

The implementation of the blade according to the proposed change in the relative thickness of the aerodynamic profiles of the transition part 3 allows you to get the necessary character of the distribution of moments of bending resistance W _x blades (see figure 10), sufficient to ensure static deflection within no more than 3% of the length of the blade.

According to the proposed technical solution, the blade was developed for a helicopter with a take-off weight of 1.5 t-2.0 t. And with a rotor diameter of 9.0 m-10 m, the static deflection of the blade was in the range of not more than 135-145 mm. This ensures, as shown in Fig. 11, the safe presence of maintenance personnel under the rotor of the helicopter in the modes of its promotion and shutdown.

Thus, the blade, designed in accordance with the essence of this invention, has, in comparison with the prototype, advantages in the basic aerodynamic characteristics in a wide range of helicopter flight speeds and ensures the safety of helicopter operation on the ground.

Claims (1)

A rotor blade of a helicopter containing butt and aerodynamic shaped parts, consisting of several types of aerodynamic profiles with chord B, joined along the front and rear edges, and along the upper and lower parts of the profile profile section of a family of ruled surfaces stretched over the contours of adjacent aerodynamic profiles, so that they form a twist of the blade, and an aerodynamic shaped tip, characterized in that the aerodynamically shaped part of the blade in the relative range radii from 0.5R to (0.95-0.98) R, where R is the rotor radius, is made with a constant relative profile thickness in the range of 0.10V-0.095V, in addition, the radii of rounding of the lower and upper parts the profile toe is in a ratio of approximately 1: 3, and their values are correlated with the relative thickness of the profile to the chord, and the contours of the upper part of the profile contour in the range of 0.30-1.0 chords are formed by convex and concave parts of the contour in the form of radii approximately equal to 2 , 5V each, which in the section from 0.62V to 0.72V are connected by a spline, nor zhny portion of said profile has a convex contour shape with a diffuse maximum in the range of the spline, thus related to the chord in said profile ordinates of the points of the upper part of the circuit Y _to / B and the lower part of the contour Y _n / B, positioned at relative distances X / B of the front profile edges are given in the table:
X / B Y _in / b -Y _n / b 0.00 0.00 0.00 0,03 0,032 0.013 0.05 0,041 0.015 0.06 0,044 0.016 0.08 0,050 0.017 0.10 0,055 0.019 0.20 0,069 0,023 0.30 0,073 0,025 0.40 0,071 0,028 0.50 0,064 0,029 0.60 0,054 0,032 0.70 0,041 0,032 0.80 0,025 0,027 0.87 0.015 0.019 0.98 0.006 0.010
and the ordinate range of the upper (Y _in / B) and lower (Y _n / V) parts of the contour at relative distances X / B from 0.03 to 0.5 allow changes up to + 5%, and for large X / B - from 0.5 to 0.98 - up to + 10%, aerodynamic profiles at relative radii of 0.4R, 0.3R and 0.2R are made with a variable relative thickness of the profile to the chord, changes in the values of which sequentially increase on each of the aforementioned relative radii by about 1/4 of the relative thickness of the profile at a relative radius of 0.5R, and in the portion of relative radii from (0.95-0.98 ) R to R, the shape of the blade in plan is formed by an elliptic curve with a relative semiaxis of 0.34 and 0.68 chords, respectively, forming a tip whose surface is formed by arcs of ellipses lying in a plane perpendicular to the plane of the cross sections of this section of the blade and tangent the corresponding sections inscribed in the contour, the feathered part of the blade begins with a relative radius (0.13-0.15) R, and the geometric twist of the blade sections in the range of relative radii from 0.2R to (0.95-0.98) R is ≈ 7 °.

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