RU2278058C2 - Propeller blade - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: leading and trailing edges of propeller blade are formed by intersection of two parabolas or three parabolas contacting the circumference at acute angle on leading and trailing edges engageable with semi-circumference on leading and trailing edges. Provision is made for stabilizing plane in form of segment at initial value on fin tip smoothly decreasing from zero to 1/3 of length from origin of blade. Leading and trailing edges are rounded-off in shape.

EFFECT: increased lifting force.

3 cl, 3 dwg

Description

The field of technology.

The invention relates to the field of aviation.

A propeller blade is known (Patent 2228882 of May 20, 2004), the profile of the lower and upper blades of which are formed by the intersection of two parabolas: Y ₁ = K ₁ x ^1/2 ; Y ₂ = 2R _o + K ₂ X ^1/2 .

These planes intersect at an acute angle at the lower edge and mate at the trailing edge with a semicircle of radius R _o . The leading edge of the propeller blade is formed along the parabola U ₃ = K ₃ X ^1/2 , the trailing edge has a stabilizing plane. The disadvantage is the low efficiency with a limited length of the blade.

Disclosure of invention

To increase the efficiency of the propeller blades (1), the front and rear edges are formed according to the formula of two or more parabolas: У ₁ = K ₁ X ^1/2 ; Y ₂ = 2R _o + K ₂ X ^1/2 ; Y ₃ = —K ₃ X ² (reduced parabola) (FIG. 1) or Y ₁ = K ₁ X ^1/2 ; Y ₂ = 2R _o + K ₂ X ^1/2 ; (2) relating to both cases circle radius R≥2R _o, the center of which is located l≥ _^2/3 L, where, L - length of the projection of the blade at the coordinate X, R _o - radius of a circle at the origin. The profile of the lower and upper lobes is formed by the intersection of two parabolas (1): Y ₄ = K ₄ X ^1/2 ; Y ₅ = 2R _o + K ₅ X ^1/2 ; however, these planes intersect at an acute angle at the rear (figure 1) or front (figure 2) edge. In the first case, a "cutting" (Fig. 1) front plane is provided on the leading edge, in the second case, the trailing edge has a stabilizing plane, which, in turn, are tangent to the front (Fig. 1), rear (Fig. 2) ) planes and represent a segment of a plane with an initial value l≥R _o at the end of the pen, and gradually decreasing to zero by 1/3 of the length of the propeller blade.

The leading sharp edge (FIG. 2) is rounded off at a distance R _i from the point of intersection of the parabolas with an arc of radius R _i to improve streamlining at subsonic speed; the trailing edge (FIG. 1) is rounded in the same way to increase strength.

The current coordinate of the blade length L _i is determined by calculation. The current radius R _i is determined by the formula: R _i = L _i / K _b ;

The coefficients are selected from the following values:

K ₃ ≥1; K ₄ ≥1; K ₅ ≥ (0.6 ÷ 0.8) K ₄ ; K ₆ ÷ 7 / K ₄ .

The coefficients K ₁ and K _{2 are} calculated by the formulas:

K ₁ = Y _1A / X _1A ^1/2 ; where K ₂ = (Y _2B -2R _o ) / X _2B ^1/2 ,

where X _1A ; At _1A ; X _2B ; Y _2B - the coordinates of the points of tangency of the parabolas Y ₁ and Y ₂ with a circle of radius R.

To find the points of tangency, the parabolas with the circle set the initial parameters for constructing the blade:

- angle of attack α≥7 °;

- radii R _o and R;

- the projection of the blade on the coordinate X-L.

Knowing that the center of the circle is located l≥ _^2/3 L, is reduced from this point perpendicular. The point of intersection of the perpendicular with the prolonged line of angle of attack α≥7 ° will be the lower point of contact of the parabola Y ₁ with the circle - point A (X _1A ; Y _1A ). Draw a circle of radius R through point A with the center lying on the restored perpendicular. We get the second point of intersection of the perpendicular with the circle - point B (X _2B ; Y _2B ). This point will be the point of contact of the parabola U ₂ with the circle. Next, the calculation of the coefficients K ₁ , K ₂ according to the above formulas.

To reduce the free vibrations of the propeller blades (turbine blades, compressor, fan, etc.) of limited radial length up to 1.5 m, it is necessary to mechanically connect the ends of the pen around the entire circumference with a guide ring; to form a limiting profile of the blade along the parabola: Y ₁ = K ₁ X ^{1/2 /} Fig.2a/. The propeller blade has a feather bend down by an angle β≥60 °, which allows the use of a centrifugal air flow to increase the lifting force (Fig.1, 2).

The thickness of the parabola blade is selected from the necessary mechanical strength.

The coefficients are selected from the following values:

K ₁ ≥0.5; K ₂ ≥1; K ₃ ≥0.7.

To reduce free vibrations, the blades can be mechanically connected around a circle.

In Fig.1, 2 shows the propeller blades, and in Fig.1 - the front edge is rounded with a radius R _o and has a sharp trailing edge; the leading edge is provided with a “cutting” plane 1. FIG. 2 has a sharp leading edge, and the rear is rounded with a radius Ro and has a stabilizing plane 1. Both blades have a feather tip bend at an angle β≥60 ° to direct the centrifugal flow that increases the lifting force ( traction force), in Fig.2A is a longitudinal profile of the blade.

Propeller operation

The speed of the incoming flow increases linearly from the comet to the periphery and reaches its maximum value at the end of the pen. Since the resistance profile of the propeller to overcome resistance when creating lifting force (traction force) artificially increases with the current radius R> 2R ₀ , the lifting force increases, while the longitudinal force for transmitting the lifting force (traction force) to the increased shoulder increases. Therefore, the following methods are provided for reducing free vibrations:

1) a parabolic transverse and longitudinal profile of the blade;

2) the use of materials with increased internal attenuation, etc.

The speed of the incident flow on the front plane creates a vacuum, and on the back plane it creates pressure, after the propeller blade leaves, these two flows meet on the stabilizing plane (Fig. 2) or at the sharp intersection of the parabolic planes (Fig. 1) and a lifting force is created.

Moreover, to reduce the drag of the propeller blade, a “cutting” plane is provided (Fig. 1), which has a size l≥R _o at the end of the pen and gradually decreases to zero by about 1/3 of the blade length. The bend of the end of the pen at an angle β≥60 ° additionally directs the centrifugal air flow (Fig.1, 2), increasing the lifting force. The pointed front edge (FIG. 2) and the cutting plane (FIG. 1) reduce the drag of the propeller. As a result of the above structural differences, the propeller efficiency increases sharply with a limited length.

The comparative tests performed on the fabricated mock-ups at R = 2R ₀ showed the following advantages compared to (1) - the lifting force (traction force) increases by about 30%.

Claims (3)

1. The blade of the propeller, characterized in that the front and rear edges of the plane are formed by the intersection of two parabolas ₁ = K ₁ X ^1/2 , ₂ = 2R ₀ + K ₂ X ^1/2 or three parabolas Y ₁ = K ₁ X ^1/2 , Y ₂ = 2R ₀ + K ₂ X ^1/2 , Y ₃ = K ₃ X ² , tangent to a circle of radius R≥R ₀ , the center of which is at a distance l≥2 / 3L, where L is the projection of the length of the blade on the X coordinate; R ₀ is the radius of the circle at the origin; the profile is formed by the intersection of two parabolas Y ₄ = K ₄ X ^1/2 , Y ₅ = 2R ₀ + K ₅ X ^1/2 , at an acute angle at the leading and trailing edges, conjugated at the trailing and leading edges with semicircles of radius R ₀ , a stabilizing plane is provided, which is a segment of a plane with an initial value at the end of the pen l≥R ₀ and gradually decreasing to zero by 1 / 3, the length from the beginning of the propeller blades, the front sharp edge is rounded off in the region R _i from a point of intersection of the parabola arc radius R _i for improved aerodynamics at subsonic speed, the rear sharp edge is rounded off in the same manner to increase strongly five, the current blade length L _i is determined by calculation, the current radius of the blade is defined by formula R _i = L _i / K ₆ , where the coefficients are selected from the following values: K ₃ ≥1, K ₄ ≥1, K ₅ = K ₄ (0.6 ÷ 0.8), K ₆ ≥7 / K ₄ , the coefficients K ₁ and K _{2 are} calculated by the formulas K ₁ = Y _1A / X _1A ^1/2 , K ₂ = (Y _2B -2R ₀ ) / X _2B ^1/2 , where X _1A , Y _1A , X _2B , Y _2B are the coordinates of the points of contact of the parabolas U ₁ and Y ₂ with a circle of radius R, the angle of attack α≥7 ° and R ₀ , R, L are set initially. 2. The propeller blade according to claim 1, characterized in that to reduce free vibrations the end of the blade up to 1.5 m long is mechanically closed by a ring around the entire circumference, and the longitudinal profile of the blade more than 1.5 m long is formed by a parabola U ₁ = K ₁ X ^1/2 , where K ₁ ≥0.7. 3. The propeller blade according to claim 2, characterized in that it has a downward bend of at least 60 ° to increase the lifting force.

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