KR20140092040A - Blade with good lift drag ratio - Google Patents

Abstract

The present invention relates to a technology in relation to a blade for attaining enhancement of lift to drag ratio by increasing lift coefficient and decreasing drag coefficient. Concretely, the present invention provides the blade where the thickness (delta) of a boundary layer at a separation point is assumed to be 1.38 mm, longitudinally forming a continuous groove on its upper surface, wherein the value of ″l″ is positive when the rear end of the groove is positioned ahead of the separation point, the value of ″l″ is negative when the rear end of the groove is positioned in the rear of the separation point where a distance between the rear end of the grooves and the separation point is ″l″, and ″A″, ″B″ and ″C″ are designed to be 1, 0.12 and -0.5 to 0.5, respectively where a width of the groove is ″d″, a maximum depth of the groove is ″h″, depth ratio (h/delta) is defined to be ″A″, width ratio (h/delta) is defined to be ″B″, and ratio of a length to the separation point (1/delta) is defined to be ″C″, thereby attaining enhancement of the lift to drag ratio (CL/CD).

Description

{BLADE WITH GOOD LIFT DRAG RATIO}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blade used for an airplane or a wind power generation, and relates to a blade capable of increasing the lift coefficient and reducing the drag coefficient, thereby achieving improvement of the port ratio.

Since the airplane's wings are responsible for the lift required to support the weight of the aircraft and the performance of the airplane depends on the characteristics of the blades, it is necessary to adopt a blade that can best satisfy the design conditions have.

The wing of a plane exhibits a large performance difference depending on its shape and surface shape. Generally, a rough surface has a higher lift-to-drag ratio than a smooth wing with a low Reynolds number This structure is easily observed even in the form of wings of flying creatures such as insects and birds that are known and exist in nature.

In the prior art related to the present invention, there is a "root airfoil of a wind power generator blade" of Korean Patent No. 10-1216308.

1 is a cross-sectional view of a root airfoil according to the prior art. The root airfoil 100 includes a chord 103 connecting the leading edge 101 and the trailing edge 102, A suction surface 104 formed on the upper side and a pressure surface 105 formed on the lower side.

In the prior art, the thickness (y / c) of the root airfoil on the pressure surface is -0.11 at the point where the length (x / c) of the visual line is 0.4 under the predetermined condition, The thickness of the airfoil is -0.085, the thickness of the root airfoil on the pressure side is -0.032 at the point where the length of the ridge line is 0.8, and the thickness of the root airfoil on the pressure side is 0.0 .

That is, the prior art is designed to have a high aspect ratio by varying the root airfoil thickness of the blade depending on the position.

However, since the prior art only considers the root side of the blade, there is a problem in that there is a lack of consideration for improving the aspect ratio of the blade having a long span.

1. Korean Registered Patent No. 10-1216308 (Registered on December 20, 2012)

SUMMARY OF THE INVENTION The present invention provides a technique for forming a predetermined groove in the longitudinal direction of a blade so as to relatively easily improve the armament ratio of the blade.

In order to attain the above-mentioned object, the present invention provides a blade having an improved portability ratio, wherein a boundary layer thickness (delta) of a separation starting point is assumed to be 1.38 mm, and a continuous groove is formed in the longitudinal direction on the upper surface of the blade L "value has a positive value when the rear end of the groove is located forward from the peeling start point, and" l "when the rear end of the groove is positioned rearward from the peeling start point. Value has a minus value, the width of the groove is "d", the maximum depth of the groove is "h", the depth ratio h / δ is defined as "A" B = 0.12, C = -0.5 to 0.5 (A / B) is defined as " B ", the ratio ratio l / So that improvement of the port ratio CL / CD can be achieved.

According to the present invention, the blade having the above-mentioned improved bulb ratio is characterized in that the armament ratio is improved by 9% or more as compared with the blade without the plain portion.

In another aspect of the present invention, there is provided a blade in which a boundary layer thickness delta of a separation starting point is 1.38 mm, Quot; 1 "when the rear end of the groove is located forward from the peeling start point, and a first groove and a second groove having the same shape are formed on the rear surface of the groove, The value of the first groove has a positive value, the value of the first groove has a positive value, the depth ratio h / d is defined as "A", the width ratio h / d is defined as "B", and the length ratio l / D) is defined as " C ", the pitch ratio p / d is defined as "D ", A = 0.8, B = 0.1, C = -0.5 to 0.5, D = 0.7 to 1.15It is designed so that the above is characterized in that in order to achieve an improvement in yanghang ratio (CL / CD).

In addition, in the present invention, the blade in which the above-mentioned inclination ratio is improved is characterized in that the armament ratio is improved by 10% or more as compared with the blade without the grooved portion.

The blade having the improved portability ratio according to the present invention is formed by forming a continuous groove in the longitudinal direction on the upper surface of the blade, considering the depth and width of the groove and the distance from the peeling start point to the rear end of the groove So that it is possible to improve the portability ratio by designing the groove.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a prior art root airfoil.
Figure 2 is a cross-sectional view of a typical NACA0015 blade.
Fig. 3 is a conceptual diagram of an angle of attack (a). Fig.
4 is a conceptual view of the peeling start point.
5 is a conceptual diagram of boundary layer thickness;
6 is a cross-sectional view of a blade in accordance with one embodiment of the present invention.
Fig. 7 is an enlarged view of the main part in Fig. 6; Fig.
8 is a table showing the results of computational analysis when one groove is formed in the blade.
9 is a cross-sectional view of a blade according to yet another embodiment;
10 is an enlarged view of a main part;
Fig. 11 is a table of results obtained by performing computational analysis while varying the values of A, B, C, and D. Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention in the drawings, portions not related to the description are omitted, and like reference numerals are given to similar portions throughout the specification.

Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise.

According to the present invention, the blade having the improved portability ratio has an arc-shaped groove formed on the surface of the blade to increase the lift coefficient CL and decrease the drag coefficient CD to thereby provide a lift to drag ratio CL / CD). ≪ / RTI >

The shape model of the blade used in the embodiment of the present invention is a general NACA0015.

Figure 2 shows the cross-sectional shape of a typical NACA0015 blade.

In the case of such a blade, it is known that the angle of attack is 7 ° as a basic precondition in the embodiment of the present invention.

Fig. 3 shows a conceptual diagram of an angle of attack (a).

As shown, the angle of attack refers to the angle between the baseline (generally a straight line connecting the leading edge of the profile and the trailing edge, also referred to as the protruding line) and the airflow, and the length of the protruding line is the chord (c) .

In the present invention, one or more grooves are formed on the upper surface of the blade so as to improve the positive / negative ratio. The forming position of the groove becomes a very important factor. In order to determine the position of the groove, And the thickness of the boundary layer at the starting point of the air flow and the starting point of peeling measured at the angle of attack 7 ° were measured.

On the other hand, the groove formed on the upper surface of the blade extends continuously along the longitudinal direction of the blade, wherein the longitudinal direction means an axis orthogonal to the code (c).

The measured separation point was x / c = 0.075 and the boundary layer thickness (delta) was 1.38 mm.

The thickness of the boundary layer and the starting point of peeling measured using a grooveless blade are used as a constant.

The definition of the peeling start point and the boundary layer thickness is as follows.

FIG. 4 is a conceptual diagram of the peeling start point. The peeling starting point means a point where peeling can not be tolerated when the airflow flows along the upper surface of the blade, The flow causes vortex, vortex, and eddy.

And Fig. 5 is a conceptual diagram of the boundary layer thickness. The boundary layer thickness (δ) means that the velocity recovery from the surface of the blade is 99% of U∞ when the uniform velocity of the airflow entering the blade is U∞ Means the height at the bottom of the velocity point.

In an embodiment of the present invention, one groove is formed on the upper surface of the blade, and a groove is formed so that the peeling start point is located inside the groove.

FIG. 6 is a cross-sectional view of a blade according to an embodiment of the present invention, and FIG. 7 is an enlarged view of a main part in FIG.

The groove G has a width = "d", the maximum depth of the groove = "h", and the rear end of the groove from the peeling start point has a distance "l". The value of the distance "l" has a positive value when the rear end of the groove is located forward from the peeling start point, and a negative value when it is located rearward.

7, when the peeling start point and the rear distance of the groove are + l, the peeling starting point is located outside the groove G. On the other hand, when the peeling starting point and the rear distance of the groove are -l, (G).

In order to increase the portability ratio in the present invention, the width, depth and distance from the peeling start point of the groove G are important, and the width d, the depth h and the peeling start point of the groove, And the distance (l) between the two.

The depth ratio h / delta of the groove is defined as " A ", the width ratio h / d is defined as "B ", and the length ratio l / ) Is defined as "C ".

The Applicant of the present invention analyzed the aerodynamic characteristics of the blades according to the embodiment of the present invention through computational analysis (CFD), and confirmed that the improvement in the portability ratio due to the presence of the grooves was confirmed.

8 is a table showing the results of computational analysis when one groove is formed in the blade.

As shown in the figure, the Applicant has carried out a total of 13 computation analyzes in various combinations with different values of A, B, and C, and confirmed that it is possible to improve the loading ratio (CL / CD).

Particularly, when the values of A, B and C were in a specific band, there was a remarkable improvement of the input ratio. When the values were in the range of A = 1, B = 0.12 and C = -0.5 ~ 0.5, At least 9%). That is, in the above condition, the blade according to the embodiment of the present invention can attain an improvement in the portability ratio of 9% or more as compared with the grooveless blade.

Test No.9 When the condition of A = 1, B = 0.12, C = 0.5, the binomial ratio was improved by 9.21% and when the condition of Test No. 8 A = 1, B = 0.12, C = 0, %, And when the condition of Test No. 7 A = 1, B = 0.12, and C = -0.5 was satisfied, the loading ratio was improved by 12.43%.

From these results, it can be seen that the preferable setting range of A, B, and C is effective in improving the port ratio by designing A = 1, B = 0.12, and C = -0.5 to 0.5.

Next, another embodiment of the present invention will be described. Fig. 9 is a sectional view of a blade according to yet another embodiment, and Fig. 10 is an enlarged view of a main part.

In another embodiment, the blade in which the portability ratio is improved has two grooves formed on the upper surface of the blade. As shown in the drawing, the first groove G1 and the second groove G2 are spaced apart from each other, and the first grooves G1 and the second grooves G2 having the same shape are spaced apart by a distance "p" .

A peeling starting point is formed adjacent to the rear end of the second groove G2 and the rear distance "l" of the second groove from the peeling starting point may have a positive value or a negative value. The value of "1" has a positive value when the rear end of the second groove portion is located before the peeling start point, and the value of "l" has the negative value when the rear end of the second groove portion is located behind the peeling start point.

That is, when the peeling starting point is located behind the rear end of the second groove, the peeling starting point is located outside the second groove G2. On the contrary, when the peeling starting point is located forward of the rear end of the second groove, And is located inside the groove G2.

It is assumed that the peeling start point (x / c) is 0.075, and the thickness of the boundary layer at the peeling start point is 1.38 mm.

The rear end of the second groove has a distance "1" from the peeling start point, and the widths of the first groove and the second groove are "d ", and the maximum depths of the first groove and the second groove are" h ".

The depth ratio h / delta is defined as "A", the width ratio h / d is defined as "B", and the length ratio l / Is defined as "C ", and the pitch ratio (p / d) is defined as" D ".

In another embodiment of the present invention, two grooves are formed on the upper surface of the blade, and the portability ratio can be improved by appropriately combining the values of A, B, C, and D for determining the shape and position of the groove.

Fig. 11 is a result of computational analysis with different values of A, B, C, and D, and it is possible to confirm a considerable increase in the ratio of the positive and negative ratios in a specific region.

From the computational results, it can be seen that the design values of A, B, C, and D are preferably in the range of A = 0.8, B = 0.1, C = -0.5 to 0.5, and D = 0.7 to 1.15.

The combination ratio A, B, C and D in the range of the specific value can improve the drop ratio by about 10% or more compared with the case where there is no groove. = 0, D = 0.7, the effect of the increase of the positive rate is 10.97%. When the conditions of test No. 7 are A = 0.8, B = 0.1, C = 0 and D = .

As described above, according to the present invention, one or two grooves are formed on the upper surface of the blade, and the position and shape of the groove are determined through the relationship between the peeling start point and the thickness of the boundary layer.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be.

It is therefore to be understood that the embodiments described above are intended to be illustrative, but not limiting, in all respects. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

The blade with improved portability ratio according to the present invention can be used as an aircraft or a blade for wind power generation.

G: Groove
G1: First groove
G2: second groove

Claims (4)

For a blade in which the boundary layer thickness delta of the peeling start point is assumed to be 1.38 mm,
The rear end of the groove has a distance "1" with respect to the peeling start point. When the rear end of the groove is located in front of the peeling start point, a "Quot;," l "value has a minus value when positioned at the rear, the width of the groove is" d ", the maximum depth of the groove is &
The depth ratio h / delta is defined as "A", the width ratio h / d is defined as "B", and the length ratio l / Is defined as "C"
(CL / CD) is improved so as to be designed in the range of A = 1, B = 0.12, C = -0.5 to 0.5. The method according to claim 1,
Wherein the blade in which the lift ratio is improved is improved by 9% or more in terms of the load ratio as compared with the blade without the grooved portion. For a blade in which the boundary layer thickness delta of the peeling start point is assumed to be 1.38 mm,
A first groove and a second groove are formed on the upper surface of the blade in the longitudinal direction at intervals of distance "p ". The rear end of the second groove has a distance" 1 " The value of " 1 "has a positive value when the rear end of the groove is located forward from the peeling start point, and the value of" l "quot; d ", the maximum depth of said first and second grooves is "h &
The depth ratio h / delta is defined as "A", the width ratio h / d is defined as "B", and the length ratio l / Is defined as "C ", the pitch ratio (p / d) is defined as" D &
(CL / CD) can be improved by designing the blade to be in the range of A = 0.8, B = 0.1, C = -0.5 to 0.5 and D = 0.7 to 1.15 . The method of claim 3,
Wherein the blade in which the insertion port ratio is improved is improved by more than 10% in terms of the port ratio as compared to the blade without the grooved portion.

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