CN214499309U

CN214499309U - Airfoil profile applicable to wind driven generator blade under low Reynolds number working condition

Info

Publication number: CN214499309U
Application number: CN202120478895.5U
Authority: CN
Inventors: 孙隽飞
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-03-05
Filing date: 2021-03-05
Publication date: 2021-10-26
Anticipated expiration: 2031-03-05

Abstract

The utility model discloses an airfoil that aerogenerator blade was suitable for under low reynolds number working condition, the ratio of the maximum thickness of airfoil and chord length is 11.1%, and the maximum thickness position is located 26% of chord length, and the ratio of maximum camber and chord length is 5.7%, and the maximum camber position is located 53.1% of chord length. The utility model discloses a maximum thickness suitably reduces, the maximum camber suitably increases, maximum camber and maximum thickness position moderate degree backward move, guarantee laminar flow separation lag, reduce the separation bubble, the position is twisted in advance, provide bigger lift coefficient and less resistance coefficient, can make target lift coefficient between 1 ~ 1.4, guarantee that target lift is not too high, prevent the easy stall of blade, guarantee simultaneously according to this wing section can possess great chord length in the in-service use, correspond better aerodynamic effect and performance, be worth being generalized to use.

Description

Airfoil profile applicable to wind driven generator blade under low Reynolds number working condition

Technical Field

The utility model relates to a aerogenerator wing section technical field, concretely relates to aerogenerator blade is applicable wing section under low reynolds number working condition.

Background

Wind power generation has been widely applied in modern society, but the mature application focuses on power generation operation under high reynolds number, and under the working conditions of low wind speed and low reynolds number, the air viscosity has great influence on the working conditions of airfoils, and the airfoils commonly used at present include NACA airfoil families, FFA airfoil families, DU series airfoils, DTU airfoils, S series, Eppler airfoils and the like.

With the popularization of small wind power generators and the application thereof to solar and wind power hybrid lighting systems, more community-based and personalized fields such as residential life power generation and the like are provided. The common wing type often has an early laminar flow separation phenomenon before transition under the pneumatic environment with a low Reynolds number, and generates large separation bubbles, so that the lift coefficient is reduced, the resistance coefficient is increased, the overall lift-drag ratio is greatly reduced, the pneumatic effect is reduced, the final working efficiency is reduced, and the good wind power generation working requirement is difficult to achieve.

SUMMERY OF THE UTILITY MODEL

The utility model discloses the technical problem that will solve lies in: how to solve present low reynolds number down (the target reynolds number selects 100000 ~ 200000 in research and design process) mainstream wing section premature laminar flow separation, the bad problem of aerodynamic effect provides the wing section that aerogenerator blade is suitable for under the low reynolds number working condition.

The utility model discloses a solve above-mentioned technical problem through following technical scheme, the utility model discloses a ratio of maximum thickness and chord length is 11.1%, and maximum thickness position is located the 26% of chord length, and the ratio of maximum camber and chord length is 5.7%, and maximum camber position is located the 53.1% of chord length.

Preferably, the target reynolds number of the airfoil-shaped pneumatic environment applicable to the wind turbine blade under the low reynolds number working condition is 100000-200000.

Compared with the prior art, the utility model has the following advantages: the maximum thickness is properly reduced, the maximum camber is properly increased, the maximum camber and the maximum thickness position are properly moved backwards, the laminar flow separation lag is guaranteed, separation bubbles are reduced, the transition position is advanced, a larger lift coefficient and a smaller resistance coefficient are provided, the target lift can be kept between 1-1.4, the target lift is not too high, the blade is prevented from stalling easily, meanwhile, the wing section can have a larger chord length in actual application, the aerodynamic effect and the performance are better, and the wing type aerodynamic structure is worthy of being popularized and used.

Drawings

FIG. 1 is an airfoil profile for a wind turbine blade suitable for low Reynolds number operating conditions in an embodiment of the present invention;

FIG. 2 is an airfoil profile illustrating an embodiment of the present invention with increased relative trailing edge thickness to 4%;

fig. 3 is a graph comparing the aerodynamic effect of Q2836 and NACA4412 at a reynolds number of 100000 in an embodiment of the invention;

FIG. 4 is a graph comparing the aerodynamic effect of Q2836 and NACA4412 at 170000 Reynolds numbers for an embodiment of the invention;

fig. 5 is a graph comparing the aerodynamic effect of Q2836 and NACA4412 at 350000 reynolds number for an embodiment of the invention;

FIG. 6 is a graph comparing the aerodynamic effect of Q2836 and NACA4412 at a Reynolds number of 550000 in an embodiment of the invention;

fig. 7 is a graph comparing the aerodynamic effect of Q2836 and NACA4412 at 800000 reynolds number in an embodiment of the invention.

Detailed Description

The embodiments of the present invention will be described in detail below, and the present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

As shown in fig. 1, the present embodiment provides a technical solution: an airfoil for a wind turbine blade suitable for low Reynolds number operation, the ratio (d/c) of the maximum thickness (d) to the chord length (c) being 11.1%, the maximum thickness position (X)_dA maximum camber position (X) of 26%, a ratio (f/c) of the maximum camber (f) to the chord length (c) of 5.7%_fThe content of/c) was 53.1%. X_dX-coordinate value, X, representing the position of maximum thickness_fThe X-coordinate value is the position of maximum camber, wherein the origin is located at the leading edge point of the airfoil, the X-axis is the abscissa and is coincident with the chord length, the positive direction is from the leading edge to the trailing edge of the airfoil, and the y-axis is perpendicular to the chord length.

The coordinate of the trailing edge point on the X axis is taken as (1, 0), and the airfoil coordinate data is shown in the following table:

TABLE 1 airfoil coordinate datasheet

Note: the data sequence of the upper surface is from the trailing edge to the leading edge of the upper surface, and then from the leading edge to the trailing edge of the lower surface.

In the actual airfoil design process, the relative thickness of the tail edge can be increased according to the target tail end thickness, so that the manufacturing is facilitated, the separation bubbles are further reduced, and the airfoil aerodynamic effect is improved. As shown in fig. 2, to increase the relative thickness of the trailing edge to 4% of the airfoil profile.

The airfoil design process in this embodiment is as follows:

according to cross calculation check of xfoil and rfoil, through input definition of Eppler code, a corresponding attack angle of a constant value of speed keeping on a defined segment is properly increased to improve the lift force to a target lift force, meanwhile, a corresponding design attack angle of a pressure surface segment is defined to ensure the smoothness of a pressure curve and improve the lift-drag ratio, and the optimal lift-drag ratio is controlled to be continuously changed and optimized in an attack angle range corresponding to the target lift force. According to

Drawing and C_l-X_trThe analogy relationship of/C, in enlarging the angle of the unit circle corresponding to the specific adjacent segments

The difference therebetween, the design angle (alpha) is reduced^*) A difference of such that C_l-X_trthe/C curve has a lower slope at a specific location, thereby achieving specific structural characteristics of the airfoil.

Compared with the conventional commercial airfoil (taking the commonly-used NACA4412 as a main comparison object), the airfoil in the embodiment has smaller maximum thickness and larger maximum camber, the maximum camber and the maximum thickness are moved backwards, the separation point is integrally delayed, the transition position under the design lift force is advanced, the two aspects of optimization prevent the laminar flow separation from generating larger separation bubbles too early, the lift coefficient is greatly improved and the resistance coefficient is reduced under the low attack angle working state (0-10 degrees) corresponding to the target lift force, the lift-drag ratio is improved, the separation bubbles under the low Reynolds number are reduced, and the performance of the blade under the corresponding low Reynolds number range and the power generation effect of the corresponding generator are improved. The reduction amount and the thickness of the maximum camber are increased, the backward movement of the position of the maximum camber is proper, the pressure distribution curve of the suction surface and the pressure surface in the range of the attack angle corresponding to the left and right of the target lift force is ensured to be smooth, the abnormal peak and the abnormal front edge negative pressure cannot occur, and the practical possibility is ensured.

The airfoil profile (Q2836) in the embodiment has better aerodynamic effect and performance in the range of 0-10 degrees of attack angle in the range of low Reynolds number of 8000-800000. Specifically, the pneumatic effect comparative analysis under different Reynolds number environments is as follows:

as shown in FIGS. 3 to 7, the lift force C is shown as a variation curve of the lift-drag ratio with the angle of attack and the lift force_lResistance C_dThe picture of the attack angle alpha describes the difference of the lift-drag ratio of the two airfoils under the working conditions of different attack angles, and the lift-drag ratio of Q2836 in the attack angle range of 0-10 degrees is generally higher than that of NACA 4412. The more key in the comparison of different wing profiles is the comparison of lift-drag ratio under the same lift force condition, lift force C_lResistance C_d-a lift force C_lThe figure can be well embodied, the lift-drag ratio of the Q2836 under the aerodynamic environment with the low Reynolds number range is obviously higher than that of NACA4412 all the time, the aerodynamic effect is obviously improved, and the design effect of high-efficiency power generation is achieved under the low Reynolds number.

The above symbols and their meanings are as follows:

C_l-a lift coefficient;

C_d-a drag coefficient;

α^*design angle of attack (for a design angle of attack for a segment in an airfoil at which the velocity profile for the corresponding segment is constant);

phi-unit circle angle (the wing profile is converted into a unit circle, the tail edge is 0 degree until the leading edge is 180 degrees, and then the unit circle returns to the tail edge for 360 degrees, and different degrees are used for describing different positions of the surface of the wing profile);

X_trthe/C-transition position x coordinate/chord length;

d-maximum thickness;

d/c-maximum thickness to chord ratio;

X_dc-maximum thickness position;

f-maximum camber;

f/c-ratio of maximum camber to chord length;

X_fc-position of maximum camber.

In conclusion, the maximum thickness of the airfoil applicable to the wind driven generator blade under the working condition of low Reynolds number is properly reduced, the maximum camber is properly increased, the positions of the maximum camber and the maximum thickness are properly moved backwards, the laminar flow separation is ensured to be delayed, separation bubbles are reduced, the transition position is advanced, and a larger lift coefficient and a smaller resistance coefficient are provided; the range of the target lift coefficient can be ensured to be located between 1 and 1.4 in the process of optimizing the aerodynamic effect, the target lift is ensured not to be too high, the blades are prevented from being easily stalled, and the airfoil profile can have larger chord length in actual application and is correspondingly better in aerodynamic effect and performance; the gentle pressure distribution curve of protection when optimizing aerodynamic effect can not appear abnormal peak and unusual leading edge negative pressure, guarantees that the wing section possesses better aerodynamic effect and can rationally come into use.

Although embodiments of the present invention have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the scope of the present invention.

Claims

1. An airfoil profile suitable for a wind driven generator blade under a low Reynolds number working condition is characterized in that: the ratio of the maximum thickness to the chord length of the airfoil is 11.1%, the maximum thickness position is located at 26% of the chord length, the ratio of the maximum camber to the chord length is 5.7%, and the maximum camber position is located at 53.1% of the chord length.

2. An airfoil of a wind turbine blade adapted for low reynolds number operation according to claim 1, wherein: the target Reynolds number of the aerodynamic environment of the airfoil is 100000-200000, and the aerodynamic effect and performance are better within the range of attack angles of 0-10 degrees in the low Reynolds number range of 8000-800000.