阅读说明：本技术 一种降低叶轮机宽频噪声的叶片尾缘构型及设计方法 (Blade trailing edge configuration for reducing broadband noise of turbine and design method ) 是由 卯鲁秦 黎霖 向康深 同航 乔渭阳 于 2021-01-18 设计创作，主要内容包括：本发明涉及一种降低叶轮机宽频噪声的叶片尾缘构型及设计方法,模仿寂静飞行猫头鹰翅膀的尾缘锯齿结构,对叶片进行改型,所述叶片的尾缘为周期性锯齿状结构,该锯齿结构沿叶片尾缘展向设置。本发明提供了一种降低叶轮机宽频噪声的叶片尾缘构型方法,利用锯齿尾缘,可以有效降低叶片宽频噪声。(The invention relates to a blade tail edge configuration for reducing broadband noise of a turbine and a design method thereof. The invention provides a blade tail edge configuration method for reducing broadband noise of a turbine, and the broadband noise of the blade can be effectively reduced by using a sawtooth tail edge.)

1. A blade trailing edge configuration for reducing broadband noise of a turbine, wherein the trailing edge of the blade is a periodic saw-tooth structure arranged along the blade trailing edge in a span-wise direction.

2. The blade trailing edge configuration for reducing broadband noise of a turbine according to claim 1, wherein said serration structure teeth spacing is 0.006 m.

3. The blade trailing edge configuration for reducing broadband noise of a turbine of claim 1, wherein the sawtooth structure has a height of 0.015 m.

4. The blade trailing edge configuration for reducing broadband noise of a turbomachine of claim 1 wherein said trailing edge is cut.

5. The method of claim 1, wherein the method comprises the following steps:

step 1: selecting a reference blade, and determining the chord length c and the extension L of the blade;

step 2: and taking the tail edge of the reference blade as a reference, and extending outwards along a tangent of a mean camber line at the tail edge.

And step 3: in order to ensure that the surface areas of the blade at the tail edge of the sawtooth are consistent with the surface area of the reference blade, the outward extension distance along the tangent line of the camber line at the tail edge is half of the height of the sawtooth ruler.

And 4, step 4: and (4) cutting the tail edge of the extended blade, and ensuring that the cutting line is vertical to the plane of the camber line of the blade during cutting.

6. The method of claim 5, wherein the vanes are isolated with SD2030 vanes.

7. The method of claim 6, wherein the chord length c of the blade in step 1 is 0.15 m.

8. The method of claim 7, wherein the blade span L of step 1 is 0.3 m.

Technical Field

The invention belongs to the technical field of noise control of aero-engines, and particularly relates to a blade trailing edge configuration for reducing broadband noise of a turbine and a design method thereof.

Background

With the development of the industry of big airplanes in China and the implementation of important special items of large airplanes and aero-engines, the problem of noise of the airplanes and the engines thereof is more and more concerned at present. Aircraft engines are a major source of noise in aircraft, where noise reduction of turbine noise becomes a key to reducing aircraft engine noise.

At present, the mainstream noise reduction means is to add a sound liner device at the position of an air inlet of an aircraft engine, and although a certain noise reduction result is obtained, the structure is complex due to the fact that the mass of the original aircraft engine is increased, the noise reduction effect is limited, and the noise reduction effect is obvious only for the noise under specific frequency.

Bionics is a research hotspot in various research fields at present, bionic content is applied to noise reduction of turbine blades, and the method is a great direction in the field of aviation noise reduction in the future. Researchers have proposed adding a serrated trailing edge configuration to blades in a turbomachine to reduce noise, but the existing method is to form a groove in the trailing edge of the blade and insert a serrated structure into the groove, which not only increases the structural complexity, but also creates a potential safety hazard to the rotating turbomachine because the inserted serrated structure increases the instability of the joint.

Disclosure of Invention

The technical problem solved by the invention is as follows: in order to overcome the defect that the conventional scientific research personnel provide an insertion type tail edge structure, the invention provides a cutting type blade tail edge structure for reducing broadband noise of a turbine and a design method thereof.

The technical scheme of the invention is as follows: a blade trailing edge configuration for reducing broadband noise of a turbine, wherein the trailing edge of the blade is a periodic saw-tooth structure arranged along the blade trailing edge in a span-wise direction.

The further technical scheme of the invention is as follows: the tooth space of the sawtooth structure is 0.006 m.

The further technical scheme of the invention is as follows: the height of the sawtooth structure ruler is 0.015 m.

The further technical scheme of the invention is as follows: the trailing edge is a cutting-type trailing edge.

The further technical scheme of the invention is as follows: a design method of a blade trailing edge configuration for reducing broadband noise of a turbine comprises the following steps:

step 1: selecting a reference blade, and determining the chord length c and the extension L of the blade;

step 2: and taking the tail edge of the reference blade as a reference, and extending outwards along a tangent of a mean camber line at the tail edge.

And step 3: in order to ensure that the surface areas of the blade at the tail edge of the sawtooth are consistent with the surface area of the reference blade, the outward extension distance along the tangent line of the camber line at the tail edge is half of the height of the sawtooth ruler.

And 4, step 4: and (4) cutting the tail edge of the extended blade, and ensuring that the cutting line is vertical to the plane of the camber line of the blade during cutting.

The further technical scheme of the invention is as follows: the blades are selected from SD2030 isolated blades.

The further technical scheme of the invention is as follows: the chord length c of the blade in the step 1 is 0.15 m.

The further technical scheme of the invention is as follows: the leaf extension L in the step 1 is 0.3 m.

Effects of the invention

The invention has the technical effects that: compared with the prior art, the invention has the following beneficial effects:

(1) the cutting type tail edge sawtooth structure is formed by cutting on the basis of the original blade, so that compared with the plug-in type tail edge sawtooth structure, the tail edge sawtooth structure is more closely connected with the original blade structure and is not easy to fall off in structural stability.

(2) The inserted type tail edge sawteeth need to be grooved at the root of the tail edge, and the grooves can cause stress concentration due to the fact that the tail edge of a blade in the turbine is generally thin, so that the tail edge is prone to being broken in the high-speed rotating process. The cutting structure only carries out sawtooth modification on the position of the tail edge of the blade, so that the blade can be more suitable for the working condition at high speed compared with the inserted tail edge.

(3) Because the inserted type tail edge structure is added with the sawtooth structure on the basis of the original blade, the flow field structure of the blade can be greatly damaged, and the extending length of the sawtooth is too long, so that the downstream blade can be influenced. The cutting type tail edge sawtooth structure firstly prolongs the blade to a certain extent, then cuts the blade, ensures that the blade surface area of the sawtooth tail edge configuration blade is the same as that of the reference blade, and further reduces the influence of the tail edge sawtooth structure on the downstream blade.

Drawings

FIG. 1 is a schematic view of a straight trailing edge blade;

FIG. 2 is a schematic view of a serrated trailing edge blade;

FIG. 3 illustrates the trailing edge sawtooth parameter definition in this embodiment;

FIG. 4 is a schematic diagram of an experimental measurement microphone array according to the present embodiment;

FIG. 5 shows the sound source identification results of the reference blade and the sawtooth trailing edge blade at an incoming flow velocity of 47m/s and an attack angle of 0 ° in this embodiment; wherein (a) is a straight trailing edge reference blade sound source identification result and (b) is a saw-tooth trailing edge blade sound source identification result

FIG. 6 is a comparison of trailing edge noise spectra of a straight trailing edge blade and a sawtooth trailing edge blade at an angle of attack of 0 ° at an incoming flow velocity of 47m/s in this example;

fig. 7 is a frequency spectrum of the sound pressure level variation of the trailing edge noise at different speeds and different angles of attack in the present embodiment.

Wherein a is a wind tunnel outlet, b is an experimental measurement blade, and c is a microphone array.

Detailed Description

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Referring to fig. 1 to 3, the invention provides a bionic blade applied to noise reduction of a turbine, which is characterized in that a periodic sawtooth structure is arranged along the tail edge of the blade in the spanwise direction; the serrations are periodic structures. The invention provides a blade trailing edge configuration method for reducing broadband noise of a turbine, which aims at the requirement of noise reduction control of broadband noise of the trailing edge of the turbine blade, adopts a bionics principle, simulates a trailing edge sawtooth structure of a owl wing, and provides the blade trailing edge configuration method for reducing the broadband noise of the turbine. The method is characterized in that: the trailing edge of the blade profile is of a sawtooth structure. The blades are respectively a straight tail edge blade and a sawtooth tail edge blade, and because the gap between the blades in the engine is relatively small, in order not to influence the downstream blades, a cutting type sawtooth tail edge is used. And for the reference blade, no modification is carried out on the tail edge, and for the sawtooth tail edge blade, the reference blade profile tail edge is used as a middle base line of the sawtooth tail edge, and the sawtooth tail edge is subjected to linear cutting. The tail edge sawtooth is in a tail edge sawtooth structure simulating the wings of the silent flying owl.

The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Referring to fig. 1, 2, and 3, the present invention is directed to an SD2030 isolated blade, and the chord length c of the blade is 0.15m and the span length L of the blade is 0.3 m. The tooth spacing of the sawtooth structure is lambda which is 0.006 m. The height 2h of the sawtooth structure ruler is 0.015 m.

In the blade with the sawtooth tail edge in the embodiment, the sawtooth at the tail edge is a tail edge sawtooth structure simulating the wings of the silent flying owl, after the configuration is finished, a microphone array experiment is adopted to research the suppression effect of the tail edge sawtooth structure on the broadband noise at the tail edge of the blade, see fig. 4, and fig. 4 shows that the sound source identification results of the straight tail edge blade and the sawtooth tail edge blade are compared when the incoming flow speed is 47m/s under the condition of an attack angle of 0 degrees. In the figure, the abscissa is a position coordinate, three peaks indicate three sound sources, 0.22m is wind tunnel noise at a wind tunnel outlet position, 0.08m is blade leading edge noise at a blade leading edge position, and 0, 06m is blade trailing edge noise at a blade trailing edge position; the ordinate in the figure is 1/3 octaves of the sound source; the darker areas in the graph indicate higher noise sound pressure levels, and lighter colors indicate lower noise sound pressure levels (i.e., lower noise). As can be seen from the figure, compared with the straight trailing edge blade, the sawtooth trailing edge configuration can effectively reduce the trailing edge noise of the blade, and the noise reduction effect of the trailing edge noise above 5000Hz is particularly obvious.

FIG. 6 is a comparison of the trailing edge noise spectra of straight trailing edge blades and sawtooth trailing edge blades at an incoming flow velocity of 47m/s for 0 ° angle of attack. The abscissa of the graph is frequency, the ordinate is sound pressure level, the smaller the sound pressure level is, the lower the noise is, and it can be seen from the graph that the sawtooth-shaped tail edge has obvious suppression effect on the intensity of the tail edge noise, and the noise reduction effect of the sawtooth-shaped tail edge is changed due to the change of the frequency range.

FIG. 7 is a frequency spectrum of the sound pressure level variation of the trailing edge noise at different speeds and different angles of attack, where a vertical coordinate greater than zero indicates that there is a noise reduction effect at the trailing edge of the sawtooth, and a vertical coordinate less than zero indicates that there is no noise reduction effect at the trailing edge of the sawtooth. From the aspect of spectrum shape, the noise reduction effect of the sawtooth-shaped trailing edge structure under all the incoming flow velocity conditions has the same trend along with the change of the attack angle: the noise reduction effect is the best under the condition of negative attack angle, the noise reduction effect is the worse under the condition of 0-degree attack angle, and the noise reduction effect is the worst under the condition of positive attack angle. However, the sawtooth trailing edge does not work well in all frequency ranges, and the sound level of the sawtooth trailing edge noise is instead increased in some frequency bands compared to a straight trailing edge. When the incoming flow speed U is 22m/s and 28m/s, the sawtooth tail edge has very good noise reduction effect almost in the whole concerned frequency range, and the maximum noise reduction effect can reach 14 dB; an increase in sound pressure level occurs in the lower frequency range only under positive angle of attack. As the incoming flow velocity further increases, the noise reduction effect of the sawtooth trailing edge gradually decreases. When the incoming flow speed U is 38m/s, the sawtooth tail edge still has good noise reduction effect under the conditions of 0-degree attack angle and negative attack angle, and the maximum noise reduction effect reaches 12 dB; however, under positive angle of attack, the sawtooth trailing edge increases the trailing edge noise by about 6dB over a frequency range around 2000 Hz. When the incoming flow speed U is 47m/s, under all attack angle conditions, the sawtooth tail edge increases the tail edge noise by 3-6 dB in a frequency range near 2000 Hz; and the maximum value of the noise reduction amount in the high frequency range is reduced to about 9 dB.