阅读说明：本技术 一种具有波浪前缘和锯齿尾缘的叶片设计方法 (Blade design method with wavy front edge and sawtooth tail edge ) 是由 王晓放 刘昊然 鲁业明 李滢玥 于 2019-11-05 设计创作，主要内容包括：一种具有波浪前缘和锯齿尾缘的叶片设计方法,主要包括以下步骤：S1、确定基准线；S2、生成波浪形前缘线；S3、波浪前缘的叶片成型；S4、生成锯齿形尾缘线；S5、叶片生成。本发明通过对基础叶片前、尾缘的变形设计,改变了现有叶片的型线和叶片表面压力波间的相位差,达到了降低叶片绕流噪声效果。本发明通过对叶片的前、尾缘分别采用正弦线和锯齿线的设计方法及参数化设计,使流动诱导噪声得改善,达到降低噪声的目的。(A design method of a blade with a wavy leading edge and a sawtooth trailing edge mainly comprises the following steps: s1, determining a reference line; s2, generating a wave-shaped front edge line; s3, forming a blade with a wavy front edge; s4, generating a sawtooth-shaped tail edge line; and S5, blade generation. According to the invention, through the deformation design of the front edge and the tail edge of the basic blade, the phase difference between the molded line of the conventional blade and the surface pressure wave of the blade is changed, and the effect of reducing the flow noise of the blade is achieved. The invention improves the flow induced noise by adopting the design method of the sine line and the sawtooth line and the parametric design for the front edge and the tail edge of the blade respectively, thereby achieving the purpose of reducing the noise.)

1. A design method of a blade with a wavy front edge and a sawtooth tail edge comprises a base blade formed by stacking a plurality of blade profiles with the same shape, and is characterized by comprising the following steps of:

s1, determining a reference line: determining a reference line on a base blade, wherein the reference line comprises a leading edge reference line and a trailing edge reference line, the leading edge reference line is a connecting line of the top points of the front ends of a plurality of blade molded lines, and the trailing edge reference line is a connecting line of the terminal points of the tail ends of the plurality of blade molded lines;

s2, generating a wave-shaped front edge line: generating a sine line on the front edge of the blade along a front edge reference line as a wavy front edge line, wherein the concave points and the convex points of the sine line are respectively recorded as front edge concave points and front edge convex points, and the generating method of the wavy front edge line comprises the following steps: setting a first front edge concave point of a wavy front edge line at the front edge of a blade root, taking the first front edge concave point as a coordinate origin, taking a horizontal line of the front edge of the blade pointing to the tail edge of the blade as an X axis, and taking a vertical line of the front edge of the blade pointing to the front edge of the blade top as a Y axis to establish a plane rectangular coordinate system, and determining an equation of the wavy front edge line:

λ＝L/n,n∈N⁺

wherein x is an abscissa value of a point (x, y) constituting the wavy leading edge line, and y is an ordinate value of the point (x, y) constituting the wavy leading edge line; a is the amplitude of the wave front edge, namely the distance between the adjacent front edge salient point and the front edge concave point along the X-axis direction; l is the expansion length of the blade; lambda is the distance between two adjacent front edge salient points or front edge concave points along the Y-axis direction; n is the number of the front edge salient points;

s3, forming the blade with the wavy front edge: finding the tail edge point of the corresponding basic blade on the tail edge datum line along the X-axis direction through each point position on the wavy front edge line to generate a blade profile with a wavy front edge, enabling the generated blade profile to be overlapped with the blade profile of the basic blade at the downstream part, amplifying the generated blade profile at the upstream part along the chord direction of the sine line, enabling the front edge concave point of the amplified blade profile to be positioned on the front edge datum line, and enabling the front edge convex point to be forwards far away from the front edge datum line; then, the blade profile with the wavy front edge is taken as a cross section, the wavy front edge line is taken as a guide line to complete the blade forming of the wavy front edge, and the blade with the wavy front edge is obtained; the downstream part is a part from the maximum thickness position of the blade to the tail edge of the blade, and the upstream part is a part from the maximum thickness position of the blade to the front edge of the blade;

s4, generating a sawtooth tail edge line: generating a sawtooth line on the tail edge of the blade along a tail edge datum line as a tail edge line, wherein salient points and concave points of the sawtooth line are respectively marked as tail edge salient points and tail edge concave points, and the generating method of the sawtooth line comprises the following steps: setting a first tail edge salient point of a zigzag tail edge line at the tail edge of a blade root, taking the tail edge salient point as a coordinate origin, taking a horizontal line of a front edge pointing to the tail edge as an X 'axis, and taking a vertical line of the tail edge of the blade root pointing to the tail edge of the top of the blade as a Y' axis to establish a plane rectangular coordinate system, and determining an equation of the zigzag tail edge line:

y′∈[(i-1)d/2,id/2],i＝(1,2,3...,2L/d)

d＝L/m,m∈N⁺

wherein x 'is an abscissa value of the point (x', y ') constituting the serrated trailing edge line, and y' is an ordinate value of the point (x ', y') constituting the serrated trailing edge line; h is the tooth height, namely the distance between the adjacent tail edge salient points and the tail edge concave points along the X 'axis direction, d is the distance between the two adjacent tail edge salient points or the tail edge concave points along the Y' axis direction, L is the extension length of the blade, and m is the number of the tail edge salient points;

s5, blade generation: and cutting the blade with the wavy front edge along the sawtooth-shaped tail edge line in a plane perpendicular to the front edge reference line and the tail edge reference line to obtain the blade with the wavy front edge and the sawtooth-shaped tail edge.

2. The method as claimed in claim 1, wherein the amplitude A of the leading edge is 5-20% of the chord length of the blade.

3. The method of claim 1, wherein the tooth height H is 4-20% of the chord length of the blade.

4. The method as claimed in claim 1, wherein the ratio of the span length L of the blade to the chord length C of the blade is in the range of 0.5-3.

Technical Field

The invention relates to a blade design method, in particular to a blade design method with a wavy front edge and a sawtooth tail edge.

Background

Noise is one of three major pollution sources, and not only influences the working environment, but also damages the device. The long-term life in a noise environment not only can affect the auditory nerve of people, but also can cause other diseases; in addition, in the case of a medium having a large specific gravity, the propagation of sound waves in the medium is not easily attenuated, and the structure is easily induced to vibrate, which causes structural fatigue.

The blades are important elements in fluid machines and are also the main source of noise in flow induced noise. As shown in fig. 1, the conventional base blade is mainly formed by stacking a plurality of blade profiles 5, and the main structure of the conventional base blade includes a blade root 4, a blade tip 3, a blade leading edge 1 and a blade trailing edge 2, where L is an extension length, and the length C of the blade root 4 is a blade chord length. In order to reduce the noise generated by the flowing around of the fluid blade, researchers have proposed blade perforation, trailing edge sawtooth, sound absorption materials and other noise reduction technologies. Compared with the common blade, the blade with the sawtooth-shaped tail edge can effectively improve the radiation noise of the blade under a large attack angle, but the noise suppression effect is weakened and sometimes even increased when the attack angle is small.

Disclosure of Invention

It is an object of the present invention to provide a blade design method that produces a leading wavy edge and a trailing sawtooth edge that achieves a noise reduction effect at low angles of attack.

The invention solves the technical problems in the prior art by adopting the following technical scheme: a design method of a blade with a wavy front edge and a sawtooth tail edge comprises a base blade formed by stacking a plurality of blade profiles with the same shape, and comprises the following steps:

s1, determining a reference line: determining a reference line on a base blade, wherein the reference line comprises a leading edge reference line and a trailing edge reference line, the leading edge reference line is a connecting line of the top points of the front ends of a plurality of blade molded lines, and the trailing edge reference line is a connecting line of the terminal points of the tail ends of the plurality of blade molded lines;

s2, generating a wave-shaped front edge line: generating a sine line on the front edge of the blade along a front edge reference line as a wavy front edge line, wherein the concave points and the convex points of the sine line are respectively recorded as front edge concave points and front edge convex points, and the generating method of the wavy front edge line comprises the following steps: setting a first front edge concave point of a wavy front edge line at the front edge of a blade root, taking the first front edge concave point as a coordinate origin, taking a horizontal line of the front edge of the blade pointing to the tail edge of the blade as an X axis, and taking a vertical line of the front edge of the blade pointing to the front edge of the blade top as a Y axis to establish a plane rectangular coordinate system, and determining an equation of the wavy front edge line:

λ＝L/n,n∈N⁺

wherein x is an abscissa value of a point (x, y) constituting the wavy leading edge line, and y is an ordinate value of the point (x, y) constituting the wavy leading edge line; a is the amplitude of the wave front edge, namely the distance between the adjacent front edge salient point and the front edge concave point along the X-axis direction; l is the expansion length of the blade; lambda is the distance between two adjacent front edge salient points or front edge concave points along the Y-axis direction; n is the number of the front edge salient points;

s3, forming the blade with the wavy front edge: finding the tail edge point of the corresponding basic blade on the tail edge datum line along the X-axis direction through each point position on the wavy front edge line to generate a blade profile with a wavy front edge, enabling the generated blade profile to be overlapped with the blade profile of the basic blade at the downstream part, amplifying the generated blade profile at the upstream part along the chord direction of the sine line, enabling the front edge concave point of the amplified blade profile to be positioned on the front edge datum line, and enabling the front edge convex point to be forwards far away from the front edge datum line; then, the blade profile with the wavy front edge is taken as a cross section, the wavy front edge line is taken as a guide line to complete the blade forming of the wavy front edge, and the blade with the wavy front edge is obtained; the downstream part is a part from the maximum thickness position of the blade to the tail edge of the blade, and the upstream part is a part from the maximum thickness position of the blade to the front edge of the blade;

s4, generating a sawtooth tail edge line: generating a sawtooth line on the tail edge of the blade along a tail edge datum line as a tail edge line, wherein salient points and concave points of the sawtooth line are respectively marked as tail edge salient points and tail edge concave points, and the generating method of the sawtooth line comprises the following steps: setting a first tail edge salient point of a zigzag tail edge line at the tail edge of a blade root, taking the tail edge salient point as a coordinate origin, taking a horizontal line of a front edge pointing to the tail edge as an X 'axis, and taking a vertical line of the tail edge of the blade root pointing to the tail edge of the top of the blade as a Y' axis to establish a plane rectangular coordinate system, and determining an equation of the zigzag tail edge line:

y′∈[(i-1)d/2,id/2],i＝(1,2,3...,2L/d)

d＝L/m,m∈N⁺

wherein x 'is an abscissa value of the point (x', y ') constituting the serrated trailing edge line, and y' is an ordinate value of the point (x ', y') constituting the serrated trailing edge line; h is the tooth height, namely the distance between the adjacent tail edge salient points and the tail edge concave points along the X 'axis direction, d is the distance between the two adjacent tail edge salient points or the tail edge concave points along the Y' axis direction, L is the extension length of the blade, and m is the number of the tail edge salient points;

s5, blade generation: and cutting the blade with the wavy front edge along the sawtooth-shaped tail edge line in a plane perpendicular to the front edge reference line and the tail edge reference line to obtain the blade with the wavy front edge and the sawtooth-shaped tail edge.

The amplitude A of the front edge of the wave is 5-20% of the chord length of the blade.

The tooth height H is 4-20% of the chord length of the blade.

The ratio of the span length L of the blade to the chord length C of the blade ranges from 0.5 to 3.

The invention has the beneficial effects that: according to the invention, through the deformation design of the front edge and the tail edge of the basic blade, the phase difference between the molded line of the conventional blade and the surface pressure wave of the blade is changed, and the effect of reducing the flow noise of the blade is achieved. The invention improves the flow induced noise by adopting the design method of the sine line and the sawtooth line and the parametric design for the front edge and the tail edge of the blade respectively, thereby achieving the aim of reducing the noise.

Drawings

FIG. 1 is a schematic view of a base blade configuration.

FIG. 2 is an enlarged view of the blade profile leading edge of the base blade.

FIG. 3 is an enlarged view of the blade profile trailing edge of the base blade.

Fig. 4 is a schematic view of the structure of the blade of the present invention.

FIG. 5 is a profile view of a blade with a wavy leading edge according to the present invention.

FIG. 6 is a state diagram of the blade profile generation produced by the present invention.

Fig. 7 is a view showing a blade structure obtained by the present invention.

FIG. 8 is a graph of the noise comparison of the blade obtained by the present invention and the conventional blade.

In the figure: 1-blade leading edge, 2-blade trailing edge, 3-blade tip, 4-blade root, 5-blade profile of basic blade, 6-leading edge datum line, 7-trailing edge datum line, 8-wavy leading edge line, 9-zigzag trailing edge line, 10-leading edge salient point, 11-leading edge concave point, 12-first leading edge concave point, 13-trailing edge salient point, 14-trailing edge concave point, 15-first trailing edge salient point, 16-blade profile of the invention, 17-maximum thickness of blade profile, 18-downstream part of blade profile, and 19-upstream part of blade profile.

Detailed Description

The invention is described below with reference to the accompanying drawings:

a design method of a blade with a wavy front edge and a sawtooth tail edge comprises a base blade formed by stacking a plurality of blade profiles 5 with the same shape (as shown in figure 1), and figures 2-3 show enlarged views of the front edge and the tail edge of the blade profile 5 of the base blade. The ratio of the spanwise length L of the blade to the chord length C of the blade is preferably 0.5-3. On the basis of the profile of the base blade, the blade of the invention is designed according to the following steps:

s1, determining a reference line: a leading edge reference line 6 and a trailing edge reference line 7 are determined on the base blade, that is, as shown in fig. 2-3, the leading edge reference line 6 is a connection line of the top points of the front ends of the plurality of blade profiles 5, and the trailing edge reference line 7 is a connection line of the terminal points of the tail ends of the plurality of blade profiles 5.

S2, generating a wave-shaped front edge line 8: generating a sine line as shown in fig. 4-5 on the blade leading edge 1 along a leading edge reference line 6 as a wavy leading edge line 8, recording the concave points and the convex points of the sine line as leading edge concave points 11 and leading edge convex points 10 respectively, and specifically generating the wavy leading edge line 8 by the following steps: arranging a first leading edge concave point 12 of the wavy leading edge line 8 at the leading edge of the blade root 4, taking the leading edge concave point 12 as a coordinate origin, taking a horizontal line of the leading edge 1 of the blade pointing to the trailing edge 2 of the blade as an X axis, and taking a vertical line of the leading edge of the blade root 4 pointing to the leading edge of the blade top 3 as a Y axis to establish a plane rectangular coordinate system, and determining an equation of the wavy leading edge line 8:

λ＝L/n,n∈N⁺

wherein x is an abscissa value of a point (x, y) constituting the wavy leading edge line 8, and y is an ordinate value of the point (x, y) constituting the wavy leading edge line 8; and A is the amplitude of the wave front, namely the distance between the adjacent front edge salient point 10 and the front edge concave point 11 along the X-axis direction. Preferably, the amplitude A of the front edge of the wave is 5-20% of the chord length of the blade; l is the expansion length of the blade; λ is the distance between two adjacent front edge salient points 10 or front edge concave points 11 along the Y-axis direction; n is the number of leading edge bumps 10.

S3, forming the blade with the wavy front edge: the blade profile 16 with the wavy leading edge as shown in fig. 5 is generated by finding the corresponding trailing edge point of the base blade on the trailing edge reference line 7 along the X-axis direction from the position of each point on the wavy leading edge line 8. And keeping the blade profile 16 and the blade profile 5 of the base blade in profile coincidence at a downstream part 18 (as shown in fig. 6), and enlarging the generated blade profile 16 at an upstream part 19 in a chord direction along a sine line, so that a leading edge concave point 11 of the enlarged blade profile 16 is positioned on a leading edge datum line 6, and a leading edge convex point 10 is forward far away from the leading edge datum line 6; then, the blade profile 16 with the wavy front edge is taken as a cross section, and the wavy front edge line 8 is taken as a guide line to complete the blade forming of the wavy front edge, so that the blade with the wavy front edge is obtained (as shown in fig. 5); wherein, as shown in fig. 6, the downstream portion 18 is a portion from the maximum thickness 17 of the blade to the trailing edge of the blade, and the upstream portion 19 is a portion from the maximum thickness 17 of the blade to the leading edge of the blade;

s4, generating a sawtooth tail edge line 9: on the basis of the formation of the wave front edge blade, a sawtooth line as shown in fig. 7 is generated on the blade tail edge 2 along a tail edge datum line 7 to serve as a tail edge line, salient points and concave points of the sawtooth line are respectively marked as tail edge salient points 13 and tail edge concave points 14, and the generating method of the sawtooth line comprises the following steps: a first tail edge salient point 15 of the sawtooth-shaped tail edge line 9 is arranged at the tail edge of the blade root 4, the tail edge salient point 15 is used as a coordinate origin, a horizontal line, pointing to the tail edge 2 of the blade from the leading edge 1 of the blade, is used as an X 'axis, a vertical line, pointing to the tail edge of the blade top 3, of the tail edge of the blade root 4 is used as a Y' axis, a plane rectangular coordinate system is established, and an equation of the sawtooth-shaped tail edge line 9 is determined:

y′∈[(i-1)d/2,id/2],i＝(1,2,3...,2L/d)

d＝L/m,m∈N⁺

wherein x 'is an abscissa value of a point (x', y ') constituting the serrated trailing edge line 9, and y' is an ordinate value of the point (x ', y') constituting the serrated trailing edge line 9; h is the tooth height, namely the distance between the adjacent tail edge salient points 13 and the tail edge concave points 14 along the X 'axis direction, preferably the tooth height H is 4-20% of the chord length of the blade, d is the distance between the adjacent two tail edge salient points 13 or the tail edge concave points 14 along the Y' axis direction, and L is the spreading length of the blade; m is the number of trailing edge bumps 13.

Preferably, the angle at the trailing edge pit 14 is θ, where θ is 2arctan (d/2H).

S5, blade generation: the blade with the wavy leading edge obtained in step S3 is cut along the sawtooth-shaped trailing edge line 9 perpendicular to the plane where the leading edge reference line 6 and the trailing edge reference line 7 are located, that is, the blade with the wavy leading edge and the sawtooth-shaped trailing edge as shown in fig. 7 is obtained.

The invention aims at the basic blade to carry out front and tail edge structure modification, so that the blade can achieve the noise reduction effect, fig. 8 is a noise comparison result graph of the blade and the basic blade designed by the invention, 36 points are taken along the chord direction of the blade for comparison, and the comparison shows that the blade with the wave front edge and the sawtooth tail edge can obviously reduce the streaming noise of the blade.

The foregoing is a more detailed description of the present invention in connection with specific preferred embodiments and is not intended to limit the practice of the invention to these embodiments. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.