A circumferentially non-uniform, spanwise cambered perforated noise reducing blade

Abstract

The present application aims to provide a circumferential non-uniform, spanwise arch-shaped perforated noise reduction blade, comprising a blade body, the blade body comprising a leading edge, a trailing edge, a pressure surface and a suction surface, a row of arch-shaped perforations being arranged on one side of the leading edge of the blade body, the arch-shaped perforations being inclined from the pressure surface to the suction surface along the airflow direction, three rows of arch-shaped perforations being arranged on one side of the trailing edge of the blade body, the arch-shaped perforations being inclined from the suction surface to the pressure surface along the airflow direction. The non-uniform perforation design of the circumferential blade makes the flow conditions of each blade surface different, and the blade wake intensity different, not only changing the sound source phase of different blade surfaces, but also changing the interference sound source phase of different blades and the volute tongue, so that the sound intensity superposition of all circumferential blade surfaces and the volute tongue sound source in the far field is reduced, directly reducing the compressor noise in the far field.

Description

Technical Field

[0001] The present invention relates to a blade, specifically an arc-shaped blade for a centrifugal compressor. Background Technology

[0002] Centrifugal compressors are widely used in industrial and civil fields due to their higher specific power transmission capacity at the same speed and flow rate. However, their aerodynamic noise problem is becoming increasingly prominent. The wakes of centrifugal compressor blades periodically impact the volute, generating periodic and random unsteady forces on the blade and volute tongue surfaces. This not only causes significant vibrations in the equipment but also produces strong aerodynamic noise.

[0003] Blade perforation design is an effective way to reduce blade aerodynamic noise. Multiple rows of perforations are arranged along the leading or trailing edge of the blade to suppress flow separation on the blade surface, causing the flow separation point to shift backward and weakening the intensity of the wake turbulence, thereby reducing noise radiation intensity. However, these perforations are located along the blade spanwise (e.g., the spanwise direction...). Figure 1 As shown, the directions are often arranged in a straight line, but the actual spanwise pressure contour lines of the blade are not uniformly distributed; the pressure contour lines exhibit an arched shape in the spanwise direction, such as... Figure 1 As shown, the linear perforation design does not take into account the uneven pressure distribution along the blade span, and its suppression of separated flows along different spans of the blade is not precise enough.

[0004] Furthermore, due to the presence of the volute, the pressure distribution on each blade surface is inconsistent, i.e., the circumferential pressure is uneven, and the consistent perforation design of each blade cannot maximize the reduction of centrifugal compressor noise. For example... Figure 2 As shown, blade 1 is closest to the volute tongue 11, and its trailing edge 14 is closest to the volute 12, resulting in the smallest space for fluid compression and a larger high-pressure region. As the blade number increases, the distance between the blade trailing edge and the volute wall increases, the flow area increases, the fluid pressure decreases, and the high-pressure region shrinks significantly. Therefore, blades with lower numbers have a larger vortex separation region at the trailing edge, and the separation point is closer to the blade leading edge 13. Thus, a perforated design for every blade is not the optimal solution for noise reduction. Summary of the Invention

[0005] The purpose of this invention is to provide a circumferentially non-uniform, spanwise arched perforated noise-reducing blade that can further reduce aerodynamic noise.

[0006] The objective of this invention is achieved as follows:

[0007] The present invention discloses a circumferentially non-uniform, spanwise arched perforated noise reduction blade, characterized in that: it includes a blade body, the blade body including a leading edge, a trailing edge, a pressure surface, and a suction surface, a row of arched perforations is provided on one side of the leading edge of the blade body, which is inclined from the pressure surface to the suction surface in the direction of airflow, and three rows of arched perforations are provided on one side of the trailing edge of the blade body, which are inclined from the suction surface to the pressure surface in the direction of airflow.

[0008] The present invention may also include:

[0009] 1. The perforated area on the blade body accounts for 1%-2% of the blade body.

[0010] 2. The perforation position at the leading edge of the blade body is located before the flow separation point, and the perforation diameter is 2-4mm. The perforation spacing is evenly distributed from the upper end cover to the lower end cover.

[0011] 3. The first row of trailing edge perforations on the blade body is located before the generation of vortices on the blade pressure surface. The three rows of perforations are evenly spaced, with each row of perforations spaced 8%-10% of the blade chord length C. The perforation diameter is 2-4mm, and the perforation spacing is evenly distributed from the upper end cap to the lower end cap.

[0012] 4. The deflection angles of the leading edge perforation and the trailing edge perforation are opposite in direction, and the deflection angle of the leading edge perforation is smaller than that of the trailing edge perforation. The deflection angle range is 30°-60°.

[0013] 5. The expression for the circumferential profile of the blade perforation is:

[0014]

[0015] In the formula, R is the distance from the leading edge of the blade to the center of the circle, C is the blade chord length, t is a variable with a value of 0-1, and a and b are variable parameters. For the circumferential profile of the perforations at the leading edge of the blade, a is 0.20-0.24 and b is 0.68-0.86; for the circumferential profile of the first row of perforations at the trailing edge of the blade, a is 0.65-0.75 and b is 0.05-0.19.

[0016] 6. The expression for the spanwise profile of the blade perforation is:

[0017] y = A1 + B1x + B2x 2 +B3x 3 +B4x 4 +B5x 5 +B6x 6 +B7x 7

[0018] In the formula, A1 and B1 to B7 are variable parameters. For the perforated arch profile of the blade leading edge, A1 is 34.20±3.66, and B1 to B7 are -3.07±0.88, 0.38±0.07, -0.02±6.49e-3, 2.90e-4±3.43e-5, -2.41e-6±2.63e-7, 7.34e-9±7.72e-10 and 0, respectively. For the perforated arch profile of the blade trailing edge, A1 is taken as 121.47±3.27, and B1 to B7 are taken as -1.78±1.15, 0.33±0.13, -0.02±6.49e-3, 4.43e-4±1.64e-4, -5.29e-6±2.20e-6, 3.02e-8±1.50e-8 and -6.57e-11±4.06e-11 respectively.

[0019] 7. The distance L1 from the first row of perforations near the lower end face of the blade leading edge to the leading edge of the blade is 3%-7% of the blade chord length C; the spacing l1 between perforations is taken as 1 / n of the blade height h1 at the corresponding perforation position; the distance from the perforation located at the blade edge to the blade edge is 1 / 2 of the perforation spacing l1; and the number of perforations n is taken as 6-12.

[0020] 8. The distance L2 from the first row of perforations near the lower end of the blade to the leading edge of the blade is 60%-70% of the blade chord length C. The spacing D between the three rows of perforations is the same and is 8%-10% of the blade chord length C. The spacing l2, l3 and l4 between the perforations are taken as 1 / n of the corresponding blade height h2, h3 and h4 at the perforation position. The distance from the perforation located at the blade edge to the blade edge is 1 / 2 of the perforation spacing. The number of perforations n is 6-12.

[0021] The advantages of this invention are as follows: First, the non-uniform perforation design of the circumferential blades results in different flow conditions and varying blade wake intensities on each blade surface. This alters not only the sound source phase of different blade surfaces but also the interference sound source phase between different blades and the volute tongue, reducing the superposition of sound intensity from all circumferential blade surfaces and the volute tongue in the far field and directly reducing compressor noise in the far field. Second, the arched perforation design at the leading and trailing edges of the blades matches the actual spanwise pressure distribution, maximizing the suppression of flow separation on the blade surface, including flow separation between the suction surface at the leading edge and the pressure surface at the trailing edge. Suppressing the former breaks down the small vortex separation structure on the blade surface, reducing pressure pulsation at the leading edge and thus reducing sound source intensity. Reducing the intensity of the latter disrupts large separation vortices on the blade surface, reducing the jet-wake effect near the trailing edge and thus reducing blade aerodynamic noise. Attached Figure Description

[0022] Figure 1 A schematic diagram of the spanwise pressure contour distribution on the blade surface;

[0023] Figure 2 This is a schematic diagram of uneven circumferential pressure distribution on the blade.

[0024] Figure 3 This is a schematic diagram of the circumferential profile of the blade perforation;

[0025] Figure 4 A schematic diagram of the spanwise arched profile of the perforated blade;

[0026] Figure 5 This is a schematic diagram showing the location of the perforation at the AA section of the blade;

[0027] Figure 6 A schematic diagram of the deflection angle of the perforation at section AA of the blade;

[0028] Figure 7 This is a schematic diagram showing the spacing between the perforations on the leading edge of the blade.

[0029] Figure 8 This is a schematic diagram showing the spacing of the perforations at the trailing edge of the blade. Detailed Implementation

[0030] The invention will now be described in more detail with reference to the accompanying drawings:

[0031] Combination Figure 1-8 This invention relates to a circumferentially non-uniform, spanwise arched perforated centrifugal compressor blade, characterized by comprising different blades numbered 1-10, a volute 12, circumferential perforation profiles 15-18, and spanwise arched profiles 21-22. The perforation form of the blades at different circumferential positions is consistent, with only the perforation position in the chord direction being determined by the circumferential perforation profiles 15-18. Figure 4-8 The perforation form of the blade 10 is described in detail, characterized by: a leading edge 13, a trailing edge 14, a suction surface 19, a pressure surface 20, a spanwise arched profile 21-22, a lower end cap 23, a row of perforations at the leading edge, and three rows of perforations at the trailing edge.

[0032] Figure 2 The circumferential perforation profiles of blades numbered 1-10 are helical lines. The circumferential perforation profiles of the leading edge 13 and trailing edge 14 are obtained by taking different values ​​of the variable parameter in the same parametric equation.

[0033] Taking blade 10 as a reference, the perforation pattern on a single blade is described. The perforation positions of other numbered blades are determined by the circumferential perforation profiles of the leading edge 13 and trailing edge 14 of the blade, and the perforation pattern is consistent with that of blade 10.

[0034] The perforated area of ​​the blade accounts for 1%-2% of the original blade.

[0035] The perforation position of the leading edge 13 of the blade 10 is located before the flow separation point, and the perforation diameter is 2-4mm. The perforation spacing is evenly distributed from the upper end cover to the lower end cover 23.

[0036] The first row of trailing edge perforations on blade 10 is located before the vortex is generated on the blade pressure surface. The three rows of perforations are evenly spaced, with each row of perforations spaced 8%-10% of the blade chord length C. The perforation diameter is 2-4 mm. The perforation spacing is evenly distributed from the upper end cap to the lower end cap 23.

[0037] The deflection angles of the perforations at the leading edge 13 and the trailing edge 14 of the blade are opposite in direction, and the deflection angle of the perforation at the leading edge 13 is smaller than that at the trailing edge 14.

[0038] The spanwise arched profiles 21 and 22 of the blade are polynomial curves. The spanwise arched profiles 21 and 22 of the blade leading edge and trailing edge perforations are determined by different single-parameter equations. The spanwise distribution of the three rows of perforations on the trailing edge 14 is controlled by the same parameter equation. The perforation positions of different blades are determined by the circumferential profile.

[0039] The position of the perforation at the leading edge 13 of the blade is determined by the circumferential profile 15 of the leading edge perforation, and the position of the perforation at the trailing edge 14 of the blade is determined by the circumferential profiles 16-18 of the trailing edge perforation. The expression for the circumferential profile of the blade perforation is as follows:

[0040]

[0041] In the formula, R is the distance from the leading edge 13 of the centrifugal compressor blade to the center, C is the blade chord length, t is a system variable with a value of 0-1, and a and b are variable parameters. For the circumferential profile 15 of the leading edge perforation of the blade, a is 0.20-0.24 and b is 0.68-0.86; for the circumferential profile 16 of the first row of perforations on the trailing edge 14 of the blade, a is 0.65-0.75 and b is 0.05-0.19.

[0042] The spanwise arrangement of the perforations 13 on the leading edge of the blade is determined by the arched profile 21 of the leading edge perforation, and the spanwise arrangement of the perforations 14 on the trailing edge of the blade is determined by the arched profile 22 of the trailing edge perforation. Figure 4 As shown. Taking the plane containing the blade chord as the reference, and the intersection of the blade leading edge 13 and the blade lower end face 23 as the origin, the expression for the blade perforation spanwise profile is:

[0043] y = A1 + B1x + B2x 2 +B3x 3 +B4x 4 +B5x 5 +B6x 6 +B7x 7

[0044] In the formula, A1 and B1 to B7 are variable parameters. For the leading edge perforated arch profile 21 of the blade, A1 is 34.20±3.66, and B1 to B7 are -3.07±0.88, 0.38±0.07, -0.02±6.49e-3, 2.90e-4±3.43e-5, -2.41e-6±2.63e-7, 7.34e-9±7.72e-10 and 0, respectively; for the trailing edge perforation of the blade... For the arch-shaped profile 22, A1 is 121.47±3.27, and B1 to B7 are -1.78±1.15, 0.33±0.13, -0.02±6.49e-3, 4.43e-4±1.64e-4, -5.29e-6±2.20e-6, 3.02e-8±1.50e-8 and -6.57e-11±4.06e-11 respectively.

[0045] The position and diameter of the perforations on the leading and trailing edges of the blade need to be standardized. If the perforation diameter is too large, a large amount of airflow will flow from the working surface of the blade to the non-working surface, and the aerodynamic characteristics of the compressor cannot be guaranteed. If the perforation diameter is too small, the airflow passing through the hole will not be sufficient to suppress flow separation. Therefore, the perforation area of ​​this invention is 1%-2% of the original blade area, and the diameter of the perforation on the leading edge of the blade is the same as that on the trailing edge, which is 2-4 mm.

[0046] Combination Figure 2 and Figure 6 Near the leading edge 13 of the blade, a small separation flow exists on the suction surface 19, and the static pressure on the pressure surface 20 is greater than that on the suction surface 19. Near the trailing edge 14, a large separation vortex exists on the pressure surface, and the static pressure on the pressure surface 20 is less than that on the suction surface 19. The principle of blade perforation is to penetrate from the high-pressure region to the low-pressure region along the internal mainstream direction. Considering the operating characteristics of a backward centrifugal compressor, a row of perforations is designed on the leading edge to suppress the small separation flow, with the direction from the pressure surface 20 to the suction surface 19. Three rows of perforations are designed on the trailing edge to break the large separation vortex, with the direction from the suction surface 19 to the pressure surface 20. Therefore, the deflection angle of the trailing edge perforations is opposite to that of the leading edge perforations; the leading edge perforation deflection angle α is smaller than the trailing edge perforation deflection angle β, and the deflection angle range is 30°-60°.

[0047] Combination Figure 1 , 2For blades 10, 5, and 7, the distance L1 from the first row of perforations near the lower end face 23 of the blade leading edge to the blade leading edge is 3%-7% of the blade chord length C. Other spanwise positions are determined by the perforation arch profile 21 of the blade leading edge, ensuring that all perforation positions in the spanwise direction are located before the flow separation point to maximize the suppression of flow separation on the suction surface of the blade leading edge, forcing the flow separation point to move axially backward. This not only reduces flow losses caused by flow separation but also breaks up large vortices at the blade leading edge, reducing pressure pulsation amplitude and thus reducing the intensity of the sound source at the blade leading edge. The spacing l1 between perforations is taken as 1 / n of the blade height h1 at the corresponding perforation position. The distance from the perforation located at the blade edge to the blade edge is 1 / 2 of the perforation spacing l1. The number of perforations n is 6-12, but the perforation area must be 1%-2% of the original blade area.

[0048] Combination Figure 1 , 2 For blades 10, 5, and 8, the distance L2 from the first row of perforations near the lower end face 23 of the blade trailing edge to the blade leading edge is 60%-70% of the blade chord length C. The spacing D between the three rows of perforations is the same and is 8%-10% of the blade chord length C. Other spanwise positions are determined by the arched profile 22 of the blade trailing edge perforations, ensuring that the trailing edge perforation positions are located before the generation of pressure surface vortices, thus suppressing large-scale vortices on the pressure surface of the blade trailing edge. The trailing edge perforations can directly guide the high-pressure airflow from the blade suction surface to the pressure surface. In addition to suppressing large separation flow at the trailing edge of the non-working surface of the blade, it can also reduce the wake-volute interference effect and reduce the wake turbulence intensity, thereby reducing the interference between the moving blade wake and the volute. This reduces the sound source intensity near the blade trailing edge and also reduces the sound source intensity near the most important sound source area of ​​the centrifugal compressor—the volute tongue 11. The spacing between perforations, l2, l3, and l4, is taken as 1 / n of the leaf heights h2, h3, and h4 at the corresponding perforation positions. The distance between perforations located at the leaf edge and the leaf edge is 1 / 2 of the perforation spacing. The number of perforations, n, is 6-12, but the perforation area must be 1%-2% of the original leaf area.

Claims

1. A circumferentially non-uniform, spanwise arched perforated noise-reducing blade, characterized in that: The blade body includes a leading edge, a trailing edge, a pressure surface, and a suction surface. A row of arched perforations is provided on one side of the leading edge of the blade body, which slopes from the pressure surface to the suction surface in the direction of airflow. Three rows of arched perforations are provided on one side of the trailing edge of the blade body, which slope from the suction surface to the pressure surface in the direction of airflow. The expression for the circumferential profile of the blade perforation is: In the formula, R is the distance from the leading edge of the blade to the center of the circle, C is the blade chord length, t is a variable with a value of 0-1, and a and b are variable parameters. For the circumferential profile of the perforations at the leading edge of the blade, a is 0.20-0.24 and b is 0.68-0.86; for the circumferential profile of the first row of perforations at the trailing edge of the blade, a is 0.65-0.75 and b is 0.05-0.

19.

2. The circumferentially non-uniform, spanwise arched perforated noise-reducing blade according to claim 1, characterized in that: The perforated area on the blade accounts for 1%-2% of the blade body.

3. The circumferentially non-uniform, spanwise arched perforated noise-reducing blade according to claim 1, characterized in that: The perforation at the leading edge of the blade is located before the flow separation point, with a perforation diameter of 2-4 mm. The perforation spacing is evenly distributed from the upper end cap to the lower end cap.

4. The circumferentially non-uniform, spanwise arched perforated noise-reducing blade according to claim 1, characterized in that: The first row of trailing edge perforations on the blade body is located before the generation of vortices on the blade pressure surface. The three rows of perforations are evenly spaced, with each row of perforations spaced 8%-10% of the blade chord length C. The perforation diameter is 2-4 mm, and the perforation spacing is evenly distributed from the upper end cap to the lower end cap.

5. The circumferentially non-uniform, spanwise arched perforated noise-reducing blade according to claim 1, characterized in that: The deflection angles of the leading edge perforation and the trailing edge perforation are opposite in direction, and the deflection angle of the leading edge perforation is smaller than that of the trailing edge perforation. The deflection angle range is 30°-60°.

6. A circumferentially non-uniform, spanwise arched perforated noise-reducing blade according to claim 1, characterized in that: the blade The expression for the perforated span profile is: In the formula, A1 and B1 to B7 are variable parameters. For the leading edge perforated arch profile of the blade, A1 is 34.20 ± 3.66, and B1 to B7 are -3.07 ± 0.88, 0.38 ± 0.07, -0.02 ± 6.49e-3, 2.90e-4 ± 3.43e-5, -2.41e-6 ± 2.63e-7, 7.34e-9 ± 7.72e-10, and 0, respectively. For the trailing edge perforated arch profile of the blade, A1 is 121.47 ± 3.27, and B1 to B7 are -1.78 ± 1.15, 0.33 ± 0.13, -0.02 ± 6.49e-3, 4.43e-4 ± 1.64e-4, and -5.29e-6 ± 0. 2.20e-6, 3.02e-8 ± 1.50e-8 and -6.57e-11 ± 4.06e-11.

7. A circumferentially non-uniform, spanwise arched perforated noise-reducing blade according to claim 1, characterized in that: the blade The distance L1 from the first row of perforations near the lower end of the blade at the leading edge of the body is 3%-7% of the blade chord length C; the spacing l1 between perforations is taken as 1 / n of the corresponding perforation height h1; the distance from the perforation located at the blade edge to the blade edge is 1 / 2 of the perforation spacing l1; and the number of perforations n is taken as 6-12.

8. The circumferentially non-uniform, spanwise arched perforated noise-reducing blade according to claim 1, characterized in that: The distance L2 from the first row of perforations near the lower end of the blade to the leading edge of the blade is 60%-70% of the blade chord length C. The spacing D between the three rows of perforations is the same and is 8%-10% of the blade chord length C. The spacing l2, l3 and l4 between the perforations are taken as 1 / n of the corresponding blade height h2, h3 and h4 at the perforation positions. The distance from the perforation located at the blade edge to the blade edge is 1 / 2 of the perforation spacing. The number of perforations n is 6-12.

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