Axial flow fan blade with double type multi-channel vent to reduce noise
By setting type A and type B vents inside the blades of the axial flow fan, the noise problem of the axial flow fan, especially the noise from leakage vortices at the blade tip clearance and trailing edge shedding vortices, was solved, achieving a lower vortex noise effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN ENG UNIV
- Filing Date
- 2022-12-28
- Publication Date
- 2026-06-19
AI Technical Summary
The aerodynamic noise problem of axial flow fans, especially the noise caused by trailing edge shedding vortices and tip clearance leakage vortices, is the main issue, and existing technologies are difficult to effectively reduce it.
The axial flow fan blades are designed with a dual-type multi-channel structure, featuring an A-type vent hole that runs through the blade tip and trailing edge and a B-type vent hole that runs through the middle of the pressure surface and trailing edge. Airflow passes through these holes to reduce the formation of leakage vortices at the blade tip and shedding vortices at the trailing edge.
It significantly reduces the noise level of axial flow fans by reducing the formation of leakage vortices at the blade tip clearance and trailing edge shedding vortices, thus achieving lower vortex noise and reducing the difficulty of opening a single A-type vent.
Smart Images
Figure CN116066409B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a blade, specifically an axial flow fan blade. Background Technology
[0002] Axial flow fans, as a type of ventilation equipment, are widely used in industries such as mining, petroleum, chemical, metallurgy, and refrigeration, as well as in daily life. However, with the widespread use of fans, the noise they generate has increasingly attracted attention. Axial flow fan noise has become one of the main sources of pollution in industrial and mining enterprises and urban environments.
[0003] For axial flow fans, aerodynamic noise is the primary noise source, while mechanical noise is much lower. The aerodynamic noise of a fan consists of broadband noise distributed across the frequency spectrum and discrete noise of various harmonics. The former is turbulent noise, caused by pressure and velocity fluctuations; the latter is rotational noise, caused by the interference between the fan's moving and stationary blades.
[0004] Theory and experiments show that the internal flow in an axial flow fan is three-dimensional, viscous, and unsteady. When the viscous fluid flows through the blades, various complex vortex systems are generated on and near the blade surface, mainly including scraping vortices, channel vortices, horseshoe vortices, tip leakage vortices, leading-edge separation vortices, and trailing-edge shedding vortices. These vortex systems not only dissipate energy but also significantly affect the aerodynamic performance of the axial flow fan, thus generating considerable aerodynamic noise. Among these aerodynamic noises, the noise generated by trailing-edge shedding vortices is dominant, followed by tip clearance leakage vortices, which also significantly impact the overall noise level.
[0005] The aerodynamic noise of a fan is a superposition of rotational noise and eddy current noise, and the relative strength of the two varies depending on the type of fan being studied. For a single-stage axial flow fan with a low tip circumferential speed, the noise is mainly broadband eddy current noise; for a multi-stage high-speed axial flow fan, the main characteristic of the noise is rotational noise with discrete peak values. Summary of the Invention
[0006] The purpose of this invention is to provide an axial flow fan blade with dual-type multi-channel vents to reduce fan noise.
[0007] The objective of this invention is achieved as follows:
[0008] This invention discloses an axial flow fan blade with dual-type multi-channel vents for noise reduction, characterized in that it includes a blade tip, blade root, leading edge, trailing edge, suction surface, and pressure surface. The blade body is provided with an A-type vent that connects the blade tip and the trailing edge, and a B-type vent that connects the middle position of the pressure surface and the trailing edge. The inlet of the A-type vent is located at the blade tip, and the outlet is located at the trailing edge. The inlet is a straight line segment with a length of D perpendicular to the blade tip. The inlet of the B-type vent is located at the middle position of the pressure surface, and the outlet is located at the trailing edge.
[0009] The straight line connecting the intersection of the tip arc and the trailing edge, and the intersection of the root arc and the trailing edge, is the first straight line. The plane formed by the chords of the tip and root profiles and the first straight line is the projection plane. A2 is the projection of the A1 type axis onto the projection plane. A coordinate system is established on the projection plane, with the origin O located on the first straight line and a distance D from the tip of the blade. D is the length of the straight line segment perpendicular to the tip of the A-type vent inlet. The straight line passing through the origin O and coinciding with the first straight line is set as the Y-axis. The straight line passing through the origin O and perpendicular to the Y-axis in the projection plane is set as the X-axis. The straight line passing through the origin O and perpendicular to the XOY plane is set as the Z-axis, with the positive direction of the Z-axis pointing towards the suction surface of the blade. The projection line A2 of the A1 type axis onto the projection plane is represented by the following equation:
[0010]
[0011] The mid-surface F1 can be represented by the following equation:
[0012]
[0013] The axis of the type A vent is represented by the following equation:
[0014]
[0015] In the above formula, i represents the distance from the axis of the i-th type A vent at the blade tip; D2 is the distance between the type A vent closest to the blade tip and the blade tip; D3 is the distance between two adjacent vents on the trailing edge; b is the chord length; and d1 is the distance between the point on the corresponding mid-arc line at b / 2 and the chord.
[0016] The present invention may also include:
[0017] 1. The inlet position of the type A vent at the blade tip is in the half section near the trailing edge. The inlet area of the type A vent at the blade tip accounts for 0.4%-0.8% of the blade tip area, and the outlet area at the trailing edge accounts for 0.5%-1% of the trailing edge area.
[0018] 2. The diameter d of type A and type B ventilation holes is 1%-2% of the leaf height h. The spacing between each ventilation hole is evenly distributed at the leaf tip and at the trailing edge. The distance between two adjacent ventilation holes at the trailing edge is D3. The distance between the type B ventilation hole closest to the leaf root and the leaf root is D1. The distance between the type A ventilation hole closest to the leaf tip and the leaf tip is D2. D1 and D2 are equal and are 4%-8% of the leaf height h. D3 is 8%-12% of the leaf height h.
[0019] 3. The axis of the type A vent is a spatial curve distributed on the mid-curved surface, and the projection of these spatial curves on the projection surface is an arc with a central angle of 45°.
[0020] 4. The angle α between the inlet of the type B vent and the pressure surface can be taken as 30°. The axis of the type B vent is distributed in a plane parallel to the blade root.
[0021] 5. The spacing between adjacent A-type vents is L2. The distance between the first A-type vent on the blade tip and the trailing edge is L1. The last vent is located at the midpoint of the centerline of the blade tip. L1 is 3%-5% of the centerline length, and L2 is 1 / 15-1 / 10 of the centerline length.
[0022] 6. B2 is the projection of the B1 type axis onto the blade root. The intersection of B2 and the pressure surface is set as the origin O. The straight line passing through the origin O and the intersection of the upper arc line and the leading edge of the blade root is set as the X-axis. The straight line in the blade root plane passing through the origin O and perpendicular to the X-axis is set as the Y-axis. The straight line passing through the origin O and perpendicular to the XOY plane is set as the Z-axis, with the positive direction of the Z-axis pointing towards the blade tip. Let the distance between the front and rear endpoints of the projection line B2 be L, and the distance between the point on the projection line B2 at L / 2 and the X-axis be d2. Then, the projection B2 of the B-type vent axis onto the blade root is represented by the following equation:
[0023]
[0024] The equation of the plane containing the axis of the i-th type B vent at the leaf root is as follows:
[0025] z = D1 + iD3
[0026] The axis of the type B vent is represented by the following equation:
[0027]
[0028] In the above formula, i represents the distance from the axis of the i-th type B vent at the leaf root, and D1 is the distance between the type B vent closest to the leaf root and the leaf root.
[0029] The advantages of this invention are as follows: First, tip clearance leakage vortices account for a significant proportion of the eddy noise in wind turbines. Tip clearance leakage vortices occur because the static pressure on the blade's pressure surface is greater than the static pressure on the blade's suction surface during operation. Furthermore, due to centrifugal force, gas on the blade's pressure surface flows through the gap between the blade tip and the casing to the blade's suction surface, forming vortices at the tip clearance and thus generating substantial eddy noise. The feature of this invention is that the blade contains a series of A-type vents penetrating from the blade tip to the blade's trailing edge. Therefore, when airflow flows from the blade's pressure surface through the tip clearance to the blade's suction surface, some airflow flows from the blade tip into the A-type vents, thus minimizing tip clearance leakage vortices and consequently reducing the noise of the axial flow fan.
[0030] Secondly, in wind turbine vortex noise, the noise caused by detached vortices at the blade trailing edge plays a major role. According to boundary layer theory, when airflow passes over the blade surface, vortex detachment occurs after the boundary layer develops to a certain extent. This detachment often reaches a very severe stage at the blade trailing edge, forming a large number of detached vortices. The feature of this invention is the installation of a series of A-type vents connecting the blade tip and trailing edge, and B-type vents connecting the middle of the pressure surface and the trailing edge inside the blade. When airflow flows into the A-type vents at the blade tip gap and into the B-type vents at the middle of the pressure surface, the airflow is ejected from the blade trailing edge, thus dispersing the vortices at the trailing edge, breaking large vortices into smaller ones, thereby significantly reducing the vortex volume at the trailing edge and thus greatly reducing wind turbine noise.
[0031] Third, in addition to setting type A ventilation holes inside the blade, setting type B ventilation holes can greatly reduce the difficulty of opening holes from the entire blade tip to the trailing edge.
[0032] In summary, this invention reduces noise caused by leakage vortices in the blade tip clearance by drawing in airflow through the A-type vent. Furthermore, the airflow exiting the vent breaks up numerous shedding vortices at the blade trailing edge, significantly reducing noise generated by these vortices. Moreover, the dual-type, multi-channel vent structure simplifies the creation of a single A-type vent. Attached Figure Description
[0033] Figure 1 This is a schematic diagram of the present invention installed in an axial flow fan;
[0034] Figure 2 This is a schematic diagram of the structure of the present invention;
[0035] Figure 3 This is a schematic diagram of the blade tip structure;
[0036] Figure 4 This is a schematic diagram of the trailing edge structure;
[0037] Figure 5 This is a schematic diagram of the axis distribution;
[0038] Figure 6 This is a projection diagram of the A1 type axis;
[0039] Figure 7 This is a B1-type axis projection diagram. Detailed Implementation
[0040] The invention will now be described in more detail with reference to the accompanying drawings:
[0041] Combination Figure 1-7 This invention relates to an axial flow fan blade that reduces noise by incorporating dual-type, multi-channel air vents. For example... Figure 1 As shown, the overall structure of the present invention includes a fan housing 1, fan blades 2, a hub 3, blade tip clearance 4, and a vent 5. Figure 2 and Figure 3 As shown, the blade includes a blade tip (8), a blade root (9), a leading edge (6), a trailing edge (7), a pressure surface (10), a suction surface (11), a type A vent, and a type B vent. (Combined with...) Figures 1-3 As the blades rotate with the hub, the static pressure on the pressure side of the blades is greater than that on the suction side due to the work done by the blades. Furthermore, the gas exhibits centrifugal force during rotation. Therefore, under the influence of the static pressure difference and centrifugal force, the gas flows from the pressure side through the tip gap to the suction side, forming vortices at the tip gap and generating considerable vortex noise. Moreover, because the rotor blades continuously perform work on the airflow as it flows from the leading edge to the trailing edge, the static pressure difference between the pressure and suction sides is even greater near the trailing edge. Consequently, the tip gap leakage vortex near the trailing edge constitutes the majority of the entire tip gap leakage vortex. This invention addresses this by creating a series of A-type vents extending to the trailing edge of the blade in the half of the tip. Figure 2 As shown, the airflow passing through the blade tip gap flows directly into the type A vent, which significantly reduces the formation of leakage vortices in the blade tip gap, thereby achieving the noise reduction purpose of the axial flow fan. On the other hand, a series of type B vents are opened in the lower half of the blade near the blade root, penetrating from the middle of the blade pressure surface to the blade trailing edge. This reduces the difficulty of opening a single type A vent, while also allowing some airflow to flow from the middle of the pressure surface into the type B vents, and then towards the blade trailing edge.
[0042] Figure 5 The spatial curves numbered ①-⑤ are used to represent the axis of the type A vent, and the curves numbered ⑥- The spatial curve used to represent the axis of the B-type vent is shown. The position and shape of the vent axis at different locations of the same model can be obtained by taking different variable values from the same equation.
[0043] The perforation at the leaf tip (point 8) is located in the half-section near the trailing edge (point 7). The perforation area at the leaf tip accounts for 0.4%-0.8% of the area of leaf tip (point 8), while the perforation area at the trailing edge accounts for 0.5%-1% of the area of trailing edge (point 7).
[0044] The diameter of the ventilation holes can be taken as 1%-2% of the leaf height h. The spacing between each ventilation hole is evenly distributed at the leaf tip (8) and at the trailing edge (7).
[0045] The type A vent is a straight line segment of length D perpendicular to the blade tip 8 at the inlet, and perpendicular to the blade trailing edge 7 at the outlet. The entire vent axis is a spatial curve distributed on the mid-curve surface. Furthermore, the projection of these spatial curves onto the projection plane (the plane passing through the blade tip chord and the blade root chord) is an arc with a central angle of 45°.
[0046] The angle α between the inlet of the type B vent and the pressure surface 10 can be 30°, the outlet is perpendicular to the trailing edge 7 of the blade, and the entire vent axis is distributed in a plane parallel to the blade root 9.
[0047] According to boundary layer theory, airflow forms relatively strong shedding vortices at the blade trailing edge, and the noise generated by these trailing edge shedding vortices constitutes a major portion of the total aerodynamic noise. Figure 2 It is known that the gas flowing into the type A and type B vents will be ejected from the trailing edge of the blade. This ejected airflow will directly impact the shedding vortex at the trailing edge of the blade, blowing the large trailing edge shedding vortex into a small vortex, which will greatly reduce the vortex noise of the fan.
[0048] like Figure 3 As shown, the blade tip structure includes the mid-arc line 12, the intersection point of the mid-arc line and the leading edge of the blade 13, the intersection point of the mid-arc line and the trailing edge of the blade 14, and a chord 15. The mid-arc line is the line connecting the centers of the inscribed circles of the blade, often simply called the midline. The chord is the straight line connecting the mid-arc line to the intersection points of the leading and trailing edges of the blade; the length of the chord is called the chord length, denoted by the letter b. The curved surface that runs through the mid-arc line at the blade tip and the mid-arc line at the blade root is called the mid-surface. Figure 5 In this context, F1 represents the mid-curved surface.
[0049] Depend on Figure 3 It can be seen that the A-type vents are distributed on the blade tip in the half near the trailing edge, and are equidistantly distributed along the centerline. The distance between adjacent vents is L2, the distance between the first vent and the trailing edge is L1, and the last vent is located at the midpoint of the mid-arc line at the blade tip. L1 can be set to 3%-5% of the centerline length, and L2 can be set to 1 / 15-1 / 10 of the centerline length.
[0050] Depend on Figure 5 and Figure 7It can be seen that the axis of the B-type vent is located in a plane parallel to the blade root. For example, the axis of the B-type vent represented by serial number ⑥ is located on plane F2. The angle α between the inlet of the B-type vent and the pressure surface can be taken as 30°. The outlet of the B-type vent is perpendicular to the trailing edge of the blade.
[0051] Depend on Figure 4 It can be seen that type A and type B ventilation holes are equidistantly distributed on the trailing edge, with the distance between two adjacent ventilation holes being D3. The distance between the type B ventilation hole closest to the leaf root and the leaf root is D1, and the distance between the type A ventilation hole closest to the leaf tip and the leaf tip is D2. D1 and D2 can be taken as equal values, both of which can be taken as 4%-8% of the leaf height h, and D3 can be taken as 8%-12% of the leaf height h.
[0052] Depend on Figure 5 It can be seen that the mid-curved surface F1 is a curved surface composed of the arc lines in the cross-sectional profiles between the blade tip and the blade root, and F2 is a plane parallel to the blade root. The axis A1 of the type A vent is located on the mid-curved surface F1, and the axis B1 of the type B vent is located on each plane parallel to the blade root.
[0053] like Figure 6 As shown, let point 14.1 be the intersection of the mid-curve at the blade tip and the trailing edge, and point 14.2 be the intersection of the mid-curve at the blade root and the trailing edge. The straight line connecting points 14.1 and 14.2 is called line 16. The chord of the blade tip profile is defined as line 15.1, and the chord of the blade root profile is defined as line 15.2. The plane formed by lines 15.1, 15.2, and 16 is the projection plane, and A2 is the projection of the A1 type axis onto the projection plane. Establish a coordinate system on the projection plane, with the origin O located on line 16 and a distance D from the blade tip, where D is the length of the straight line segment perpendicular to the blade tip at the inlet of the A-type vent. The straight line passing through the origin O and coinciding with line 16 is defined as the Y-axis, and the straight line passing through the origin O and perpendicular to the Y-axis in the projection plane is defined as the X-axis. The straight line passing through the origin O and perpendicular to the XOY plane is defined as the Z-axis, with the positive direction of the Z-axis pointing towards the blade suction surface. The projection line A2 of the A1 type axis onto the projection plane can be represented by the following equation:
[0054]
[0055] On the other hand, the mid-curved surface F1 can be represented by the following equation:
[0056]
[0057] Therefore, the axis of the type A vent can be represented by the following equation:
[0058]
[0059] In the above formula, i represents the distance from the axis of the i-th type A vent at the blade tip; D2, D3, and D are... Figure 4and Figure 6 The structural parameters on; d1 and b are Figure 3 The structural parameters are: b is the chord length, and d1 is the distance between the point on the middle arc corresponding to b / 2 and the chord.
[0060] like Figure 7 As shown, B2 is the projection of the B1 type axis onto the blade root. The intersection of B2 and the pressure surface is set as the origin O of the coordinate system. The straight line passing through the origin O and the intersection of the upper arc line and the leading edge of the blade root is set as the X-axis. The straight line in the blade root plane passing through the origin O and perpendicular to the X-axis is set as the Y-axis. Conversely, the straight line passing through the origin O and perpendicular to the XOY plane is set as the Z-axis, with the positive direction of the Z-axis pointing towards the blade tip. Let the distance between the leading and trailing endpoints of the projection line B2 be L, and the distance between the point on the projection line B2 at L / 2 and the X-axis be d2. Then, the projection B2 of the B-type vent axis onto the blade root can be represented by the following equation:
[0061]
[0062] On the other hand, the equation of the plane containing the axis of the i-th type B vent at the leaf root is as follows:
[0063] z = D1 + iD3
[0064] Therefore, the axis of the type B vent can be represented by the following equation:
[0065]
[0066] In the above formula, i represents the distance from the i-th B-type vent axis at the leaf root; different values of i can represent the B-type vent axis at different positions; D1 and D3 are... Figure 4 The structural parameters on; d2 and L are Figure 7 The structural parameters on.
Claims
1. A axial fan blade with double type multi-channel vent to reduce noise, characterized in that: Including leaves The blade body has an A-type vent hole that connects the blade tip and the trailing edge, and a B-type vent hole that connects the middle of the pressure surface and the trailing edge. The inlet of the A-type vent hole is located at the blade tip and the outlet is located at the trailing edge. The inlet is a straight line segment with a length of D perpendicular to the blade tip. The inlet of the B-type vent hole is located at the middle of the pressure surface and the outlet is located at the trailing edge. The straight line connecting the intersection of the tip arc and the trailing edge, and the intersection of the root arc and the trailing edge, is the first straight line. The plane formed by the chords of the tip and root profiles and the first straight line is the projection plane. A2 is the projection of the A1 type axis onto the projection plane. A coordinate system is established on the projection plane, with the origin O located on the first straight line and a distance D from the tip of the blade. D is the length of the straight line segment perpendicular to the tip of the A-type vent inlet. The straight line passing through the origin O and coinciding with the first straight line is set as the Y-axis. The straight line passing through the origin O and perpendicular to the Y-axis in the projection plane is set as the X-axis. The straight line passing through the origin O and perpendicular to the XOY plane is set as the Z-axis, with the positive direction of the Z-axis pointing towards the suction surface of the blade. The projection line A2 of the A1 type axis onto the projection plane is represented by the following equation: The mid-surface F1 can be represented by the following equation: The axis of the type A vent is represented by the following equation: In the above formula, i represents the distance from the axis of the i-th type A vent at the blade tip; D2 is the distance between the type A vent closest to the blade tip and the blade tip; D3 is the distance between two adjacent vents on the trailing edge; b is the chord length; and d1 is the distance between the point on the corresponding mid-arc line at b / 2 and the chord.
2. The axial fan blade with double multi-channel venting holes for noise reduction according to claim 1, characterized in that The inlet of the A-type vent at the blade tip is located in the half-section near the trailing edge. The inlet area of the A-type vent at the blade tip accounts for 0.4%-0.8% of the blade tip area, while the outlet area at the trailing edge accounts for 0.5%-1% of the trailing edge area.
3. The axial fan blade with double multi-channel venting holes to reduce noise according to claim 1, characterized in that: The diameter d of type A and type B ventilation holes is 1%-2% of the leaf height h. The spacing between each ventilation hole is evenly distributed at the leaf tip and at the trailing edge. The distance between two adjacent ventilation holes at the trailing edge is D3. The distance between the type B ventilation hole closest to the leaf root and the leaf root is D1. The distance between the type A ventilation hole closest to the leaf tip and the leaf tip is D2. D1 and D2 are equal and are 4%-8% of the leaf height h. D3 is 8%-12% of the leaf height h.
4. The axial fan blade with double multi-channel venting holes to reduce noise according to claim 1, characterized in that: The axes of the type A vents are spatial curves distributed on the mid-curved surface, and the projections of these spatial curves on the projection surface are all arcs with a central angle of 45°.
5. The axial fan blade with double multi-channel venting holes to reduce noise according to claim 1, characterized in that: The angle α between the inlet of the type B vent and the pressure surface can be taken as 30°, and the axis of the type B vent is distributed in a plane parallel to the blade root.
6. The axial fan blade with double multi-channel venting holes to reduce noise according to claim 1, characterized in that: The spacing between adjacent A-type vents is L2. The distance between the first A-type vent on the blade tip and the trailing edge is L1. The last vent is located at the midpoint of the centerline of the blade tip. L1 is 3%-5% of the centerline length, and L2 is 1 / 15-1 / 10 of the centerline length.
7. The axial fan blade with double multi-channel venting holes to reduce noise according to claim 1, characterized in that: B2 is the projection of the B1 type axis onto the blade root. The intersection of B2 and the pressure surface is set as the origin O of the coordinate system. The straight line passing through the origin O and the intersection of the upper middle arc of the blade root and the leading edge is set as the X-axis. The straight line in the blade root plane passing through the origin O and perpendicular to the X-axis is set as the Y-axis. The straight line passing through the origin O and perpendicular to the XOY plane is set as the Z-axis. The positive direction of the Z-axis points towards the blade tip. The distance between the front and rear endpoints of projection line B2 is L, and the distance between the point on projection line B2 at L / 2 and the X-axis is d2. Then, the projection B2 of the B-type vent axis on the blade root is represented by the following equation: The equation of the plane containing the axis of the i-th type B vent at the leaf root is as follows: z = D1 + iD3 The axis of the type B vent is represented by the following equation: In the above formula, i represents the distance from the axis of the i-th type B vent at the leaf root, and D1 is the distance between the type B vent closest to the leaf root and the leaf root.