Noise Reduction Structure and Design Method of Fans, Fans

Abstract

This invention discloses a fan noise reduction structure and its design method in the field of fan structure, and a fan including an inlet structure and an outlet structure on the casing; the inlet structure gradually increases in height H1 and gradually decreases in width W1 from the channel inlet to the rotor cavity inlet, and the overall cross-sectional area S1 gradually increases; the outlet structure gradually decreases in height H2 and gradually increases in width W2 from the rotor cavity outlet to the channel outlet, and the overall cross-sectional area S2 gradually decreases; the fan noise reduction structure provided by this invention has an inlet structure that is gradually expanding along the fluid intake direction, with a gradually increasing height and a gradually decreasing width, and an outlet structure that is gradually contracting along the fluid discharge direction, with a gradually decreasing height and a gradually increasing width. The fluid is pre-expanded in the inlet structure and then enters the rotor cavity, and the fluid is slowly compressed in the outlet structure, avoiding large noise and vibration generated when the fluid is compressed or expanded instantaneously.

Description

Technical Field

[0001] This invention relates to the field of wind turbine structure, and more particularly to a wind turbine noise reduction structure and its design method, and a wind turbine. Background Technology

[0002] like Figure 11 As shown, the Roots blower achieves fluid intake, transport, and discharge through the synchronous counter-rotation of two non-contact rotors 7. Multiple independent closed cavities are formed between the rotors 7 and the casing 1. The rotors within the cavities divide the cavities into an inlet zone 201, a transition zone 202, and an outlet zone 203. The inlet zone 201 is connected to the air inlet, and the outlet zone 203 is connected to the air outlet. The transition zone 202 is not connected to either the inlet zone 201 or the outlet zone 203. Therefore, the fluid in the transition zone 202 is stable. The rotating rotor 7 transports the fluid from the transition zone 202 to the outlet zone, where the stable fluid disturbs the fluid in the outlet zone. The inlet zone 201, connected to the air inlet, expands to draw in fluid. The fluid is gradually pressurized through the transition zone 202 and transported to the outlet zone 203 as the rotor rotates. Finally, the cavity is compressed, discharging the high-pressure fluid.

[0003] Based on its operating characteristics, Roots blowers have advantages such as high vacuum and stable flow, but noise is a prominent issue, and aerodynamic noise is one of the main noise sources of Roots blowers.

[0004] Therefore, how to solve the above-mentioned technical problems is a technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a noise reduction structure for a fan and its design method. The fan has an inlet structure that is gradually expanding along the fluid intake direction, so that the fluid volume is pre-expanded in the inlet pipe. The outlet structure is a gradually contracting structure along the fluid discharge direction, so that the fluid is further compressed in the outlet pipe, thereby reducing inlet and outlet flow and pressure fluctuations and achieving noise reduction.

[0006] To solve the above technical problems, the following technical solution is adopted: In a first aspect, the present invention provides a fan noise reduction structure, including an inlet structure and an outlet structure on a housing, wherein a rotor cavity for mounting a rotor is provided inside the housing, and both the inlet structure and the outlet structure are connected to the rotor cavity, wherein the two ends of the inlet structure are a channel inlet and a rotor cavity inlet, and the two ends of the outlet structure are a channel outlet and a rotor cavity outlet, respectively. The height H1 of the inlet structure gradually increases and the width W1 gradually decreases from the channel inlet to the rotor cavity inlet, i.e., along the fluid suction direction, while the overall cross-sectional area S1 gradually increases. The outlet structure gradually decreases in height H2 and gradually increases in width W2 from the rotor cavity outlet to the channel outlet along the fluid discharge direction; the overall cross-sectional area S2 gradually decreases. The planes with height and width on the inlet and outlet structures are perpendicular to the direction of fluid flow inside the shell.

[0007] Optionally, the width of the rotor cavity inlet is smaller than the width of the rotor cavity outlet.

[0008] Optionally, the cross-section of the channel inlet is circular, and the cross-section of the rotor cavity inlet is elongated.

[0009] Optionally, the cross-section of the channel outlet is circular, and the cross-section of the rotor cavity outlet is elongated.

[0010] Optionally, the outer periphery of the channel inlet is connected to the inlet pipe via a flange, and the outer periphery of the channel outlet is connected to the outlet pipe via a flange.

[0011] Optionally, the cross-sectional area of ​​the inlet structure changes from increasing to decreasing along the fluid intake direction, while the cross-sectional area of ​​the outlet structure changes from decreasing to increasing along the fluid discharge direction. The cross-sectional changes of the inlet and outlet structures near the rotor cavity tube section tend to be gradual, resulting in a relatively slow expansion or compression rate of the fluid within the inlet or outlet structure near the rotor cavity tube section.

[0012] Optionally, the outlet structure is further provided with a return channel to reduce flow pulsation.

[0013] Optionally, the reflux groove is located at the rotor cavity outlet. The reflux groove is a constant depth reflux groove or a gradually deepening reflux groove. The constant depth reflux groove has a consistent depth in the fluid flow direction, while the gradually deepening reflux groove has a gradually increasing depth in the fluid flow direction.

[0014] In a second aspect, the present invention provides a fan, including the fan noise reduction structure described in the first aspect.

[0015] Thirdly, the present invention provides a design method for a fan noise reduction structure, wherein the fan casing has an inlet structure and an outlet structure, and the casing is provided with a rotor cavity for mounting the rotor. The inlet structure and the outlet structure are both connected to the rotor cavity. The two ends of the inlet structure are a channel inlet and a rotor cavity inlet, respectively, and the two ends of the outlet structure are a channel outlet and a rotor cavity outlet, respectively. The design method includes: The height H1 of the inlet structure gradually increases and the width W1 gradually decreases from the channel inlet to the rotor cavity inlet, i.e., along the fluid suction direction; and the overall cross-sectional area S1 gradually increases; The height H2 of the outlet structure gradually decreases and the width W2 gradually increases from the rotor cavity outlet to the channel outlet, i.e., along the fluid discharge direction; the overall cross-sectional area S2 gradually decreases. The planes with height and width on the inlet and outlet structures are perpendicular to the direction of fluid flow inside the shell.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. The fan noise reduction structure provided by the present invention has an inlet structure that is gradually expanding along the fluid intake direction, with its height gradually increasing and its width gradually decreasing, and an outlet structure that is gradually contracting along the fluid discharge direction, with its height gradually decreasing and its width gradually increasing. The fluid is pre-expanded in the inlet structure and then enters the rotor cavity. The fluid is further slowly compressed in the outlet structure, which avoids generating large noise and vibration when the fluid is compressed or expanded instantaneously.

[0017] 2. The fan noise reduction structure provided by the present invention also has a return groove on the outlet structure. The return groove is located at the rotor cavity outlet, which can reduce the flow pulsation of the outlet structure and improve the system stability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the inlet structure in an embodiment of the present invention; Figure 2 This is a schematic diagram of the outlet structure in an embodiment of the present invention; Figure 3 This is a schematic diagram of the rotor cavity inlet and rotor cavity outlet structures in an embodiment of the present invention; Figure 4 This is a graph showing the relationship between the rotor cavity inlet width and flow pulsation in an embodiment of the present invention. Figure 5 This is a graph showing the relationship between the rotor cavity outlet width and flow pulsation in an embodiment of the present invention. Figure 6 This is one of the cross-sectional structural diagrams of the shell in the embodiments of the present invention; Figure 7 This is an enlarged structural schematic diagram of the equal-depth reflux tank in an embodiment of the present invention; Figure 8 This is the second cross-sectional structural diagram of the shell in the embodiment of the present invention; Figure 9 This is an enlarged structural schematic diagram of the gradually deepening reflux groove in an embodiment of the present invention; Figure 10 This is a schematic diagram of the cross-sectional structure of the equal-depth reflux channel in an embodiment of the present invention; Figure 11 This is a schematic diagram of the cross-sectional structure of the gradually deepening reflux channel in an embodiment of the present invention; Figure 12 This is a schematic diagram of the cross-sectional structure of a Roots blower in the background art of this invention.

[0019] Explanation of reference numerals in the attached figures: 1. Shell; 2. Rotor cavity; 201. Inlet area; 202. Transition area; 203. Outlet area; 3. Inlet structure; 31. Channel inlet; 32. Rotor cavity inlet; 4. Outlet structure; 41. Channel outlet; 42. Rotor cavity outlet; 5. Reflux groove; 51. Equal depth reflux groove; 52. Gradually deeper reflux groove; 6. Flange; 7. Rotor. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] As described in the background section, Roots blowers have advantages such as high vacuum and stable flow rate, but noise is a prominent issue, and aerodynamic noise is one of the main noise sources of Roots blowers.

[0023] The inventors discovered that the aforementioned technical problems were mainly caused by the periodic flow and pressure pulsations at the inlet and outlet.

[0024] The defects in the above solutions and the reasons for their occurrence are the results of the inventors' practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed in this disclosure should be considered as the inventors' contributions to this disclosure.

[0025] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] To avoid noise problems caused by periodic flow and pressure pulsations at the inlet and outlet, at least one embodiment provides a fan noise reduction structure, including an inlet structure 3 and an outlet structure 4 on the housing 1. A rotor cavity 2 communicating with the inlet structure 3 and the outlet structure 4 is also provided inside the housing 1. The rotor cavity 2 is used to install the rotor. When the rotor rotates, the fluid enters the rotor cavity 2 from the inlet structure 3 and then exits from the outlet structure 4 to realize the fluid transport.

[0027] like Figure 1 As shown, the two ends of the inlet structure 3 are the channel inlet 31 and the rotor cavity inlet 32, respectively. The height H1 of the inlet structure 3 gradually increases from the channel inlet 31 to the rotor cavity inlet 32, while the width W1 gradually decreases. The overall cross-sectional area S1 of the inlet structure 3 gradually increases from the channel inlet 31 to the rotor cavity inlet 32. The flow direction of the fluid in the inlet structure 3 is from the channel inlet 31 to the rotor cavity inlet 32. Figure 1 The lower middle section (a, b, c, d, e, f) shows the overall cross-sectional area S1 and cross-sectional shape changes of the inlet structure 3. The direction from Figure a to Figure f is from the channel inlet 31 to the rotor cavity inlet 32. As can be seen from the figure, the height H1 gradually increases, the width W1 gradually decreases, the overall cross-sectional area S1 gradually increases, and the transition from the channel inlet 31 to the rotor cavity inlet 32 ​​is smooth.

[0028] like Figure 2 As shown, the two ends of the outlet structure 4 are the channel outlet 41 and the rotor cavity outlet 42, respectively. The height H2 of the outlet structure 4 gradually decreases from the rotor cavity outlet 42 to the channel outlet 41, while the width W2 gradually increases. The overall structural area S2 of the outlet structure 4 gradually decreases from the rotor cavity outlet 42 to the channel outlet 41. The flow direction of the fluid in the outlet structure 4 is from the rotor cavity outlet 42 to the channel outlet 41. Figure 2 The diagrams A, B, C, D, E, and F at the bottom center show the overall cross-sectional area S2 and cross-sectional shape changes of the outlet structure 4. The direction from A to F is from the rotor cavity outlet 42 to the channel outlet 41. As can be seen from the diagrams, the height H2 gradually decreases, the width W2 gradually increases, and the overall cross-sectional area S2 gradually decreases. The transition from the channel outlet 41 to the rotor cavity outlet 42 is smooth.

[0029] The inlet structure 3 is a gradually expanding structure in the direction of the rotor cavity 2 (i.e. fluid intake), so that the fluid enters the rotor cavity 2 from the inlet structure 3 and has sufficient path to expand within the inlet structure 3. The outlet structure 4 is a gradually contracting structure in the direction away from the rotor cavity 2 (i.e. fluid discharge), so that the fluid flows from the rotor cavity 2 into the outlet structure 4 and has sufficient path to contract within the outlet structure 4, thereby avoiding noise and vibration caused by the instantaneous expansion or contraction of the fluid.

[0030] like Figure 3 As shown, a simulation experiment was conducted to determine the width W of the rotor cavity inlet 32 ​​and the rotor cavity outlet 42. The height H of the rotor cavity inlet 32 ​​and the rotor cavity outlet 42 remains constant in the figure. Figure 3 Simulation experiments were conducted in which the width W of the rotor cavity inlet 32 ​​and rotor cavity outlet 42 gradually increased in directions 1-4. The results were as follows: Figure 4 , Figure 5 As shown, where, Figure 4 This is a curve showing the gradual increase in width at rotor cavity inlet 32. Figure 5 The graph shows the gradually increasing width at rotor cavity outlet 42. Figure 4 , Figure 5 The horizontal axis numbers 1, 2, 3, and 4 correspond to... Figure 3 The four widths are 1, 2, 3, and 4. From Figure 4 , Figure 5 It can be concluded that as the width of the rotor cavity inlet 32 ​​gradually increases, both the flow pulsation coefficient and the pulsation amplitude gradually increase, and vice versa. Similarly, as the width of the rotor cavity outlet 42 gradually increases, both the flow pulsation coefficient and the pulsation amplitude gradually decrease, and vice versa. During the experiment, when the rotor cavity inlet 32 ​​was at its minimum width, the flow pulsation was 4%–11% lower than that of other widths, and the amplitude was 13–26 L / s lower; when the rotor cavity outlet 42 was at its maximum width, the flow pulsation was 7%–16% lower than that of other widths, and the amplitude was 32–122 L / s lower. Therefore, in this embodiment, a smaller width is chosen for the rotor cavity inlet 32, such as… Figure 3 The width of the figure with subscript 1; the rotor cavity outlet 42 should have a larger width, such as Figure 3 The width of the figure with subscript 4 is shown. Therefore, the width at rotor cavity inlet 32 ​​is less than the width at rotor cavity outlet 42.

[0031] like Figure 12 As shown, two rotors 7 are arranged vertically inside the rotor cavity 2. In this embodiment, the planes with height and width on the inlet structure 3 and outlet structure 4 are perpendicular to the fluid flow direction in the channel.

[0032] At least one embodiment also provides a fan noise reduction structure.

[0033] like Figure 1 , Figure 2 , Figure 3 As shown, the inlet channel 31 on the inlet structure 3 has a circular cross-section, and the rotor cavity inlet 32 ​​has a long strip cross-section. The outer periphery of the circular cross-section is connected to the inlet pipe via flange 6, and the long strip cross-section is connected to the rotor cavity 2 body. The outlet channel 41 on the outlet structure 4 also has a circular cross-section, and the rotor cavity outlet 42 has a long strip cross-section. The outer periphery of the outlet channel 41 is connected to the outlet pipe via flange 6, and the long strip cross-section is connected to the rotor cavity 2. On the outlet structure 4 and the inlet structure 3, the circular cross-section gradually transitions smoothly to the long strip cross-section, the length L gradually stretches to the edge of the rotor cavity 2, and the width A shrinks. The overall cross-sectional area of ​​the inlet structure 3 gradually increases along the fluid suction direction, and the rate of area increase first increases and then decreases; the overall cross-sectional area of ​​the outlet structure 4 gradually decreases along the fluid discharge direction, and the rate of area decrease first decreases and then increases. The shape of the long strip cross-section on the outlet structure 4 and the inlet structure 3 is not limited to the one shown in the figure; multiple straight lines, multiple circular arcs, or a combination of circular arcs and straight lines are all acceptable. The cross-sectional dimensions of the inlet structure 3 and the outlet structure 4 are not required to be the same.

[0034] The length L of the rotor cavity inlet 32 ​​and rotor cavity outlet 42 connected to rotor cavity 2 is almost the same as the axial width inside rotor cavity 2. Therefore, when the fluid enters rotor cavity 2 from inlet structure 3, its axial expansion along the rotor is very small, only filling rotor cavity 2 radially. When the fluid enters outlet structure 4 from rotor cavity 2, its axial compression along the rotor is very small, only compressing into the channel of outlet structure 4 radially. From the direction of fluid entering rotor cavity 2, the cross-section of the inlet channel gradually expands, causing the fluid to expand slowly in advance within inlet structure 3. From the direction of fluid exiting rotor cavity 2, the cross-section of outlet structure 4 gradually contracts, further compressing the fluid within outlet structure 4. This inlet and outlet structure design effectively restricts the instantaneous flow of fluid entering or exiting rotor cavity 2, avoiding sudden expansion or contraction of the cross-section that causes drastic changes in flow. The flow within the cavity is more stable, and the flow and pressure pulsations are smoother, reducing noise caused by turbulence and pulsation.

[0035] The inlet structure 3 is a gradually expanding structure towards the rotor cavity 2, with the overall cross-sectional area gradually increasing, and the rate of increase of the cross-sectional area is first increasing and then decreasing. The outlet structure 4 is a gradually contracting structure away from the rotor cavity 2, with the overall cross-sectional area gradually decreasing, and the rate of decrease of the cross-sectional area is first decreasing and then increasing. The inlet structure 3 and the outlet structure 4 are smoothly connected to the shell 1 or are an integral structure to achieve the noise reduction effect when the internal fluid flows.

[0036] like Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 As shown, Figure 6 ,and Figure 8 The arrows in the diagram indicate the direction of fluid flow. In this embodiment, a return channel 5 is further provided within the outlet structure 4 to further pulsate the flow. The return channel 5 is located at the rotor cavity outlet 42 and consists of symmetrically arranged slots on both sides of the rotor cavity outlet 42. The depth of the return channel 5 (depth in the fluid flow direction) ranges from 3 to 20 mm. The structure of the return channel 5 can be a constant-depth return channel 51 or a gradually deepening return channel 52. The constant-depth return channel 51 has a consistent depth in the fluid flow direction, while the gradually deepening return channel 52 gradually increases in depth in the fluid flow direction. The cross-sectional shape of both the constant-depth return channel 51 and the gradually deepening return channel 52 can be rectangular or arc-shaped. Therefore, the return channel 5 includes four types: a constant-depth rectangular return channel 5, a constant-depth arc-shaped return channel 5, a gradually deepening rectangular return channel 5, and a gradually deepening arc-shaped return channel 5.

[0037] Simulation experiments were conducted on the four types of reflux troughs 5 proposed above, and the relationship between the shape of the reflux trough 5 and the flow pulsation coefficient is shown in the following graph: Return channel shape (outlet) No reflux tank rectangle of equal depth Equal depth arc Gradient Rectangle Gradual arc Flow fluctuation coefficient 51.57 39.71 29.36 33.14 39.85 As can be seen from the table above, setting a return channel 5 on the outlet structure reduces the pulsation coefficient compared to not having a return channel. Among the four return channel shapes, the equal-depth arc shape has the smallest flow pulsation coefficient, followed by the gradually deepening rectangle. Therefore, when designing the return channel 5, an equal-depth arc shape or a gradually deepening rectangle return channel structure should be adopted.

[0038] At least one embodiment also provides a Roots blower that employs the blower noise reduction mechanism described in the above embodiments to reduce the noise during operation of the Roots blower.

[0039] At least one embodiment also provides a design method for a fan noise reduction structure, wherein the fan noise reduction structure of the above embodiment is designed, and the design method includes: The height H1 of the inlet structure gradually increases and the width W1 gradually decreases from the channel inlet to the rotor cavity inlet, i.e., along the fluid suction direction; and the overall cross-sectional area S1 gradually increases; The height H2 of the outlet structure gradually decreases and the width W2 gradually increases from the rotor cavity outlet to the channel outlet, i.e., along the fluid discharge direction; the overall cross-sectional area S2 gradually decreases. The planes with height and width on the inlet and outlet structures are perpendicular to the direction of fluid flow inside the shell.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fan noise reduction structure, characterized in that, The device includes an inlet structure (3) and an outlet structure (4) on a housing (1). The housing (1) is provided with a rotor cavity (2) for mounting a rotor. The inlet structure (3) and the outlet structure (4) are both connected to the rotor cavity (2). The two ends of the inlet structure (3) are a channel inlet (31) and a rotor cavity inlet (32), respectively. The two ends of the outlet structure (4) are a channel outlet (41) and a rotor cavity outlet (42), respectively. The inlet structure (3) gradually increases in height H1 and gradually decreases in width W1 along the fluid suction direction from the channel inlet (31) to the rotor cavity inlet (32), and the overall cross-sectional area S1 gradually increases. The outlet structure (4) gradually decreases in height H2 and gradually increases in width W2 from rotor cavity outlet (42) to channel outlet (41) along the fluid discharge direction; the overall cross-sectional area S2 gradually decreases. Wherein, the planes of height and width on the inlet structure and the outlet structure are perpendicular to the fluid flow direction inside the shell (1); The cross-sectional area of ​​the inlet structure (3) changes from increasing to decreasing along the fluid intake direction, while the cross-sectional area of ​​the outlet structure (4) changes from decreasing to increasing along the fluid discharge direction. The cross-sectional changes of the inlet structure (3) and the outlet structure (4) near the rotor cavity (2) tend to be gradual.

2. The fan noise reduction structure according to claim 1, characterized in that, The width of the rotor cavity inlet (32) is smaller than the width of the rotor cavity outlet (42).

3. The fan noise reduction structure according to claim 1, characterized in that, The cross-section of the channel inlet (31) is circular, and the cross-section of the rotor cavity inlet (32) is elongated.

4. The fan noise reduction structure according to claim 1, characterized in that, The cross-section of the channel outlet (41) is circular, and the cross-section of the rotor cavity outlet (42) is elongated.

5. The fan noise reduction structure according to claim 1, characterized in that, The outer periphery of the channel inlet (31) is connected to the inlet pipe via a flange (6), and the outer periphery of the channel outlet (41) is connected to the outlet pipe via a flange (6).

6. The fan noise reduction structure according to claim 1, characterized in that, The outlet structure (4) is also equipped with a return channel (5) for reducing flow pulsation.

7. The fan noise reduction structure according to claim 6, characterized in that, The reflux groove (5) is located at the rotor cavity outlet (42). The structure of the reflux groove is a constant depth reflux groove (51) or a gradually deepening reflux groove (52). The constant depth reflux groove (51) has a consistent depth in the fluid flow direction, while the gradually deepening reflux groove (52) has a gradually increasing depth in the fluid flow direction.

8. A Roots blower, characterized in that, Includes the fan noise reduction structure as described in any one of claims 1-7.

9. A design method for a fan noise reduction structure, characterized in that, The design method is used to design the fan noise reduction structure according to any one of claims 1-7.

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