Design methods for modified volute casings, centrifugal fans, range hoods, and modified volute casings

Abstract

This application relates to a variable-curve volute, a centrifugal fan, a range hood, and a design method for the variable-curve volute. The variable-curve volute includes an annular wall for constructing a volute profile. The annular wall has a telescopic portion that can switch between an extended state and a folded state. In the extended state, the annular wall defines a first volute profile; in the folded state, it defines a second volute profile. The first volute profile is longer than the second volute profile. The variable-curve volute provided by this application exhibits low noise under different operating conditions, good fluid performance, high structural stability, low cost, and lightweight design. This application also provides a design method for the aforementioned variable-curve volute, as well as a centrifugal fan and a range hood incorporating the aforementioned variable-curve volute.

Description

Technical Field

[0001] This application relates to the field of fan system technology, and in particular to a design method for a modified volute, a centrifugal fan, a range hood, and a modified volute. Background Technology

[0002] The noise level of a fan system is an important indicator for evaluating its quality. The noise level of a fan system varies under different operating conditions. For example, the main noise evaluation indicators for range hoods include the semi-anechoic chamber noise level and the operating noise level. Noise indicators are an important basis for users to intuitively compare product performance, and noise also directly affects the user experience. Therefore, reducing the semi-anechoic chamber noise and operating noise of range hoods is crucial.

[0003] Among the many methods for reducing range hood noise, designing a reasonable volute profile is a common approach. However, currently, the volute profile with the lowest noise level under semi-anechoic chamber conditions is not the same as the profile with the lowest noise level under full-duration conditions. That is, some volute profiles have low noise under semi-anechoic chamber conditions but higher noise under full-duration conditions; conversely, some volute profiles have low noise under full-duration conditions but higher noise under semi-anechoic chamber conditions. Therefore, the volute profiles currently used in products usually need to comprehensively consider both semi-anechoic chamber noise and full-duration noise levels, making necessary trade-offs.

[0004] To balance noise levels under different operating conditions, the industry has developed variable profile volutes. These volutes switch to the profile with the lowest noise level when operating in a semi-anechoic chamber, and switch to the profile with the lowest operating noise level when operating in a high-noise chamber, thus maintaining low noise levels under various conditions. However, the different profiles have different perimeters, and how to address the excess material in the volute annulus wall when switching between profiles is the primary challenge for variable profile volutes. Existing technologies employ segmented annulus walls and methods to wind and store the excess material. However, segmented annulus walls lead to decreased fluid performance and reduced structural stability; the winding and storage method requires additional electronic control components, resulting in a larger volute mass and reduced drop resistance.

[0005] Therefore, it is necessary to propose a new technical solution to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] Based on this, this application provides a design method for a modified volute, a centrifugal fan, a range hood, and a modified volute, which has low noise under different operating conditions, good fluid performance, high structural stability, low cost, and lightweight.

[0007] Therefore, this application adopts the following technical solution: a variable-profile volute, including an annular wall for constructing a volute profile, the annular wall having a telescopic portion, the telescopic portion being switchable between an extended state and a folded state, wherein the annular wall defines a first volute profile when the telescopic portion is in an extended state, and defines a second volute profile when the telescopic portion is in a folded state, the first volute profile being longer than the second volute profile.

[0008] In one embodiment, the telescopic portion is a corrugated segment in the annular wall that undulates up and down, wherein, when the telescopic portion is in a folded state, the troughs of the corrugated segment and the inner surface of the annular wall define the second volute profile.

[0009] In one embodiment, the first volute profile and the second volute profile partially overlap, and the end position of the first volute profile is higher than the end position of the second volute profile.

[0010] In one embodiment, the telescopic portion is disposed at the end of the annular wall.

[0011] In one embodiment, the modified volute includes sidewalls located on both sides of the annular wall, the sidewalls and the annular wall forming an air duct, the air duct having an air duct outlet, and a limiting groove defining the position of the end of the annular wall provided on the sidewall near the air duct outlet.

[0012] In one embodiment, the limiting groove is an elongated groove extending in the vertical direction, and the annular wall is provided with a protrusion that slides with the limiting groove; wherein, when the protrusion slides to the lower part of the limiting groove, the telescopic part is compressed into the folded state, and when the protrusion slides to the upper part of the limiting groove, the telescopic part is stretched into the extended state.

[0013] In one embodiment, the sidewall is provided with a first support portion and a second support portion, wherein the first support portion supports the annular wall when the annular wall defines the first volute profile, and the second support portion supports the annular wall when the annular wall defines the second volute profile.

[0014] In one embodiment, the first support portion is a flange that bends and extends from the top of the sidewall, and the second support portion is a rib that protrudes from the inner surface of the sidewall.

[0015] In one embodiment, the deformable volute includes a push rod that presses the annular wall to switch the telescopic portion between the extended state and the folded state.

[0016] In one embodiment, the push rod is located on one side of the outer surface of the ring wall, and the push rod pushes the ring wall to switch the telescopic part from the extended state to the folded state.

[0017] In one embodiment, the modified volute further includes an outer shell, one end of the push rod is connected to the outer shell, and the beginning end of the annular wall is fixed to the outer shell.

[0018] This application also adopts the following technical solution: a centrifugal fan, including a volute and a fan disposed inside the volute, wherein the volute is a modified volute as described in any of the above embodiments.

[0019] This application also adopts the following technical solution: a range hood, including the centrifugal fan as described above.

[0020] This application also adopts the following technical solution: a design method for a variable profile volute, wherein the annular wall of the variable profile volute can switchably define a first volute profile and a second volute profile, the design method comprising:

[0021] Determine the length difference ΔC between the first and second volute profile lines and the folding space spacing P between the first and second volute profile lines;

[0022] The bending line spacing L of the folding unit is determined based on the folding space spacing P, and the bending line spacing L is less than the folding space spacing P.

[0023] The number of folding units N is calculated based on the length difference ΔC and the bend line spacing L; and

[0024] A section of the ring wall is folded to form a telescopic part using the bending line spacing L and the number N.

[0025] The portion between two adjacent peaks or two adjacent troughs constitutes one of the folding units.

[0026] In one embodiment, the bending line spacing L is 0.6 to 0.8 of the folding space spacing P.

[0027] In one embodiment, the quantity N is calculated according to the following formula and rounded up:

[0028]

[0029] Where K1 is the crease coefficient, K2 is the bending coefficient, and t is the wall thickness of the ring wall.

[0030] In one embodiment, the crease coefficient K1 is 0.95 to 0.99, the bending coefficient K2 is 1 to 3, and the wall thickness t of the ring wall is 0.5 to 1 mm.

[0031] The modified volute provided in this application has a telescopic part in its annular wall, which can switch between an extended state and a folded state. When the telescopic part is in the extended state, the annular wall defines a first volute profile, and when the telescopic part is in the folded state, it defines a second volute profile. Thus, its annular wall is a complete structure, and the switching between different profiles can be achieved simply by driving the telescopic part to extend or retract. It has low noise under different operating conditions, good fluid performance, high structural stability, low cost, and lightweight. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A perspective view of an embodiment of the modified volute provided in this application.

[0034] Figure 2 This is a perspective view of another embodiment of the modified volute provided in this application.

[0035] Figure 3 A cross-sectional view of an embodiment of the modified volute provided in this application.

[0036] Figure 4 for Figure 3 A magnified view of the end of the air duct in the middle volute.

[0037] Figure 5 This is a perspective view of an embodiment of the modified volute provided in this application, with the outer shell removed.

[0038] Figure 6 This is a partial enlarged view of the telescopic portion in one embodiment of the modified volute provided in this application.

[0039] Figure 7 This is a schematic diagram of a folding unit in one embodiment of the modified volute provided in this application.

[0040] The component labels are as follows:

[0041] 100. Deformed volute; 101. Air duct; 102. Air duct outlet; 1. Annular wall; 11. Beginning end; 12. End end; 13. Telescopic part; 131. Protrusion; 2. Side wall; 201. Limiting groove; 21. First support part; 22. Second support part; 3. Connecting piece; 4. Push rod; 5. Outer shell. Detailed Implementation

[0042] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0043] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application's specification are for illustrative purposes only and do not represent the only possible implementation.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0046] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0047] Please see Figures 1 to 6This application provides a modified volute 100, including an annular wall 1 for constructing a volute profile, the annular wall 1 having a telescopic portion 13, the telescopic portion 13 being switchable between an extended state and a folded state; wherein, when the telescopic portion 13 is in the extended state, the annular wall 1 defines a first volute profile, and when the telescopic portion 13 is in the folded state, it defines a second volute profile, the first volute profile being longer than the second volute profile.

[0048] The modified volute 100 provided in this application has two switchable volute profiles, enabling low noise levels under various operating conditions. For example, the first volute profile exhibits excellent noise performance under semi-anechoic chamber conditions, while the second volute profile offers excellent noise performance under high-noise operating conditions. Furthermore, the annular wall 1 of the modified volute 100 provided in this application is a complete structure, resulting in high structural stability and good fluid guiding performance. Switching between different profiles can be achieved by driving the telescopic portion 13 on the annular wall 1 to extend or retract using a single drive component, eliminating the need for excessive additional electrical control components. This solution is low-cost, lightweight, and has excellent drop resistance, making it a low-cost, lightweight, and structurally reliable solution.

[0049] Please see Figures 1 to 3 As shown, the annular wall 1 is a curved sheet, and its curved shape defines the path for guiding airflow in the deformed volute 100. The deformed volute 100 includes sidewalls 2 located on both sides of the annular wall 1, and the sidewalls 2 are generally flat sheets. The sidewalls 2 and the annular wall 1 form an air duct 101, which has an air duct outlet 102. The deformed volute 100 also has a plurality of connectors 3, which are used to connect the sidewalls 2 and the annular wall 1. In this embodiment, the connectors 3 are U-shaped metal strips that span across both sides of the annular wall 1 and are connected to the sidewalls 2.

[0050] Please see Figures 3 to 5As shown, the annular wall 1 and the side wall 2 are movably connected, meaning the annular wall 1 can move relative to the side wall 2, thereby enabling switching between different profiles. The ability of the annular wall 1 to move relative to the side wall 2 should be understood as at least a portion of the annular wall 1 being movable relative to the side wall 2. In this embodiment, the starting end 11 of the annular wall 1 is fixed relative to the side wall 2, while the ending end 12 of the annular wall 1 is movable relative to the side wall 2. The starting end 11 refers to the upstream end in the airflow direction, and the ending end 12 refers to the downstream end in the airflow direction. It should also be noted that since the annular wall 1 is a gradual curve from the starting end 11 to the ending end 12, there is no clear boundary between the portion of the annular wall 1 that is fixed relative to the side wall 2 and the portion that can move relative to the side wall 2. In this embodiment, the range of movement of the annular wall 1 relative to the side wall gradually increases from the starting end 11 to the ending end 12. In this embodiment, when the annular wall 1 moves downward relative to the side wall 2 to its lower limit position, a second volute profile is constructed; when it moves upward relative to the side wall 2 to its upper limit position, a first volute profile is constructed. The first volute profile and the second volute profile partially overlap, and the end 12 of the first volute profile is higher than the end 12 of the second volute profile. The overlapping portion of the first volute profile and the second volute profile is the portion near the beginning 11 of the annular wall 1.

[0051] Please refer to this carefully. Figure 4 As shown, the upper and lower limits of the movement of the annular wall 1 are defined by the structure formed on the side wall 2. In this embodiment, the side wall 2 is provided with a first support portion 21 and a second support portion 22. The first support portion 21 supports the annular wall 1 when the annular wall 1 defines the first volute profile, and the second support portion 22 supports the annular wall 1 when the annular wall 1 defines the second volute profile. The first support portion 21 is a flange extending from the top of the side wall 2, and the second support portion 22 is a rib protruding from the inner surface of the side wall 2. The flange abuts against the outer surface of the annular wall 1 to define the first volute profile, and the rib abuts against the inner surface of the annular wall 1 to define the second volute profile.

[0052] Please refer to this carefully. Figure 5 As shown, the side wall 2 is provided with a limiting groove 201 near the air duct outlet 102, which defines the position of the end 12 of the annular wall 1. The two sides of the end 12 of the annular wall 1 can slide within the limiting groove 201. In this embodiment, the limiting groove 201 is an elongated groove extending in the vertical direction, and the annular wall 1 is provided with a protrusion 131 that slides in cooperation with the limiting groove 201. When the end 12 of the annular wall 1 slides towards the lower part of the limiting groove 201 via the protrusion 131, the telescopic part 13 on the annular wall 1 is compressed into a folded state; when the end 12 of the annular wall 1 slides towards the upper part of the limiting groove 201 via the protrusion 131, the telescopic part 13 is extended into the extended state.

[0053] Please see Figures 3 to 6 As shown, the telescopic portion 13 is a corrugated segment in the annular wall 1 that undulates vertically. When the telescopic portion 13 is in a folded state, the troughs of the corrugated segment and the inner surface of the annular wall 1 define the second volute profile. When the telescopic portion 13 is in an extended state, the corrugated segment is flattened, and the entire inner surface of the annular wall 1 defines the first volute profile. It should also be noted that when the telescopic portion 13 is in an extended state, the corrugated segment is not required to be completely flattened; some creases are permissible.

[0054] In this embodiment, the telescopic part 13 is disposed at the end 12 of the annular wall 1. Both the annular wall 1 and the side wall 2 are thin metal sheets. When the annular wall 1 moves downward, the limiting groove 201 prevents the end 12 of the annular wall 1 from extending forward through the protrusion 131, thereby causing the telescopic part 13 to be squeezed and folded. The telescopic part 13 is disposed at the end 12 of the annular wall 1, which has a shorter transmission path of the squeezing force due to the limiting groove 201, and the folding deformation is more reliable. Of course, in other embodiments, the telescopic part 13 can also be disposed at other positions in the middle of the annular wall 1. The deformed volute 100 includes a push rod 4, which pushes the annular wall 1 to switch the telescopic part 13 between the extended state and the folded state by whether or not it pushes the annular wall 1. In this embodiment, the push rod 4 is located on one side of the outer surface of the annular wall 1. The push rod 4 pushes the annular wall 1 to switch the telescopic part 13 from the extended state to the folded state; when the push rod 4 releases the pressure on the annular wall 1, the telescopic part 13 returns to the extended state by its own elasticity. The modified volute 100 also includes an outer shell 5. One end of the push rod 4 is connected to the outer shell 5, and the other end abuts against the annular wall 1. The beginning end of the annular wall 1 is fixed to the outer shell 5. In this embodiment, the push rod 4 is telescopic, including a push rod and a push rod sleeve for extending and retracting the push rod. The push rod can be driven to move electrically or pneumatically. In other embodiments, the push rod 4 can also push against the annular wall 1 by being driven to rotate.

[0055] Of course, the switching drive method between the extended and folded states is not limited to this. In other embodiments, the push rod 4 can be configured to apply force to the ring wall 1 in two directions. For example, when force is applied in the pushing direction, the telescopic part 13 switches to the folded state, and when force is applied in the pulling direction, the telescopic part 13 switches to the extended state. That is, the telescopic part 13 does not completely rely on its own elasticity to return to the extended state. In another embodiment, the push rod 4 can be placed on one side of the inner surface of the ring wall 1. The push rod 4 pushes the ring wall 1 to make the telescopic part 13 switch from the folded state to the extended state. The push rod 4 releases the pushing force or applies a pulling force to make the telescopic part 13 switch from the extended state to the folded state.

[0056] Please see Figure 6 and Figure 7 As shown, this application also provides a design method for a modified volute 100. The modified volute 100 can be any of the volutes described in the above embodiments, and its annular wall 1 can switchably define a first volute profile and a second volute profile. The design method includes:

[0057] Determine the length difference ΔC between the first and second volute profile lines and the folding space spacing P between the first and second volute profile lines;

[0058] The bending line spacing L of the folding unit S is determined based on the folding space spacing P, and the bending line spacing L is less than the folding space spacing P.

[0059] The number N of folding units S is calculated based on the length difference ΔC and the bend line spacing L; and

[0060] A section of the annular wall 1 is folded to form a telescopic part 13 using the bending line spacing L and the number N;

[0061] The portion between two adjacent peaks or two adjacent troughs constitutes one folding unit S.

[0062] like Figure 6 As shown, a folded unit S is a segment of a corrugated section containing a complete crest or a complete trough; the corrugated section is formed by the repeated extension of multiple folded units S. The folded space refers to the space where the annular wall 1 can move vertically. For example... Figure 6 As shown, in one embodiment, the first support 21 defines the upper limit position of the movement of the ring wall 1, and the second support 22 defines the lower limit position of the movement of the ring wall 1. Then, the folding space is the space between the lower surface of the first support 21 and the upper surface of the second support 22. The folding space spacing P is the vertical distance of the folding space, that is, the distance between the lower surface of the first support 21 and the upper surface of the second support 22.

[0063] The bending line spacing L is the distance between two adjacent bending points, or in other words, the width of the portion between two adjacent creases. Since the telescopic part 13 needs to be folded within the folding space, the bending line spacing L formed by the folding of the telescopic part 13 cannot be greater than the folding space spacing P. Generally speaking, based on the consideration of processing convenience, if the folding space size allows, the solution with fewer folds will be preferred. Therefore, if the bending line spacing L is less than the folding space spacing P, a longer bending line spacing L is preferred. At the same time, considering the folding performance of metal materials, in this embodiment, the bending line spacing L is 0.6 to 0.8 of the folding space spacing P.

[0064] In one embodiment, the design method proceeds as follows.

[0065] First, the optimal volute profile for different working conditions has been obtained through theoretical calculations and testing. For example, the volute profile A with the lowest noise in the semi-anechoic chamber and the volute profile B with the lowest working noise have been obtained. The perimeter Ca of volute profile A and the perimeter Cb of volute profile B can be obtained through mathematical methods. Then, the length change distance that the telescopic part 13 needs to be able to achieve is the length difference ΔC = Ca - Cb. When the telescopic part 13 is composed of N folding units S, each folding unit S must be able to achieve a length change of ΔC / N.

[0066] When the annular wall 1 is in its longest state, that is, when the telescopic part 13 is fully extended and flat, each folding unit S is at its maximum length L. max Maximum length L max The length of the folded unit S is twice the bending line spacing L; considering that creases usually prevent the ring wall 1 from being completely straightened, a crease coefficient K1 is added, preferably 0.95 to 0.99; then the maximum length L of the folded unit S is... max It can be expressed as follows: L max =2*K1*L.

[0067] like Figure 7 As shown, when the annular wall 1 is in its shortest state, that is, when the folding units S included in the telescopic part 13 are in a state of close proximity to each other, each folding unit S is at its shortest length L. min The shortest length L min It is twice the wall thickness t of the annular wall, plus twice the minimum bending diameter d. That is: L min = 2t + 2d; where the minimum bending diameter d of the sheet metal part is usually proportional to the wall thickness of the ring wall 1, that is: d = K2 * t, where K2 is the bending coefficient, which is usually taken as 1 to 3. In one embodiment, the wall thickness t of the ring wall 1 is preferably 0.5 to 1 mm.

[0068] Therefore, the length difference ΔL of each folded unit S in its longest and shortest states satisfies:

[0069] ΔL=L max -L mim =2*K1*L-2t-2*K2*t=2*(K1*L-(1+K2)*t); then ΔC=N*ΔL=2*N*(K1*L-(1+K2)*t).

[0070] Generally speaking, considering ease of processing, the option with fewer folds will be preferred when the folding space size allows. Therefore, if the bending line spacing L is less than the folding space spacing P, a longer bending line spacing L is preferred. At the same time, considering the folding performance of metal materials, the relationship between the bending line spacing L and the folding space spacing P is expressed as follows: L = K3 * P; where K3 is the folding coefficient added to consider the folding performance of metal, which is preferably 0.6 to 0.8.

[0071] By substituting the above formula, we can calculate the appropriate number of folding units N, that is:

[0072]

[0073] Since N should be a positive integer, its value calculated using the above formula can be rounded up.

[0074] The following calculation of the reasonable design parameters of the telescopic part 13 is based on specific experimental data. The perimeter Ca of the volute profile A is 1000 mm, the perimeter Cb of the volute profile B is 900 mm, the distance P between the first support part 21 and the second support part 22 at the end of the volute is 20 mm, the wall thickness t of the annular wall 1 is 0.7 mm, the crease coefficient K1 is 0.95, the bending coefficient K2 is 2, and the folding coefficient K3 is 0.75. Substituting these values ​​into the above formula, the number N of the folding unit S is calculated to be 4.12, which rounds up to 5. Based on the rounded number N, the bending line spacing L is calculated by substituting it into the formula, resulting in a bending line spacing L value of 12.7 mm.

[0075] As can be seen from the above description of the specific embodiments, the modified volute 100 provided in this application has a telescopic part 13 in its annular wall 1. The telescopic part 13 can switch between an extended state and a folded state. When the telescopic part 13 is in the extended state, the annular wall 1 defines a first volute profile, and when the telescopic part 13 is in the folded state, it defines a second volute profile. Thus, its annular wall 1 is a complete structure, and the switching between different profiles can be achieved simply by driving the telescopic part 13 to extend or retract. It has low noise under different working conditions, good fluid performance, high structural stability, low cost, and lightweight.

[0076] This application also provides a centrifugal fan, which includes a volute and a fan disposed within the volute, wherein the volute is a modified volute 100 as described in any of the above embodiments.

[0077] This application also provides a range hood that includes the centrifugal fan described above.

[0078] The centrifugal fan and range hood provided in this application, since they include the aforementioned modified volute 100, naturally also have the aforementioned beneficial effects.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the patent protection scope of this application should be determined by the appended claims.

Claims

1. A profiled volute, comprising an annular wall for constructing the volute profile, characterized in that: The annular wall has a telescopic portion that can switch between an extended state and a folded state. When the telescopic portion is in the extended state, the annular wall defines a first volute profile, and when the telescopic portion is in the folded state, it defines a second volute profile. The first volute profile is longer than the second volute profile. The modified volute includes sidewalls located on both sides of the annular wall, the sidewalls and the annular wall forming an air duct, the air duct having an air duct outlet, and a limiting groove defining the end position of the annular wall near the air duct outlet on the sidewall. The sidewall is provided with a first support portion and a second support portion. The first support portion supports the annular wall when the annular wall defines the first volute profile, and the second support portion supports the annular wall when the annular wall defines the second volute profile. The first support portion is a flange that bends and extends from the top of the side wall, and the second support portion is a rib that protrudes from the inner surface of the side wall.

2. The modified volute according to claim 1, characterized in that, The telescopic portion is a corrugated segment in the annular wall that undulates up and down. When the telescopic portion is in a folded state, the troughs of the corrugated segment and the inner surface of the annular wall define the second volute profile.

3. The modified volute according to claim 1, characterized in that, The first volute profile and the second volute profile partially overlap, and the end position of the first volute profile is higher than the end position of the second volute profile.

4. The modified volute according to claim 3, characterized in that, The telescopic part is located at the end of the annular wall.

5. The modified volute according to claim 1, characterized in that, The limiting groove is an elongated groove extending in the vertical direction, and the annular wall is provided with a protrusion that slides with the limiting groove; wherein, when the protrusion slides to the lower part of the limiting groove, the telescopic part is squeezed into the folded state, and when the protrusion slides to the upper part of the limiting groove, the telescopic part is stretched into the extended state.

6. The modified volute according to claim 1, characterized in that, The deformed volute includes a push rod that presses the annular wall to switch the telescopic portion between the extended state and the folded state.

7. The modified volute according to claim 6, characterized in that, The push rod is located on one side of the outer surface of the ring wall, and the push rod pushes the ring wall to switch the telescopic part from the extended state to the folded state.

8. The modified volute according to claim 7, characterized in that, The modified volute also includes an outer shell, one end of the push rod is connected to the outer shell, and the beginning end of the annular wall is fixed to the outer shell.

9. A centrifugal fan, comprising a volute and a fan disposed within the volute, characterized in that, The volute is a modified linear volute as described in any one of claims 1 to 8.

10. A range hood, characterized in that, Includes the centrifugal fan as described in claim 9.

11. A design method for a variable profile volute, wherein the annular wall of the variable profile volute can switchably define a first volute profile and a second volute profile, characterized in that, The design method includes: Determine the length difference ∆C between the first volute profile and the second volute profile, and the folding space spacing P between the first volute profile and the second volute profile; The bending line spacing L of the folding unit is determined based on the folding space spacing P, and the bending line spacing L is less than the folding space spacing P. The number of folding units N is calculated based on the length difference ∆C and the bend line spacing L; and A section of the ring wall is folded to form a telescopic part using the bending line spacing L and the number N. The portion between two adjacent peaks or two adjacent troughs constitutes one of the folding units.

12. The design method of the modified volute according to claim 11, characterized in that, The bending line spacing L is 0.6 to 0.8 of the folding space spacing P.

13. The design method of the modified volute according to claim 11, characterized in that, The quantity N is calculated according to the following formula and rounded up: Where K1 is the crease coefficient, K2 is the bending coefficient, and t is the wall thickness of the ring wall.

14. The design method of the modified volute according to claim 13, characterized in that, The crease coefficient K1 is 0.95~0.99, the bending coefficient K2 is 1~3, and the wall thickness t of the ring wall is 0.5~1mm.

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