Volute, air duct structure and range hood

Abstract

The utility model provides a volute, an air duct structure and a range hood, the molded line of the volute comprises a first straight line segment, a volute tongue molded line segment, a spiral line segment and a second straight line segment which are sequentially arranged along the circumferential direction and are mutually and smoothly connected, the design of the correction factor comprises the change caused by the leakage flow of the oil leakage hole. According to the volute, the air duct structure and the range hood, the correction factor is used for determining the equation of the spiral line segment, the molded line of the volute in the spiral line segment is corrected, the corrected size of the molded line of the volute enables flowing of fluid to better conform to the angular momentum conservation principle, flowing loss is reduced, streamline change caused by leakage of an oil leakage hole is also reduced, and the service life of the volute is prolonged. And the air flow at the outlet impacts the wall surface of the volute, so that mutual interference is caused.

Description

Technical Field

[0001] The utility model relates to the technical field of range hoods, in particular to a volute, an air duct structure and a range hood. Background Art

[0002] The volute is one of the core components of the fan system. Its function is to guide the gas leaving the impeller to the volute outlet and convert part of the kinetic energy of the gas into static pressure. The traditional volute design usually assumes that the fluid flows out evenly along the circumference of the entire impeller, that is, along the flow direction of the fluid, the flow rate of the fluid through different sections of the volute is proportional to the angle formed between the section and the starting section of the volute; at the same time, in this traditional design, it is also necessary to ignore the influence of friction, and then obtain the volute profile design according to the principle of constant angular momentum, and such a volute profile is usually a logarithmic spiral.

[0003] The air outlet hood is also a component of the fan system. The air outlet hood serves to connect the range hood (i.e., the range hood) and the smoke duct. Specifically, the air outlet hood connects the volute and the smoke duct of the range hood. The air outlet hood connected to one side of the range hood body is a rectangular air inlet, and the side connected to the smoke duct is a circular air outlet. The current common method for designing the air outlet hood shell is to design the air outlet hood shell independently. The distance between the circular surface of the air outlet and the rectangular surface of the air inlet is determined according to the design requirements. The side of the air outlet hood is a rectangular air inlet with the vertices connected to the four equal points of the circle, so each side has a triangular plane.

[0004] In the existing fan system technology, firstly, the volute design does not take into account the flow loss caused by the oil leakage hole in the volute, and the volute profile design cannot match the flow change at various positions of the volute, that is, the ratio of the flow on different cross-sections of the volute to the angle formed from the cross-section to the starting cross-section of the volute is not an ideal proportional relationship, which can easily lead to disruption of the fluid flow in the volute, causing streamline deviation, possible flow separation, and increased flow loss.

[0005] Secondly, the existing air hood shell is designed independently, so it usually cannot match the volute profile well. The fluid flowing out of the volute often hits the wall when entering the air hood, and also forms flow separation in the corner area, resulting in increased flow loss, increased pressure pulsation, and increased noise. In addition, the side wall of the traditional air hood is a plane, and the fluid enters the air hood and hits the wall, which is easy to cause flow separation and increase flow loss due to the large angle. Utility Model Content

[0006] The technical problem to be solved by the utility model is to overcome the defect that the volute profile design of the range hood in the prior art cannot reflect the flow loss caused by the oil leakage hole of the volute, which leads to flow separation in the volute and increased flow loss, and to provide a volute, an air duct structure and a range hood.

[0007] The utility model solves the above technical problems through the following technical solutions:

[0008] A volute for a centrifugal fan of a range hood, wherein an impeller is arranged in the volute, and the profile of the volute comprises a first straight line segment, a volute tongue-shaped line segment, a spiral line segment, and a second straight line segment which are sequentially arranged in the circumferential direction and smoothly connected to each other, wherein the starting point of the first straight line segment and the end point of the second straight line segment correspond to the two ends of the air outlet of the volute respectively;

[0009] The spiral line segment includes a spiral line starting point connected to the volute tongue-shaped line segment, a spiral line end point connected to the second straight line segment, and a spiral line middle point between the spiral line starting point and the spiral line end point; the circumferential section of the volute perpendicular to the circumference includes an intermediate section and a starting section, the intermediate section is a section of the circumferential section passing through the center of the impeller and at the intermediate point of the spiral line, and the starting section is a section of the circumferential section passing through the center of the impeller and parallel to the outlet section of the volute; the volute is provided with an oil leakage hole in the spiral line segment;

[0010] The helical segment is given by the equation Sure,

[0011] Wherein, q is the flow rate of the centrifugal fan, R2 is the outer diameter of the impeller, B is the width of the volute, C′ 2u is the tangential velocity of the fluid after leaving the impeller, e is a constant, is the angle between the starting section and the middle section along the flow direction of the fluid in the volute;

[0012] θ is a correction factor, which is

[0013] θ4 is the angle between the starting section and the starting point of the spiral line along the flow direction, q 泄 is the leakage flow rate of the fluid through the oil leakage hole, θ 45 It is the angle of the circumferential section rotating from the starting point of the helix to the end point of the helix along the flow direction.

[0014] In this solution, the ratio of the flow rate on the middle section of the spiral segment along the flow direction to the angle between the middle section and the starting section is corrected by the correction factor, reflecting the flow change caused by the oil leakage hole. The volute uses the correction factor to determine the equation of the spiral segment, and corrects the profile of the volute in the spiral segment. The corrected volute profile size can make the flow of the fluid more consistent with the principle of conservation of angular momentum, reduce flow losses, and reduce the streamline changes caused by leakage from the oil leakage hole, so that the outlet airflow impacts the volute wall, thereby causing mutual interference problems.

[0015] Preferably, the first straight line is tangent to the snail tongue-shaped line segment, and / or the second straight line segment is tangent to the spiral line segment.

[0016] In this solution, the impact of the airflow on the volute wall at the outlet of the volute is reduced through the above-mentioned tangent relationship, which is beneficial to reducing flow losses.

[0017] A duct structure, comprising a volute as described above and an air outlet hood connected to the air outlet of the volute, the body of the air outlet hood comprising a first spline smoothly connected to the first straight line segment and a second spline smoothly connected to the second straight line segment, the first spline and / or the second spline being a curve.

[0018] In this solution, the duct structure adopts the above-mentioned volute to correct the volute profile size, so that the flow of the fluid is more in line with the principle of conservation of angular momentum, reducing flow losses and reducing the impact of the airflow on the volute wall. The air outlet cover of the duct structure adopts a curve through the above-mentioned two splines (the first spline and the second spline) so that the volute of the corrected profile and the air outlet cover have a smooth transition, reducing the impact of the fluid on the wall when entering the air outlet cover, reducing flow separation (flow separation refers to the resistance generated by the fluid impacting the volute wall, which causes the airflow at different positions to separate), and reducing noise.

[0019] Preferably, the air outlet cover comprises the body and a base arranged at the bottom of the body, and the base is connected to the air outlet of the volute;

[0020] The first spline is tangent to the auxiliary tangent line at the end point of the auxiliary tangent line, wherein the auxiliary tangent line is an extension of the first straight line segment to the base, and the first straight line segment is tangent to the snail tongue-shaped line segment, the starting point of the auxiliary tangent line is the starting point of the first straight line segment, and the end point of the auxiliary tangent line is the intersection point where the auxiliary tangent line extends to the upper surface of the base;

[0021] The radius r of the first spline is determined by the equation r=b-(ba)cosα;

[0022] Wherein, a is the length of the straight line between the auxiliary intersection point and the starting point of the first spline, b is the length of the straight line between the auxiliary intersection point and the end point of the first spline, the auxiliary intersection point is the intersection point of a first auxiliary circle with the end point of the first spline as the center and a second auxiliary circle with the end point of the auxiliary tangent straight line as the center, and the starting point of the first spline is the connection point with the first straight line segment;

[0023] α is the angle between the first auxiliary line and the starting line, the first auxiliary line is the straight line between the middle point on the first spline and the auxiliary intersection point, and the starting line is the straight line between the starting point of the first spline and the auxiliary intersection point.

[0024] In this solution, the first spline is tangent to the extension of the first straight line segment, and the first straight line segment is tangent to the volute tongue segment, thereby establishing a smooth transition from the volute tongue segment to the first spline, reducing the flow resistance of the fluid, thereby helping to reduce flow separation and noise. The radius of the first spline is set using the above equation, so that the curvature of the first spline adapts to the flow of the fluid from the first straight line segment of the volute to the air outlet cover, reducing resistance, and helping to reduce noise impact.

[0025] Preferably, the radius of the first auxiliary circle is the straight line length between the end point of the first spline and the end point of the auxiliary tangent line;

[0026] Preferably, the radius of the second auxiliary circle is half of the length of a straight line from the end point of the auxiliary tangent straight line to the end point of the second straight line segment.

[0027] In this solution, the above-mentioned dimensional relationship is used to determine the radius of the first auxiliary circle and / or the radius of the second auxiliary circle, thereby determining the curvature of the first spline, which is beneficial to reducing resistance and noise.

[0028] Preferably, the second spline is tangent to the second straight line segment at an end point of the second straight line segment, and the radius of the second spline is the radius of the helical segment at a connection point between the helical segment and the second straight line segment.

[0029] In this solution, the second spline determined by the above setting establishes a smooth transition from the second straight line segment of the volute to the second spline of the air outlet cover, reducing the flow resistance of the fluid, which is beneficial to reducing flow separation and noise.

[0030] Preferably, the air outlet hood includes a housing air inlet and a housing air outlet along the flow direction of the fluid, the housing air inlet is rectangular and communicates with the air outlet of the volute, and the housing air outlet is circular;

[0031] The air outlet hood is located on one side of the first spline and also includes a third spline and a fourth spline. The third spline and the fourth spline are curves where the air outlet hood is located on one side of the first spline at the air inlet of the casing and the two end points along the width direction extend toward the air outlet of the casing respectively. The third spline and the fourth spline are symmetrical with respect to the first spline.

[0032] In this solution, the third spline and the fourth spline are arranged as above to match the profile of the first spline, which is helpful to reduce the flow resistance in the surrounding area of ​​the first spline, and reduce the flow loss and noise.

[0033] Preferably, the air outlet hood includes a housing air inlet and a housing air outlet along the flow direction of the fluid, the housing air inlet is rectangular and communicates with the air outlet of the volute, and the housing air outlet is circular;

[0034] The air outlet hood is located on one side of the second spline and also includes a fifth spline and a sixth spline. The fifth spline and the sixth spline are curves where the air outlet hood is located on one side of the second spline at the air inlet of the casing and the two end points along the width direction extend toward the air outlet of the casing respectively. The fifth spline and the sixth spline are symmetrical with respect to the second spline.

[0035] In this solution, the fifth spline and the sixth spline are arranged as above to match the profile of the second spline, which is beneficial to reducing the flow resistance in the area around the second spline, and reducing the flow loss and noise.

[0036] A range hood comprises the above-mentioned air duct structure.

[0037] In this solution, the range hood adopts the above-mentioned air duct structure to correct the size of the volute profile, so that the flow of the fluid is more in line with the principle of conservation of angular momentum, reducing flow losses and reducing the impact of the airflow on the volute wall. The air outlet hood of the air duct structure adopts a curve through the above-mentioned two splines (the first spline and the second spline), so that the volute of the modified profile and the air outlet hood have a smooth transition, reducing the impact of the fluid on the wall when entering the air outlet hood, reducing flow separation (flow separation refers to the resistance generated by the fluid impacting the volute wall, which causes the airflow at different positions to separate), and reducing noise.

[0038] The positive progressive effect of the utility model is that the volute, the air duct structure and the range hood are used to determine the equation of the spiral segment through the above-mentioned correction factor, thereby correcting the profile of the volute in the spiral segment. The corrected volute profile size can make the flow of the fluid more consistent with the principle of conservation of angular momentum, reduce flow losses, and also reduce streamline changes caused by leakage from the oil leakage hole, causing the outlet airflow to impact the volute wall, thereby causing mutual interference problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the volute profile of Example 1 of the utility model.

[0040] Figure 2 This is a schematic diagram of the connection structure between the volute and the air outlet cover of Example 1 of the utility model.

[0041] Figure 3 Schematic diagram of determining the spline of the air outlet hood of Example 1 of the utility model Figure 1 .

[0042] Figure 4 This is a schematic diagram of the shape structure of the air outlet cover at the air inlet and the air outlet of Example 1 of the utility model.

[0043] Figure 5 Schematic diagram of determining the spline of the air outlet hood of Example 1 of the utility model Figure 2 .

[0044] Figure 6 This is a spline diagram of the air outlet cover of Example 1 of the utility model.

[0045] Description of reference numerals:

[0046] Snail 1

[0047] The first straight line segment S2S3

[0048] Snail tongue line segment S3S4

[0049] Spiral Segment S4S5

[0050] The second straight line segment S1S5

[0051] Air outlet of the volute 2

[0052] The end point of the second straight line segment S1

[0053] The starting point of the first straight line segment S2

[0054] Helix starting point S4

[0055] Spiral end point S5

[0056] Helix midpoint S40

[0057] Starting section 3

[0058] Middle section 4

[0059] Air outlet hood 5

[0060] The main body of the air outlet cover 51

[0061] Base 52

[0062] The first sample line S8S9

[0063] Second spline S6S7

[0064] Third Spline 53

[0065] Fourth spline 54

[0066] Fifth Spline 55

[0067] Sixth Spline 56

[0068] Cover air inlet 6

[0069] Cover air outlet 7

[0070] Auxiliary intersection point A

[0071] First auxiliary circle 8

[0072] Second auxiliary circle 9

[0073] Auxiliary tangent line S2S9

[0074] The starting point of the first line S6

[0075] The end point of the first line S7

[0076] The starting point of the second spline S8

[0077] End point of the second spline S9 DETAILED DESCRIPTION

[0078] A preferred embodiment is given below, and the present invention is described more clearly and completely in conjunction with the accompanying drawings.

[0079] Example 1

[0080] like Figure 1 As shown, this embodiment provides a volute 1 for a centrifugal fan of a range hood, and an impeller is arranged in the volute 1 (not shown in the figure, the impeller is located at Figure 1 The profile of the volute 1 includes a first straight line segment S2S3, a volute tongue segment S3S4, a spiral segment S4S5 and a second straight line segment S1S5 which are sequentially arranged along the circumferential direction and smoothly connected to each other. The starting point S2 of the first straight line segment and the end point S1 of the second straight line segment correspond to the two ends of the air outlet 2 of the volute, respectively.

[0081] The spiral line segment S4S5 includes a spiral line starting point S4 connected to the volute tongue-shaped line segment S3S4, a spiral line end point S5 connected to the second straight line segment S1S5, and a spiral line middle point S40 between the spiral line starting point S4 and the spiral line end point S5; the circumferential section of the volute 1 perpendicular to the circumference includes an intermediate section 4 and a starting section 3, the intermediate section 4 is a section of the circumferential section passing through the center of the impeller and at the middle point of the spiral line, and the starting section 3 is a section of the circumferential section passing through the center of the impeller and parallel to the outlet section of the volute 1; the volute 1 is provided with an oil leakage hole in the spiral line segment.

[0082] The spiral segment is given by the equation Sure.

[0083] Where, q is the flow rate of the centrifugal fan, R2 is the outer diameter of the impeller, B is the width of the volute 1, C′2u is the tangential velocity of the fluid after leaving the impeller, e is a constant (e = 2.71828), is the angle between the starting section 3 and the middle section 4 along the flow direction of the fluid in the volute 1. In this embodiment, the flow direction of the fluid is Figure 1 counterclockwise direction.

[0084] θ is the correction factor, which is

[0085] θ4 is the angle between the starting section 3 and the starting point of the spiral line S4 along the flow direction, q 泄 is the leakage flow rate of the fluid through the oil leakage hole, θ 45 It is the angle of the circumferential section rotating from the starting point S4 of the helix to the end point S5 of the helix along the flow direction.

[0086] When the above correction factor is not used, the logarithmic spiral equation used by the original volute profile in the spiral segment is: After the above correction factor is adopted in this embodiment, the corrected volute profile will be offset inward as a whole within the range of the spiral segment compared to the volute profile before correction. This offset can correct the flow change caused by the flow leaked from the oil leakage hole. That is, the volute 1 corrects the ratio of the flow on the middle section 4 of the spiral segment along the flow direction and the angle between the middle section 4 and the starting section 3 through the above correction factor, reflecting the flow change caused by the oil leakage hole. The volute 1 uses the above correction factor to determine the equation of the spiral segment, and corrects the profile of the volute 1 in the spiral segment. The corrected volute 1 profile size can make the flow of the fluid more in line with the principle of conservation of angular momentum, reduce flow losses, and also reduce the streamline changes caused by the leakage of the oil leakage hole, so that the outlet airflow impacts the wall of the volute 1, thereby causing mutual interference problems.

[0087] Among them, the first straight line segment S2S3 is tangent to the volute tongue segment S3S4, and the second straight line segment S1S5 is tangent to the spiral segment S4S5. In other embodiments, the tangent relationship may not be adopted, but the effect is not as good as the embodiment adopting the above tangent relationship, which reduces the impact of the airflow on the wall of the volute 1 at the outlet of the volute 1, which is conducive to reducing flow losses.

[0088] like Figure 2-6 As shown, the present embodiment further provides an air duct structure, which includes the volute 1 as described above and an air outlet hood 5 connected to the air outlet of the volute, the main body 51 of the air outlet hood includes a first spline S8S9 smoothly connected to the first straight line segment S2S3 and a second spline S6S7 smoothly connected to the second straight line segment S1S5, the first spline S8S9 and the second spline S6S7 are curves.

[0089] The duct structure adopts the above-mentioned volute 1, and corrects the size of the volute 1 profile, so that the flow of the fluid is more in line with the principle of conservation of angular momentum, reducing flow losses and reducing the impact of the airflow on the wall of the volute 1. The air outlet hood 5 of the duct structure adopts a curve through the above-mentioned two splines (the first spline S8S9 and the second spline S6S7), so that the volute 1 with the corrected profile and the air outlet hood 5 have a smooth transition, reducing the impact of the fluid on the wall when entering the air outlet hood 5, reducing flow separation (flow separation refers to the resistance generated by the fluid impacting the wall of the volute 1, which causes the airflow at different positions to separate), and reducing noise.

[0090] like Figure 5 and Figure 6 As shown, the air outlet hood 5 includes a main body 51 and a base 52 arranged at the bottom of the main body 51, and the base 52 is connected to the air outlet 2 of the volute; the first spline S8S9 is tangent to the auxiliary tangent straight line S2S9 at the end point S9 of the auxiliary tangent straight line, wherein the auxiliary tangent straight line S2S9 is an extension of the first straight line segment S2S3 to the base 52, and the first straight line segment S2S3 is tangent to the volute tongue-shaped line segment S3S4, the starting point of the auxiliary tangent straight line S2S9 is the starting point S2 of the first straight line segment, and the end point S9 of the auxiliary tangent straight line S2S9 is the intersection point where the auxiliary tangent straight line S2S9 extends to the upper surface of the base 52. By the above-mentioned setting, the first stripe line S8S9 is tangent to the extension of the first straight line segment S2S3, and the first straight line segment S2S3 is tangent to the volute tongue-shaped line segment S3S4, thereby establishing a smooth transition from the volute tongue-shaped line segment S3S4 to the first stripe line S8S9, reducing the flow resistance of the fluid, which is beneficial to reducing flow separation and noise.

[0091] The radius r of the first spline is determined by the equation r=b-(ba)cosα.

[0092] like Figure 5 As shown, a is the length of the straight line between the auxiliary intersection A and the starting point S9 of the first sample line, b is the length of the straight line between the auxiliary intersection A and the end point S8 of the first sample line, the auxiliary intersection is the intersection of the first auxiliary circle 8 with the end point S8 of the first sample line S8S9 as the center and the second auxiliary circle 9 with the end point S9 of the auxiliary tangent line S2S9 as the center, and the starting point S9 of the first sample line is the connection point with the first straight line segment; α is the angle between the first auxiliary line and the starting line, the first auxiliary line is the straight line between the middle point on the first sample line S8S9 and the auxiliary intersection A, and the starting line is the straight line between the starting point S9 of the first sample line and the auxiliary intersection A.

[0093] The above equation is used to set the radius of the first sample line S8S9, so that the curvature of the first sample line S8S9 adapts to the flow of the fluid from the first straight line segment of the volute 1 to the air outlet cover 5, reduces resistance, and is conducive to reducing noise impact.

[0094] Among them, the radius of the first auxiliary circle 8 is the straight line length between the end point S8 of the first line and the end point S9 of the auxiliary tangent line; and / or, the radius of the second auxiliary circle 9 is half of the straight line length between the end point S9 of the auxiliary tangent line and the end point S1 of the second straight line segment.

[0095] The radius of the first auxiliary circle 8 and / or the radius of the second auxiliary circle 9 is determined by using the above-mentioned dimensional relationship, thereby determining the curvature of the first spline, which is beneficial to reducing resistance and noise.

[0096] Among them, the second spline S6S7 is tangent to the second straight line segment S1S5 at the end point S1 of the second straight line segment, and the radius of the second spline S6S7 is the radius of the spiral segment at the connection point of the spiral segment and the second straight line segment S1S5. The second spline S6S7 determined by the above setting establishes a smooth transition from the second straight line segment S1S5 of the volute 1 to the second spline of the air outlet cover 5, reducing the flow resistance of the fluid, thereby facilitating the reduction of flow separation and noise.

[0097] like Figure 4 and Figure 6 As shown, the air outlet hood 5 includes a housing air inlet 6 and a housing air outlet 7 along the flow direction of the fluid. The housing air inlet 6 is rectangular and connected to the air outlet 2 of the volute, and the housing air outlet 7 is circular. The air outlet hood 5 is located on one side of the first spline and also includes a third spline 53 and a fourth spline 54. The third spline 53 and the fourth spline 54 are curves extending from the housing air inlet 6 to the housing air outlet 7 at both ends along the width direction of the air outlet hood 5 on one side of the first spline. The third spline 53 and the fourth spline 54 are symmetrical with respect to the first spline. The third spline 53 and the fourth spline 54 are arranged as above, which match the profile of the first spline, and are conducive to reducing the flow resistance in the surrounding area of ​​the first spline, and reducing the flow loss and noise.

[0098] The air outlet hood 5 is located on one side of the second spline and further includes a fifth spline 55 and a sixth spline 56. The fifth spline 55 and the sixth spline 56 are curves extending from the air outlet 6 of the housing and the two ends in the width direction of the air outlet hood 5 on one side of the second spline to the housing air outlet 7. The fifth spline 55 and the sixth spline 56 are symmetrical with respect to the second spline. The fifth spline 55 and the sixth spline 56 are matched with the profile of the second spline by the fifth spline 55 and the sixth spline 56, which are helpful to reduce the flow resistance of the peripheral area of ​​the second spline, and reduce the flow loss and noise.

[0099] Example 2

[0100] The present embodiment provides a range hood, which includes an air duct structure as in Embodiment 1. The range hood adopts the above-mentioned air duct structure to correct the size of the volute 1 profile, so that the flow of the fluid is more in line with the principle of conservation of angular momentum, reducing flow losses and reducing the impact of the airflow on the wall of the volute 1. The air outlet hood 5 of the air duct structure adopts a curve through the above-mentioned two splines (the first spline and the second spline), so that the volute 1 with the corrected profile and the air outlet hood 5 have a smooth transition, reducing the impact of the fluid on the wall when entering the air outlet hood 5, reducing flow separation (flow separation refers to the resistance generated by the fluid impacting the wall of the volute 1, which causes the airflow at different positions to separate), and reducing noise.

[0101] Although the specific implementations of the utility model are described above, those skilled in the art should understand that this is only an example, and the protection scope of the utility model is defined by the attached claims. Those skilled in the art can make various changes or modifications to these implementations without departing from the principle and essence of the utility model, but these changes and modifications fall within the protection scope of the utility model.

Claims

1. A volute, used for a centrifugal fan of a range hood, wherein an impeller is arranged in the volute, and the profile of the volute comprises a first straight line segment, a volute tongue-shaped line segment, a spiral line segment, and a second straight line segment which are sequentially arranged along the circumference and smoothly connected to each other, wherein the starting point of the first straight line segment and the end point of the second straight line segment correspond to the two ends of the air outlet of the volute respectively; The spiral line segment includes a spiral line starting point connected to the volute tongue-shaped line segment, a spiral line end point connected to the second straight line segment, and a spiral line middle point between the spiral line starting point and the spiral line end point; the circumferential section of the volute perpendicular to the circumference includes a middle section and a starting section, the middle section is a section of the circumferential section passing through the center of the impeller and at the middle point of the spiral line, and the starting section is a section of the circumferential section passing through the center of the impeller and parallel to the outlet section of the volute; The volute is provided with an oil leakage hole in the spiral line segment; It is characterized in that The helical segment is given by the equation Sure, Wherein, q is the flow rate of the centrifugal fan, R2 is the outer diameter of the impeller, B is the width of the volute, C′ 2u is the tangential velocity of the fluid after leaving the impeller, e is a constant, is the angle between the starting section and the middle section along the flow direction of the fluid in the volute; θ is a correction factor, which is θ4 is the angle between the starting section and the starting point of the spiral line along the flow direction, q 泄 is the leakage flow rate of the fluid through the oil leakage hole, θ 45 It is the angle of the circumferential section rotating from the starting point of the helix to the end point of the helix along the flow direction.

2. The volute according to claim 1, characterized in that: The first straight line is tangent to the tongue-shaped line segment, and / or the second straight line segment is tangent to the spiral line segment.

3. An air duct structure, characterized in that: The air duct structure includes a volute as described in claim 1 or 2 and an air outlet hood connected to the air outlet of the volute, the body of the air outlet hood includes a first spline smoothly connected to the first straight line segment and a second spline smoothly connected to the second straight line segment, and the first spline and / or the second spline are curves.

4. The air duct structure according to claim 3, characterized in that: The air outlet cover comprises the body and a base arranged at the bottom of the body, and the base is connected to the air outlet of the volute; The first spline is tangent to the auxiliary tangent line at the end point of the auxiliary tangent line, wherein the auxiliary tangent line is an extension of the first straight line segment to the base, and the first straight line segment is tangent to the snail tongue-shaped line segment, the starting point of the auxiliary tangent line is the starting point of the first straight line segment, and the end point of the auxiliary tangent line is the intersection point where the auxiliary tangent line extends to the upper surface of the base; The radius r of the first spline is determined by the equation r=b-(ba)cosα; Wherein, a is the length of the straight line between the auxiliary intersection point and the starting point of the first spline, b is the length of the straight line between the auxiliary intersection point and the end point of the first spline, the auxiliary intersection point is the intersection point of a first auxiliary circle with the end point of the first spline as the center and a second auxiliary circle with the end point of the auxiliary tangent straight line as the center, and the starting point of the first spline is the connection point with the first straight line segment; α is the angle between the first auxiliary line and the starting line, the first auxiliary line is the straight line between the middle point on the first spline and the auxiliary intersection point, and the starting line is the straight line between the starting point of the first spline and the auxiliary intersection point.

5. The air duct structure according to claim 4, characterized in that: The radius of the first auxiliary circle is the straight line length between the end point of the first spline and the end point of the auxiliary tangent line.

6. The air duct structure according to claim 4, characterized in that: The radius of the second auxiliary circle is half of the length of a straight line between the end point of the auxiliary tangent straight line and the end point of the second straight line segment.

7. The air duct structure according to claim 3, characterized in that: The second spline is tangent to the second straight line segment at an end point of the second straight line segment, and the radius of the second spline is the radius of the helical segment at a connection point between the helical segment and the second straight line segment.

8. The air duct structure according to claim 4, characterized in that: The air outlet cover includes a cover air inlet and a cover air outlet along the flow direction of the fluid, the cover air inlet is rectangular and communicates with the air outlet of the volute, and the cover air outlet is circular; The air outlet hood is located on one side of the first spline and also includes a third spline and a fourth spline. The third spline and the fourth spline are curves where the air outlet hood is located on one side of the first spline at the air inlet of the casing and the two end points along the width direction extend toward the air outlet of the casing respectively. The third spline and the fourth spline are symmetrical with respect to the first spline.

9. The air duct structure according to claim 4, characterized in that: The air outlet cover includes a cover air inlet and a cover air outlet along the flow direction of the fluid, the cover air inlet is rectangular and communicates with the air outlet of the volute, and the cover air outlet is circular; The air outlet hood is located on one side of the second spline and also includes a fifth spline and a sixth spline. The fifth spline and the sixth spline are curves where the air outlet hood is located on one side of the second spline at the air inlet of the casing and the two end points along the width direction extend toward the air outlet of the casing respectively. The fifth spline and the sixth spline are symmetrical with respect to the second spline.

10. A range hood, characterized in that: It comprises the air duct structure as described in any one of claims 3-9.

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