Centrifugal fan, range hood and design method of centrifugal fan

Abstract

The invention relates to a centrifugal fan, a range hood and a design method of the centrifugal fan, and relates to the technical field of range hoods. According to the centrifugal fan, the three-section type lines of the first arc section, the second arc section and the third arc section of the arc section protrusion are designed differently, diffusion is conducted on the volute in the axial direction, compared with two-dimensional flow of a traditional volute, diffusion in the axial direction is considered, and therefore the flow efficiency of the volute is greatly improved. And three-dimensional flow of airflow in a flow channel in the volute is considered. On one hand, the arc section protrusions designed in this way can well eliminate angle vortexes, and airflow can flow in a flow channel in the volute better; secondly, the arc section protrusions designed in this way are better attached to real flow in the volute, and the air inlet efficiency is improved; and thirdly, the arc section protrusions designed in this way can eliminate the assembling gap between a volute and a case of a traditional range hood, noise of the range hood is reduced, and user experience is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of range hoods, and in particular to a centrifugal fan, a range hood and a design method for the centrifugal fan. Background Art

[0002] A range hood is a kitchen appliance used to absorb oil smoke. Range hoods have become a must-have appliance in home kitchens. They absorb cooking smoke and effectively discharge it to the outside, freeing the kitchen from the trouble of oil smoke. Among them, the volute of the range hood can collect the gas entering the impeller and discharge it to the volute outlet. The volute plays the role of gas collection and pressure expansion. In a range hood, the impeller and volute are both core components. The quality of their design plays a decisive role in the overall performance of the range hood.

[0003] The inventors have found that the volute case of a traditional range hood consists of multiple parts, namely, a case top plate, a volute flange, a volute rear plate, a case enclosure, a connecting plate, a volute enclosure, a volute front plate, a case rear plate, a case side plate, a motor and an impeller. When these parts are combined, there is always an assembly gap. When the centrifugal fan is started, the high-speed moving gas passes through the case and the volute, which will produce a whistling sound, thereby increasing the noise of the range hood and affecting the user experience. Summary of the invention

[0004] The purpose of the present invention includes providing a centrifugal fan, a range hood and a design method for a centrifugal fan, which can eliminate the assembly gap between the volute and the chassis of a traditional range hood, reduce the noise of the range hood and improve the user experience.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a centrifugal fan, comprising:

[0007] The volute includes a volute enclosure, a volute back plate and a volute front plate, the front side of the volute enclosure is connected to the volute front plate, and the back side of the volute enclosure is connected to the volute back plate to form an air duct;

[0008] The outer edge of the volute forms an arc segment protrusion; the cross-section of the arc segment protrusion includes a first arc segment, a second arc segment and a third arc segment; one end of the first arc segment is connected to the volute back plate, and the other end is connected to one end of the second arc segment; the third arc segment is connected to the volute front plate, and the other end is connected to the other end of the second arc segment.

[0009] In an optional embodiment, the centrifugal fan further includes a chassis, the volute is disposed in the chassis, the volute front plate is connected to the chassis, and the volute enclosure, the volute back plate and the chassis are an integrally formed structure.

[0010] In an optional embodiment, the chassis includes a chassis top plate, a chassis front plate, a chassis enclosure and a connection plate, the top of the chassis enclosure is connected to the chassis top plate, the bottom of the chassis enclosure is connected to the connection plate, the chassis enclosure includes a chassis left side plate, a chassis right side plate, and a chassis back plate connected in sequence, and one side of the chassis enclosure is an open side;

[0011] The front panel of the chassis is located on the opening side and is detachably connected to the chassis enclosure;

[0012] The volute enclosure, the volute back plate, the chassis top plate, the chassis enclosure and the connecting plate are an integrally formed structure.

[0013] In an optional embodiment, the volute has an air outlet and an air inlet, the air inlet is arranged on the volute front plate, the volute enclosure, the volute back plate and the volute front plate are connected to form an air outlet, and the air outlet is located at the end of the air duct;

[0014] The connecting plate is provided with a first air outlet connected to the air duct, the top plate of the chassis is provided with a second air outlet connected to the air duct, and the volute enclosure, the volute back plate and the volute front plate are connected to the edge of the second air outlet of the volute top plate so that the second air outlet cooperates with the air outlet;

[0015] The front side of the volute enclosure is detachably connected to the volute front plate.

[0016] In an optional embodiment, the lateral inner walls of the chassis enclosure are connected to the lateral outer walls of the volute enclosure, so that the lateral sides of the volute enclosure are respectively tangent to the lateral sides of the chassis enclosure.

[0017] In a second aspect, the present invention provides a range hood comprising the centrifugal fan of any one of the aforementioned embodiments.

[0018] In a third aspect, the present invention provides a design method for a centrifugal fan, including the centrifugal fan of any one of the aforementioned embodiments;

[0019] Design methods include:

[0020] A first coordinate system is established on the radial cross section of the volute, with the extension direction of the volute back plate as the Y-axis direction, the midpoint of the volute back plate as the coordinate origin O, and the horizontal line passing through the coordinate origin O as the X-axis;

[0021] The connection point between the volute back plate and the first arc segment M1O1P1 is M1, the connection point between the first arc segment M1O1P1 and the second arc segment P1O3P2 is P1, the connection point between the second arc segment P1O3P2 and the third arc segment M2O2P2 is P2, the connection point between the third arc segment M2O2P2 and the volute front plate is M2, the center of the first arc segment M1O1P1 is O1, the center of the second arc segment P1O3P2 is O3, and the center of the third arc segment M2O2P2 is O2;

[0022] According to the average flow rate of the volute on the current radial cross section, the positions of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2 of the volute in the first coordinate system are calculated.

[0023] In an optional embodiment, according to the average flow rate of the volute on the current radial section, calculating the positions of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2 of the volute in the first coordinate system, further comprising the following steps:

[0024] The coordinates of point 01 are Substituting the coordinates (X1, Y1) of P1 in the first arc segment M1O1P1 into the radius formula, we can obtain the first control equation:

[0025] The coordinates of point 02 are Substituting the coordinates of P2 (X2, Y2) in the third arc segment M2O2P2 into the radius formula, we can obtain the second control equation:

[0026] Substituting the P1 coordinates (X1, Y1) and P2 coordinates (X2, Y2) into the radius formula yields the third control equation:

[0027]

[0028] Determine the values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) according to the first control equation, the second control equation, and the third control equation;

[0029] Calculate the arc lengths of the first arc segment M1O1P1, the second arc segment P1O3P2, and the third arc segment M2O2P2 according to the P1 coordinates (X1, Y1) and the P2 coordinates (X2, Y2);

[0030] Among them, A is the opening of the outlet section of the volute at an angle θ of 360°; B is the width of the volute, and if the volute is a constant width volute, B is a constant value.

[0031] In an optional embodiment, the values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) are confirmed according to the first control equation, the second control equation and the third control equation, and the following steps are also included:

[0032] The radius of the first arc segment M1O1P1 is equal to the radius of the third arc segment M2O2P2, resulting in the following fourth control equation:

[0033]

[0034] The values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) are confirmed by the above-mentioned fourth control equation.

[0035] In an optional implementation, the arc lengths of the first arc segment M1O1P1, the second arc segment P1O3P2, and the third arc segment M2O2P2 are calculated according to the P1 coordinates (X1, Y1) and the P2 coordinates (X2, Y2), further comprising the following steps:

[0036] With point 01 as the center, point M1 is rotated clockwise by θ1 around the center 01 to obtain point P1. The arc length of the first arc segment M1O1P1 is obtained according to the center angle θ1 and arc length formula 1.

[0037] Arc length formula 1 is: L1 = θ1 × π × r1 / 180°;

[0038] Wherein, L1 is the arc length of the first arc segment M1O1P1, θ1 is the center angle of the first arc segment M1O1P1, π is the pi, and r1 is the radius of the first arc segment M1O1P1.

[0039] In an optional embodiment, point 02 is taken as the center of the third arc segment M2O2P2, point M2 is rotated counterclockwise by θ2 around the center of the circle 01 to obtain point P2, and the arc length of the third arc segment M2O2P2 is obtained according to the center angle θ2 and arc length formula 2;

[0040] Arc length formula 2 is: L2 = θ2 × π × r2 / 180°;

[0041] Wherein, L2 is the arc length of the third arc segment M2O2P2, θ2 is the center angle of the third arc segment M2O2P2, π is the pi, and r2 is the radius of the third arc segment M2O2P2.

[0042] In an optional embodiment, the central angle θ1 of the first arc segment M1O1P1 ranges from 30° to 60°;

[0043] The central angle θ2 of the third arc segment M2O2P2 ranges from 30° to 60°.

[0044] In an optional embodiment, point 03 is taken as the center of the second arc segment P1O3P2, point P1 is rotated clockwise by θ3 around the center of the circle 03 to obtain point P2, and the arc length of the second arc segment P1O3P2 is obtained according to the center angle θ3 and arc length formula 3;

[0045] Arc length formula 3 is: L3 = θ3 × π × R3 / 180°;

[0046] Wherein, L3 is the arc length of the second arc segment P1O3P2, θ3 is the center angle of the second arc segment P1O3P2, π is the pi, and R3 is the radius of the second arc segment P1O3P2.

[0047] In an optional embodiment, the method further includes the following steps: designing the inner surface contour line of the volute shroud.

[0048] In an optional embodiment, designing the inner profile contour line of the volute shroud comprises the following steps:

[0049] The inner profile contour line of the volute enclosure is designed to be a first profile line, a second profile line and a volute profile line connected in sequence, the second profile line is located at the starting position of the volute profile line, the second profile line and the volute profile line are arranged at an angle so that the volute enclosure forms a volute tongue, and the first profile line and the volute profile line are part of the air outlet of the volute;

[0050] A second coordinate system is established on the inner profile contour line of the volute shroud, with the center of the impeller as the coordinate origin O, the horizontal line passing through the coordinate origin O as the X-axis, and the vertical line passing through the origin O as the Y-axis;

[0051] The inner surface contour line of the volute enclosure is designed according to the value of A.

[0052] In an optional embodiment, the inner profile contour line of the volute shroud is designed according to the value of A, comprising the following steps:

[0053] Design A according to the following relationship 4 θ ;

[0054] Relation 4: A θ =E-E0;

[0055] Among them, A θ is the volute opening at angle θ, R is the outer radius of the volute, R0 is the outlet radius of the impeller, and θ is the angle between any radial section and the radial section at the end of the volute profile;

[0056] The inner walls on both sides of the chassis enclosure are designed to be connected to the outer walls on both sides of the volute enclosure, so that the two sides of the volute enclosure are tangent to the two sides of the chassis enclosure, and the lateral length of the chassis satisfies the following relationship: L = L1 + L2;

[0057] Wherein, L is the transverse length of the casing, L1 is the distance between the leftmost side wall of the volute enclosure and the center of the impeller, and L2 is the distance between the rightmost side wall of the volute enclosure and the center of the impeller.

[0058] The beneficial effects of the centrifugal fan, range hood and centrifugal fan design method provided by the embodiments of the present invention include:

[0059] This application expands the volute in the axial direction by designing the three-section profiles of the first arc segment, the second arc segment and the third arc segment of the arc segment protrusion differently. Compared with the binary flow of the traditional volute, this application considers the axial expansion more and the three-dimensional flow of the airflow in the flow channel inside the volute. On the one hand, the arc segment protrusion designed in this way can eliminate corner vortices very well, which is more conducive to the flow of air in the flow channel inside the volute; on the other hand, the arc segment protrusion designed in this way is more in line with the actual flow inside the volute, improving the air intake efficiency; on the third hand, the arc segment protrusion designed in this way can eliminate the assembly gap between the volute and the chassis of the traditional range hood, reduce the noise of the range hood, and improve the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0061] Figure 1 An exploded view of the centrifugal fan provided in this embodiment;

[0062] Figure 2 A front view of the centrifugal fan provided in this embodiment;

[0063] Figure 3 A front view of the installation of the volute and the impeller provided in this embodiment;

[0064] Figure 4 A schematic diagram of the installation of the volute and the impeller provided in this embodiment;

[0065] Figure 5 A bottom view of the volute provided for this embodiment;

[0066] Figure 6 The volute provided in this embodiment is S n a first schematic diagram of a cross section;

[0067] Figure 7 A second schematic diagram of the volute in the Sn section provided for this embodiment.

[0068] Icons: 010- centrifugal fan; 100- volute; 110- volute enclosure; 111- first profile; 112- second profile; 113- volute profile; 114- volute tongue; 120- volute back plate; 130- volute front plate; 140- air inlet; 150- air outlet; 160- driving member; 170- impeller; 180- arc segment protrusion; 181- first arc segment; 182- second arc segment; 183- third arc segment; 200- chassis; 210- chassis top plate; 220- chassis front plate; 230- chassis enclosure; 231- chassis left side plate; 232- chassis right side plate; 233- chassis back plate; 240- connecting plate; 241- first air outlet. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0070] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0072] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0073] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0074] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0075] The overall structure, working principle and technical effects of the centrifugal fan, range hood and centrifugal fan design method provided by the present invention are described in detail below through embodiments and in conjunction with the accompanying drawings.

[0076] Please refer to Figure 1 The centrifugal fan 010 provided by the present invention is applied to a range hood.

[0077] Please refer to Figure 1 The centrifugal fan 010 proposed by the present invention comprises:

[0078] The volute 100 includes a volute enclosure 110, a volute back plate 120 and a volute front plate 130, wherein the front side of the volute enclosure 110 is connected to the volute front plate 130, and the back side of the volute enclosure 110 is connected to the volute back plate 120 to form an air duct;

[0079] The outer edge of the volute 100 forms an arc segment protrusion 180; the cross-section of the arc segment protrusion 180 includes a first arc segment 181, a second arc segment 182 and a third arc segment 183; one end of the first arc segment 181 is connected to the volute back plate 120, and the other end is connected to one end of the second arc segment 182; the third arc segment 183 is connected to the volute front plate 130, and the other end is connected to the other end of the second arc segment 182.

[0080] It is understandable that the present application takes into account the three-dimensional flow of the airflow in the flow channel inside the volute 100, and compared with the binary flow of the traditional volute, more consideration is given to the pressure expansion in the axial direction; among them, different designs are adopted for the three-segment profiles of the first arc segment 181, the second arc segment 182 and the third arc segment 183 of the arc segment protrusion 180, which ultimately makes the equidistant volute 100 expand in the axial direction. On the one hand, the arc segment protrusion 180 designed in this way can well eliminate the corner vortex, which is more conducive to the flow of airflow in the flow channel inside the volute 100; on the other hand, the arc segment protrusion 180 designed in this way is more in line with the real flow inside the volute 100, improving the air intake efficiency; on the third hand, the arc segment protrusion 180 designed in this way can eliminate the assembly gap between the volute 100 and the chassis 200 of the traditional range hood, reduce the noise of the range hood, and improve the user experience.

[0081] In this embodiment, please refer to Figure 1 and Figure 2 The centrifugal fan 010 includes a chassis 200 .

[0082] In this embodiment, the centrifugal fan 010 also includes a chassis 200, the volute 100 is disposed in the chassis 200, the volute front plate 130 is connected to the chassis 200, and the volute enclosure 110, the volute back plate 120 and the chassis 200 are an integrally formed structure.

[0083] It can be understood that by integrally forming the volute enclosure 110, the volute back plate 120 and the chassis 200, the volute 100 and the chassis 200 do not need to be assembled and fixed by connecting flanges and connecting parts, thereby eliminating the assembly gap generated when the volute 100 and the chassis 200 are assembled and fixed by connecting flanges and connecting parts, thereby reducing the noise of the range hood and improving the user experience.

[0084] In this embodiment, please refer to Figure 1 The chassis 200 includes a chassis top plate 210, a chassis front plate 220, a chassis panel 230 and a connecting plate 240. The top of the chassis panel 230 is connected to the chassis top plate 210, and the bottom of the chassis panel 230 is connected to the connecting plate 240. The chassis panel 230 is a U-shaped plate, and one side of the chassis panel 230 is an open side. The chassis front plate 220 is located on the open side and is detachably connected to the chassis panel 230.

[0085] The U-shaped chassis panel 230 includes a left chassis panel 231 , a right chassis panel 232 and a back chassis panel 233 , and the left chassis panel 231 , the right chassis panel 232 and the back chassis panel 233 are connected to form a U-shaped opening side of the chassis panel 230 .

[0086] Among them, a first connecting hole located on the left side plate 231 of the chassis and a second connecting hole located on the right side plate 232 of the chassis are provided on the opening side of the chassis enclosure 230, and a third connecting hole is provided on the chassis top plate 210 relative to the chassis front plate 220, and the chassis front plate 220 is detachably connected to the first connecting hole, the second connecting hole and the third connecting hole of the chassis 200 through a connecting piece.

[0087] The connecting plate 240 is provided with a first air port 241 communicating with the air duct, and the chassis top plate 210 is provided with a second air port communicating with the air duct. It is understandable that the motor drives the impeller 170 to rotate, so that the oil smoke enters from the first air port 241 of the connecting plate 240, and is driven by the impeller 170 in the air duct to be discharged from the second air port.

[0088] In this embodiment, please refer to Figure 1 and Figure 2 The centrifugal fan 010 includes a volute 100 .

[0089] In this embodiment, please refer to Figure 1 The volute 100 is arranged in the chassis 200, and the volute 100 includes a volute enclosure 110, a volute back plate 120 and a volute front plate 130. The front side of the volute enclosure 110 is connected to the volute front plate 130, and the back side of the volute enclosure 110 is connected to the volute back plate 120 to form an air duct.

[0090] The volute front plate 130 is located at the front side of the volute enclosure 110 , and the volute back plate 120 and the chassis back plate 233 are on the same side.

[0091] The volute front plate 130 is detachably connected to the volute enclosure 110 .

[0092] In this embodiment, please refer to Figure 1 and Figure 2 The volute 100 has an air outlet 150 and an air inlet 140, the air inlet 140 is arranged on the volute front plate 130, the volute enclosure 110, the volute back plate 120 and the volute front plate 130 are connected to form an air outlet 150, and the air outlet 150 is located at the end of the air duct; wherein, the volute enclosure 110, the volute back plate 120 and the volute front plate 130 are connected to the second air outlet edge of the top plate of the volute 100 so that the second air outlet cooperates with the air outlet 150.

[0093] It is worth mentioning that please refer to Figure 1 , the volute enclosure 110, the volute back plate 120, the chassis top plate 210, the chassis enclosure 230 and the connecting plate 240 are an integrally formed structure, and the chassis front plate 220 and the volute front plate 130 are detachably connected to the chassis enclosure 230. Among them, the volute enclosure 110, the volute back plate 120, the chassis top plate 210, the chassis enclosure 230 and the connecting plate 240 are die-cast as an integrally formed structure through an integrated die-casting process, which can eliminate the assembly gap generated when the volute 100 and the chassis 200 are assembled and fixed through connecting flanges and connectors, reduce the noise of the range hood, and improve the user experience; however, when the impeller 170 and the motor are installed in the volute 100, the chassis front plate 220 and the volute front plate 130 need to be disassembled, so the chassis front plate 220 and the volute front plate 130 are set to be detachably connected. This arrangement does not affect the overall assembly of the range hood and the centrifugal fan 010, and can also reduce the noise of the range hood and improve the user experience by eliminating the assembly gap.

[0094] In this embodiment, please refer to Figure 1 and Figure 2 The centrifugal fan 010 further includes a driving member 160 and an impeller 170 . The driving member 160 and the impeller 170 are arranged in the air duct of the volute 100 , and the output end of the driving member 160 is transmission-connected to the impeller 170 .

[0095] In this embodiment, please refer to Figure 3 The inner surface contour line of the volute enclosure 110 includes a first contour line 111, a second contour line 112 and a volute contour line 113 which are connected in sequence. The second contour line 112 is located at the starting position of the volute contour line 113. The first contour line 111 and the volute contour line 113 are arranged at an angle so that the second contour line 112 forms a volute tongue 114. The first contour line 111 and the volute contour line 113 are part of the air outlet 150 of the volute 100.

[0096] It is understandable that the volute 100 formed by integral injection molding can ensure the integrity of the inner surface contour line of the volute enclosure 110, thereby making the first contour line 111, the second contour line 112 and the volute contour line 113 and the volute tongue 114 adapt to form a complete centrifugal fan 010 contour line.

[0097] The volute profile 113 is in the form of a logarithmic spiral.

[0098] The volute profile 113 is designed according to the equal annular volume principle, and the flow of gas in the volute 100 follows the law of constant angular momentum.

[0099] In this embodiment, please refer to Figure 3 and Figure 4 The lateral inner walls of the chassis enclosure 230 are connected to the lateral outer walls of the volute enclosure 110 so that the lateral sides of the volute enclosure 110 are tangent to the lateral sides of the chassis enclosure 230 respectively.

[0100] In this embodiment, please refer to Figure 4 The end of the first profile 111, the volute back plate 120, the end of the volute profile 113 and the volute front plate 130 are sequentially connected to form an air outlet 150, and the air outlet 150 is a rectangular structure.

[0101] In this embodiment, please refer to Figure 5 and Figure 6 The outer edge of the volute 100 forms an arc segment protrusion 180; the cross-section of the arc segment protrusion 180 includes a first arc segment 181, a second arc segment 182 and a third arc segment 183; one end of the first arc segment 181 is connected to the volute back plate 120, and the other end is connected to one end of the second arc segment 182; the third arc segment 183 is connected to the volute front plate 130, and the other end is connected to the other end of the second arc segment 182.

[0102] It can be understood that through the unique advantages of one-piece injection molding, the right-angle overlapping method of the existing sheet metal volute can be changed to the arc segment protrusion 180 in the present application. The outer edge of the volute 100 is easier to be molded into an arc segment protrusion 180 through one-piece injection molding, which is more conducive to the flow of air in the flow channel inside the volute 100.

[0103] Furthermore, the right-angled edges of existing sheet metal volutes are prone to flow corner vortices. Compared with the right-angled edges of existing sheet metal volutes, the arc segment protrusion 180 in the present application can effectively eliminate the corner vortices, thereby improving the flow efficiency of the fan and improving the flow noise inside the volute 100.

[0104] Please refer to Figure 7 In this embodiment, a design method of a centrifugal fan 010 is also proposed, including a centrifugal fan 010; the design method includes:

[0105] S1: Establish a first coordinate system on the radial cross section of the volute 100, with the extension direction of the volute back plate 120 as the Y-axis direction, the midpoint of the volute back plate 120 as the coordinate origin O, and the horizontal line passing through the coordinate origin O as the X-axis;

[0106] S2: the connection point between the volute back plate 120 and the first arc segment M1O1P1 is M1, the connection point between the first arc segment M1O1P1 and the second arc segment P1O3P2 is P1, the connection point between the second arc segment P1O3P2 and the third arc segment M2O2P2 is P2, the connection point between the third arc segment M2O2P2 and the volute front plate is M2, the center of the first arc segment M1O1P1 is O1, the center of the second arc segment P1O3P2 is O3, and the center of the third arc segment M2O2P2 is O2;

[0107] S3: Calculate the positions of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2 of the volute 100 in the first coordinate system according to the average flow rate of the volute 100 on the current radial cross section.

[0108] It is understandable that the present application uses the above-mentioned design method to design the three-section profiles of the first arc segment 181, the second arc segment 182 and the third arc segment 183 of the arc segment protrusion 180 differently, and expands the volute 100 in the axial direction. Compared with the binary flow of the traditional volute, the present application considers the expansion in the axial direction and the ternary flow of the airflow in the flow channel inside the volute 100. On the one hand, the arc segment protrusion 180 designed in this way can eliminate corner vortices very well, and is more conducive to the flow of airflow in the flow channel inside the volute 100; on the other hand, the arc segment protrusion 180 designed in this way is more in line with the actual flow inside the volute 100, and improves the air intake efficiency; on the third hand, the arc segment protrusion 180 designed in this way can eliminate the assembly gap between the traditional range hood volute 100 and the chassis 200, reduce the noise of the range hood, and improve the user experience.

[0109] In this embodiment, please refer to Figure 7 , S3 also includes the following steps:

[0110] S31: Take the coordinates of point 01 as Substituting the coordinates (X1, Y1) of P1 in the first arc segment M1O1P1 into the radius formula, we can obtain the first control equation:

[0111] S32: Take the coordinates of point 02 as Substituting the coordinates of P2 (X2, Y2) in the third arc segment M2O2P2 into the radius formula, we can obtain the second control equation:

[0112] It can be understood that in S31 and S32, A is the opening of the outlet section of the volute 100 at an angle θ of 360°, which can also be understood as the axial width of the volute 100 on the X-axis; B is the width of the volute back plate 120 of the volute 100.

[0113] Among them, since the midpoint position of the volute back plate 120 is the coordinate origin O and the connection point of the volute back plate 120 and the first arc segment M1O1P1 is M1, the coordinates of M1 are The coordinates of M3 are

[0114] The axial width of the volute 100 is divided into four equal parts along the X-axis, and point 01 is located at 1 / 4 of the axial width of the volute 100. Therefore, the coordinates of 01 are Point 02 is located at 3 / 4 of the axial width of the volute 100, so the coordinates of 02 are Point 03 is located at 1 / 2 of the axial width of the volute 100, so the coordinates of 03 are

[0115] It can be understood that in S31, the line segment 01M1 is substituted into the radius formula, then Substitute line segment 01P1 into the radius formula, then Line segment 01P1 and line segment 01M1 are both r1 and have the same length, so we can get This leads to the first control equation.

[0116] It can be understood that in S32, the line segment 02M2 is substituted into the radius formula, then Substitute the line segment 02P2 into the radius formula, then Line segment 02P2 and line segment 02M2 are both r2 and have the same length, so we can get This leads to the second control equation.

[0117] S33: Substitute the P1 coordinate (X1, Y1) and the P2 coordinate (X2, Y2) into the radius formula to obtain the third control equation:

[0118] It can be understood that in S33, the line segment 03P1 is substituted into the radius formula, then Substitute line segment 03P2 into the radius formula, then R3 2 =(X2-A / 2) 2 +Y2 2 ; Line segment 03P1 and line segment 03P2 are both R3 and have the same length, so we can get This leads to the third control equation.

[0119] S34: Confirm the values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) according to the first control equation, the second control equation and the third control equation.

[0120] S35: Calculate the arc lengths of the first arc segment M1O1P1, the second arc segment P1O3P2, and the third arc segment M2O2P2 according to the P1 coordinates (X1, Y1) and the P2 coordinates (X2, Y2);

[0121] Wherein, A is the opening of the outlet cross section of the volute 100 at an angle θ of 360°; B is the width of the volute 100, and the volute 100 is a volute of equal width, and B is a constant value.

[0122] It can be understood that the volute 100 of the centrifugal fan 010 is designed with equal width, and when the structure of the volute 100 is determined, B is a constant value.

[0123] Wherein, S34 further includes the following steps:

[0124] S341: The radius of the first arc segment M1O1P1 is equal to the radius of the third arc segment M2O2P2, and the following fourth control equation is obtained:

[0125]

[0126] It can be understood that the radius of the first arc segment M1O1P1 The radius of the third arc segment M2O2P2 It can be seen that the radius r1 of the first arc segment M1O1P1 is equal to the radius r2 of the third arc segment M2O2P2, and the lengths of the line segments 01P1 and 01P2 are equal; therefore, It can be concluded that the fourth control equation

[0127] S342: Confirm the values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) through the above-mentioned fourth control equation.

[0128] It can be understood that the above control equations can be used to obtain the values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2), so as to determine the positions of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2 in the first coordinate system.

[0129] Wherein, S35 also comprises the following steps:

[0130] S351: With point 01 as the center, point M1 is rotated clockwise by θ1 around the center 01 to obtain point P1, and the arc length of the first arc segment M1O1P1 is obtained according to the center angle θ1 and arc length formula 1;

[0131] Arc length formula 1 is: L1 = θ1 × π × r1 / 180°;

[0132] Wherein, L1 is the arc length of the first arc segment M1O1P1, θ1 is the center angle of the first arc segment M1O1P1, π is the pi, and r1 is the radius of the first arc segment M1O1P1.

[0133] S352: With point 02 as the center of the third arc segment M2O2P2, point M2 is rotated counterclockwise by θ2 around the center of the circle 01 to obtain point P2, and the arc length of the third arc segment M2O2P2 is obtained according to the center angle θ2 and arc length formula 2;

[0134] Arc length formula 2 is: L2 = θ2 × π × r2 / 180°;

[0135] Wherein, L2 is the arc length of the third arc segment M2O2P2, θ2 is the center angle of the third arc segment M2O2P2, π is the pi, and r2 is the radius of the third arc segment M2O2P2.

[0136] S353: With point 03 as the center of the second arc segment P1O3P2, point P1 is rotated clockwise by θ3 around the center of the circle 03 to obtain point P2, and the arc length of the second arc segment P1O3P2 is obtained according to the center angle θ3 and arc length formula 3;

[0137] Arc length formula 3 is: L3 = θ3 × π × R3 / 180°;

[0138] Wherein, L3 is the arc length of the second arc segment P1O3P2, θ3 is the center angle of the second arc segment P1O3P2, π is the pi, and R3 is the radius of the second arc segment P1O3P2.

[0139] It is worth mentioning that the central angle θ1 of the first arc segment M1O1P1 ranges from 30° to 60°; the central angle θ2 of the third arc segment M2O2P2 ranges from 30° to 60°.

[0140] It can be understood that by substituting the center angle θ1 of the first arc segment M1O1P1 and the center angle θ2 of the third arc segment M2O2P2 into the corresponding arc formulas, the arc lengths of the first arc segment M1O1P1 and the third arc segment M2O2P2 can be calculated.

[0141] In this embodiment, an equidistant volute is taken as an example, the width of the equidistant volute is B, and the rectangular volute 100 of equal width is divided into n sections from the volute tongue 114 along the rotation direction of the impeller 170, marked as S n , extract any section therein, and design the cross-sectional profile of the volute after expansion according to the area of ​​the section. The arc radius r1 of the first arc segment M1O1P1 and the arc radius r2 of the third arc segment M2O2P2 can be calculated according to equations 1-3.

[0142] The arc radius r1 of the first arc segment M1O1P1 and the arc radius r2 of the third arc segment M2O2P2 and the average flow rate of the volute 100 on the current radial cross section satisfy the following relational expression 1;

[0143] Relation 1:

[0144] Where r is the arc radius r1 of the first arc segment M1O1P1 and the arc radius r2 of the third arc segment M2O2P2, q s is the average flow rate of the volute 100 on the current radial section, D2 is the outer diameter of the impeller 170, τ2 is the cross-sectional contraction coefficient, and ω is the relative speed of the volute 100 at the same radius R.

[0145] τ2 satisfies the following relation 2:

[0146] Relation 2:

[0147] The volute 100 is divided into n radial sections from the volute tongue 114 along the rotation direction of the impeller 170 and marked as S1 to S2. n , S1 is the area of ​​the first radial section, S n is the area of ​​the nth radial section, S n-1 It is the area of ​​the radial cross section of the volute 100 before the current radial cross section along the airflow direction.

[0148] ω satisfies the following relationship 3:

[0149] Relation 3:

[0150] Among them, R n is the outer radius of the volute 100 in the current radial section, R n-1 is the area of ​​the radial section of the volute 100 before the current radial section along the airflow direction, β A is the blade inlet installation angle, β B Install the angle for the blade outlet.

[0151] It can be understood that after determining the arc radii of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2, the corresponding coordinate points can be controlled, and then the value of A can be determined by judging whether the current air volume reaches the set air volume and the target air volume.

[0152] In this embodiment, the design method further includes the following steps: S4: designing the inner profile contour line of the volute shroud 110 .

[0153] Please refer to Figure 4 , S4 further includes the following steps:

[0154] S41: The inner surface contour line of the volute enclosure 110 is designed to be a first contour line 111, a second contour line 112 and a volute contour line 113 which are connected in sequence, the second contour line 112 is located at the starting position of the volute contour line 113, the second contour line 112 is arranged at an angle with the volute contour line 113 so that the volute enclosure 110 forms a volute tongue 114, and the first contour line 111 and the volute contour line 113 are part of the air outlet 150 of the volute 100.

[0155] S42: A second coordinate system is established on the inner surface contour line of the volute shroud 110, with the center of the impeller 170 as the coordinate origin O, the horizontal line passing through the coordinate origin O as the X-axis, and the vertical line passing through the origin O as the Y-axis.

[0156] Among them, in S42, the X-axis located on the left side of the origin O is the +X-axis, and the X-axis located on the right side of the origin O is the -X-axis.

[0157] S43: Design the inner profile contour line of the volute shroud 110 according to the value of A.

[0158] Wherein, S43 further includes the following steps:

[0159] S431: Design A according to the following relationship 4 θ ;

[0160] Relation 4: A θ =R-R0;

[0161] Among them, A θ is the opening of the volute 100 at the angle θ, R is the outer radius of the volute 100 , R0 is the outlet radius of the impeller 170 , and θ is the angle between any radial section and the radial section where the volute profile 113 ends.

[0162] S432: Design the inner walls on both sides of the chassis enclosure 230 to be connected to the outer walls on both sides of the volute enclosure 110, so that the two sides of the volute enclosure 110 are tangent to the two sides of the chassis enclosure 230, respectively, and the lateral length of the chassis 200 satisfies the following relationship: L=L1+L2;

[0163] Among them, L is the lateral length of the chassis 200, L1 is the distance between the leftmost side wall of the volute shroud 110 and the center of the impeller 170, and L2 is the distance between the rightmost side wall of the volute shroud 110 and the center of the impeller 170.

[0164] It can be understood that, taking the -X axis of the second coordinate system as the starting position, when θ=180°, the opening A of the volute 100 at the angle θ of 180° is θ =R-R0=L1-R0; when θ=360°, the volute opening A at the angle θ of 360° is 100 θ =R-R0=L2-R0.

[0165] The volute 100 is designed with equal width, that is, B is a constant value. With the axis of the impeller 170 as the center of the circle, the volute 100 is divided into n sections starting from the volute tongue 114 in the direction of rotation of the impeller 170 and marked as Si. At the same time, the volute profile 113 is designed according to the equal annular principle, and the flow of gas in the volute 100 follows the law of constant angular momentum.

[0166] Accordingly, the functional relationship between θ and R of any cross section of the inner wall of the volute 100 is:

[0167]

[0168] Among them, R0 is the outlet radius of the impeller 170, b2 is the outlet width of the impeller 170, c is the outlet circumferential speed of the impeller 170, α2 is the outlet airflow angle of the impeller 170, Q is the volume flow of the volute 100, and θ is the angle between any section and the section at the end of the volute profile 113. And when the structure of the volute 100 is determined, B and b2 are constant values.

[0169] It is understandable that the relationship between the inner surface contour line of the volute shroud 110 and A can be calculated based on the above-mentioned relationship 1-4 and the functional relationship, and the inner surface contour line of the volute shroud 110 can be calculated based on the above-mentioned relationship.

[0170] In summary, the centrifugal fan 010, the range hood, and the design method of the centrifugal fan 010 provided by the embodiment of the present invention, the present application performs different designs on the three-segment profiles of the first arc segment 181, the second arc segment 182, and the third arc segment 183 of the arc segment protrusion 180, and expands the volute 100 in the axial direction. Compared with the binary flow of the traditional volute, the present application considers the expansion in the axial direction and the ternary flow of the airflow in the flow channel inside the volute 100. On the one hand, the arc segment protrusion 180 designed in this way can eliminate the corner vortex very well, which is more conducive to the flow of the airflow in the flow channel inside the volute 100; on the other hand, the arc segment protrusion 180 designed in this way is more in line with the real flow inside the volute 100, and the air intake efficiency is improved; on the third hand, the arc segment protrusion 180 designed in this way can eliminate the assembly gap between the volute 100 and the chassis 200 of the traditional range hood, reduce the noise of the range hood, and improve the user experience.

[0171] Furthermore, the inner profile contour line of the volute enclosure 110 is designed to be a first profile line 111 , a second profile line 112 and a volute profile line 113 , and the volute 100 formed by integral injection molding can ensure the integrity of the inner profile contour line of the volute enclosure 110 .

[0172] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A centrifugal fan, characterized in that: include: A volute (100), the volute (100) comprising a volute enclosure (110), a volute back plate (120) and a volute front plate (130), the front side of the volute enclosure (110) being connected to the volute front plate (130), and the back side of the volute enclosure (110) being connected to the volute back plate (120), so as to enclose an air duct; The outer edge of the volute (100) forms an arc segment protrusion (180); the cross-section of the arc segment protrusion (180) includes a first arc segment (181), a second arc segment (182) and a third arc segment (183); one end of the first arc segment (181) is connected to the volute back plate (120), and the other end is connected to one end of the second arc segment (182); the third arc segment (183) is connected to the volute front plate (130), and the other end is connected to the other end of the second arc segment (182).

2. The centrifugal fan according to claim 1, characterized in that: The centrifugal fan (010) further comprises a chassis (200), the volute (100) being arranged in the chassis (200), the volute front plate (130) being connected to the chassis (200), and the volute enclosure (110), the volute back plate (120) and the chassis (200) being an integrally formed structure.

3. The centrifugal fan according to claim 2, characterized in that: The chassis (200) comprises a chassis top plate (210), a chassis front plate (220), a chassis enclosure (230) and a connection plate (240); the top of the chassis enclosure (230) is connected to the chassis top plate (210); the bottom of the chassis enclosure (230) is connected to the connection plate (240); the chassis enclosure (230) comprises a chassis left side plate (231), a chassis right side plate (232) and a chassis back plate (233) which are connected in sequence; and one side of the chassis enclosure (230) is an open side; The chassis front plate (220) is located at the opening side and is detachably connected to the chassis enclosure plate (230); The volute enclosure (110), the volute back plate (120), the chassis top plate (210), the chassis enclosure (230) and the connecting plate (240) are an integrally formed structure.

4. The centrifugal fan according to claim 3, characterized in that: The volute (100) has an air outlet (150) and an air inlet (140), the air inlet (140) is arranged on the volute front plate (130), the volute enclosure (110), the volute back plate (120) and the volute front plate (130) are connected to form the air outlet (150), and the air outlet (150) is located at the end of the air duct; The connecting plate (240) is provided with a first air outlet (241) in communication with the air duct, the chassis top plate (210) is provided with a second air outlet in communication with the air duct, and the volute enclosure (110), the volute back plate (120) and the volute front plate (130) are connected to the edge of the second air outlet of the volute (100) top plate, so that the second air outlet cooperates with the air outlet (150); The front side of the volute enclosure (110) is detachably connected to the volute front plate (130).

5. The centrifugal fan according to claim 3, characterized in that: The inner walls on both sides of the chassis enclosure (230) are connected to the outer walls on both sides of the volute enclosure (110), so that the two sides of the volute enclosure (110) are tangent to the two sides of the chassis enclosure (230).

6. A range hood, characterized in that: It comprises the centrifugal fan (010) as described in any one of claims 1 to 5.

7. A design method for a centrifugal fan, characterized in that: A centrifugal fan (010) comprising the centrifugal fan (010) according to any one of claims 1 to 5; The design method comprises: A first coordinate system is established on the radial cross section of the volute (100), with the extension direction of the volute back plate (120) being the Y-axis direction, the midpoint of the volute back plate (120) being the coordinate origin O, and the horizontal line passing through the coordinate origin O being the X-axis; The connection point between the volute back plate (120) and the first arc segment M1O1P1 is M1, the connection point between the first arc segment M1O1P1 and the second arc segment P1O3P2 is P1, the connection point between the second arc segment P1O3P2 and the third arc segment M2O2P2 is P2, the connection point between the third arc segment M2O2P2 and the volute front plate (130) is M2, the center of the first arc segment M1O1P1 is O1, the center of the second arc segment P1O3P2 is O3, and the center of the third arc segment M2O2P2 is O2; According to the average flow rate of the volute (100) on the current radial cross section, the positions of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O1P2 of the volute (100) in the first coordinate system are calculated.

8. The design method of the centrifugal fan according to claim 7, characterized in that: Calculating the positions of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2 of the volute (100) in the first coordinate system according to the average flow rate of the volute (100) on the current radial cross section, further comprising the following steps: The coordinates of point 01 are Substituting the coordinates (X1, Y1) of P1 in the first arc segment M1O1P1 into the radius formula, the first control equation is obtained: The coordinates of point 02 are Substituting the coordinates (X2, Y2) of P2 in the third arc segment M2O2P2 into the radius formula, the second control equation is obtained: Substituting the P1 coordinates (X1, Y1) and P2 coordinates (X2, Y2) into the radius formula yields the third control equation: Determine the values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) according to the first control equation, the second control equation, and the third control equation; Calculate the arc lengths of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2 according to the P1 coordinates (X1, Y1) and the P2 coordinates (X2, Y2); Wherein, A is the opening of the outlet cross section of the volute (100) at an angle θ of 360°; B is the width of the volute (100), the volute (100) is a volute of equal width, and B is a constant value.

9. The design method of the centrifugal fan according to claim 8, characterized in that: According to the first control equation, the second control equation and the third control equation, the values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) are confirmed, and the following steps are also included: The radius of the first arc segment M1O1P1 is equal to the radius of the third arc segment M2O2P2, and the following fourth control equation is obtained: The values ​​of X1 and Y1 in the P1 coordinate (X1, Y1) and the values ​​of X2 and Y2 in the P2 coordinate (X2, Y2) are confirmed by the above-mentioned fourth control equation.

10. The design method of a centrifugal fan according to claim 8, characterized in that: Calculating the arc lengths of the first arc segment M1O1P1, the second arc segment P1O3P2 and the third arc segment M2O2P2 according to the P1 coordinate (X1, Y1) and the P2 coordinate (X2, Y2), further comprising the following steps: With point 01 as the center, point M1 is rotated clockwise by θ1 around the center 01 to obtain point P1, and the arc length of the first arc segment M1O1P1 is obtained according to the center angle θ1 and arc length formula 1; Arc length formula 1 is: L1 = θ1 × π × r1 / 180°; Wherein, L1 is the arc length of the first arc segment M1O1P1, θ1 is the center angle of the first arc segment M1O1P1, π is the pi, and r1 is the radius of the first arc segment M1O1P1.

11. The design method of a centrifugal fan according to claim 10, characterized in that: With point 02 as the center of the third arc segment M2O2P2, point M2 is rotated counterclockwise by θ2 around the center of the circle 01 to obtain point P2, and the arc length of the third arc segment M2O2P2 is obtained according to the center angle θ2 and arc length formula 2; Arc length formula 2 is: L2 = θ2 × π × r2 / 180°; Wherein, L2 is the arc length of the third arc segment M2O2P2, θ2 is the center angle of the third arc segment M2O2P2, π is the pi, and r2 is the radius of the third arc segment M2O2P2.

12. The design method of a centrifugal fan according to claim 11, characterized in that: The central angle θ1 of the first arc segment M1O1P1 ranges from 30° to 60°; The central angle θ2 of the third arc segment M2O2P2 ranges from 30° to 60°.

13. The design method of a centrifugal fan according to claim 11, characterized in that: With point 03 as the center of the second arc segment P1O3P2, point P1 is rotated clockwise by θ3 around the center of the circle 03 to obtain point P2, and the arc length of the second arc segment P1O3P2 is obtained according to the center angle θ3 and arc length formula 3; Arc length formula 3 is: L3 = θ3 × π × R3 / 180°; Wherein, L3 is the arc length of the second arc segment P1O3P2, θ3 is the center angle of the second arc segment P1O3P2, π is the pi, and R3 is the radius of the second arc segment P1O3P2.

14. The design method of a centrifugal fan according to claim 8, characterized in that: The following steps are also included: Design the inner surface contour line of the volute shroud.

15. The design method of a centrifugal fan according to claim 14, characterized in that: Designing the inner profile contour line of the volute shroud (110) comprises the following steps: The inner profile contour line of the volute shroud (110) is designed to be a first profile line (111), a second profile line (112) and a volute profile line (113) connected in sequence, the second profile line (112) is located at the starting position of the volute profile line (113), the second profile line (112) and the volute profile line (113) are arranged at an angle so that the volute shroud (110) forms a volute tongue (114), and the first profile line (111) and the volute profile line (113) are part of an air outlet (150) of the volute (100); A second coordinate system is established on the inner profile contour line of the volute shroud (110), with the center of the impeller (170) as the coordinate origin O, the horizontal line passing through the coordinate origin O as the X-axis, and the vertical line passing through the origin O as the Y-axis; The inner profile contour line of the volute shroud (110) is designed according to the value of A.

16. The design method of a centrifugal fan according to claim 15, characterized in that: Designing the inner profile contour line of the volute shroud (110) according to the value of A comprises the following steps: Design A according to the following relationship 4 θ ; Relation 4: A θ =R-R0; Among them, A θ is the opening of the volute (100) at an angle θ, R is the outer radius of the volute (100), R0 is the outlet radius of the impeller (170), and θ is the angle between any one of the radial sections and the radial section at the end of the volute profile (113); The inner walls on both sides of the chassis enclosure (230) are designed to be connected to the outer walls on both sides of the volute enclosure (110), so that the two sides of the volute enclosure (110) are tangent to the two sides of the chassis enclosure (230), respectively, and the lateral length of the chassis (200) satisfies the following relationship: L=L1+L2; Wherein, L is the transverse length of the casing (200), L1 is the distance between the leftmost side wall of the volute shroud (110) and the center of the impeller (170), and L2 is the distance between the rightmost side wall of the volute shroud (110) and the center of the impeller (170).

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