Air inlet ring, centrifugal fan and range hood

Abstract

The application discloses an air inlet ring, a centrifugal fan and an extractor hood, wherein the air inlet ring comprises an air inlet area, the air inlet area has a contour line, the contour line is an epitrochoid, the epitrochoid is a locus formed by a fixed point on the circumference of a moving circle when the moving circle rolls along a fixed circle without sliding, and the epitrochoid is a cardioid epitrochoid. Compared with the prior art, the application has the advantages that: the air inlet area is formed by the epitrochoid, the epitrochoid can adapt to the air inlet difference of the centrifugal fan at different angles, the backflow leakage in the high back pressure environment is reduced, the air pressure effect is increased, and the efficiency and working condition are more matched in the case that the extractor hood has a large resistance (large back pressure) and a public flue; in addition, the epitrochoid is formed by the rolling of a mathematical circle, the circumferential change is smoother in the other areas except the intersection point, and the change is more adaptive to the gradual change of the air inlet of the volute of the centrifugal fan at different areas.

Description

Technical Field

[0001] This invention relates to power devices, and more particularly to an air inlet ring, a centrifugal fan using the air inlet ring, and a range hood using the centrifugal fan. Background Technology

[0002] Range hoods have become an indispensable kitchen appliance in modern homes. They operate on the principles of fluid dynamics, using a centrifugal fan inside to draw in cooking fumes and a filter to remove some grease particles. The centrifugal fan consists of a volute, an impeller housed within the volute, and a motor that drives the impeller. As the impeller rotates, a negative pressure is generated at the center of the fan, drawing in the cooking fumes from below. After being accelerated by the fan, the volute collects the fumes and guides them outdoors.

[0003] Traditional range hoods currently employ multi-blade centrifugal fans, which are relatively small in size but have high flow rates and pressures. The inlet ring (collector ring) of these multi-blade centrifugal fans follows the same assumption of circumferential uniform airflow as axial flow fans, meaning they are designed with uniform air intake as a given. This is illustrated by a collector disclosed in Chinese patent applications 202121450038.0 and 202010106219.5. However, multi-blade centrifugal fans used in range hoods are radial flow fans with variable-expansion volutes collecting the airflow from the impeller. Unlike axial flow fans, they do not have 360° circumferential uniform air intake. This results in significant leakage and low overall efficiency when using ordinary collectors that aim for uniform airflow.

[0004] See Figure 8 The figure shows a simulated pressure cloud map of the flow field of a centrifugal fan under certain resistance conditions. It is easy to see that the pressure distribution varies greatly at different angles (the initial horizontal line is 0°, clockwise is positive and counterclockwise is negative); in particular, the backflow is severe in the area near the volute tongue, and the circled part in the figure is the main backflow area.

[0005] Therefore, some asymmetrical air inlet rings have been developed. For example, Chinese Patent Application No. 202223130323.1 discloses a D-type collector for a forward-curving multi-blade centrifugal fan, comprising a collector body composed of regular and irregularly shaped collectors, forming a D-shaped structure. This type of collector mainly creates differences by altering the curvature of its cross-sectional profile. For instance, the irregularly shaped collector has a larger curvature in its meridional cross-sectional profile compared to the regular collector (i.e., a smaller radius or a more drastic change in curvature). This provides more space for the vortices formed by the secondary flow between the collector and the impeller cover. This larger space reduces the obstruction of the blade outlet fluid by the vortices formed by the secondary flow, thereby increasing the impeller outlet pressure, reducing impeller power, and improving fan efficiency.

[0006] For example, Chinese Patent Application No. 202122744957.5 discloses a collector with a non-circular guide structure on the inner edge of the inlet. This non-circular guide structure is obtained by sweeping the sidewall profile along the end face profile. The end face profile is formed by connecting at least four closed-loop arc segments, and includes two sets of profile combinations. Each set consists of two symmetrically arranged fixed arcs, with the axes of symmetry of the two sets perpendicular to each other. Its main purpose is to increase airflow. The non-circular guide structure can effectively reduce the restriction on inlet airflow, decrease the low-speed zone area of ​​the volute outlet, optimize the uniformity of the volute outlet airflow velocity distribution, and increase the airflow of the centrifugal fan. However, under different operating conditions, increasing airflow does not necessarily lead to a positive increase in air pressure. Especially in stable environments with low back pressure, increasing airflow often sacrifices air pressure.

[0007] The existing air inlet rings mentioned above cannot adapt to the different air intake angles of the centrifugal fan to increase the air pressure. Under high back pressure conditions, backflow leakage is large and the fan efficiency is low. Summary of the Invention

[0008] The first technical problem to be solved by the present invention is to provide an air inlet ring that can reduce backflow leakage and increase air pressure, in order to address the shortcomings of the prior art.

[0009] The third technical problem to be solved by the present invention is to provide a centrifugal fan that uses the above-mentioned air inlet ring.

[0010] The third technical problem to be solved by the present invention is to provide a range hood that uses the above-mentioned centrifugal fan.

[0011] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: an air inlet ring, including an air inlet area, wherein the air inlet area has an outline, characterized in that:

[0012] The outline is an epicycloid, which is the trajectory formed by a fixed point on the circumference of a moving circle when the moving circle rolls without slipping along a fixed circle, and the epicycloid is a cardioid epicycloid.

[0013] By utilizing the epicycloid to form the air intake area shape, it can adapt to the air intake differences at different angles of the centrifugal fan, thereby reducing backflow leakage in high back pressure environments and increasing the air pressure effect. It is more suitable for high resistance (high back pressure) conditions such as range hoods with shared flues, and its efficiency is better matched with the operating conditions. In addition, the epicycloid itself is formed by the rolling of a mathematical circle, and the circumferential change is smoother in areas other than the intersection point, which is more suitable for the gradual change of air intake in different areas of the centrifugal fan casing.

[0014] The technical solution adopted by the present invention to solve the second technical problem mentioned above is: a centrifugal fan, including a volute and an impeller disposed inside the volute, wherein an air inlet and a volute tongue are formed on the volute, characterized in that: an air inlet ring as described above is provided at the air inlet, and the tip of the epicycloid is close to the volute tongue.

[0015] To facilitate the installation of the air inlet ring and guide airflow, the air inlet ring includes an annular mounting portion and a flow guide structure located on the inner circumference of the mounting portion to guide airflow into the volute. The inner circumferential contour line of the projection of the flow guide structure onto a plane perpendicular to the impeller axis constitutes the contour line of the air inlet area.

[0016] Preferably, the following coordinate system is established based on the vertical placement of the centrifugal fan: with the center of the impeller as the origin, the horizontal line passing through the origin as the X-axis, and the vertical line passing through the origin as the Y-axis. The volute tongue is located in the second quadrant of this coordinate system, and the center of the fixed circle constituting the epicycloid coincides with the origin.

[0017] Preferably, with the negative direction of the X-axis as 0° and the clockwise direction as the positive angle, the radius of the impeller is R2, r1 = k × R2, where k ranges from [0.65, 0.95]. The epicycloid is obtained by the following curve equation: r = r1 * (1 + cos(θ)), where θ ranges from [0°, 360°]. This is to prevent the epicycloid from exceeding the outer diameter of the impeller, thus avoiding leakage.

[0018] Preferably, the angle between the line connecting the apex and the origin and the negative direction of the X-axis constitutes the installation offset angle φ, and the value range of φ is [40°, 90°]. Using an installation offset angle within the above range can better reduce back pressure environment backflow leakage, facilitate overall air intake, reduce air intake obstruction caused by irregular design, and is better for improving wind pressure and efficiency compared to other angles.

[0019] Preferably, in order to facilitate the gradual diversion and guidance of airflow into the impeller, the profile of the flow guiding structure includes a first straight segment, a curved segment, and a second straight segment connected end to end in sequence. The first straight segment corresponds to the part that transitions with the mounting part and this part constitutes the inflow guiding segment. The second straight segment corresponds to the end part that extends into the volute and this part constitutes the outflow guiding segment.

[0020] Preferably, the angle between the first straight segment and the impeller axis is β, and the value of β is within the range of [45°, 90°]. If the angle is too large, it will be difficult for the converged airflow to enter the impeller from the inlet ring; if the angle is too small, the guiding effect on the volute or front-end airflow will be poor, and boundary layer separation will increase.

[0021] Preferably, the ratio of the length of the first straight segment to the impeller radius ranges from [0.01, 0.08]. This is in conjunction with the inlet guide section; if it is too short, the guiding effect is poor, while if it is too long, it encroaches on the intake area and increases frictional resistance.

[0022] Preferably, the angle between the second straight segment and the impeller axis is α, and the value of α is within the range of [0°, 15°]. If α < 0, it is a negative angle, which has a large impact on the impeller area. If α > 15°, it deviates too much from the axis, which is not conducive to the deflection of the incoming airflow into the impeller.

[0023] Preferably, the ratio of the length of the second straight segment to the impeller radius ranges from [0.01, 0.12]. In conjunction with the outflow guide section, if it is too short, the guiding effect is poor; if it is too long, it encroaches on the intake area, increases frictional resistance, and hinders airflow towards the impeller area.

[0024] The technical solution adopted by the present invention to solve the third technical problem mentioned above is: a range hood, characterized in that: it uses a centrifugal fan as described above.

[0025] Compared with the prior art, the advantages of the present invention are as follows: the use of an epicycloid to form the air intake area shape can adapt to the air intake differences at different angles of the centrifugal fan, thereby reducing backflow leakage in high back pressure environments and increasing the wind pressure effect. It is more suitable for high resistance (high back pressure) conditions such as range hoods with shared flues, and the efficiency and operating conditions are better matched. In addition, the epicycloid itself is formed by the rolling of a mathematical circle, and the circumferential change is smoother in areas other than the intersection point, which is more adaptable to the gradual change of air intake in different areas of the centrifugal fan casing. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a centrifugal fan according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the profile of a centrifugal fan according to an embodiment of the present invention (the dashed line represents the impeller profile);

[0028] Figure 3 This is a schematic diagram of the air inlet ring of a centrifugal fan according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the air inlet ring of the centrifugal fan according to an embodiment of the present invention (and...). Figure 3 (Different perspectives);

[0030] Figure 5 This is a cross-sectional view of the air inlet ring of a centrifugal fan according to an embodiment of the present invention;

[0031] Figure 6 For Figure 5 A magnified schematic diagram of part I;

[0032] Figure 7 This is a schematic diagram of the air guide section of the air inlet ring of a centrifugal fan according to an embodiment of the present invention;

[0033] Figure 8 This is a pressure cloud diagram for the flow field simulation of existing centrifugal fans under certain resistance conditions in user operating conditions. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Since the embodiments disclosed in this invention can be arranged in different directions, these terms indicating direction are only for illustration and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity. In addition, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0036] See Figures 1-4A centrifugal fan includes a volute 1, an impeller 2 disposed within the volute 1, and a motor (not shown) for driving the impeller 2 to rotate. The volute 1 includes two spaced-apart cover plates 11 and an annular wall 12 disposed between the cover plates 11. At least one cover plate 11 has an air inlet 13, and an air inlet ring 3 is disposed at the air inlet 13. The cover plates 11 and the annular wall 12 together form an air outlet 14, and a volute tongue 15 is also formed on the annular wall 12. The centrifugal fan of the present invention is preferably a multi-blade centrifugal fan, mainly used in range hoods, but can also be used in applications requiring a similar power unit.

[0037] Because the actual operating conditions of range hoods connected to the flue are generally quite harsh, an uneven design is adopted for the air inlet ring 3 to improve the anti-backflow / leakage effect and increase efficiency. The air inlet ring 3 includes an annular mounting part 31, a radial guide part 32 located on the inner circumference of the mounting part 31, and an axial guide part 33 extending radially inward from the radially inner side of the radial guide part 32 into the volute 1. Preferably, the air inlet ring 3 can be a single piece, with the mounting part 31 installed on the outer circumference of the air inlet 13, the radial guide part 32 extending radially inward, and the axial guide part 33 passing through the air inlet 13 and extending into the volute 1.

[0038] See Figure 2 A coordinate system is established with the centrifugal fan placed vertically as follows: the center of impeller 2 is the origin O, the horizontal line passing through the origin O is the X-axis, and the vertical line passing through the origin O is the Y-axis. The air outlet 14 and the volute tongue 15 of the volute 1 are located in the second quadrant of this coordinate system. The direction of the X-axis is the width direction of the volute 1. The negative direction of the X-axis is 0°, and the clockwise direction is the positive angle. The axial direction of impeller 2 is perpendicular to the XOY plane (i.e., the radial plane of impeller 2).

[0039] The projection of the airflow guiding structure formed by the radial guide section 32 and the axial guide section 33 onto the XOY plane has an outer cycloid of its inner circumference (this outer circumference is the outer circumference of the air inlet area Q, which is the area where airflow enters the volute 1, i.e., the hollow area inside the airflow guiding structure). The outer cycloid refers to the trajectory formed by a fixed point on the circumference of a moving circle when it rolls without slipping along a fixed circle. In this invention, a heart-shaped outer cycloid (heart line) is formed. The radius of the fixed circle is the same as the radius of the moving circle, and the center of the fixed circle is O. This is used to construct the shape of the air inlet area Q of the air inlet ring 3.

[0040] Let the radius of impeller 2 be R2 (half of the outer diameter). The design basis for the epicycloid (radius of the moving circle) is r1 = k × R2, where k ∈ [0.65, 0.95]. The epicycloid can be obtained through the following curve equation: r = r1 * (1 + cos(θ)), where θ varies from [0°, 360°]. The anti-backflow area of ​​the inlet ring 3 has an installation angle of φ relative to the above coordinate system. Considering the differences in air intake at different angles of the centrifugal fan (uneven circumferential distribution), combined with... Figure 8 The flow field characteristics shown are preferably defined by a value of φ within the range of [40°, 90°]. The anti-backflow zone refers to the apex P of the epicycloid, near the volute tongue 15. The angle between the line connecting this apex P and the origin O and the negative direction of the X-axis constitutes the aforementioned installation offset angle. Using an installation offset angle φ within the aforementioned range can better reduce backflow leakage in the back pressure environment, facilitate overall air intake, reduce air intake obstruction caused by irregular designs, and is better for improving wind pressure and efficiency compared to other angles.

[0041] See Figures 5-7 The profiles (contour lines projected axially onto the impeller 2) of the radial guide section 32 and the axial guide section 33 include a first straight segment AB, a curved segment BC, and a second straight segment CD connected end to end. These are smooth line segments. The first straight segment AB corresponds to the radial guide section 32, i.e., the part that transitions to the mounting part 31, and is the inlet guide section. The second straight segment CD corresponds to the end of the axial guide section 33, close to the impeller 2, and is the outlet guide section. The curved segment BC corresponds to the transition part that curves from the radial guide section 32 and gradually extends axially, and is part of the axial guide section 33. The angle between the second straight segment CD and the axial direction of the impeller 2 is α, and the angle between the first straight segment AB and the axial direction of the impeller 2 is β. The value of α ranges from [0°, 15°], and the value of β ranges from [45°, 90°]. The ratio of the length of the second straight segment CD to the radius of the impeller 2 ranges from [0.01, 0.12].

[0042] The first straight section AB primarily guides the airflow within the fan frame or at the front inlet to gradually converge towards the center of the inlet ring 3. An excessively large angle hinders the converged airflow from entering the impeller 2 from the inlet ring 3, while an excessively small angle results in poor guidance of the volute 1 or the front airflow, potentially increasing boundary layer separation. The ratio of the length of the first straight section AB to the radius of the impeller 2 ranges from [0.01, 0.08]. This, combined with the inlet guide section at angle β, results in poor guidance if too short, and encroaches on the inlet area while increasing frictional resistance if too long.

[0043] The second straight section CD primarily guides the airflow as it approaches impeller 2. It directs airflow from different directions towards the axis of impeller 2 through the angle of this wall. If α < 0, it's a negative angle, resulting in a large impact on the impeller 2 area. If α > 15°, it deviates too much from the axial direction, hindering the incoming airflow from entering impeller 2 (because centrifugal fans are radial fans, they must rotate 90° from the axial direction to enter the radial direction). For the outflow guide section with angle α, too short a section results in poor guidance, while too long a section encroaches on the inlet area, increases frictional resistance, and hinders airflow towards the impeller 2 area.

[0044] The curve segment BC is a quadratic curve, which is defined as y = ax². 2 The function curve is defined by +bx+c, where a, b, and c are real numbers. The forms of quadratic curves include parabolas, hyperbolas, ellipses, circles, cycloids, Li He curves, etc.

[0045] This invention mainly adopts an asymmetrical air inlet ring with an external cycloidal design and deflection to adapt to the air intake differences of centrifugal fans at different angles, thereby reducing backflow leakage in high back pressure environments and increasing air pressure. Therefore, it is more suitable for high resistance (high back pressure) conditions such as range hoods with shared flues, and its efficiency is better matched with the operating conditions.

Claims

1. A centrifugal fan, comprising a volute (1) and an impeller (2) disposed within the volute (1), wherein an air inlet (13) and a volute tongue (15) are formed on the volute (1), an air inlet ring is disposed at the air inlet (13), the air inlet ring comprising an air inlet region (Q), the air inlet region (Q) having a contour line (L), characterized in that: The outline (L) is an epicycloid, which is the trajectory formed by a fixed point on the circumference of a moving circle when the moving circle rolls without slipping along a fixed circle. The epicycloid is a heart-shaped epicycloid, and the tip (P) of the epicycloid is close to the volute tongue (15).

2. The centrifugal fan according to claim 1, characterized in that: The air inlet ring includes an annular mounting portion (31) and a flow guide structure located on the inner circumference of the mounting portion (31) to guide the airflow into the interior of the volute (1). The inner circumferential contour line of the projection of the flow guide structure onto a plane perpendicular to the axial direction of the impeller (2) constitutes the contour line (L) of the air inlet area (Q).

3. The centrifugal fan according to claim 2, characterized in that: The following coordinate system is established with the centrifugal fan placed vertically: the center of the impeller (2) is the origin (O), the horizontal line passing through the origin (O) is the X-axis, the vertical line passing through the origin (O) is the Y-axis, the volute tongue (15) is located in the second quadrant of the coordinate system, and the center of the fixed circle forming the epicycloid coincides with the origin (O).

4. The centrifugal fan according to claim 3, characterized in that: With the negative direction of the X-axis as 0° and the clockwise direction as the positive angle, the radius of the impeller (2) is R2, r1=k×R2, and the value range of k is [0.65, 0.95]. The epicycloid is obtained by the following curve equation: r= r1*(1+cos(θ)), and the value range of θ is [0°, 360°].

5. The centrifugal fan according to claim 4, characterized in that: The angle between the line connecting the apex (P) and the origin (O) and the negative direction of the X-axis constitutes the installation deflection angle φ, and the value range of φ is [40°, 90°].

6. The centrifugal fan according to claim 2, characterized in that: The profile of the flow guide structure includes a first straight segment (AB), a curved segment (BC), and a second straight segment (CD) connected end to end in sequence. The first straight segment (AB) corresponds to the part that transitions to the mounting part (31) and this part constitutes the inflow guide section. The second straight segment (CD) corresponds to the end part that extends into the volute (1) and this part constitutes the outflow guide section.

7. The centrifugal fan according to claim 6, characterized in that: The angle between the first straight line segment (AB) and the axial direction of the impeller (2) is β, and the value range of β is [45°, 90°].

8. The centrifugal fan according to claim 7, characterized in that: The ratio of the length of the first straight segment (AB) to the radius of the impeller (2) ranges from [0.01, 0.08].

9. The centrifugal fan according to claim 6, characterized in that: The angle between the second straight line segment (CD) and the axial direction of the impeller (2) is α, and the value of α is in the range of [0°, 15°].

10. The centrifugal fan according to claim 8, characterized in that: The ratio of the length of the second straight segment (CD) to the radius of the impeller (2) ranges from [0.01, 0.12].

11. A range hood, characterized in that: The application uses a centrifugal fan as described in any one of claims 1 to 10.

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