Centrifugal fan, embedded air conditioner indoor unit and embedded air conditioner

Abstract

The invention relates to the technical field of electric appliances, particularly provides a centrifugal fan, an indoor unit of an embedded air conditioner and the embedded air conditioner, and aims to solve the problems of insufficient air volume and high noise during air suction due to unreasonable structural design of fan blades of the centrifugal fan. Therefore, the centrifugal fan comprises a wheel cover and a fan wheel disc which are oppositely arranged in the vertical direction, a plurality of blades are arranged between the wheel cover and the fan wheel disc and distributed in the circumferential direction of the fan wheel disc at intervals, the extending direction of the blades intersects with the radial direction of the fan wheel disc, and each blade is provided with a front edge and a tail edge. The front edge is used for introducing outside air among the multiple blades, and the front edge is in an arc shape with the tangent slope gradually increasing from the top end of the front edge to the bottom end of the front edge. The slope of the tangent line of the front edge is gradually increased from top to bottom, airflow can be more smoothly attached to the suction surface of the blade to flow, separation vortexes are eliminated, noise generated during air inlet is effectively eliminated, and the flow of sucked and exhausted air is remarkably increased.

Description

Technical Field

[0001] This invention relates to the field of electrical technology, specifically providing a centrifugal fan, an embedded air conditioner indoor unit, and an embedded air conditioner. Background Technology

[0002] In buildings with high ceilings, such as supermarkets, office buildings, and shops, ceiling-mounted air conditioners (embedded units) are widely used and favored by consumers due to their significant advantages, such as large single-unit radiation area, large air volume, fast cooling and heating speed, and convenient installation and use.

[0003] When an embedded air conditioner is working, the indoor airflow is driven by the rotation of the centrifugal fan blades. It first turns 90° and flows out from the blade outlet, then flows through the indoor heat exchanger, and then turns 90° again under the action of the air outlet channel and blows out, thus completing the cooling or heating process of the indoor airflow.

[0004] However, in the actual operation of ceiling-embedded air conditioner indoor units, the structural characteristics of the centrifugal fan become a key factor affecting noise and airflow. Currently available centrifugal fans have significant design flaws in their blade structure. During the air intake phase, when air enters the fan, the blade structure cannot effectively guide the air in smoothly, resulting in limited air intake and insufficient airflow. Simultaneously, an unreasonable blade structure can also cause airflow turbulence, generating large eddies and turbulence, leading to intense friction and collisions between the air and the blades, thus producing significant noise.

[0005] Therefore, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problem that the centrifugal fan in the existing ceiling-embedded air conditioner indoor unit has insufficient air volume and high noise when drawing in air due to unreasonable fan blade structure design.

[0007] In a first aspect, the present invention provides a centrifugal fan, comprising a wheel cover and a fan disc arranged opposite each other in a vertical direction, wherein a plurality of blades are disposed between the wheel cover and the fan disc, the plurality of blades being distributed circumferentially at intervals along the fan disc, the extending direction of the blades being arranged to intersect the radial direction of the fan disc, the blades having a leading edge and a trailing edge, the leading edge being used to introduce outside air between the plurality of blades, and the leading edge having an arc shape with a gradually increasing tangential slope from the top end to the bottom end of the leading edge.

[0008] In the preferred embodiment of the centrifugal fan described above, the leading edge is inclined toward the leeward side of the blade.

[0009] In the preferred embodiment of the centrifugal fan described above, the thickness of the blades gradually decreases from the leading edge to the trailing edge.

[0010] In the preferred embodiment of the centrifugal fan described above, the blades are bent into an arc-shaped structure toward the windward side of the blades.

[0011] In the preferred embodiment of the centrifugal fan described above, one of the two adjacent blades has an outlet feature line on its windward surface from top to bottom. The outlet feature line is formed by connecting the points on the windward surface of the blade closest to the trailing edge of the adjacent blade. The trailing edge of the blade corresponds to the outlet feature line of the adjacent blade, and the two form the air outlet of the centrifugal fan. The width of the air outlet decreases first and then increases from top to bottom.

[0012] In the preferred embodiment of the centrifugal fan described above, in two adjacent blades, the trailing edge of one blade includes a first segment and a second segment distributed vertically. The first segment is inclined from top to bottom toward the windward side of the blade, and the second segment is inclined from top to bottom toward the leeward side of the blade. The outlet feature line of the other blade is curved into an arc shape from top to bottom toward the windward side. The first segment has a first feature point P1. The width of the air outlet is the smallest at the first feature point P1, and the width of the top of the air outlet is smaller than the width of the bottom of the air outlet.

[0013] In the preferred embodiment of the centrifugal fan described above, the first segment also has a second feature point P2, which is located above the first feature point P1. The second feature point P2 and the first feature point P1 divide the first segment into a first sub-segment, a second sub-segment, and a third sub-segment from top to bottom, and the inclination of the first sub-segment, the second sub-segment, and the third sub-segment increases sequentially.

[0014] In the preferred technical solution of the centrifugal fan described above, both the first segment and the second segment are Bézier curves or B-spline curves.

[0015] In a second aspect, the present invention provides an embedded air conditioner indoor unit, including a housing, an indoor heat exchanger installed in the housing, and a centrifugal fan as described in any of the above claims, wherein the indoor heat exchanger is arranged around the centrifugal fan and opposite to the air outlet of the centrifugal fan.

[0016] In a third aspect, the present invention provides an embedded air conditioner, including an outdoor unit and the aforementioned embedded air conditioner indoor unit, wherein the outdoor unit is connected to the embedded air conditioner indoor unit.

[0017] Those skilled in the art will understand that the technical solution of the present invention provides a centrifugal fan, including a wheel cover and a fan disc arranged opposite each other in a vertical direction. Multiple blades are disposed between the wheel cover and the fan disc, with the blades spaced circumferentially along the fan disc. The extension direction of the blades intersects the radial direction of the fan disc. Each blade has a leading edge and a trailing edge. The leading edge is used to introduce outside air between the blades, and from the top to the bottom of the leading edge, the leading edge has an arc shape with a gradually increasing tangential slope. By adopting the above technical solution, the present invention can increase the airflow of the centrifugal fan and reduce noise. Specifically, by gradually increasing the tangential slope of the leading edge along the height direction of the blades, from near the top of the wheel cover to near the bottom of the fan disc, the airflow can more smoothly adhere to the suction surface of the blades, eliminating separation vortices and allowing airflow to effectively pass through the bottom area of ​​the flow channel. The increase in effective flow area and the reduction in flow loss improve the volumetric efficiency of the fan, thereby effectively eliminating noise during air intake and significantly increasing the intake and exhaust airflow.

[0018] Furthermore, the leading edge of the present invention is inclined toward the leeward side of the blade. This arrangement significantly reduces the angle of attack of the airflow impacting the leading edge of the blade, allowing the airflow to flow more smoothly and closely into the flow channel between the blades. This gives the air a more suitable direction and speed when entering the blade area, further optimizing the air intake process and helping to improve the fan's suction capacity and reduce fan noise.

[0019] Furthermore, in this invention, the thickness of the blade gradually decreases from the leading edge to the trailing edge. This design reduces air turbulence and energy loss during entry, thereby improving airflow efficiency, increasing fan airflow, and reducing vibration and noise caused by sudden pressure changes on the blade surface.

[0020] Furthermore, the blades of the present invention are curved into an arc-shaped structure facing the windward side of the blades. This arrangement can more effectively guide air into the channel between the blades, thereby further increasing the air volume entering the fan and allowing the air to flow more closely to the blade surface, reducing airflow separation and eddy current generation, thereby reducing noise caused by airflow turbulence. Attached Figure Description

[0021] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0022] Figure 1 This is a schematic diagram of the centrifugal fan of the present invention;

[0023] Figure 2 This is a front view of the centrifugal fan of the present invention;

[0024] Figure 3This is a schematic diagram showing the positional relationship between the trailing edge and the exit feature line of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of the embedded air conditioner indoor unit of the present invention.

[0026] List of reference numerals in the attached diagram:

[0027] 1. Wheel cover;

[0028] 2. Fan disc;

[0029] 3. Blade; 31. Leading edge; 32. Trailing edge; 321. First segment; 322. Second segment; 33. Exit feature line;

[0030] 4. Air outlet;

[0031] 5. Shell;

[0032] 6. Indoor heat exchanger. Detailed Implementation

[0033] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the invention and are not intended to limit the scope of protection of the invention. For example, although the following embodiments are described in conjunction with an embedded air conditioner, the centrifugal fan provided by the present invention is equally applicable to other products that need to solve the problem of insufficient airflow and high noise during air intake due to unreasonable fan blade structure design.

[0034] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly, for example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] As noted in the background section, existing ceiling-mounted air conditioner indoor units suffer from centrifugal fans that exhibit insufficient airflow and high noise levels due to unreasonable fan blade design. This invention provides a centrifugal fan designed to effectively solve these problems by improving the fan blades.

[0036] like Figure 1As shown, the present invention provides a centrifugal fan, including a wheel cover 1 and a fan disc 2 arranged opposite each other in a vertical direction. A plurality of blades 3 are arranged between the wheel cover 1 and the fan disc 2. The plurality of blades 3 are distributed at intervals along the circumference of the fan disc 2. The extending direction of the blades 3 is intersected with the radial direction of the fan disc 2. The blades 3 have a leading edge 31 and a trailing edge 32. The leading edge 31 is used to introduce outside air between the plurality of blades 3. From the top end of the leading edge 31 to the bottom end of the leading edge 31, the leading edge 31 is an arc shape with a gradually increasing tangential slope.

[0037] The wheel cover 1 and the fan disc 2 are the core structures of the centrifugal fan. The fan disc 2 is the rotating base for mounting the blades 3, while the wheel cover 1 covers the top of the blades 3 and is set parallel to the fan disc 2 to form an annular airflow channel.

[0038] In this invention, the blades 3 extend in a direction that intersects radially with the fan disc 2, thereby altering the direction and state of airflow after it enters the fan. This design allows for more effective guidance of airflow as it enters the area of ​​the blades 3, reducing airflow turbulence and energy loss, thus enabling more air to be smoothly drawn in and pass through the fan, increasing airflow volume.

[0039] From the top to the bottom of the leading edge 31, the leading edge 31 is an arc with a gradually increasing tangential slope. In this invention, it means that along the height direction of the blade 3, from the top near the wheel cover 1 to the bottom near the fan disc 2, the tangential slope of the leading edge 31 gradually increases. That is, near the wheel cover 1 (top), the leading edge 31 is relatively gentle, and near the fan disc 2 (bottom), the leading edge 31 is relatively steep. From the top to the bottom, the curvature of the leading edge 31 gradually becomes steeper in a continuous and smooth manner.

[0040] Ideally, the airflow should enter the flow channel at an angle (zero angle of attack or small angle of attack) that aligns with the tangential direction of the leading edge 31 of the blade. At the root (the end where the leading edge 31 connects to the fan disk 2), the lower linear velocity causes the relative velocity direction of the airflow to differ from that at the high-speed rotating blade tip (the end where the leading edge 31 connects to the wheel cover 1). If the shape of the leading edge 31 is fixed (such as a straight line or a constant curvature arc), it is difficult to achieve a good angle of attack at both the blade root and the blade tip simultaneously.

[0041] This invention, by designing a steeper leading edge 31 near the bottom of the fan disc 2, better matches the relative velocity direction when the airflow relative velocity is low at that location, significantly reducing the angle of attack when the airflow enters the blade 3 flow channel, bringing it closer to the ideal small or zero angle of attack state. As a result, the airflow can adhere more smoothly to the suction surface of the blade 3, eliminating separation vortices and allowing airflow to effectively pass through the bottom area of ​​the flow channel. Therefore, the increased effective flow area and reduced flow losses improve the volumetric efficiency of the fan, effectively eliminating intake noise and significantly increasing the intake and exhaust airflow.

[0042] Furthermore, near the top of the wheel cover 1, the leading edge 31 is designed to be relatively gentle (with a small tangential slope). This is more suitable for the relative velocity direction when the relative airflow velocity is relatively high at that location. As a result, the airflow impact and possible minor separation in the blade tip area are reduced. The gentle leading edge 31 at the top helps the airflow enter smoothly, avoids the noise caused by the sudden impact of air on the blade 3, and makes the airflow intake more reasonable and uniform along the entire height direction of the blade 3 (from the wheel cover 1 to the fan disc 2).

[0043] Preferably, the leading edge 31 is tilted toward the leeward side of the blade 3.

[0044] In the centrifugal fan blade 3, when the impeller rotates, the airflow flows through the space between the blades 3. The windward side (pressure side) is the side of the blade 3 that faces the direction of the incoming flow and is directly impacted by the airflow. The airflow speed is relatively low and the pressure is high on this side. The leeward side (suction side) is the side of the blade 3 that faces away from the direction of the incoming flow. The airflow is accelerated on this side, resulting in higher speed and lower pressure.

[0045] When airflow rushes toward the leading edge 31 of a stationary or rotating blade 3 at a certain angle, if the airflow direction does not match the tangential direction of the leading edge 31, a strong airflow impact will be generated. This impact not only consumes energy, but is also the main source of high-frequency noise (hissing, whistling).

[0046] By tilting the leading edge 31 toward the leeward side, this invention can significantly reduce the angle of attack of the airflow impacting the leading edge 31 of the blade 3, allowing the airflow to flow more smoothly and closely into the flow channel between the blades 3, so that the air has a more suitable direction and speed when entering the area of ​​the blade 3, further optimizing the air introduction process and helping to improve the fan's suction capacity.

[0047] Furthermore, the tilt of the leading edge 31 towards the leeward side allows for a smoother transition when air enters the blade 3 area from the outside. The air is not suddenly obstructed by the leading edge 31 of blade 3, preventing strong impacts and pressure changes. This smooth transition reduces noise caused by sudden pressure changes, making the fan quieter during operation.

[0048] Preferably, such as Figure 4As shown, the thickness of the blade 3 gradually decreases from the leading edge 31 to the trailing edge 32.

[0049] For example, in the centrifugal fan provided by the present invention, the blade 3 is thickest at the leading edge 31, and then its thickness gradually and smoothly decreases along the direction of airflow (from the leading edge 31 to the trailing edge 32), reaching its thinnest at the trailing edge 32.

[0050] The thicker leading edge 31 of blade 3 provides stronger structural support and guidance when air first enters the blade 3 region. The thicker leading edge 31 better withstands the impact of airflow, smoothly guiding it into the channel between blades 3 and reducing turbulence and energy loss during entry. As air flows along blade 3, the thickness gradually decreases, a design that conforms to the characteristics of airflow. As air gradually accelerates during flow, the thinner trailing edge 32 reduces resistance during exit, allowing air to leave blade 3 more smoothly, thereby improving airflow efficiency and increasing fan airflow.

[0051] Furthermore, the gradually decreasing thickness design of the blades 3 in this invention can optimize the pressure distribution on the surface of the blades 3, making the deceleration process of the airflow on the suction surface smoother. This smooth transition reduces the vibration and noise caused by sudden pressure changes on the surface of the blades 3, making the fan quieter during operation and also improving the fan's air output efficiency.

[0052] Preferably, such as Figure 4 As shown, blade 3 is bent into an arc-shaped structure towards the windward side of blade 3.

[0053] Blade 3 is curved into an arc-shaped structure towards the windward side, which can better conform to the natural flow trend of air when it flows in. When the fan rotates, the air rushes towards blade 3 at a certain angle and speed. The arc-shaped structure can more effectively guide the air into the channel between blades 3, reduce the reflection and scattering of air at the leading edge 31 of blade 3, and allow more air to enter the fan smoothly, thereby increasing the air volume entering the fan.

[0054] Compared to the planar blade 3, the curved blade 3 has a larger surface area. The larger surface area means that the contact area between the air and the blade 3 is increased. During the rotation of the blade 3, more force can be applied to the air, promoting airflow and thus improving the fan's suction capacity and increasing air volume output.

[0055] Furthermore, the curved surface structure allows air to gradually change its flow direction along the curvature of blade 3 as it flows past it, achieving a smoother deflection. This smooth deflection reduces energy loss during airflow, enabling air to be accelerated and exhausted more efficiently, thus improving the overall airflow performance of the fan.

[0056] Because planar blades 3 are prone to airflow separation and eddies during airflow, resulting in turbulent airflow and significant noise. In this invention, blades 3 are curved into an arc-shaped structure towards the windward side, which allows air to adhere more closely to the surface of blades 3, reducing airflow separation and eddy generation, thereby reducing noise caused by turbulent airflow.

[0057] Preferably, such as Figure 2 and Figure 3 As shown, in two adjacent blades 3, one blade 3 has an outlet feature line 33 on its windward surface from top to bottom. The outlet feature line 33 is formed by connecting the points on the windward surface of the blade 3 that are closest to the trailing edge 32 of the adjacent blade 3. The trailing edge 32 of the blade 3 corresponds to the outlet feature line 33 of the adjacent blade 3, and the two form the air outlet 4 of the centrifugal fan. The width of the air outlet 4 decreases and then increases from top to bottom.

[0058] For example, for each blade 3, a "virtual line" is found on its pressure surface (windward side). Each point on this line is the closest point to the trailing edge 32 of the adjacent blade 3. Connecting these "closest points" yields the outlet feature line 33. Compared to the prior art, the outlet 4 is no longer a simple "trailing edge 32-trailing edge 32" channel, but a three-dimensional slit formed by the trailing edge 32 and the outlet feature line 33.

[0059] During operation, the centrifugal fan of this invention draws gas in from the top of the impeller cover 1, and after the blades 3 perform work, it flows out radially. Because the width of the outlet 4 is non-uniformly distributed along the vertical direction (the height direction of the blades 3) in a "contraction-expansion" pattern (similar to an hourglass shape), the contraction section increases the airflow velocity, reduces the boundary layer displacement thickness, and lowers blockage; the expansion section avoids flow separation caused by excessive expansion. Therefore, at the same rotational speed and power consumption, the effective flow area is increased, and the airflow is improved.

[0060] In addition, in traditional fans, the air outlet area of ​​each layer at the same blade height 3 is the same, but due to the influence of boundary layer and radial pressure gradient, the flow rate at the top and bottom is different, resulting in discrete noise. This design makes the width of the air outlet 4 "decrease first and then increase" from top to bottom, so that the outlet area at each axial position matches the actual flow rate, thereby "flattening" the flow peak and balancing the flow rate in each area, thus significantly reducing discrete frequency noise.

[0061] Preferably, such as Figure 3As shown, in two adjacent blades 3, the trailing edge 32 of one blade 3 includes a first segment 321 and a second segment 322 distributed vertically. The first segment 321 is inclined from top to bottom toward the windward side of the blade 3, and the second segment 322 is inclined from top to bottom toward the leeward side of the blade 3. The outlet feature line 33 of the other blade 3 is curved into an arc from top to bottom toward the windward side. The first segment 321 has a first feature point P1. The width of the air outlet 4 is the smallest at the first feature point P1, and the width of the top of the air outlet 4 is smaller than the width of the bottom of the air outlet 4.

[0062] Understandably, in two adjacent blades 3, the first segment 321 of one blade 3 tilts downwards towards the windward side (pressure side of blade 3), while the second segment 322 tilts downwards towards the leeward side (suction side of blade 3). Overall, the trailing edge 32 is S-shaped or inverted S-shaped, resulting in different angles and distances between the trailing edge 32 and the exit feature line 33 at different axial heights. The exit feature line 33 on the other blade 3 is an arc curving downwards towards the windward side, which dynamically matches the segmented structure of the trailing edge 32 of the adjacent blade 3. This arc design coordinates the tilt angle of the exit feature line 33 with that of the first segment 321, guiding the airflow along a specific path.

[0063] The first section 321 is tilted towards the windward side, allowing the airflow to transition along a smoother path when leaving the blade 3, reducing airflow separation at the trailing edge 32; the second section 322 is tilted towards the leeward side, forming an expansion channel, allowing the airflow to fully diffuse after leaving the blade 3, suppressing the formation of wake vortices, thereby significantly reducing the intensity of vortices at the trailing edge 32 and significantly reducing energy loss.

[0064] The arc-shaped structure of the outlet feature line 33 matches the inclination angle of the first segment 321 of the trailing edge 32, forming a "contraction-expansion" flow channel structure. The airflow accelerates when passing through the narrowest point (P1), and then decelerates and increases pressure in the expansion section, conforming to the Venturi effect principle. This makes the pressure distribution at the outlet 4 more uniform, avoiding backflow caused by local high-pressure areas or airflow adsorption caused by low-pressure areas.

[0065] Furthermore, the width of the air outlet 4 is smallest at P1, forming a "throat" structure that accelerates airflow and enhances centrifugal projection capability; the narrower top width maintains high-speed airflow, while the wider bottom width allows more gas to be discharged, resulting in an overall increase in air volume. Compared to a traditional air outlet 4 with a uniform width, this design can significantly increase air volume.

[0066] Preferably, such as Figure 3As shown, the first segment 321 also has a second feature point P2, which is located above the first feature point P1. The second feature point P2 and the first feature point P1 divide the first segment 321 into a first sub-segment, a second sub-segment, and a third sub-segment from top to bottom, and the inclination of the first sub-segment, the second sub-segment, and the third sub-segment increases sequentially.

[0067] This invention divides the first segment 321 into three sub-segments with progressively increasing inclination, allowing the airflow to undergo a gradual process as it passes through each segment. This design conforms to the principle of "laminar acceleration" in fluid dynamics, preventing separation or vortices caused by sudden contraction or expansion of the airflow. It also makes the contraction and expansion gradient of the air outlet 4 from top to bottom smoother, avoiding uneven flow caused by excessively rapid contraction and expansion in local areas, thereby improving acceleration efficiency.

[0068] Preferably, both the first segment 321 and the second segment 322 are Bézier curves or B-spline curves.

[0069] By using both the first segment 321 and the second segment 322 as Bézier curves or B-spline curves, high-order continuity within the curves and between segments is ensured, providing an extremely smooth flow guiding surface, significantly improving flow stability, suppressing turbulence and separation, and effectively reducing high-frequency noise induced by geometric factors.

[0070] It should be noted that in other embodiments, the first segment 321 and the second segment 322 can also be straight segments. The present invention does not limit the specific shape of the first segment 321 and the second segment 322, as long as it can meet the requirements of reducing the noise of the centrifugal fan during operation and improving the uniformity of the air volume and air flow.

[0071] In addition, such as Figure 4 As shown, the present invention provides an embedded air conditioner indoor unit, including a housing 5, an indoor heat exchanger 6 installed in the housing 5, and the centrifugal fan mentioned above. The indoor heat exchanger 6 is arranged around the centrifugal fan and is arranged opposite to the air outlet 4 of the centrifugal fan.

[0072] The indoor heat exchanger 6 is arranged around the centrifugal fan, allowing the air blown from the centrifugal fan outlet 4 to come into contact with the heat exchanger from all directions. This design greatly increases the contact area and contact time between the air and the heat exchanger. In cooling mode, the air can more fully absorb the cooling capacity of the refrigerant in the heat exchanger; in heating mode, the air can more effectively acquire the heat released by the refrigerant, thereby improving the efficiency of heat exchange and enabling the air conditioner to reach the set temperature more quickly, thus enhancing its cooling or heating performance.

[0073] From the top to the bottom of the leading edge 31, the leading edge 31 is an arc with a gradually increasing tangential slope, which makes it easier for air to enter the fan, thereby increasing the air intake and reducing noise generation. This can improve the air volume entering the heat exchanger and the uniformity of airflow, reduce the overall wind noise, and improve the heat exchange efficiency of the heat exchanger.

[0074] Furthermore, the present invention provides an embedded air conditioner, including an outdoor unit and the aforementioned embedded air conditioner indoor unit, wherein the outdoor unit is connected to the embedded air conditioner indoor unit.

[0075] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A centrifugal fan, characterized in that, It includes a wheel cover (1) and a fan disc (2) arranged opposite each other in the vertical direction. A plurality of blades (3) are arranged between the wheel cover (1) and the fan disc (2). The plurality of blades (3) are distributed circumferentially along the fan disc (2). The extension direction of the blades (3) is intersected with the radial direction of the fan disc (2). The blades (3) have a leading edge (31) and a trailing edge (32). The leading edge (31) is used to introduce outside air between the plurality of blades (3). From the top end of the leading edge (31) to the bottom end of the leading edge (31), the leading edge (31) is an arc shape with a gradually increasing tangent slope.

2. The centrifugal fan according to claim 1, characterized in that, The leading edge (31) is inclined toward the leeward side of the blade (3).

3. The centrifugal fan according to claim 1, characterized in that, The thickness of the blade (3) gradually decreases from the leading edge (31) to the trailing edge (32).

4. The centrifugal fan according to claim 1, characterized in that, The blade (3) is bent into an arc-shaped structure towards the windward side of the blade (3).

5. The centrifugal fan according to claim 1, characterized in that, In two adjacent blades (3), one of the blades (3) has an outlet feature line (33) from top to bottom on its windward surface. The outlet feature line (33) is formed by connecting the points on the windward surface of the blade (3) that are closest to the trailing edge (32) of the adjacent blade (3). The trailing edge (32) of the blade (3) corresponds to the outlet feature line (33) of the adjacent blade (3), and the two form the air outlet (4) of the centrifugal fan. The width of the air outlet (4) decreases first and then increases from top to bottom.

6. The centrifugal fan according to claim 5, characterized in that, In two adjacent blades (3), the trailing edge (32) of one blade (3) includes a first segment (321) and a second segment (322) distributed vertically. The first segment (321) is inclined from top to bottom toward the windward side of the blade (3), and the second segment (322) is inclined from top to bottom toward the leeward side of the blade (3). The outlet feature line (33) of the other blade (3) is curved into an arc from top to bottom toward the windward side. The first segment (321) has a first feature point P1. The width of the air outlet (4) is the smallest at the first feature point P1, and the width of the top of the air outlet (4) is smaller than the width of the bottom of the air outlet (4).

7. The centrifugal fan according to claim 6, characterized in that, The first segment (321) also has a second feature point P2, which is located above the first feature point P1. The second feature point P2 and the first feature point P1 divide the first segment (321) into a first sub-segment, a second sub-segment and a third sub-segment from top to bottom, and the inclination of the first sub-segment, the second sub-segment and the third sub-segment increases sequentially.

8. The centrifugal fan according to claim 6, characterized in that, Both the first segment (321) and the second segment (322) are Bézier curves or B-spline curves.

9. An embedded air conditioner indoor unit, characterized in that, The device includes a housing (5), an indoor heat exchanger (6) installed in the housing (5), and a centrifugal fan according to any one of claims 1 to 8, wherein the indoor heat exchanger (6) is arranged around the centrifugal fan and opposite to the air outlet (4) of the centrifugal fan.

10. An embedded air conditioner, characterized in that, It includes an outdoor unit and an embedded air conditioner indoor unit as described in claim 9, wherein the outdoor unit is connected to the embedded air conditioner indoor unit.

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