Centrifugal movable impeller and centrifugal axial flow combined fan comprising same

Abstract

The utility model provides a centrifugal type movable impeller and a centrifugal axial flow combined fan including the same, the centrifugal type movable impeller is arranged between an impeller front cover plate and an impeller rear cover plate, the centrifugal type movable impeller comprises a plurality of blades, outlets of the blades are provided with first trailing edge points close to the impeller front cover plate, and the first trailing edge points are provided with second trailing edge points close to the impeller rear cover plate. A second trailing edge point is arranged at the position, close to the impeller rear cover plate, of an outlet of each blade, a third trailing edge point is located at the position, between the first trailing edge point and the second trailing edge point, of the outlet of each blade, the radius of the first trailing edge point is larger than that of the second trailing edge point, and the radius of the third trailing edge point is larger than that of the second trailing edge point. The radius of the second trailing edge point is larger than that of the third trailing edge point, and the first trailing edge point, the third trailing edge point and the second trailing edge point are sequentially connected through an arc-shaped molded line to form an outlet trailing edge, sunken towards the axis of the blade, of the blade.

Description

TECHNICAL FIELD

[0001] The utility model relates to centrifugal impeller technical field, especially centrifugal impeller and centrifugal axial flow combined fan containing it. BACKGROUND

[0002] The centrifugal-axial flow combined fan is widely used in the current range hood industry. The centrifugal-axial flow fan, that is, the fan using the centrifugal impeller to increase pressure and the axial flow static blade grid to recover kinetic energy, has much smaller volume than the conventional forward multi-wing fan, and the airflow direction is axial in and axial out.

[0003] Under normal working conditions, the centrifugal impeller is prone to flow separation near the root of the static blade grid of the centrifugal impeller, especially the root of the first-stage static blade grid. Moreover, the outlet of the impeller is prone to stall near the front cover plate side.

[0004] Since the range hood sometimes works in a scenario with high back pressure, such as a villa or a blocked public flue, higher and higher requirements are put forward for the maximum back pressure of the range hood. The above two shortcomings, that is, the stall tendency of the static blade root and the impeller front cover plate, restrict the performance of the fan under small flow conditions. SUMMARY

[0005] The utility model solves the technical problem of overcoming the defects of the stall tendency of the static blade root and the impeller front cover plate, improving the suction of the fan under small flow conditions, and providing a centrifugal impeller and a centrifugal axial flow combined fan containing the same.

[0006] The utility model solves the above technical problems through the following technical solutions:

[0007] A centrifugal impeller is arranged between an impeller front cover plate and an impeller rear cover plate. The centrifugal impeller includes a plurality of blades. The outlet of each blade has a first tail edge point near the impeller front cover plate, a second tail edge point near the impeller rear cover plate, and a third tail edge point between the first tail edge point and the second tail edge point. The radius of the first tail edge point is greater than the radius of the second tail edge point, and the radius of the second tail edge point is greater than the radius of the third tail edge point. The first tail edge point, the third tail edge point, and the second tail edge point are connected in sequence by an arc-shaped profile to form an outlet tail edge of the blade that is concave toward the axis of the blade.

[0008] In the scheme, the outlet trailing edge of the blade is concave towards the blade axis by setting a third trailing edge point at the blade outlet and connecting the first trailing edge point, the third trailing edge point and the second trailing edge point in sequence by an arc-shaped profile, which not only ensures the maximum pressure rise unchanged, but also meets the requirement of pressure rise improvement when the flow rate is small, such as 0 flow rate in the case of blockage, and avoids the problem of reduced working efficiency of the impeller when the flow passage is narrowed along with the outlet of the impeller. In addition, the radius of the first trailing edge point is greater than the radius of the third trailing edge point, thereby ensuring the outlet trailing edge size of the blade outlet near the front shroud of the impeller, enhancing the work capacity at this position, suppressing separation, and avoiding the suction of the airflow near the rear shroud of the impeller to the airflow near the front shroud of the impeller, thereby reducing the separation vortex at the hub between the centrifugal impeller and the axial static blade. The radius of the second trailing edge point is greater than the radius of the third trailing edge point, thereby ensuring the outlet trailing edge size of the blade outlet near the rear shroud of the impeller, and the quantitative relationship between the radii of the first trailing edge point, the second trailing edge point and the third trailing edge point overcomes the stall tendency at the root of the static blade and the front shroud of the impeller.

[0009] Preferably, the ratio of the difference between the radius of the first trailing edge point and the radius of the third trailing edge point to the difference between the radius of the first trailing edge point and the radius of the second trailing edge point is greater than 1.005.

[0010] In the scheme, the position of the third trailing edge point is obtained by the above setting.

[0011] Preferably, along the meridional direction of the blade, the axis of the blade is the Z axis and the radial direction of the blade is the R axis, wherein the curvature expression of the arc-shaped profile between the first trailing edge point and the third trailing edge point is dR / dZ, and dR / dZ<0.

[0012] In the scheme, by the above setting, the curvature of the arc-shaped profile between the first trailing edge point and the third trailing edge point changes monotonously along the meridional direction, i.e. the curvature of the arc-shaped profile decreases from the first trailing edge point to the third trailing edge point in sequence.

[0013] Preferably, the curvature of the arc-shaped profile near the third trailing edge point is equal to 0.

[0014] In the scheme, by the above setting, the curvature of the arc-shaped profile near the third trailing edge point is increased, thereby increasing the outlet trailing edge size of the blade at this position to reduce flow separation.

[0015] Preferably, the curvature of the arcuate profile between the first trailing edge point and the third trailing edge point is expressed as dR / dZ, and dR / dZ>0.

[0016] In the present solution, by the above arrangement, the arcuate profile between the first trailing edge point and the third trailing edge point is limited in a manner that the first curvature decreases in turn and has a smaller slope, while the second curvature decreases in turn and has a larger slope. Compared with the arcuate profile with the same curvature, the blade size near the first trailing edge point, i.e. near the front shroud of the impeller, is ensured, and the blade size near the third trailing edge point can reduce the separation vortex at the hub between the centrifugal moving blade and the axial static vane, while overcoming the stall tendency of the blade near the outlet of the front shroud of the impeller.

[0017] Preferably, the curvature of the arcuate profile between the third trailing edge point and the second trailing edge point is expressed as dR / dZ, and dR / dZ>0.

[0018] In the present solution, by the above arrangement, the curvature of the arcuate profile between the third trailing edge point and the second trailing edge point changes monotonously in the meridian direction, i.e. the curvature of the arcuate profile increases in turn from the third trailing edge point to the second trailing edge point.

[0019] Preferably, the curvature of the arcuate profile near the second trailing edge point is equal to 0.

[0020] In the present solution, by the above arrangement, the curvature of the arcuate profile near the second trailing edge point is increased, so that the outlet trailing edge size of the blade at this position is increased, thereby ensuring the centrifugal force at the rear shroud of the impeller, reducing the flow separation at this position, while overcoming the stall tendency of the blade near the outlet of the static vane root.

[0021] Preferably, the curvature of the arcuate profile between the third trailing edge point and the second trailing edge point is expressed as dR / dZ, and dR / dZ>0.

[0022] In the scheme, by the above setting, the third curvature and the fourth curvature are expressed in a segmented manner, the third curvature is sequentially increased and has a large slope, and the fourth curvature is sequentially increased and has a small slope, compared with the arc-shaped line with the same curvature, the blade size near the third trailing edge point is ensured, and the blade size near the second trailing edge point can reduce the separation vortex between the centrifugal impeller and the axial static blade at the hub, and the stall tendency of the blade near the outlet of the static blade root is overcome.

[0023] Preferably, the ratio of the radius of the first trailing edge point to the radius of the second trailing edge point is greater than or equal to 1 and less than or equal to 1.08.

[0024] In the scheme, the size of the blade is limited by the above setting.

[0025] A centrifugal-axial combined fan includes the centrifugal impeller as described above, and further includes an axial static blade, and the centrifugal impeller and the axial static blade are coaxially arranged.

[0026] In the scheme, the centrifugal-axial combined fan includes the centrifugal impeller as described above, so that the stall tendency defects of the static blade root and the impeller front cover plate are improved by the blade structure, the suction of the fan under small flow conditions is improved, the cost is low, the working efficiency of the impeller is ensured, and the centrifugal-axial combined fan can meet the user demand.

[0027] The positive progress effect of the centrifugal-axial combined fan is that: the third trailing edge point is arranged at the blade outlet, the first trailing edge point, the third trailing edge point and the second trailing edge point are sequentially connected by the arc-shaped line to form the outlet trailing edge which is concave to the blade axis, compared with the method of reducing the size of the impeller outlet, the maximum pressure rise is ensured, the pressure rise requirement under the condition of small flow, such as 0 flow under the blocking condition, is met, and the problem of reduced working efficiency of the impeller when the flow channel is narrowed along with the impeller outlet is avoided. In addition, the radius of the first trailing edge point is greater than the radius of the third trailing edge point, so that the size of the outlet trailing edge near the impeller front cover plate at the blade outlet is ensured, the doing function of the place is enhanced, the separation is inhibited, and the suction of the airflow near the impeller rear cover plate is avoided, so that the separation vortex between the centrifugal impeller and the axial static blade at the hub is reduced. The radius of the second trailing edge point is greater than the radius of the third trailing edge point, so that the size of the outlet trailing edge near the impeller rear cover plate at the blade outlet is ensured, and the quantity relationship between the radii of the first trailing edge point, the second trailing edge point and the third trailing edge point overcomes the stall tendency of the static blade root and the impeller front cover plate. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1The utility model discloses a centrifugal shaft flow combined fan's structure diagram for a preferred embodiment.

[0029] Figure 2 The utility model discloses a centrifugal impeller's blade meridian plane view for a preferred embodiment.

[0030] Figure 3 The utility model discloses a centrifugal impeller's airflow streamline diagram for a preferred embodiment.

[0031] Mark explanation:

[0032] Impeller front cover plate 10

[0033] Impeller rear cover plate 20

[0034] Blade 30

[0035] Outlet 31

[0036] First tail edge point 1

[0037] Second tail edge point 2

[0038] Third tail edge point 3 Specific implementation

[0039] Below, a preferred embodiment is held, and the utility model is more clearly complete with the description for the embodiment of the utility model.

[0040] This embodiment provides a centrifugal impeller, and the specific structure is as shown in Figure 1 And Figure 2 Centrifugal impeller is arranged between impeller front cover plate 10 and impeller rear cover plate 20, and the centrifugal impeller includes several blades 30, and the first tail edge point 1 is arranged at the outlet 31 of the blade 30 and is close to the impeller front cover plate 10, the second tail edge point 2 is arranged at the outlet 31 of the blade 30 and is close to the impeller rear cover plate 20, and the third tail edge point 3 is arranged between the first tail edge point 1 and the second tail edge point 2 at the outlet 31 of the blade 30, wherein the radius of the first tail edge point 1 is greater than the radius of the second tail edge point 2, the radius of the second tail edge point 2 is greater than the radius of the third tail edge point 3, and the first tail edge point 1, the third tail edge point 3 and the second tail edge point 2 are sequentially connected by arc-shaped lines to form the outlet tail edge of the blade 30, which is recessed towards the axis of the blade 30.

[0041] Specifically, along the meridian direction of the blade 30, the blade 30 has a first trailing edge point 1 and a second trailing edge point 2 at the outlet 31 of the blade 30, the radius of the first trailing edge point 1 is greater than the radius of the second trailing edge point 2, the radius of the second trailing edge point 2 is greater than the radius of a third trailing edge point 3, and the region between the first trailing edge point 1 and the second trailing edge point 2 is the outlet 31 region of the blade 30. The first trailing edge point 1, the third trailing edge point 3 and the second trailing edge point 2 are sequentially connected by an arc-shaped profile to form an outlet trailing edge of the blade 30 which is concave towards the axis of the blade 30. It can be understood that, compared with the way of reducing the size of the impeller outlet, the outlet trailing edge of the blade 30 connected by the arc-shaped profile not only ensures that the maximum pressure rise remains unchanged, but also meets the requirement of pressure rise improvement when the flow rate is small, such as 0 flow rate in the case of blockage, and avoids the problem of reduced efficiency of the impeller when the flow passage is narrowed along with the outlet of the impeller.

[0042] In addition, the radius of the first trailing edge point 1 is greater than the radius of the third trailing edge point 3, thereby ensuring the size of the outlet trailing edge of the blade 30 outlet 31 near the impeller front cover plate 10, enhancing the work capacity at this position, suppressing separation, and at the same time avoiding the suction of the airflow near the impeller rear cover plate 20 near the impeller front cover plate 10, thereby reducing the separation vortex at the hub between the centrifugal impeller and the axial static blade cascade. Similarly, the radius of the second trailing edge point 2 is greater than the radius of the third trailing edge point 3, thereby ensuring the size of the outlet trailing edge of the blade 30 outlet 31 near the impeller rear cover plate 20, and the quantitative relationship between the radii of the first trailing edge point 1, the second trailing edge point 2 and the third trailing edge point 3 overcomes the stall tendency at the static blade root and the impeller front cover plate 10, thereby improving the suction of the fan under small flow conditions, so as to be suitable for special conditions such as villas or completely blocked public chimneys, and to meet the user's needs.

[0043] In addition, as shown in the drawings, Figure 3 the radius of the blade 30 near the impeller front cover plate 10 is large, so the work capacity at the impeller front cover plate 10 is the strongest, and the fluid can be more adsorbed on the side of the impeller front cover plate 10 to suppress separation; at the same time, from the impeller rear cover plate 20 to the third trailing edge point 3, the radius of the blade 30 decreases, so the airflow not only will not be sucked away from the side of the impeller rear cover plate 20, but will migrate from the third trailing edge point 3 to the side of the impeller rear cover plate 20, thereby reducing the separation bubble at the hub corner, so that there is a more obvious tendency to gather towards the side of the impeller front cover plate 10 and the side of the impeller rear cover plate 20 at the outlet 31 of the blade 30, that is, the stall tendency at the static blade root and the impeller front cover plate 10 is overcome, and the suction of the fan under small flow conditions is improved.

[0044] In the present embodiment, the ratio of the difference between the radius of the first trailing edge point 1 and the radius of the third trailing edge point 3 to the difference between the radius of the first trailing edge point 1 and the radius of the second trailing edge point 2 is greater than 1.005. By bringing the radius of the first trailing edge point 1 and the radius of the second trailing edge point 2, the position of the third trailing edge point 3 is obtained, thereby ensuring that the outlet 31 of the blade 30 is concavely arranged towards the axis of the blade 30.

[0045] In another preferred embodiment, the ratio of the difference between the radius of the first trailing edge point 1 and the radius of the third trailing edge point 3 to the difference between the radius of the first trailing edge point 1 and the radius of the second trailing edge point 2 is greater than 1.015. By bringing the radius of the first trailing edge point 1 and the radius of the second trailing edge point 2, compared to the ratio being greater than 1.005, when the ratio is 1.015, the concave depth of the blade 30 is greater, and when the airflow flows through the blade 30, the flow rate is reduced under the same rotational speed and pressure rise. That is, the flow rate-pressure rise characteristic line is moved to the direction of smaller flow rate, while the maximum pressure rise remains unchanged. On this basis, further increasing the rotational speed can make the characteristic line move to the direction of large flow rate and high pressure rise at the same time, and finally meet the requirement of greater pressure rise under a certain small flow rate, for example, the full blockage condition of the public flue flow rate being 0.

[0046] In the present embodiment, along the meridian direction of the blade 30, the axis of the blade 30 is the Z axis, and the radial direction of the blade 30 is the R axis. The curvature expression of the arc-shaped profile between the first trailing edge point 1 and the third trailing edge point 3 is dR / dZ, and dR / dZ<0.

[0047] Specifically, the curvature, also known as the slope, of the arc-shaped profile between the first trailing edge point 1 and the third trailing edge point 3 is explained by the derivative. On the basis of determining the value range of the third trailing edge point 3, the values of the third trailing edge point 3 and the first trailing edge point 1 are substituted into dR / dZ, and dR / dZ<0. It can be understood that the arc-shaped profile between the first trailing edge point 1 and the third trailing edge point 3 changes monotonously, that is, the arc-shaped profile along the lower line of the first trailing edge point 1 and the second trailing edge point 2 decreases from the first trailing edge point 1 to the third trailing edge point 3 in turn, so as to form a concave part of the outlet trailing edge. From the impeller front cover plate 10 to the middle region of the outlet 31 of the blade 30, the radius of the outlet 31 of the blade 30 is monotonously reduced, and the radius of the outlet 31 of the blade 30 is the largest near the impeller front cover plate 10. Therefore, the work capacity at this position is the strongest, and the fluid can be more adsorbed on the side of the impeller front cover plate 10, so as to overcome the situation of airflow stalling on the side of the impeller front cover plate 10.

[0048] Preferably, in the present embodiment, the curvature of the arc-shaped profile near the third trailing edge point 3 is equal to 0.

[0049] Specifically, the arc-shaped profile decreases from the first trailing edge point 1 to the third trailing edge point 3, and the curvature of the arc-shaped profile close to the third trailing edge point 3 is equal to 0. By increasing the curvature of the arc-shaped profile close to the third trailing edge point 3, the radius of the blade 30 at this position is increased, and the outlet trailing edge size at this position is increased correspondingly, which prevents the air flow from being sucked away by the air flow close to the impeller back cover plate 20, and reduces flow separation.

[0050] In this embodiment, the arc-shaped profile between the first trailing edge point 1 and the third trailing edge point 3 includes a first curvature and a second curvature, wherein the curvature of the arc-shaped profile close to the first trailing edge point 1 is the first curvature, the curvature of the arc-shaped profile close to the third trailing edge point 3 is the second curvature, the expression of the first curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≤0, and the expression of the second curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≥0.

[0051] Specifically, the curvature of the arc-shaped profile between the first trailing edge point 1 and the third trailing edge point 3 is divided into a first curvature and a second curvature, the first curvature is the curvature of the arc-shaped profile close to the first trailing edge point 1, and the second curvature is the curvature of the arc-shaped profile close to the third trailing edge point 3, and the curvatures of the two are different, which is described by the second derivative. The first curvature decreases in turn and has a small slope, and the second curvature decreases in turn and has a large slope. The slope of the outlet trailing edge corresponding to the blade 30 shows a trend of first small and then large from the first trailing edge point 1 to the third trailing edge point 3. That is, the first curvature and the second curvature are expressed in a segmented manner, which limits the shape of the arc-shaped profile between the first trailing edge point 1 and the third trailing edge point 3, that is, the specific shape of the arc-shaped profile is obtained. Compared with the arc-shaped profile with the same curvature, the size of the blade 30 close to the first trailing edge point 1, that is, close to the impeller front cover plate 10, is guaranteed, and the size of the blade close to the third trailing edge point 3 can reduce the separation vortex at the hub between the centrifugal moving blade and the axial static blade, and overcome the stall tendency of the blade 30 close to the outlet 31 of the impeller front cover plate 10.

[0052] In this embodiment, the curvature expression of the arc-shaped profile between the third trailing edge point 3 and the second trailing edge point 2 is dR / dZ, and dR / dZ>0.

[0053] Specifically, in the meridian direction, the curvature of the arc-shaped profile between the third trailing edge point 3 and the second trailing edge point 2 is monotonously changed, the values of the third trailing edge point 3 and the second trailing edge point 2 are substituted into dR / dZ on the basis of determining the value range of the third trailing edge point 3, and dR / dZ>0. That is, the arc-shaped profile is sequentially increased from the third trailing edge point 3 to the second trailing edge point 2 to form another part of the concave outlet trailing edge, and the other part of the concave outlet trailing edge is connected with the part of the outlet trailing edge sequentially decreased from the first trailing edge point 1 to the third trailing edge point 3 to form a complete outlet trailing edge. At the same time, from the middle region of the outlet 31 of the blade 30 to the back shroud 20 of the impeller, the radius of the outlet 31 of the blade 30 is monotonously decreased and increased with a small magnitude, thereby ensuring the size of the blade 30 at the position to overcome the stall condition near the back shroud 20 of the impeller on the side of the blade root.

[0054] Preferably, in the embodiment, the curvature of the arc-shaped profile near the second trailing edge point 2 is equal to 0.

[0055] Specifically, the arc-shaped profile is sequentially increased from the third trailing edge point 3 to the second trailing edge point 2, and the curvature of the arc-shaped profile near the second trailing edge point 2 is equal to 0, that is, by increasing the curvature of the arc-shaped profile near the second trailing edge point 2, the radius of the blade 30 at the position is increased, the size of the outlet trailing edge at the position is increased, thereby ensuring the centrifugal force at the back shroud of the impeller and reducing the flow separation at the position.

[0056] In the embodiment, the arc-shaped profile between the third trailing edge point 3 and the second trailing edge point 2 includes a third curvature and a fourth curvature, wherein the curvature of the arc-shaped profile near the third trailing edge point 3 is the third curvature, the curvature of the arc-shaped profile near the second trailing edge point 2 is the fourth curvature, the expression of the third curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≥0, and the expression of the second curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≤0.

[0057] Specifically, the curvature of the arc-shaped profile between the third trailing edge point 3 and the second trailing edge point 2 is divided into a third curvature and a fourth curvature, the third curvature is the curvature of the arc-shaped profile close to the third trailing edge point 3, and the fourth curvature is the curvature of the arc-shaped profile close to the second trailing edge point 2, the curvatures of the two are different, which is described by the second derivative, wherein the first curvature is sequentially increased and has a large slope, and the fourth curvature is sequentially increased and has a small slope, and the slope of the outlet trailing edge corresponding to the blade 30 has a trend of first large and then small from the third trailing edge point 3 to the second trailing edge point 2. That is, the third curvature and the fourth curvature are expressed in a segmented manner, which limits the shape of the arc-shaped profile between the third trailing edge point 3 and the second trailing edge point 2, that is, the specific shape of the arc-shaped profile is obtained. Compared with the arc-shaped profile with the same curvature, the size of the blade 30 close to the third trailing edge point 3 is ensured, the airflow is prevented from being sucked away by the airflow close to the impeller back cover plate 20 side, and the flow separation is reduced. The size of the blade 30 close to the second trailing edge point 2 can reduce the separation vortex at the hub between the centrifugal moving blade wheel and the axial static blade row, and overcome the stall tendency of the blade 30 close to the outlet 31 of the static blade root.

[0058] In the embodiment, the ratio of the radius of the first trailing edge point 1 to the radius of the second trailing edge point 2 is greater than or equal to 1 and less than or equal to 1.08. By bringing the radius of the first trailing edge point 1 and the second trailing edge point 2, the size of the blade is limited.

[0059] In another preferred embodiment, in the embodiment, the ratio of the radius of the first trailing edge point 1 to the radius of the second trailing edge point 2 is greater than or equal to 1.05 and less than or equal to 1.06. By bringing the radius of the first trailing edge point 1 and the second trailing edge point 2, compared with the ratio greater than or equal to 1 and less than or equal to 1.08, the airflow flowing through the blade 30 is more uniform and smooth.

[0060] The embodiment also provides a centrifugal-axial combined fan, which comprises the centrifugal moving blade wheel described above, and further comprises an axial static blade row, and the centrifugal moving blade wheel and the axial static blade row are coaxially arranged.

[0061] Specifically, the centrifugal-axial combined fan comprises the centrifugal moving blade wheel described above, and in the air inlet direction, the centrifugal moving blade wheel and the axial static blade row are coaxially arranged to improve the stall tendency defects of the static blade root and the impeller front cover plate 10, improve the suction of the fan under small flow conditions, have low cost, ensure the working efficiency of the impeller, and meet the user's demand.

[0062] Although the specific embodiments of the present application are described above, those skilled in the art should understand that this is only an example, the protection scope of the present application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present application, but these changes and modifications all fall within the protection scope of the present application.

Claims

1. A centrifugal impeller disposed between an impeller front shroud and an impeller rear shroud, the centrifugal impeller including a plurality of blades, wherein, The first tail edge point has a radius greater than a radius of the second tail edge point, the second tail edge point has a radius greater than a radius of the third tail edge point, and the first tail edge point, the third tail edge point and the second tail edge point are connected in sequence by an arc-shaped profile to form an outlet tail edge of the blade which is concave towards an axis of the blade.

2. The centrifugal impeller of claim 1, wherein A ratio of a difference between the radius of the first tail edge point and the radius of the third tail edge point to a difference between the radius of the first tail edge point and the radius of the second tail edge point is greater than 1.

005.

3. The centrifugal impeller of claim 1 wherein, In a meridian direction of the blade, the axis of the blade is a Z axis and a radial direction of the blade is an R axis, wherein a curvature expression of the arc-shaped profile between the first tail edge point and the third tail edge point is dR / dZ, and dR / dZ<0.

4. The centrifugal impeller of claim 3 wherein, The curvature of the arc-shaped profile close to the third tail edge point is equal to 0.

5. The centrifugal impeller of claim 4 wherein, The arc-shaped profile between the first tail edge point and the third tail edge point comprises a first curvature and a second curvature, wherein the curvature of the arc-shaped profile close to the first tail edge point is the first curvature, the curvature of the arc-shaped profile close to the third tail edge point is the second curvature, an expression of the first curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≤0, and an expression of the second curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≥0.

6. The centrifugal impeller of claim 5 wherein, The curvature expression of the arc-shaped profile between the third tail edge point and the second tail edge point is dR / dZ, and dR / dZ>0.

7. The centrifugal impeller of claim 6 wherein, The curvature of the arc-shaped profile close to the second tail edge point is equal to 0.

8. The centrifugal impeller of claim 7, wherein The arc-shaped profile between the third tail edge point and the second tail edge point comprises a third curvature and a fourth curvature, wherein the curvature of the arc-shaped profile close to the third tail edge point is the third curvature, the curvature of the arc-shaped profile close to the second tail edge point is the fourth curvature, an expression of the third curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≥0, and an expression of the fourth curvature is d(dR / dZ) / dZ, and d(dR / dZ) / dZ≤0.

9. The centrifugal impeller of claim 1 wherein, A ratio of the radius of the first tail edge point to the radius of the second tail edge point is greater than or equal to 1 and less than or equal to 1.

08.

10. A centrifugal mixed flow fan characterized by The centrifugal-axial combined fan comprises the centrifugal moving blade as claimed in any one of claims 1-9, and further comprises an axial static blade row, wherein the centrifugal moving blade is coaxially arranged with the axial static blade row.

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