CN223634973U - Centrifugal impeller and centrifugal axial flow combined fan containing it - Google Patents

Abstract

The utility model provides a centrifugal moving impeller and a centrifugal axial flow combined fan comprising the same, wherein the centrifugal moving impeller is arranged between an impeller front cover plate and an impeller rear cover plate, the centrifugal moving impeller comprises a plurality of blades, a first tail edge point is arranged at the position, close to the impeller front cover plate, of the outlets of the blades, a second tail edge point is arranged at the position, close to the impeller rear cover plate, of the outlets of the blades, a third tail edge point is arranged between the first tail edge point and the second tail edge point, the radius of the third tail edge point is the average value of the sum of the radius of the first tail edge point and the radius of the second tail edge point, and the third tail edge point is positioned below a connecting line of the first tail edge point and the second tail edge point along the meridian plane direction of the blades, and the first tail edge point, the third tail edge point and the second tail edge point are sequentially connected through an arc-shaped line to form the tail edge of the outlets of the blades.

Description

Centrifugal impeller and centrifugal axial flow combined fan comprising same

Technical Field

The utility model relates to the technical field of centrifugal impellers, in particular to a centrifugal impeller and a centrifugal axial flow combined fan comprising the same.

Background

Centrifugal-axial flow combined fans are commonly used in the current range hood industry. The centrifugal-axial flow fan, i.e. the fan which uses centrifugal movable impeller to boost and axial flow static blade grid to recover kinetic energy, has much smaller volume than the conventional forward multi-wing fan, and the air flow direction is axial in-axial out. The three-aspect sound absorption and insulation structure has the advantages that thicker sound absorption and insulation structures are convenient to install in the fan box, flexible arrangement in the whole air duct is also convenient, and the sound absorption and insulation structure is convenient to use in cooperation with the low-resistance sound absorption air duct.

However, the disadvantages of centrifugal impellers are also evident in that under normal conditions the flow velocity is always higher on the side closer to the back shroud than on the side closer to the front shroud, and flow separation tends to occur in the vicinity of the front shroud. This results in a large area separation at the impeller outlet, creating a pronounced wake-to-main flow stagger, and when such a form of outflow enters the downstream vane, a strong pressure pulsation is created at the vane inlet, resulting in a strong blade frequency noise.

In order to solve the above problem, the blade outlet is designed to be a bevel edge or the length or number of the blades is increased, but the design of the blade outlet to be a bevel edge causes the front side of the blades to have a relatively strong suction effect, so that the airflow at the impeller outlet has a significant tendency to deviate from the rear cover plate side to the front cover plate side. This results in increased separation vortices at the hub, and increased blade length or number, narrowing the flow path, reduced work efficiency, or reduced blade camber, resulting in higher rotational speeds required to achieve the same performance index, and increased noise.

Disclosure of utility model

The utility model aims to overcome the defects that in the prior art, a front cover plate of an impeller is easy to flow and separate, and vortex separation at a hub between a centrifugal movable impeller and an axial-flow stationary blade grid is large, and provides the centrifugal movable impeller and a centrifugal axial-flow combined fan comprising the centrifugal movable impeller.

The utility model solves the technical problems by the following technical scheme:

The utility model provides a centrifugal impeller, centrifugal impeller sets up between impeller front shroud and impeller back shroud, centrifugal impeller is including a plurality of blade, the exit of blade is close to the impeller front shroud has first trailing edge point, the exit of blade is close to the impeller back shroud has second trailing edge point, is located the exit of blade just first trailing edge point with have third trailing edge point between the second trailing edge point, wherein, the radius of third trailing edge point is the radius of first trailing edge point with the average of the radius sum of second trailing edge point, and along in the meridian direction of blade, third trailing edge point is located first trailing edge point with the below of second trailing edge point line, first trailing edge point, third trailing edge point and second trailing edge point connect gradually through the arc molded lines and form the exit trailing edge of blade.

In this scheme, through setting up the third trailing edge point with the blade export to connect gradually first trailing edge point, third trailing edge point and second trailing edge point through the arc molded lines, form towards the sunken export trailing edge of blade axis, compare in the mode that the export trailing edge of blade is the hypotenuse, the export trailing edge size that is close to the impeller front shroud part is guaranteed, reduce the flow separation in blade front shroud department, and then reduce impeller export flow separation, reduce the staggered structure of wake-mainstream simultaneously, avoid the air current of outflow can form strong pressure pulsation at the stator blade import when getting into the downstream stator blade, thereby reduce the abnormal sound of blade frequency. In addition, the concave blade outlets can overcome the suction of the airflow near the impeller front cover plate and the impeller rear cover plate, so that the separation vortex between the centrifugal impeller and the hub of the axial-flow static blade grid is reduced. The impeller has low cost, does not increase noise and avoid narrowing the flow passage, and ensures the working efficiency of the impeller.

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 0.6.

In this scheme, through the above-mentioned setting, in order to obtain the position that the third trailing edge point is located.

Preferably, in the meridian plane direction of the blade, the axis of the blade is a Z axis, and the radial direction of the blade is an R axis, wherein the curvature expression of the arc-shaped line between the first tail edge point and the third tail edge point is dR/dZ, and dR/dZ <0.

In this scheme, through above-mentioned setting, along the meridian plane direction, the camber of the arc molded lines between first trailing edge point to the third trailing edge point is monotonically changed, and the arc molded lines along the below of first trailing edge point and second trailing edge point line progressively decrease to the third trailing edge point from first trailing edge point in proper order.

Preferably, the curvature of the curved line near the first trailing edge point is equal to 0.

In the scheme, through the arrangement, the curvature of the arc-shaped molded line at the position close to the first tail edge point is increased, so that the size of the tail edge of the outlet of the blade at the position is increased, the working efficiency of the impeller is ensured, the air flow at the position close to the front cover plate of the impeller is smoother, and the flow separation is reduced.

Preferably, the arc-shaped line 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 line close to the first tail edge point is the first curvature, the curvature of the arc-shaped line close to the third tail edge point is the second curvature, the expression of the first curvature is d (dR/dZ)/dZ, d (dR/dZ)/dZ is less than or equal to 0, and the expression of the second curvature is d (dR/dZ)/dZ, and d (dR/dZ)/dZ is more than or equal to 0.

In this scheme, through the setting, with the mode of segmentation expression first camber and second camber, to restrict the arc molded lines shape between first trailing edge point to the third trailing edge point, first camber is progressively decreased in proper order and the slope is less, and the second camber is progressively decreased in proper order and the slope is great, compare in the same arc molded lines of camber, be close to first trailing edge point, be close to the blade size of impeller front shroud department and obtain guaranteeing promptly, and be close to the blade size of third trailing edge point can reduce centrifugal impeller and axial-flow stator blade between the wheel hub department separation vortex.

Preferably, the curvature expression of the arc-shaped line between the third trailing edge point and the second trailing edge point is dR/dZ, and dR/dZ <0.

In this scheme, through above-mentioned setting, along meridian plane direction, the camber of the arc shaped line between third trailing edge point to the second trailing edge point is monotonically changed, and the arc shaped line along the below of first trailing edge point and second trailing edge point line progressively reduces to the second trailing edge point from third trailing edge point in proper order.

Preferably, the curvature of the curved line near the second trailing edge point is equal to 0.

In this scheme, through above-mentioned setting to increase the camber of arc molded lines in being close to second trailing edge point department, and then make the export trailing edge size increase of the blade of here, guarantee the centrifugal force of impeller back shroud department from this, reduce this department flow separation.

Preferably, the curvature of the arc-shaped line between the third tail edge point and the second tail edge point gradually increases from the third tail edge point to the second tail edge point and d (dR/dZ)/dZ is more than or equal to 0.

In this scheme, through above-mentioned setting to make the camber of the arc molded lines between third trailing edge point to the second trailing edge point increase gradually, guarantee the blade size that is close to impeller back shroud department.

Preferably, the ratio of the radius of the first trailing edge point to the radius of the second trailing edge point is 1 or more and 1.1 or less.

In this solution, the blade size is limited by the above arrangement.

The centrifugal axial flow combined fan comprises the centrifugal movable impeller, the centrifugal axial flow combined fan further comprises an axial flow type static blade grid, and the centrifugal movable impeller and the axial flow type static blade grid are coaxially arranged.

In this scheme, this centrifugal axial flow combined fan includes above-mentioned centrifugal impeller to improve flow separation and separation vortex through the blade structure, the cost is lower and can overcome flow separation and separation vortex simultaneously, has promoted impeller work efficiency, and the noise is little, makes this centrifugal axial flow combined fan can satisfy the user demand.

The utility model has the positive progress effects that the third tail edge point is arranged at the blade outlet, and the first tail edge point, the third tail edge point and the second tail edge point are sequentially connected through the arc-shaped molded line to form the outlet tail edge which is sunken towards the axis of the blade, compared with the mode that the outlet tail edge of the blade is in a bevel edge shape, the size of the outlet tail edge close to the front cover plate part of the impeller is ensured, the flow separation at the front cover plate part of the blade is reduced, the flow separation at the blade outlet is further reduced, meanwhile, the staggered structure of wake and main flow is reduced, and the strong pressure pulsation is prevented from being formed at the inlet of the static blade when the flowing out airflow enters the downstream static blade, so that the blade frequency abnormal sound is reduced. In addition, the concave blade outlets can overcome the suction of the airflow near the impeller front cover plate and the impeller rear cover plate, so that the separation vortex between the centrifugal impeller and the hub of the axial-flow static blade grid is reduced. The impeller has low cost, does not increase noise and avoid narrowing the flow passage, and ensures the working efficiency of the impeller.

Drawings

Fig. 1 is a schematic structural view of a centrifugal axial flow combined fan according to a preferred embodiment of the present utility model.

Fig. 2 is a view showing a radial view of a centrifugal impeller according to a preferred embodiment of the present utility model.

Fig. 3 is an angular cloud of impeller outlet airflow according to a preferred embodiment of the utility model.

FIG. 4 is a graph showing impeller outlet separation vortex contrast according to a preferred embodiment of the present utility model.

Reference numerals illustrate:

Impeller front shroud 10

Impeller back shroud 20

Blade 30

Outlet 31

First trailing edge point 1

Second trailing edge point 2

Third trailing edge point 3

Detailed Description

The present utility model will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments are shown.

The embodiment provides a centrifugal impeller, as shown in fig. 1 and 2, the specific structure of the centrifugal impeller is shown in fig. 1 and 2, the centrifugal impeller is arranged between a front cover plate 10 and a rear cover plate 20 of the impeller, the centrifugal impeller comprises a plurality of blades 30, a first tail edge point 1 is arranged at an outlet 31 of each blade 30 and close to the front cover plate 10 of the impeller, a second tail edge point 2 is arranged at an outlet 31 of each blade 30 and close to the rear cover plate 20 of the impeller, a third tail edge point 3 is arranged between the first tail edge point 1 and the second tail edge point 2, the radius of the third tail edge point 3 is the average of the sum of the radius of the first tail edge point 1 and the radius of the second tail edge point 2, and in the meridian direction of each blade 30, the third tail edge point 3 is arranged below a connecting line of the first tail edge point 1 and the second tail edge point 2, and the first tail edge point 1, the third tail edge point 3 and the second tail edge point 2 are sequentially connected through arc-shaped lines to form an outlet tail edge of each blade 30.

Specifically, along the meridian plane direction of the blade 30, the outlet 31 of the blade 30 is provided with a first trailing edge point 1 and a second trailing edge point 2, the radius of the first trailing edge point 1 is larger than that of the second trailing edge point 2, the area between the first trailing edge point 1 and the second trailing edge point 2 is the area of the outlet 31 of the blade 30, the first trailing edge point 1 and the second trailing edge point 2 are connected by a connecting line, which is a straight line and is represented by a broken line, so as to form the blade 30 with the outlet 31 being a bevel edge, and a third trailing edge point 3 is arranged below the connecting line, namely the area close to the axis of the blade 30, and the first trailing edge point 1, the third trailing edge point 3 and the second trailing edge point 2 are sequentially connected by arc-shaped lines so as to form the outlet trailing edge of the blade 30.

The radius of the third trailing edge point 3 is the sum of the radius of the first trailing edge point 1 and the radius of the second trailing edge point 2 divided by 2, and it is understood that the outlet 31 is concavely arranged toward the axis of the blade 30 when the outlet trailing edge of the blade 30 formed by arc-shaped line connection is compared with the blade 30 with the outlet 31 as the bevel edge. And the radius of the third tail edge point 3 is limited, so that the size of the tail edge of the outlet close to the impeller front cover plate 10 is ensured, the working capacity of the blades 30 close to the impeller front cover plate 10 is enhanced, the flow separation at the positions of the blade front cover plate 10 is reduced, the flow separation at the outlet of the impeller is further reduced, meanwhile, the staggered structure of wake-main flow is reduced, and the strong pressure pulsation is avoided when the flowing-out airflow enters the downstream stationary blade, so that the abnormal sound of the blade frequency is reduced.

In addition, as shown in fig. 3 and 4, compared with the vane 30 with the outlet 31 being the inclined edge, the outlet 31 of the concavely arranged vane 30 can overcome the suction of the air flow near the impeller front cover plate 10 and the vane 30 near the impeller rear cover plate 20, because the radius of the concavely arranged vane 30 near the impeller front cover plate 10 is large, in order to ensure that the vane 30 can weaken the original flow separation at the impeller front cover plate 10, the radius of the vane 30 is 5-10% larger than the radius near the impeller rear cover plate 20, and the outlet 31 of the concavely arranged vane 30 can overcome the problems on the basis of reducing the flow separation, namely, simultaneously reducing the separation vortex at the hub between the centrifugal impeller and the axial flow stationary blade grid. In this embodiment, the vane 30 is not only low in cost, but also does not increase noise and avoid narrowing the flow passage, thereby ensuring the working efficiency of the impeller.

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 0.6. By bringing in the radii of the first trailing edge point 1 and the second trailing edge point 2, the position of the third trailing edge point 3 is derived, thereby ensuring that the outlet 31 of the blade 30 is concavely arranged towards the axis of the blade 30.

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 0.75. By bringing in the radii of the first and second trailing edge points 1, 2, the recess depth of the blade 30 is smaller and the airflow is more uniform and smooth through the blade 30 than when the ratio is 0.75, compared to when the ratio is greater than 0.6.

In the present embodiment, in the meridian plane direction of the blade 30, the axis of the blade 30 is the Z axis, the radial direction of the blade 30 is the R axis, wherein the curvature expression of the arc-shaped line between the first trailing edge point 1 to the third trailing edge point 3 is dR/dZ, and dR/dZ <0.

Specifically, the curvature, also called slope, of the arc-shaped line between the first tail edge point 1 and the third tail edge point 3 is described by a derivative, and the values of the third tail edge point 3 and the first tail edge point 1 are substituted into dR/dZ on the basis of determining the value range of the third tail edge point 3, and dR/dZ is <0. It can be understood that the arc-shaped lines between the first tail edge point 1 and the third tail edge point 3 are in a monotonic change rule, that is, the lower arc-shaped line along the connection line between the first tail edge point 1 and the second tail edge point 2 sequentially decreases from the first tail edge point 1 to the third tail edge point 3, so as to form a concave part of the outlet tail edge. The radius of the outlets 31 of the blades 30 is monotonically decreasing from the impeller front cover plate 10 to the intermediate region of the outlets 31 of the blades 30, the radius of the outlets 31 of the blades 30 being greatest near the impeller front cover plate 10. Therefore, the working capacity is the strongest, and the fluid can be adsorbed on the impeller front cover plate 10 side more, so that separation is inhibited.

Preferably, in this embodiment, the curvature of the arcuate profile near the first trailing edge point 1 is equal to 0.

Specifically, the arc-shaped line gradually decreases from the first tail edge point 1 to the third tail edge point 3, and the curvature of the arc-shaped line close to the first tail edge point 1 is equal to 0, that is, the radius of the blade 30 at the position close to the first tail edge point 1 is increased by increasing the curvature of the arc-shaped line, and the size of the corresponding outlet tail edge at the position is increased, so that the working efficiency of the impeller is ensured, the air flow at the position close to the impeller front cover plate 10 is smoother, and the flow separation is reduced.

In addition, in the vicinity of the side close to the impeller front cover plate 10, the change of the radius of the outlet 31 of the blade 30 is smaller than that of the blade 30 with the outlet 31 being the bevel edge, so that the excessive radius of the outlet 31 of the blade 30 at the side close to the impeller front cover plate 10 is avoided, and the wheel resistance loss is increased.

In this embodiment, the curved line 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 curved line near the first trailing edge point 1 is the first curvature, the curvature of the curved line near the third trailing edge point 3 is the second curvature, the expression of the first curvature is d (dR/dZ)/dZ, d (dR/dZ)/dZ is less than or equal to 0, and the expression of the second curvature is d (dR/dZ)/dZ, d (dR/dZ)/dZ is more than or equal to 0.

Specifically, the curvature of the arc-shaped line between the first tail edge point 1 and the third tail edge point 3 is divided into a first curvature and a second curvature, the first curvature is the curvature of the arc-shaped line close to the first tail edge point 1, the second curvature is the curvature of the arc-shaped line close to the third tail edge point 3, the two curvatures are different, and the two curvatures are described through a second derivative, wherein the first curvature is gradually decreased and the slope is smaller, the second curvature is gradually decreased and the slope is larger, and the slope of the outlet tail edge corresponding to the blade 30 is in a trend of being smaller from the first tail edge point 1 to the third tail edge point 3 and larger from the first tail edge point 1 to the third tail edge point 3. That is, the arc-shaped line shape between the first trailing edge point 1 and the third trailing edge point 3 is limited in a manner of expressing the first curvature and the second curvature in a segmented manner, that is, the specific shape of the arc-shaped line is obtained, compared with the arc-shaped line with the same curvature, the size of the blade 30 near the first trailing edge point 1, that is, near the impeller front cover plate 10 is ensured, and the size of the blade near the third trailing edge point 3 can reduce the separation vortex between the centrifugal impeller and the axial flow stator blade grid at the hub.

In the present embodiment, the curvature expression of the arc-shaped line between the third trailing edge point 3 and the second trailing edge point 2 is dR/dZ, and dR/dZ <0.

Specifically, in the meridian plane direction, the curvature of the arc-shaped line between the third tail edge point 3 and the second tail edge point 2 changes monotonically, and the numerical values of the third tail edge point 3 and the second tail edge point 2 are substituted into dR/dZ on the basis of determining the value range of the third tail edge point 3, wherein dR/dZ is smaller than 0. Namely, along the lower arc-shaped line connecting the first tail edge point 1 and the second tail edge point 2, the arc-shaped line sequentially decreases from the third tail edge point 3 to the second tail edge point 2 to form another part of the concave outlet tail edge, and the other part of the concave outlet tail edge is connected with the part of the outlet tail edge sequentially decreasing from the first tail edge point 1 to the third tail edge point 3 to form a complete outlet tail edge. At the same time, from the middle area of the outlets 31 of the vanes 30 to the impeller back cover plate 20, the radius of the outlets 31 of the vanes 30 is monotonically decreasing and of small magnitude, so that the flow of fluid near the side of the impeller back cover plate 20 is not substantially sucked, disturbed, and the separation vortex at the hub corner is not increased.

Preferably, in this embodiment, the curvature of the arcuate profile near the second trailing edge point 2 is equal to 0.

Specifically, the arc-shaped lines gradually decrease from the third trailing edge point 3 to the second trailing edge point 2, and the curvature of the arc-shaped line close to the second trailing edge point 2 is equal to 0, namely, by increasing the curvature of the arc-shaped line close to the second trailing edge point 2, the radius of the blade 30 at the position is further increased, and the size of the corresponding outlet trailing edge at the position is increased, so that the centrifugal force at the impeller rear cover plate is ensured, and the flow separation at the position is reduced.

In the present embodiment, the curvature of the arc-shaped line between the third trailing edge point 3 and the second trailing edge point 2 gradually increases from the third trailing edge point 3 to the second trailing edge point 2 and d (dR/dZ)/dZ is equal to or greater than 0.

Specifically, the curvature of the arcuate profile between the third trailing edge point 3 and the second trailing edge point 2 changes monotonically, and the slope of the corresponding outlet trailing edge of the blade 30 tends to increase in sequence from the third trailing edge point 3 to the second trailing edge point 2. The shape of the arc-shaped line between the third tail edge point 3 and the second tail edge point 2 is limited by the second derivative, namely, the specific shape of the arc-shaped line is obtained, and compared with the arc-shaped line with the same curvature, the size of the blade 30 close to the second tail edge point 2, namely, close to the impeller rear cover plate 20 is ensured.

In the present embodiment, the ratio of the radius of the first trailing edge point 1 to the radius of the second trailing edge point 2 is 1 or more and 1.1 or less. The dimensions of the blade are limited by bringing in the radii of the first and second trailing edge points 1, 2.

In another preferred embodiment, the ratio of the radius of the first trailing edge point 1 to the radius of the second trailing edge point 2 is 1.05 or more and 1.08 or less. By bringing in the radii of the first trailing edge point 1 and the second trailing edge point 2, the airflow is more uniform and smooth when flowing through the blade 30 than when the ratio is 1 or more and 1.1 or less.

The embodiment also provides a centrifugal axial flow combined fan, which comprises the centrifugal movable impeller, and the centrifugal axial flow combined fan also comprises an axial flow static blade grid, wherein the centrifugal movable impeller and the axial flow static blade grid are coaxially arranged.

Specifically, this centrifugal axial flow combined fan includes above-mentioned centrifugal impeller, along the direction of admitting air, centrifugal impeller and axial flow type stator bars coaxial arrangement, and this centrifugal impeller improves flow separation and separation vortex through the blade structure, and the cost is lower and has promoted impeller work efficiency, and the noise is little for this centrifugal axial flow combined fan can satisfy the user demand.

While specific embodiments of the utility model have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and the scope of the utility model is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the principles and spirit of the utility model, but such changes and modifications fall within the scope of the utility model.

Claims (10)

1. The centrifugal impeller comprises a plurality of blades, and is characterized in that the outlet of each blade is close to the front cover plate of the impeller and is provided with a first tail edge point, the outlet of each blade is close to the rear cover plate of the impeller and is provided with a second tail edge point, the outlet of each blade is provided with a third tail edge point between the first tail edge point and the second tail edge point, the radius of the third tail edge point is the average of the sum of the radius of the first tail edge point and the radius of the second tail edge point, and the third tail edge point is located below the connecting line of the first tail edge point and the second tail edge point in the meridian direction of the blade, and the first tail edge point, the third tail edge point and the second tail edge point are sequentially connected through arc-shaped lines to form the outlet tail edge of the blade.

2. The centrifugal impeller of claim 1 wherein 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 0.6.

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

4. A centrifugal impeller according to claim 3, wherein the curvature of the arcuate profile near the first trailing edge point is equal to 0.

5. The centrifugal impeller of claim 4 wherein said arcuate profile between said first trailing edge point and said third trailing edge point includes a first curvature and a second curvature, wherein the curvature of said arcuate profile proximate said first trailing edge point is said first curvature, the curvature of said arcuate profile proximate said third trailing edge point is said second curvature, the expression of said first curvature is d (dR/dZ)/dZ, and d (dR/dZ)/dZ is less than or equal to 0, and the expression of said second curvature is d (dR/dZ)/dZ, and d (dR/dZ)/dZ is greater than or equal to 0.

6. The centrifugal impeller of claim 5 wherein the curved line between the third trailing edge point and the second trailing edge point has a curvature expression of dR/dZ, and dR/dZ <0.

7. The centrifugal impeller of claim 6 wherein the curvature of said arcuate profile near said second trailing edge point is equal to 0.

8. The centrifugal impeller of claim 7 wherein said arcuate profile curvature between said third trailing edge point and said second trailing edge point increases gradually from said third trailing edge point to said second trailing edge point and is d (dR/dZ)/dZ > 0.

9. The centrifugal impeller of claim 1, wherein a ratio of a radius of the first trailing edge point to a radius of the second trailing edge point is 1 or more and 1.1 or less.

10. A centrifugal axial flow combined fan, characterized in that the centrifugal axial flow combined fan comprises a centrifugal moving impeller according to any one of claims 1-9, and further comprises an axial flow static blade grid, wherein the centrifugal moving impeller and the axial flow static blade grid are coaxially arranged.