CN109519416B - A centrifugal fan - Google Patents

Abstract

The centrifugal fan comprises a volute, an impeller and a motor, wherein the volute comprises a front wall, a rear wall and an annular wall connected between the front wall and the rear wall, the front side air inlet and the rear side air inlet are respectively formed in the front side and the rear side of the volute, the impeller comprises a middle plate, a front inner volute is installed on the inner wall surface of the front wall of the volute, and a rear inner volute is installed on the inner wall surface of the rear wall of the volute. The front inner volute is arranged on the inner wall surface of the front wall of the volute, the rear inner volute is arranged on the inner wall surface of the rear wall of the volute, namely, the double-suction inner volute structure matched with the double-suction impeller is adopted, the diffusion capacity of the volute can be further improved, the recovery of the kinetic energy of an impeller outlet is realized, the effective acting capacity of the impeller is enhanced, the flow loss is effectively reduced, the noise of the fan is reduced, the front inner volute and the rear inner volute also play the role of the vortex ring, the gaps between the front disc and the rear disc of the blade and the volute are reduced, and the leakage loss inside the fan system is further reduced.

Description

A centrifugal fan

Technical field

The invention relates to a centrifugal fan.

Background technique

The impeller of the double-suction multi-wing centrifugal fan is a double-suction impeller. The double-suction impeller is widely used in European range hoods because of its large flow coefficient. The blades of the current double-suction multi-blade centrifugal fan blades have short blade flow channels and relatively long blades. If you want to enhance the effect of absorbing oil smoke, you need to further improve its aerodynamic performance. If the blades are further lengthened, since the impeller is a rotating part, the Dynamic imbalance is prone to occur during rotation, resulting in additional noise. Improving performance by increasing the rotational speed will lead to an increase in noise. Moreover, due to the limitation of the installation method of the double-suction multi-blade centrifugal fan in the whole machine, the air inlet flow difference between the front and rear sides is large, and the air flow at the blade outlet is very different. If the same volute profile is used for expansion, The airflow at the outlet of the hood will be uneven, which will lead to increased noise and deterioration of fan performance. The main purpose of the double-suction volute is to recover the kinetic energy at the outlet of the double-suction impeller and increase the pressure of the entire fan system. Therefore, the matching design of the volute and the impeller type is particularly important.

For existing double-suction multi-wing centrifugal fan systems used in range hoods, due to limitations in external dimensions, the drive motor is generally installed on one side of the volute. At the same time, there is also a difference in the air inlet height on both sides of the impeller. These reasons ultimately All lead to the fact that the flow rates entering the impeller on both sides at the same time are not equal. Under the same blade parameters, the airflow flowing from the impeller outlet to the volute on both sides is extremely uneven, which not only brings A large amount of flow is lost and the noise is also increased. Therefore, in order to improve this situation and considering the particularity of multi-wing centrifugal fans, it is necessary to improve the volute structure to improve the uniformity of the outlet airflow, thereby improving fan efficiency and reducing noise.

Contents of the invention

The technical problem to be solved by the present invention is to provide a double-suction multi-blade centrifugal fan with a relatively small size that can improve the unevenness of the outlet air flow and is aimed at the above-mentioned current state of the art.

The technical solution adopted by the present invention to solve the above technical problems is: the centrifugal fan includes a volute, an impeller and a motor. The volute includes a front wall, a rear wall and an annular wall connected between the front wall and the rear wall. The front and rear sides of the shell have front air inlets and rear air inlets respectively. The impeller includes a middle plate. The motor is installed on the rear side of the volute. The output shaft of the motor is connected to the middle plate. It is characterized in that: a front inner volute is installed on the inner wall surface of the front wall of the volute, and a rear inner volute is installed on the inner wall surface of the rear wall of the volute.

Preferably, the front inner volute is provided around the front air inlet, and the rear inner volute is provided around the rear air inlet.

Further preferably, the rear edge of the front inner volute is adjacent to the front end surface of the impeller, and the front edge of the rear inner volute is adjacent to the rear end surface of the impeller.

The profile lines of the front inner volute and the rear inner volute can have various structures. Preferably, the profile lines of the front inner volute and the rear inner volute include straight segments and curved segments. , the straight segment is adjacent to the air outlet of the fan, the starting end of the curve segment is the lower end of the straight segment, the end of the curve segment is connected to the straight segment and the connection point is close to the upper end of the straight segment.

Further preferably, the axial component of the impeller front-end exit velocity is C2m, the circumferential component of the impeller front-end exit velocity is C2u, the impeller outer diameter is R2, the base circle diameter of the volute is R0, and the front inner volute is The polar radius of the impeller is R, the vertical distance between the impeller's middle disk and the front inner volute is B0, the width of the front inner volute is B1, and the initial angle of the front inner volute is θ0, then the following formula is satisfied:

Further preferably, the axial component of the impeller rear end exit velocity is C2m′, the circumferential component of the impeller rear end exit velocity is C2u′, the impeller outer diameter is R2, the base circle diameter of the volute is R0, and the rear end The polar radius of the side inner volute is R', the vertical distance between the impeller's middle disk and the rear inner volute is B2, the width of the rear inner volute is B3, and the initial angle of the rear inner volute is θ0' , then the following formula is satisfied:

The motor can have a variety of installation structures. Preferably, a motor mounting bracket is installed on the rear side of the volute, and the motor is installed on the motor mounting bracket.

Compared with the prior art, the advantage of the present invention is that the centrifugal fan installs a front inner volute on the inner wall surface of the front wall of the volute, and a rear inner volute is installed on the inner wall surface of the rear wall of the volute. That is to say, the double-suction inner volute structure is used to match the double-suction impeller. The friction distance of the air flow in the volute is small, which can reduce the friction loss of the impeller and reduce the fan noise, further improve the pressure expansion capacity of the volute, and realize the impeller The outlet kinetic energy is recovered, thereby enhancing the effective working capacity of the impeller. Moreover, the front inner volute and the rear inner volute also play the role of anti-vortex rings, reducing the gaps between the front and rear blade discs and the volute. , thereby reducing the leakage loss inside the fan system. In addition, the centrifugal fan can achieve higher aerodynamic performance with shorter blades, allowing the fan to be relatively smaller in size.

Description of the drawings

Figure 1 is a schematic structural diagram of an embodiment of the present invention;

Figure 2 is a schematic structural diagram of the embodiment of the present invention from another angle;

Figure 3 is an exploded schematic diagram of an embodiment of the present invention;

Figure 4 is a structural cross-sectional view of an embodiment of the present invention;

Figure 5 is a side view of the embodiment of the present invention;

Figure 6 is a structural cross-sectional view along the B-B direction in Figure 5;

Figure 7 is a structural cross-sectional view along C-C direction in Figure 5.

Detailed ways

The present invention will be described in further detail below with reference to the embodiments of the drawings.

As shown in Figures 1 to 3, the centrifugal fan in this embodiment includes a volute 1, an impeller 2, a motor 3, a front inner volute 4, a rear inner volute 5 and a motor mounting bracket 6.

Taking the direction indicated by arrow A in Figure 1 as the forward direction, the volute 1 includes a front wall 11, a rear wall 12 and an annular wall 13 connected between the front wall and the rear wall. The front and rear sides of the volute 1 have front and rear walls respectively. The side air inlet 14 and the rear air inlet 15. The impeller 2 includes a middle plate 21, a front plate 22 and a rear plate 23. The front and rear sides of the middle plate 21 respectively form the front air inlet and the rear air inlet of the impeller 2. The motor mounting bracket 6 is installed. On the rear side of the volute 1, the motor 3 is mounted on the motor mounting bracket 6. The output shaft of the motor 3 is connected to the middle plate 21. When the motor 3 rotates, it drives the middle plate 21 to rotate, and then drives the impeller 2 to rotate. The above structure is the same as that of the existing double-suction multi-blade centrifugal fan, and will not be described in detail here.

In this embodiment, the front inner volute 4 is installed on the inner wall surface of the front wall 11 of the volute. The front inner volute 4 is arranged around the front air inlet 14 , and the rear edge of the front inner volute 4 is adjacent to The front end surface of impeller 2. The rear inner volute 5 is installed on the inner wall surface of the rear wall 12 of the volute. The rear inner volute 5 is located around the rear air inlet 15 , and the front edge of the rear inner volute 5 is adjacent to the rear end surface of the impeller 2 . In addition, the profile line of the front inner volute 4 and the profile line of the rear inner volute 5 both include a straight segment 71 and a curved segment 72. The straight segment 71 is adjacent to the air outlet of the fan, and the starting end of the curved segment 72 is a straight line. The lower end of the segment 71 and the end end of the curve segment 72 are connected to the straight segment 71 and the connection point is close to the upper end of the straight segment 71 .

As shown in Figures 4 to 6, assume that the axial component of the front-end exit velocity of impeller 2 is C2m. C2m can be calculated from the front-end outlet air volume and the number of blades of the impeller. According to the circumferential component of the impeller 2 front-end exit velocity, C2u, C2u can be calculated based on the blade installation angle, rotation speed and air volume. The outer diameter of impeller 2 is R2, the base circle diameter of volute 1 is R0, the polar radius of the front inner volute 4 is R, and the middle disk 21 of impeller 2 is connected with the front The vertical distance between the side inner volutes 4 is B0, the width of the front inner volute 4 is B1, and the initial angle of the front inner volute 4 is θ0, then the following formula is satisfied:

As shown in Figure 4, Figure 5 and Figure 7, assuming that the axial component of the exit velocity of the rear end of the impeller 2 is C2m', C2m' can be calculated based on the rear outlet air volume and the number of blades of the impeller. The exit velocity of the rear end of the impeller 2 is The component in the circumferential direction is C2u'. C2u' can be calculated based on the blade placement angle, rotation speed and air volume. The outer diameter of the impeller 2 is R2, the base circle diameter of the volute 1 is R0, and the polar radius of the rear inner volute 5 is R', the vertical distance between the middle plate 21 of the impeller 2 and the rear inner volute 5 is B2, the width of the rear inner volute 5 is B3, and the initial angle of the rear inner volute 5 is θ0', then it satisfies The following formula:

The above are only preferred embodiments of the present invention. It should be noted that, for those of ordinary skill in the art, various modifications or improvements can be made to the present invention without departing from the principles of the present invention, and these are considered to be within the protection scope of the present invention.

Claims (5)

1. A centrifugal fan, including a volute (1), an impeller (2) and a motor (3). The volute (1) includes a front wall (11), a rear wall (12) and a wall connected to the front wall and the rear wall. The annular wall (13) between the walls, the front and rear sides of the volute (1) have a front air inlet (14) and a rear air inlet (15) respectively, and the impeller (2) includes a middle plate (21) ), the motor (3) is installed on the rear side of the volute (1), and the output shaft of the motor (3) is connected to the middle plate (21), which is characterized in that: on the front wall of the volute (11) ) is installed on the inner wall surface of the front inner volute (4), and a rear inner volute (5) is installed on the inner wall surface of the rear wall (12) of the volute. The front inner volute (4) ) is located around the front air inlet (14), the rear inner volute (5) is located around the rear air inlet (15), and the outlet speed of the front end of the impeller (2) is The component of the impeller (2) front outlet velocity in the circumferential direction is C2m, the outer diameter of the impeller (2) is R2, the base circle diameter of the volute (1) is R0, and the front inner volute (4) ) is R, the vertical distance between the middle plate (21) of the impeller (2) and the front inner volute (4) is B0, the width of the front inner volute (4) is B1, and the width of the front inner volute (4) is B1. The initial angle of the volute (4) is θ0, which satisfies the following formula: 2. The centrifugal fan according to claim 1, characterized in that: the rear edge of the front inner volute (4) is adjacent to the front end surface of the impeller (2), and the rear inner volute (5) The front edge is adjacent to the rear end surface of the impeller (2). 3. The centrifugal fan according to claim 1, characterized in that: the profile lines of the front inner volute (4) and the rear inner volute (5) both include straight segments (71) and Curve section (72), the straight section (71) is adjacent to the air outlet of the fan, the starting end of the curve section (72) is the lower end of the straight section (71), and the end end of the curve section (72) is connected to the air outlet of the fan. on the straight line segment (71) and the connection point is close to the upper end of the straight line segment (71). 4. The centrifugal fan according to claim 1, characterized in that: the axial component of the rear end exit velocity of the impeller (2) is C2m', and the circumferential component of the rear end exit velocity of the impeller (2) is C2m'. C2u', the outer diameter of the impeller (2) is R2, the base circle diameter of the volute (1) is R0, the polar radius of the rear inner volute (5) is R', the middle disk (21) of the impeller (2) and The vertical distance between the rear inner volutes (5) is B2, the width of the rear inner volutes (5) is B3, and the initial angle of the rear inner volutes (5) is θ0', then the following formula is satisfied: 5. The centrifugal fan according to any one of claims 1 to 4, characterized in that: a motor mounting bracket (6) is installed on the rear side of the volute (1), and the motor (3) is installed On the motor mounting bracket (6).