CN117212251A - Centrifugal fan and range hood with same - Google Patents

Abstract

The invention discloses a centrifugal fan and a range hood with the same, wherein the centrifugal fan comprises a volute, and the volute comprises two cover plates which are arranged at intervals and a ring wall arranged between the two cover plates; the centrifugal fan further comprises a flow guide assembly, wherein the flow guide assembly comprises flow guide sheets which are positioned at the periphery of the impeller of the centrifugal fan at intervals, and the flow guide sheets extend between the two cover plates along the direction parallel to the axial direction of the centrifugal fan. Compared with the prior art, the invention has the advantages that: the flow deflector is arranged in the volute, so that the development of secondary flow and the loss caused by flow channel diffusion in the expansion process of the volute can be reduced, and meanwhile, the noise can be reduced.

Description

Centrifugal fan and range hood with same

Technical Field

The invention relates to a power device, in particular to a centrifugal fan and a range hood using the centrifugal fan.

Background

The range hood has become one of the indispensable kitchen appliances in modern families. The range hood works by utilizing the fluid dynamics principle, and the range hood sucks and discharges oil smoke through a centrifugal fan arranged in the range hood and filters part of grease particles by using a filter screen. The centrifugal fan comprises a volute, an impeller arranged in the volute and a motor for driving the impeller to rotate. When the impeller rotates, negative pressure suction is generated at the center of the fan, and oil smoke below the range hood is sucked into the fan and is collected by the volute after being accelerated by the fan to be guided to be discharged out of the room.

The common multi-wing centrifugal fan of the range hood has the advantages of smaller volume and higher flow and pressure. But it also has the following problems: (1) the impeller is close to the middle disc area (for single suction close to the rear disc with short axial dimension) as a main acting area, because the air inflow in the axial direction is uneven, the pressure difference is easy to cause the air flow to flow out of the impeller channel and then form a large secondary flow vortex in the volute, as shown in fig. 13, the speed close to the inner side of the volute is high, the speed of the outer side is gradually reduced, obvious speed difference exists between the inner side and the outer side, and even the speed is developed to the front disc area and the rear disc area and flows back to the inlet area, the overall pneumatic efficiency is reduced, the noise is increased, the effective acting blade segment ratio is low, the air quantity is often increased by means of rotating speed or the size is increased, the rotating speed is increased further, and the size is increased further to occupy the space of the cabinet; (2) the back pressure of the public flue connected with the range hood changes along with the change of the starting rate, so that the working condition changes, the range hood fan often works deviating from the design working condition, the common fixed flow guide piece or the separation piece is generally difficult to adapt to the multiple wide working conditions when being added into the volute, and the range hood fan is easy to become a resistance source when deviating from the design working condition, as shown in fig. 14.

Disclosure of Invention

The first technical problem to be solved by the invention is to provide a centrifugal fan, which aims at overcoming the defects of the prior art, and reduces secondary flow of the impeller outflow and noise.

The second technical problem to be solved by the invention is to provide the range hood with the centrifugal fan.

The technical scheme adopted by the invention for solving the first technical problem is as follows: the centrifugal fan comprises a volute, wherein the volute comprises two cover plates which are arranged at intervals and an annular wall which is arranged between the two cover plates; the method is characterized in that:

the centrifugal fan further comprises a flow guide assembly, wherein the flow guide assembly comprises flow guide sheets which are positioned at the periphery of the impeller of the centrifugal fan at intervals, and the flow guide sheets extend between the two cover plates along the direction parallel to the axial direction of the centrifugal fan.

The flow deflector is arranged in the volute, so that the development of secondary flow and the loss caused by flow channel diffusion in the expansion process of the volute can be reduced, and meanwhile, the noise can be reduced.

Further, the guide vane is rotationally connected with the volute, and the rotation axis of the guide vane is parallel to the axial direction of the centrifugal fan. The guide vane can rotate relative to the volute, so that the guide vane can deflect outwards at high rotating speed, the cross section area of the outer layer channel is reduced, the reduction channel accelerates the outside air flow, and the loss of the outer layer collecting air flow due to the long path (the inner layer air flow collecting path is short, and the loss is relatively small).

Further, for the rotation installation of guide vane, the guide vane still includes first pivot and second pivot, one of them tip in the spiral case circumference is followed to the guide vane is connected with the spiral case through first pivot, another tip in the spiral case circumference is followed to the guide vane is then connected with the spiral case through the second pivot, the junction of second pivot and spiral case is the center of rotation of guide vane.

Further, in order to facilitate the rotation of the two ends of the guide vane relative to the volute under constraint so as to avoid the separation of the guide vane and the volute, a fixed slot is formed in one of the cover plates of the volute, and the first rotating shaft is movably matched with the fixed slot.

Further, the flow guiding component further comprises an elastic piece, the elastic piece is arranged in the fixing groove, one end of the elastic piece is fixed with the first rotating shaft, the other end of the elastic piece is fixed with the cover plate, and therefore the flow guiding sheet can dynamically adjust and balance by means of elasticity of the elastic piece and internal and external lamination difference, and deflection angles can be automatically adjusted according to working conditions.

Further, the air blowing holes are formed in the guide vane, the air blowing holes extend between the two cover plates and penetrate through the thickness of the guide vane, so that the boundary layer can be actively controlled by the air blowing holes, the boundary air flow with low speed or 0 or even countercurrent on the outer layer of the guide vane is blown by the inner layer high pressure, the boundary air flow is accelerated again to form a full kinetic energy boundary layer, the resistance and energy dissipation caused by boundary layer separation are reduced, and the flow and the efficiency are improved.

Further, in order to facilitate the blowing of the air flow, the caliber of the air blowing hole gradually decreases from the side of the guide vane away from the annular wall to the side of the annular wall.

The width of the outlet of the air blowing hole facing one side of the annular wall is t1, and the value range of t1 is 0.3-5 mm. The outlet of the air blowing hole mainly adopts gap flow, the size is the section size of the main internal and external pressure difference air flow, the flow rate of the air flow is too small, the speed of the air flow blown out is too large to be weakened, and the accelerating effect is not achieved.

The width of the inlet of the air blowing hole facing one side of the impeller is t2, the value range of t2 is 2-15 t1, the air blowing hole inlet is mainly convenient for air flow to flow into a gap flow, abnormal noise possibly exists in the ratio, and the air blowing is insufficient in shrinkage and poor in acceleration effect if the ratio is too large.

The tangential included angle between the air blowing hole and the guide vane is alpha, the value range of alpha is [3 degrees, 60 degrees ], the re-acceleration effect on the boundary layer after the airflow of the inner layer with small alpha blows out is weakened, and the airflow steering effect driven by jet flow is easily achieved when the airflow of the boundary layer is too large alpha is weakened. Further, along the axial direction of the centrifugal fan, the guide vane is in a shape that the middle thickness is smaller than the thicknesses of the two ends, so that a drum-shaped channel with better flow performance is realized on a common volute by utilizing the small middle part and the large front and rear sides of the guide vane, the middle main flow area of the impeller is relatively increased, the secondary flow is relatively reduced in the front and rear end ring channels, and the secondary flow is further restrained.

Further, the following coordinate system is established in a state when the centrifugal fan is vertically placed: the center of the impeller is taken as an origin, a line passing through the origin horizontally is taken as an X axis, a line passing through the origin vertically is taken as a Y axis, an air outlet of the volute is positioned in a second quadrant of the coordinate system, the negative direction of the X axis is 0 degrees, the positive angle is formed along the clockwise direction, the negative angle of the guide vane relative to the X axis is omega, the value range of omega is [200 degrees, 360 degrees ], invalid flow division is easily generated when the expansion degree of the volute is small when the omega is too close, the resistance is increased, and the airflow flow of the impeller towards the air outlet is easily influenced when the omega is too close.

The circumferential wrap angle of the guide vane is theta, the value range of theta is [50 degrees, 160 degrees ] and the local secondary flow can be restrained only when the value of theta is too small, the restraining effect of the secondary flow can be weakened, the flexibility of adjustment according to the spring and the pressure difference is reduced when the value of theta is too large, and the flow resistance is correspondingly increased.

The invention solves the second technical problem by adopting the technical proposal that: a range hood, characterized in that: the centrifugal fan as described above is applied.

Compared with the prior art, the invention has the advantages that: the flow guide sheet is arranged in the volute, so that the development of secondary flow and the loss caused by flow channel diffusion in the expansion process of the volute can be reduced, and meanwhile, the noise can be reduced; the guide vane can rotate relative to the volute, so that the guide vane can deflect outwards at high rotation speed, the cross section area of the outer layer channel is reduced, the reduction channel accelerates the outside air flow, and the loss of the outer layer collecting air flow due to the long path (the inner layer air flow collecting path is short, and the loss is relatively small); the guide vane realizes dynamic adjustment and balance by utilizing the elasticity of the elastic piece and the difference between the inner layer and the outer layer, and realizes automatic adjustment of deflection angle according to working conditions; the boundary layer can be actively controlled by utilizing the air blowing holes, and boundary air flows with low speed or 0 and even countercurrent on the outer layer of the inner layer high-pressure blowing guide vane are utilized, so that the boundary air flows are accelerated again to form a full-kinetic-energy boundary layer, the resistance and energy dissipation caused by boundary layer separation are reduced, and the flow and the efficiency are improved; the middle of the guide vane is small, and the front side and the rear side are large, so that a drum-shaped channel with better flow performance is realized on a common volute, the middle main flow area of the impeller is relatively increased, the secondary flow is relatively reduced in the front end ring channel and the rear end ring channel, and the secondary flow is further restrained.

Drawings

FIG. 1 is a schematic view of a centrifugal fan according to an embodiment of the present invention;

FIG. 2 is an enlarged schematic view of part I of FIG. 1;

FIG. 3 is a cross-sectional view (radial cross-section) of a centrifugal blower according to an embodiment of the invention;

FIG. 4 is an enlarged schematic view of portion II of FIG. 3;

FIG. 5 is a cross-sectional view (axial cross-section) of a centrifugal blower according to an embodiment of the invention;

FIG. 6 is a schematic diagram of a flow directing assembly of a centrifugal fan according to an embodiment of the invention;

FIG. 7 is a cross-sectional view (radial cross-section, different from FIG. 3) of a centrifugal fan according to an embodiment of the invention;

FIG. 8 is an enlarged schematic view of portion III of FIG. 7;

FIG. 9 is a cross-sectional view of a centrifugal fan (with a deflector assembly mounted in cooperation with an impeller) according to an embodiment of the present invention;

FIG. 10 is a cross-sectional view of a baffle of a centrifugal fan (the cross-section being a vertical plane through or parallel to the axis of the centrifugal fan, the vertical direction being referenced to that shown in FIG. 9) according to an embodiment of the invention;

FIG. 11 is a schematic view of airflow in the direction indicated by the arrow in FIG. 3 in a centrifugal fan according to an embodiment of the invention;

FIG. 12 is a schematic view of airflow within a prior art centrifugal fan in the direction indicated by the arrow in FIG. 3;

FIG. 13 is a schematic illustration of the prior art centrifugal fan in which the high-speed airflow from the impeller is collected along the volute, gradually accumulated and then discharged;

fig. 14 is a graph showing the velocity profile of a centrifugal fan of the prior art under different conditions.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for purposes of describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and because the disclosed embodiments of the present invention may be arranged in different orientations, these directional terms are merely for illustration and should not be construed as limitations, such as "upper", "lower" are not necessarily limited to orientations opposite or coincident with the direction of gravity. Furthermore, features defining "first", "second" may include one or more such features, either explicitly or implicitly.

Referring to fig. 1 to 6 and 9, a centrifugal fan comprises a volute 1 and a flow guiding assembly 2. The volute 1 comprises two cover plates 11 which are arranged at intervals, an annular wall 12 which is arranged between the two cover plates 11, an air inlet 13 is formed in at least one cover plate 11, and an air outlet 14 is formed by enclosing the cover plate 11 and the annular wall 12. An impeller 3 is arranged in the volute 1. The centrifugal fan can be mainly used for a range hood, and can be used for other occasions needing similar power.

The flow guiding assembly 2 comprises a flow guiding sheet 21 and an elastic piece 22, wherein the flow guiding sheet 21 is arranged in the volute 1 and is positioned at the periphery of the impeller 3 at intervals, and the whole preferably can be arc-shaped and protrudes towards the annular wall 12. The guide vane 21 also extends between the two cover plates 11 in a direction parallel to the axial direction of the centrifugal fan, and the guide vane 21 is rotatably connected to the scroll casing 1. The flow guiding assembly 2 further comprises a first rotation shaft 231 and a second rotation shaft 232, each of which is parallel to the axial direction of the centrifugal fan. The guide vane 21 is connected to the scroll 1 along both ends in the circumferential direction of the scroll 1, one of which is connected to the scroll 1 through a first rotation shaft 231 and the other of which is connected to the scroll 1 through a second rotation shaft 232. Each rotating shaft can penetrate out of the spiral case 1 from the spiral case 1, and two ends of each rotating shaft are respectively matched with a cover plate 11 at the corresponding position of the spiral case 1. The second rotating shaft 232 is only in running fit with the volute 1, and cannot slide relatively, and the connection part of the second rotating shaft 232 and the volute 1 is the rotation center of the guide vane 21.

The elastic member 22 is preferably a spring. One of the cover plates 11 of the volute 1 is provided with a fixing groove 111, the fixing groove 111 extends from a position close to the air inlet 13 to a position far away from the air inlet 13 (equivalent to a position close to the impeller 3 to a position far away from the impeller 3 on the projection along the axis of the centrifugal fan), and the end part of the first rotating shaft 231 can be movably matched with the fixing groove 111, so that the first rotating shaft can relatively rotate or relatively slide. In order to facilitate the restoration of the guide vane 21, an elastic member 22 is disposed in the fixing groove 111, one end of the elastic member 22 is fixed to the end of the first rotation shaft 231 passing through the cover plate 11 of the scroll 1, and the other end is fixed to the cover plate 11. When the elastic member 22 is in a free state, the initial position of the first rotating shaft 231 is the initial position, as shown in fig. 1 and 2, when the air deflector 21 is acted by the air flow pressure of the volute 1, the first rotating shaft 231 is moved away from the impeller 3 from the initial position because the second rotating shaft 232 can only rotate relative to the volute 1, the elastic member 22 is compressed, after the impeller 3 stops rotating, the air deflector 21 is not pressed, and the elastic restoring force of the elastic member 22 restores the first rotating shaft 231, so that the air deflector 21 is restored.

The following coordinate system is established in a state when the centrifugal fan is vertically placed: the center of the impeller 3 is taken as an origin O, a line passing through the origin O horizontally is taken as an X axis, a line passing through the origin O vertically is taken as a Y axis, the air outlet and the volute tongue of the volute 1 are positioned in a second quadrant of the coordinate system, and the direction of the X axis is the width direction of the volute 1. The negative direction of the X axis is 0 DEG, the clockwise direction is a positive angle, and the angle of any point in the coordinate system relative to 0 DEG is omega. The axial direction of the impeller 3 is perpendicular to the XOY plane (i.e., the radial plane of the impeller 3).

The angle ω set by the deflector 21 has a value range of [200 °,360 ° ], and when the scroll expansion is small, the ω is too front to generate ineffective flow division, which increases resistance, and when the ω is too rear to influence the airflow of the impeller 3 toward the air outlet 14. The circumferential wrap angle of the guide vane 21 is θ, the value range of θ is [50 °,160 ° ], and when θ is too small, only partial secondary flow can be suppressed, the suppression effect of secondary flow can be weakened, and when θ is too large, the flexibility of adjustment according to the spring and the pressure difference is reduced, and the flow resistance is correspondingly increased.

By providing the flow deflector 21, the development of secondary flow at the lobed wheel face 31 and loss due to flow path diffusion during volute expansion can be reduced, see fig. 10. In the conventional solution without the guide vane, a vortex (secondary flow) is generated at both axial ends of the impeller outflow surface 31, see fig. 11. The air blowing holes 211 are formed in the guide vane 21, and the air blowing holes 211 extend between the two cover plates 11 and penetrate through the thickness of the guide vane 21, namely penetrate through both sides of the guide vane 21 facing and away from the annular wall 12. The air hole 211 gradually reduces in diameter from the side toward the impeller 3 (i.e., the side away from the annular wall 12) to the side toward the annular wall 12 (i.e., the outside), and serves to accelerate the air flow. The boundary layer can be actively controlled, and the inner layer high-pressure gas (arrow A in fig. 3) is blown through the air blowing holes 211 to blow the boundary air flow (arrow B in fig. 3) with low speed or 0 and even countercurrent outside the guide vane 21, so that the boundary air flow is accelerated again to form a full-kinetic boundary layer (arrow C in fig. 3), and the resistance and energy dissipation caused by boundary layer separation are reduced, and the flow and the efficiency are improved.

Referring to fig. 9 again, the tangential included angle between the air hole 211 and the deflector 21 is α, the value range of α is [3 °,60 ° ], the re-acceleration effect on the boundary layer after the inner-layer air flow is blown out is weakened, and the air flow is easily accelerated and weakened by the jet flow when α is too large. The width of the outlet of the air blowing hole 211 is t1, the value range of t1 is 0.3-5 mm, the outlet of the air blowing hole 211 mainly adopts slit flow, the size is the section size of the main internal and external differential pressure air flow, the flow rate of the too small air flow is too large, the blowing speed is weakened, and the accelerating effect is not achieved. The width of the inlet of the air blowing hole 211 is t2, the value range of t2 is 2-15 t1, the inlet of the air blowing hole 211 is mainly convenient for the air flow to flow into the gap flow, the ratio is too large, abnormal noise possibly exists, and if the ratio is too small, the contraction of the air flow is insufficient, so that the accelerating effect is poor.

In addition, since the elastic member 22 is provided, the guide vane 21 can dynamically adjust and balance by using the elastic force and the difference between the inner and outer lamination of the elastic member 22, automatically adjust the deflection angle according to the working conditions, and automatically deflect outwards at high rotation speeds, see fig. 6 and 7, the guide vane 21 rotates around the second rotation shaft 232, the first rotation shaft 231 moves along the fixing groove 111 towards the annular wall 12, the elastic member 22 is compressed, the cross-sectional area of the outer channel is intentionally reduced, the reduction channel accelerates the air flow outside, and the loss of the collecting air flow of the outer layer due to the long path (the collecting path of the air flow of the inner layer is short, and the loss is relatively small).

Referring again to fig. 4, 5 and 10, along the axial direction of the centrifugal fan, the guide vane 21 presents a shape with thin middle and thick two ends, so that the middle main flow area of the corresponding impeller 3 is relatively increased, the secondary flow is relatively reduced in the front and rear end ring channels (the front and rear end ring area channels are artificially reduced) of the impeller 3, the development of the secondary flow is restrained, and the secondary flow is further restrained. Where Z in fig. 10 is the axial direction of the centrifugal fan, the upper and lower drum lines of the cross section of the guide vane 21 preferably adopt a conic, for example, y=az ² +bz+c, and a, b, and c are constants.

Claims (14)

1. A centrifugal fan comprising a volute (1) and an impeller (3) arranged in the volute (1), wherein the volute (1) comprises two cover plates (11) which are arranged at intervals and a ring wall (12) arranged between the two cover plates (11); the method is characterized in that:

the centrifugal fan further comprises a flow guide assembly (2), the flow guide assembly (2) comprises flow guide sheets (21) which are arranged on the periphery of the impeller (3) at intervals, and the flow guide sheets (21) extend between the two cover plates (11) along the direction parallel to the axial direction of the centrifugal fan.

2. The centrifugal fan according to claim 1, wherein: the guide vane (21) is rotationally connected with the volute (1), and the rotation axis of the guide vane (21) is parallel to the axial direction of the centrifugal fan.

3. The centrifugal fan according to claim 2, wherein: the flow guide assembly (2) further comprises a first rotating shaft (231) and a second rotating shaft (232), one end part of the flow guide sheet (21) along the circumferential direction of the volute (1) is connected with the volute (1) through the first rotating shaft (231), the other end part of the flow guide sheet (21) along the circumferential direction of the volute (1) is connected with the volute (1) through the second rotating shaft (232), and the connecting part of the second rotating shaft (232) and the volute (1) is the rotating center of the flow guide sheet (21).

4. A centrifugal fan according to claim 3, wherein: one of the cover plates (11) of the volute (1) is provided with a fixed groove (111), and the first rotating shaft (231) is movably matched with the fixed groove (111).

5. The centrifugal fan according to claim 4, wherein: the flow guiding assembly (2) further comprises an elastic piece (22), the elastic piece (22) is arranged in the fixing groove (111), one end of the elastic piece (22) is fixed with the first rotating shaft (231), and the other end of the elastic piece (22) is fixed with the cover plate (11).

6. The centrifugal fan according to claim 1, wherein: the air blowing holes (211) are formed in the guide vane (21), and the air blowing holes (211) extend between the two cover plates (11) and penetrate through the thickness of the guide vane (21).

7. The centrifugal fan according to claim 6, wherein: the caliber of the air blowing hole (211) gradually decreases from the side of the guide vane (21) away from the annular wall (12) to the side of the annular wall (12).

8. The centrifugal fan according to claim 7, wherein: the width of the outlet of the air blowing hole (211) facing the side of the annular wall (12) is t1, and the value range of t1 is 0.3-5 mm.

9. The centrifugal fan according to claim 8, wherein: the width of the air blowing hole (211) at the inlet of one side of the impeller (3) is t2, and the value range of t2 is 2-15 t1.

10. The centrifugal fan according to claim 6, wherein: the tangential included angle between the air blowing hole (211) and the guide vane (21) is alpha, and the value range of alpha is [3 degrees, 60 degrees ].

11. The centrifugal fan according to claim 1, wherein: along the axial direction of the centrifugal fan, the guide vane (21) is in a shape that the thickness of the middle part is smaller than that of the two ends.

12. The centrifugal fan according to claim 1, wherein: the following coordinate system is established in a state when the centrifugal fan is vertically placed: the center of the impeller (3) is taken as an origin (O), a line passing through the origin (O) horizontally is taken as an X axis, a line passing through the origin (O) vertically is taken as a Y axis, an air outlet (14) of the volute (1) is positioned in a second quadrant of the coordinate system, the negative direction of the X axis is 0 degrees, the clockwise direction is taken as a positive angle, the negative angle of the deflector (21) relative to the X axis is omega, and the value range of omega is [200 degrees, 360 degrees ].

13. The centrifugal fan according to claim 1, wherein: the circumferential wrap angle of the guide vane (21) is theta, and the value range of theta is [50 degrees, 160 degrees ].

14. A range hood, characterized in that: use of a centrifugal fan according to any one of claims 1-12.