EP1070849B1 - Axial flow fan - Google Patents
Axial flow fan Download PDFInfo
- Publication number
- EP1070849B1 EP1070849B1 EP20000114849 EP00114849A EP1070849B1 EP 1070849 B1 EP1070849 B1 EP 1070849B1 EP 20000114849 EP20000114849 EP 20000114849 EP 00114849 A EP00114849 A EP 00114849A EP 1070849 B1 EP1070849 B1 EP 1070849B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- axial flow
- blade
- flow fan
- blades
- fan
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/40—Casings; Connections of working fluid
- F04D29/52—Casings; Connections of working fluid for axial pumps
- F04D29/54—Fluid-guiding means, e.g. diffusers
- F04D29/541—Specially adapted for elastic fluid pumps
- F04D29/545—Ducts
- F04D29/547—Ducts having a special shape in order to influence fluid flow
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/26—Rotors specially for elastic fluids
- F04D29/32—Rotors specially for elastic fluids for axial flow pumps
- F04D29/325—Rotors specially for elastic fluids for axial flow pumps for axial flow fans
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/26—Rotors specially for elastic fluids
- F04D29/32—Rotors specially for elastic fluids for axial flow pumps
- F04D29/38—Blades
- F04D29/384—Blades characterised by form
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
- F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
- F04D29/666—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps by means of rotor construction or layout, e.g. unequal distribution of blades or vanes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D2317/00—Details or arrangements for circulating cooling fluids; Details or arrangements for circulating gas, e.g. air, within refrigerated spaces, not provided for in other groups of this subclass
- F25D2317/06—Details or arrangements for circulating cooling fluids; Details or arrangements for circulating gas, e.g. air, within refrigerated spaces, not provided for in other groups of this subclass with forced air circulation
- F25D2317/068—Details or arrangements for circulating cooling fluids; Details or arrangements for circulating gas, e.g. air, within refrigerated spaces, not provided for in other groups of this subclass with forced air circulation characterised by the fans
- F25D2317/0681—Details thereof
Definitions
- the present invention relates, in general, to an axial flow fan for refrigerators, used for feeding cool air from an evaporator into both a freezer compartment and a fresh compartment in refrigerators, and, more particularly, to an axial flow fan for refrigerators optimally designed in a variety of designing factors, such as the number of blades, hub ratio, sweep angle, pitch angle and maximum camber ratio, thus accomplishing a reduction in operational noise of the refrigerators and in vortex formed around the fan and thereby finally reducing its flow resistance.
- Fig. 1 is a perspective view of a conventional axial flow fan for refrigerators.
- Fig. 2 is a sectional view of the blade tip of the conventional axial flow fan.
- the conventional axial flow fan comprises a hub 1, which is firmly mounted to the rotating shaft of the drive motor, with a plurality of blades 5 regularly fixed around the hub 1.
- the number of the blades 5 is typically set to three to five, with a hub ratio of the hub diameter to the outer diameter of the fan being set to 0.25 ⁇ 0.3 and a pitch angle of each blade 5 ranging from 25° to 35°.
- the pitch angle is formed between the radial straight line of each blade 5 and another straight line extending from the blade leading edge to the blade trailing edge. This pitch angle is determined by an inclination of each blade 5 relative to a plane perpendicular to the rotating axis of the fan.
- each trailing blade 5 undesirably confronts the vortex stream formed by a leading blade 5, thus generating fluid noise.
- BVI blade vortex interaction
- the blade tip 5a of an axial flow fan forms a smoothly curved cross-section consisting of a pressure surface 5b and a negative pressure surface 5c.
- air pressure caused by an air current acts on the pressure surface 5b, while negative pressure acts on the negative pressure surface 5c opposite to the surface 5b. Due to such a smoothly curved cross-section of the blade tip 5a, static pressure of the air current flowing from the pressure surface 5b to the negative pressure surface 5c is restored abruptly and quickly.
- the blade passing frequency (BPF) which is the main frequency of fluid noise caused by a collision of the air current against the blades 5 during operation of the fan and is calculated by a plus integral times of the result of multiplication of the number of blades 5 by rpm of the fan, is reduced to a low level.
- the conventional doors of a refrigerator used for intercepting noise leaking from the compressor and fan of the machine room and from the axial flow fan used for accomplishing a circulation of cool air within the refrigerator into the outside of the cabinet of the refrigerator through a variety of passages, have been typically designed to intercept high frequency noise of not lower than 700Hz. Therefore, it is almost impossible for such conventional doors to intercept such a low blade passing frequency (BPF) generated from the conventional axial flow fan.
- BPF blade passing frequency
- the conventional axial flow fan typically generates operational noise having a large low frequency band and a low BPF, and so the conventional doors of refrigerators fail to accomplish a desired noise intercepting effect in the case of operational noise of the conventional axial flow fan, but regrettably allow the noise to leak from the axial flow fan to the outside of the cabinet of the refrigerator. Such operational noise disturbs those around the refrigerator.
- Fig. 3 is a front view, showing a conventional shroud installed around the axial flow fan for refrigerators.
- Fig. 4 is a sectional view, showing the construction of the conventional shroud for axial flow fans.
- the conventional shroud 7 is installed around the blades 5 of the fan, with an annular rim 9 being formed closely around the blades 5 while being bulged to the front of the fan in an air inlet direction.
- Such a conventional shroud 7 is installed around the blade tips 5a of the fan while leaving a predetermined annular gap between the tips 5a and the inside edge of the shroud 7.
- the above shroud 7 guides the cool air current when the air current flows in an axial direction of the fan during operation.
- the annular rim 9 formed closely around the blades 5 while being bulged to the front of the fan in the air inlet direction, induces a smooth airflow during operation of the fan. That is, the cool air current flows over the bulged annular rim 9, thus smoothly flowing on the shroud 7 without forming an undesirable flow resistance.
- the conventional shroud 7 has the following problem. That is, since the annular rim 9 is formed closely around the blades 5 while being bulged to the front of the fan in the air inlet direction as best seen in Fig. 5 , the rear surface of the rim 9 in the air outlet side of the fan is concaved, and so cool air discharged from the fan comes into undesirable collision against the concave surface of the rim 9 and forms an intensive and large-scaled vortex, thus finally increasing the flow loss.
- the annular rim 9, positioned around the blades of the axial flow fan has so large a diameter that the inlet air is partially brought into collision against the concave surface of the rim 9 while undesirably forming an intensive and large-scaled vortex around the concave surface, thus resulting in a substantial flow loss during operation of the fan.
- EP 0 913 584 A1 which represents the closest prior art discloses an axial flow fan comprising seven fan blades symmetrically arranged around a hub. Each blade has the shape of an airfoil.
- EP 0 557 239 A2 discloses an axial flow fan provided with a plurality of fan blades having also an airfoil cross section profile.
- the blade pitch angle decreases from the blade root to the blade tip and a mid chord skew angle is five to six tenths of a blade spacing angle.
- EP 0 583 091 A2 discloses an axial fan having five fan blades and a hub ratio which is about 30% of the outer diameter of the fan.
- EP 0 174 487 A1 discloses an axial fan having seven fan blades each of which is curved in a forward direction and gives a technical teaching concerning mathematical equations for defining the curved design of the blade surface.
- the present invention has been made keeping in mind the above problems occurring in the prior art, and the object of the present invention is to provide an axial flow fan for refrigerators, which is optimally designed in a variety of designing factors, such as the number of blades, hub ratio, sweep angle, pitch angle and maximum camber ratio, thus accomplishing a desired reduction in operational noise of the refrigerators and in vortex formed around the fan and thereby finally reducing its flow resistance.
- Another object of the present invention is to provide an axial flow fan for refrigerators, which is improved in the structure of its shroud so as to be free from a formation of a vortex in the discharged cool air current in the air outlet side of the fan, thus minimizing its flow loss.
- the primary embodiment of the present invention provides an axial flow fan for refrigerators, comprising a hub mounted to the rotating shaft of a drive motor, with at least seven blades regularly fixed around the hub, wherein a variety of designing factors of the blades as defined in the characterizing portion of claim 1, such as the number of plates, hub ratio, sweep angle, pitch angle and maximum camber ratio, are optimally designed to allow a smooth flow of cool air agreeable with both the large pressure loss and complex flow passage of refrigerators while accomplishing a reduction in air flow noise of the refrigerators.
- an axial flow fan for refrigerators comprising a hub mounted to a rotating shaft of a motor, with a plurality of blades regularly fixed around the hub and a shroud installed around the blades to guide an air current, wherein the shroud consists of an annular rim formed closely around the blades while being bulged to the front of the fan in an air inlet direction, and a vortex prevention means provided on a concave back surface of the annular rim for preventing discharged air from forming a vortex stream in back of the fan.
- Fig. 6 is a perspective view of an axial flow fan for refrigerators in accordance with the preferred embodiment of the present invention.
- Figs. 7a and 7b are front and side views of the axial flow fan according to the preferred embodiment of this invention.
- Figs. 8a and 8b are sectional views, showing the shape of a blade included in the axial flow fan according to the preferred embodiment of this invention.
- Fig. 9 is a sectional view of the blade tip of the axial flow fan according to this invention.
- the axial flow fan of this invention comprises a hub 51, which is firmly mounted to the rotating shaft of the drive motor, with a plurality of blades 55 regularly fixed around the hub 51.
- the number of the blades 55 is preferably set to at least seven.
- the hub ratio of the hub diameter ID to the outer diameter OD of the fan is set to 0.45 ⁇ 0.55, with the diameter ID of the hub 51 being set to 55 mm ⁇ 5 mm and the outer diameter OD of the fan being set to 110 mm ⁇ 10 mm.
- each blade 55 ranges from 30° to 34°.
- each blade 55 is an angle formed between a straight line extending between the center of the blade hub 55b and the center of the blade tip 55a and another straight line extending between the center of the blade hub 55b and the center of the hub 51.
- This sweep angle ⁇ of each blade 55 expresses the tilt of the blade 55 in the rotating direction of the blades 55.
- the pitch angle ⁇ of each blade 55 is 32° ⁇ 2° at the blade tip 55a and 45° ⁇ 2° at the blade hub 55b.
- each blade 55 is an angle formed between a straight line extending between the blade leading edge 57a to the blade trailing edge 57b and an X-axis perpendicular to a Z-axis that is the rotating axis of the fan.
- This pitch angle ⁇ of each blade 55 expresses the slope of the blade 55 relative to a plane perpendicular to the Z-axis.
- the maximum camber position of each blade 55 is set to 0.65, with the camber positions being uniformly distributed on each blade 55 from the blade hub 55b to the blade tip 55a.
- the maximum camber ratio of each blade 55 is 11.5% at the blade tip 55a and 8% at the blade hub 55b.
- the maximum camber position of each blade 55 is indicated as a ratio(CP/CX) of the distance CP from the blade leading edge 57a to a point being spaced furthest from the blade 55 on a cord CL that is a straight line extending from the blade leading edge 57a to the blade trailing edge 57b to the length CX of the cord CL.
- the distance between said straight line and said position on the blade 55 is the maximum camber C.
- the maximum camber ratio is a ratio of the maximum camber C to the cord length CX.
- each blade 55 is zero. This rake angle expresses the slope of the blade 55 relative to a positive axial direction.
- each blade of the axial flow fan when designing each blade of the axial flow fan to have a large sweep angle ⁇ , a large pitch angle ⁇ , and a large maximum camber ratio, it is possible to desirably reduce fluid noise generated by the fan during operation.
- the blade passing frequency (BPF) which is the main frequency of fluid noise caused by a collision of the air current against the blades 55 during operation of the fan and is calculated by a plus integral times of the result of multiplication of the number of blades 55 by rpm of the fan, is increased to a high level. Therefore, the doors of a refrigerator typically designed to intercept high frequency noise effectively intercept such a BPF. It is thus possible to desirably reduce operational noise of refrigerators.
- the blade tip 55a of each blade 55 of the axial flow fan forms a curved cross-section consisting of a pressure surface 56b and a negative pressure surface 56a.
- air pressure caused by an air current acts on the pressure surface 56b, while negative pressure acts on the negative pressure surface 56a opposite to the surface 56b.
- the blade tip 55a is curved from the pressure surface 56b to the negative pressure surface 56a while forming a predetermined radius of curvature. In such a case, it is preferable to set the radius of curvature of the blade tip 55a to the same as the radius of not larger than 0.1 times of the diameter of the fan.
- Figs. 10 to 14 are graphs showing operational noise of the axial flow fan of the invention as a function of a variety of designing factors of the axial flow fan.
- Fig. 10 is a graph showing operational noise of the axial flow fan as a function of the hub ratio of the fan. This graph shows that it is possible to accomplish a desired low operational noise of 22.3 ⁇ 0.2dB when the hub ratio of the blades 55 is set to 0.45 ⁇ 0.55. Particularly when setting the hub ratio of the blades to 0.5, it is possible to accomplish a minimum operational noise of the fan.
- Fig. 11 is a graph showing operational noise of the axial flow fan as a function of the sweep angle ⁇ of the blades 55. This graph shows that it is possible to accomplish a desired minimum operational noise of 22.4 ⁇ 0.2dB when the sweep angle ⁇ of each blade 55 is set to 32° ⁇ 34°.
- Fig. 12 is a graph showing the operational noise of the axial flow fan as a function of the pitch angle ⁇ of the blades 55. This graph shows that it is possible to accomplish a desired minimum operational noise of 22.3 ⁇ 0.2dB when the pitch angle ⁇ of each blade 55 is set to 32° ⁇ 2° at the blade tip 55a and to 45° ⁇ 2° at the blade hub (55b).
- Fig. 13 is a graph showing the operational noise of the axial flow fan as a function of the maximum camber position of the axial flow fan. This graph shows that it is possible to accomplish a desired minimum operational noise of 22.5dB when the maximum camber position is set to 0.65, with the maximum camber ratio of each blade 55 being set to 11.5% at the blade tip 55a and to 8% at the blade hub 55b.
- Fig. 14 is a graph showing operational noise of the axial flow fan according to the invention as a function of the rake angle of the axial flow fan. This graph shows that it is possible to accomplish a desired minimum operational noise of 23dB when the rake angle is set to zero.
- the shrouds of this invention effectively reduce the operational noise of the axial flow fan by 1.2dB to 2.3dB in comparison with the conventional shroud.
- the present invention provides an axial flow fan for refrigerators.
- This axial flow fan is optimally designed in a variety of designing factors, such as the number of blades, hub ratio, sweep angle, pitch angle and maximum camber ratio, thus allowing a smooth flow of cool air agreeable with both the large pressure loss and complex flow passage of refrigerators while accomplishing a reduction in air flow noise of the refrigerators.
- the axial flow fan of this invention increases the blade passing frequency (BPF), which is the main frequency of fluid noise caused by a collision of the air current against the blades during operation of the fan, at least two times.
- BPF blade passing frequency
- the doors of a refrigerator typically designed to intercept high frequency noise effectively intercept such a high level BPF. It is thus possible to desirably reduce operational noise of refrigerators.
- the blade tip of each blade is curved from its pressure surface to its negative pressure surface while forming a predetermined radius of curvature.
- the blades during rotation are thus less likely to form a vortex stream in their trailing positions and desirably reduce the blade vortex interaction (BVI), in which each trailing blade undesirably confronts a vortex stream formed by a leading blade during operation of a conventional axial flow fan, thus generating fluid noise.
- BVI blade vortex interaction
- a vortex prevention means is provided on the back surface of the shroud's annular rim for preventing an undesirable collision of a discharged air current against the concave back surface of the rim, thus preventing a formation of a vortex stream in back of the rim and reducing air flow loss of the fan, and reducing operational noise of the fan.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Cold Air Circulating Systems And Constructional Details In Refrigerators (AREA)
Description
- The present invention relates, in general, to an axial flow fan for refrigerators, used for feeding cool air from an evaporator into both a freezer compartment and a fresh compartment in refrigerators, and, more particularly, to an axial flow fan for refrigerators optimally designed in a variety of designing factors, such as the number of blades, hub ratio, sweep angle, pitch angle and maximum camber ratio, thus accomplishing a reduction in operational noise of the refrigerators and in vortex formed around the fan and thereby finally reducing its flow resistance.
-
Fig. 1 is a perspective view of a conventional axial flow fan for refrigerators.Fig. 2 is a sectional view of the blade tip of the conventional axial flow fan. - The construction and operation of such a conventional axial flow fan will be described herein below in conjunction with
Figs. 1 and 2 . - As shown in the drawings, the conventional axial flow fan comprises a
hub 1, which is firmly mounted to the rotating shaft of the drive motor, with a plurality ofblades 5 regularly fixed around thehub 1. - In the conventional axial flow fan, the number of the
blades 5 is typically set to three to five, with a hub ratio of the hub diameter to the outer diameter of the fan being set to 0.25 ∼ 0.3 and a pitch angle of eachblade 5 ranging from 25° to 35°. - In such an axial flow fan, the pitch angle is formed between the radial straight line of each
blade 5 and another straight line extending from the blade leading edge to the blade trailing edge. This pitch angle is determined by an inclination of eachblade 5 relative to a plane perpendicular to the rotating axis of the fan. - However, such a conventional axial flow fan for refrigerators has been designed while considering only some designing factors, such as the number of
blades 5, hub ratio and pitch angle, and so it is almost impossible for the axial flow fan to form appropriate flow agreeable with the large pressure loss and the complex flow passage required in large-sized modern refrigerators. This finally increases operational noise of such large-sized refrigerators. - In addition, during operation of such a conventional axial flow fan, each
trailing blade 5 undesirably confronts the vortex stream formed by a leadingblade 5, thus generating fluid noise. In the art of this invention, such a phenomenon is so-called "blade vortex interaction (BVI)". - In the recent designing process for axial flow fans, a technique for accomplishing a desired reduction in BVI has been actively studied.
- As shown in
Fig. 2 , theblade tip 5a of an axial flow fan forms a smoothly curved cross-section consisting of apressure surface 5b and a negative pressure surface 5c. In operation of the fan, air pressure caused by an air current acts on thepressure surface 5b, while negative pressure acts on the negative pressure surface 5c opposite to thesurface 5b. Due to such a smoothly curved cross-section of theblade tip 5a, static pressure of the air current flowing from thepressure surface 5b to the negative pressure surface 5c is restored abruptly and quickly. - Therefore, the blade passing frequency (BPF), which is the main frequency of fluid noise caused by a collision of the air current against the
blades 5 during operation of the fan and is calculated by a plus integral times of the result of multiplication of the number ofblades 5 by rpm of the fan, is reduced to a low level. - However, the conventional doors of a refrigerator, used for intercepting noise leaking from the compressor and fan of the machine room and from the axial flow fan used for accomplishing a circulation of cool air within the refrigerator into the outside of the cabinet of the refrigerator through a variety of passages, have been typically designed to intercept high frequency noise of not lower than 700Hz. Therefore, it is almost impossible for such conventional doors to intercept such a low blade passing frequency (BPF) generated from the conventional axial flow fan.
- In other words, the conventional axial flow fan typically generates operational noise having a large low frequency band and a low BPF, and so the conventional doors of refrigerators fail to accomplish a desired noise intercepting effect in the case of operational noise of the conventional axial flow fan, but regrettably allow the noise to leak from the axial flow fan to the outside of the cabinet of the refrigerator. Such operational noise disturbs those around the refrigerator.
-
Fig. 3 is a front view, showing a conventional shroud installed around the axial flow fan for refrigerators.Fig. 4 is a sectional view, showing the construction of the conventional shroud for axial flow fans. - As shown in the drawings, the
conventional shroud 7 is installed around theblades 5 of the fan, with anannular rim 9 being formed closely around theblades 5 while being bulged to the front of the fan in an air inlet direction. - Such a
conventional shroud 7 is installed around theblade tips 5a of the fan while leaving a predetermined annular gap between thetips 5a and the inside edge of theshroud 7. Theabove shroud 7 guides the cool air current when the air current flows in an axial direction of the fan during operation. - On the other hand, the
annular rim 9, formed closely around theblades 5 while being bulged to the front of the fan in the air inlet direction, induces a smooth airflow during operation of the fan. That is, the cool air current flows over the bulgedannular rim 9, thus smoothly flowing on theshroud 7 without forming an undesirable flow resistance. - However, the
conventional shroud 7 has the following problem. That is, since theannular rim 9 is formed closely around theblades 5 while being bulged to the front of the fan in the air inlet direction as best seen inFig. 5 , the rear surface of therim 9 in the air outlet side of the fan is concaved, and so cool air discharged from the fan comes into undesirable collision against the concave surface of therim 9 and forms an intensive and large-scaled vortex, thus finally increasing the flow loss. - That is, the
annular rim 9, positioned around the blades of the axial flow fan, has so large a diameter that the inlet air is partially brought into collision against the concave surface of therim 9 while undesirably forming an intensive and large-scaled vortex around the concave surface, thus resulting in a substantial flow loss during operation of the fan. -
EP 0 913 584 A1 -
EP 0 557 239 A2 -
DE 196 31 093 A1 discloses an axial fan with seven fan blades having a small hub ratio. -
EP 0 583 091 A2 -
EP 0 174 487 A1 -
DE 85 25 674 U1 discloses an axial fan having a hub ratio of about 30% of the outer fan diameter. - Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and the object of the present invention is to provide an axial flow fan for refrigerators, which is optimally designed in a variety of designing factors, such as the number of blades, hub ratio, sweep angle, pitch angle and maximum camber ratio, thus accomplishing a desired reduction in operational noise of the refrigerators and in vortex formed around the fan and thereby finally reducing its flow resistance.
- This object is achieved by an axial flow fan with the features of
claim 1. - Another object of the present invention is to provide an axial flow fan for refrigerators, which is improved in the structure of its shroud so as to be free from a formation of a vortex in the discharged cool air current in the air outlet side of the fan, thus minimizing its flow loss.
- In order to accomplish the above object, the primary embodiment of the present invention provides an axial flow fan for refrigerators, comprising a hub mounted to the rotating shaft of a drive motor, with at least seven blades regularly fixed around the hub, wherein a variety of designing factors of the blades as defined in the characterizing portion of
claim 1, such as the number of plates, hub ratio, sweep angle, pitch angle and maximum camber ratio, are optimally designed to allow a smooth flow of cool air agreeable with both the large pressure loss and complex flow passage of refrigerators while accomplishing a reduction in air flow noise of the refrigerators. - Another embodiment of this invention provides an axial flow fan for refrigerators, comprising a hub mounted to a rotating shaft of a motor, with a plurality of blades regularly fixed around the hub and a shroud installed around the blades to guide an air current, wherein the shroud consists of an annular rim formed closely around the blades while being bulged to the front of the fan in an air inlet direction, and a vortex prevention means provided on a concave back surface of the annular rim for preventing discharged air from forming a vortex stream in back of the fan.
- The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
-
Fig. 1 is a perspective view of a conventional axial flow fan for refrigerators; -
Fig. 2 is a sectional view of the blade tip of the conventional axial flow fan; -
Fig. 3 is a front view, showing a conventional shroud installed around the axial flow fan for refrigerators; -
Fig. 4 is a sectional view taken along the line A-A ofFig. 3 , showing the construction of the conventional shroud for axial flow fans; -
Fig. 5 is a view, showing an air current formed around the conventional shroud; -
Fig. 6 is a perspective view of an axial flow fan for refrigerators in accordance with the preferred embodiment of the present invention; -
Figs. 7a and 7b are front and side views of the axial flow fan according to the preferred embodiment of this invention; -
Figs. 8a and 8b are sectional views, showing the shape of a blade included in the axial flow fan according to the preferred embodiment of this invention; -
Fig. 9 is a sectional view of the blade tip of the axial flow fan according to this invention; -
Fig. 10 is a graph showing operational noise of the axial flow fan according to the invention as a function of the hub ratio of the axial flow fan; -
Fig. 11 is a graph showing operational noise of the axial flow fan according to the invention as a function of the sweep angle of the axial flow fan; -
Fig. 12 is a graph showing operational noise of the axial flow fan according to the invention as a function of the pitch angle of the axial flow fan; -
Fig. 13 is a graph showing operational noise of the axial flow fan according to the invention as a function of the maximum camber position of the axial flow fan; -
Fig. 14 is a graph showing operational noise of the axial flow fan according to the invention as a function of the rake angle of the axial flow fan; and -
Fig. 15 is a graph, comparatively showing the operational noise characteristics of the front sections of refrigerators using a conventional axial flow fan and the axial flow fan of this invention. -
Fig. 6 is a perspective view of an axial flow fan for refrigerators in accordance with the preferred embodiment of the present invention.Figs. 7a and 7b are front and side views of the axial flow fan according to the preferred embodiment of this invention.Figs. 8a and 8b are sectional views, showing the shape of a blade included in the axial flow fan according to the preferred embodiment of this invention.Fig. 9 is a sectional view of the blade tip of the axial flow fan according to this invention. - The construction and operation of the axial flow fan for refrigerators according to the preferred embodiment of this invention will be described herein below in conjunction with
Figs. 6 to 9 . - As shown in the drawings, the axial flow fan of this invention comprises a
hub 51, which is firmly mounted to the rotating shaft of the drive motor, with a plurality ofblades 55 regularly fixed around thehub 51. - In the axial flow fan of this invention, the number of the
blades 55 is preferably set to at least seven. When considering a variety of factors, such as desired operational efficiency, desired air volume and desired air pressure of the fan, it is most preferable to set the number of theblades 55 to nine. - In the axial flow fan of this invention, the hub ratio of the hub diameter ID to the outer diameter OD of the fan is set to 0.45 ∼ 0.55, with the diameter ID of the
hub 51 being set to 55 mm ± 5 mm and the outer diameter OD of the fan being set to 110 mm ± 10 mm. - In addition, the sweep angle θ of each
blade 55 ranges from 30° to 34°. - The above sweep angle θ of each
blade 55 is an angle formed between a straight line extending between the center of theblade hub 55b and the center of theblade tip 55a and another straight line extending between the center of theblade hub 55b and the center of thehub 51. This sweep angle θ of eachblade 55 expresses the tilt of theblade 55 in the rotating direction of theblades 55. - In the axial flow fan of this invention, the pitch angle Ψ of each
blade 55 is 32° ± 2° at theblade tip blade hub 55b. - The above pitch angle Ψ of each
blade 55 is an angle formed between a straight line extending between theblade leading edge 57a to theblade trailing edge 57b and an X-axis perpendicular to a Z-axis that is the rotating axis of the fan. This pitch angle Ψ of eachblade 55 expresses the slope of theblade 55 relative to a plane perpendicular to the Z-axis. - On the other hand, the maximum camber position of each
blade 55 is set to 0.65, with the camber positions being uniformly distributed on eachblade 55 from theblade hub 55b to theblade tip 55a. In addition, the maximum camber ratio of eachblade 55 is 11.5% at theblade tip blade hub 55b. - In such a case, the maximum camber position of each
blade 55 is indicated as a ratio(CP/CX) of the distance CP from theblade leading edge 57a to a point being spaced furthest from theblade 55 on a cord CL that is a straight line extending from theblade leading edge 57a to theblade trailing edge 57b to the length CX of the cord CL. The distance between said straight line and said position on theblade 55 is the maximum camber C. The maximum camber ratio is a ratio of the maximum camber C to the cord length CX. - In addition, the rake angle of each
blade 55 is zero. This rake angle expresses the slope of theblade 55 relative to a positive axial direction. - As described above, when designing each blade of the axial flow fan to have a large sweep angle θ, a large pitch angle Ψ, and a large maximum camber ratio, it is possible to desirably reduce fluid noise generated by the fan during operation.
- In addition, the blade passing frequency (BPF), which is the main frequency of fluid noise caused by a collision of the air current against the
blades 55 during operation of the fan and is calculated by a plus integral times of the result of multiplication of the number ofblades 55 by rpm of the fan, is increased to a high level. Therefore, the doors of a refrigerator typically designed to intercept high frequency noise effectively intercept such a BPF. It is thus possible to desirably reduce operational noise of refrigerators. - As shown in
Fig. 9 , theblade tip 55a of eachblade 55 of the axial flow fan forms a curved cross-section consisting of apressure surface 56b and anegative pressure surface 56a. In operation of the fan, air pressure caused by an air current acts on thepressure surface 56b, while negative pressure acts on thenegative pressure surface 56a opposite to thesurface 56b. In the present invention, theblade tip 55a is curved from thepressure surface 56b to thenegative pressure surface 56a while forming a predetermined radius of curvature. In such a case, it is preferable to set the radius of curvature of theblade tip 55a to the same as the radius of not larger than 0.1 times of the diameter of the fan. - When designing the
blade tip 55a as described above, static pressure of the air current flowing from thepressure surface 56b to thenegative pressure surface 56a is restored slowly and gently. Theblades 55 during rotation are thus less likely to form a vortex stream in their trailing positions and desirably reduce the blade vortex interaction (BVI). -
Figs. 10 to 14 are graphs showing operational noise of the axial flow fan of the invention as a function of a variety of designing factors of the axial flow fan. - That is,
Fig. 10 is a graph showing operational noise of the axial flow fan as a function of the hub ratio of the fan. This graph shows that it is possible to accomplish a desired low operational noise of 22.3 ± 0.2dB when the hub ratio of theblades 55 is set to 0.45 ∼ 0.55. Particularly when setting the hub ratio of the blades to 0.5, it is possible to accomplish a minimum operational noise of the fan. -
Fig. 11 is a graph showing operational noise of the axial flow fan as a function of the sweep angle θ of theblades 55. This graph shows that it is possible to accomplish a desired minimum operational noise of 22.4 ± 0.2dB when the sweep angle θ of eachblade 55 is set to 32° ∼ 34°. -
Fig. 12 is a graph showing the operational noise of the axial flow fan as a function of the pitch angle Ψ of theblades 55. This graph shows that it is possible to accomplish a desired minimum operational noise of 22.3 ± 0.2dB when the pitch angle Ψ of eachblade 55 is set to 32° ± 2° at theblade tip 55a and to 45° ± 2° at the blade hub (55b). -
Fig. 13 is a graph showing the operational noise of the axial flow fan as a function of the maximum camber position of the axial flow fan. This graph shows that it is possible to accomplish a desired minimum operational noise of 22.5dB when the maximum camber position is set to 0.65, with the maximum camber ratio of eachblade 55 being set to 11.5% at theblade tip 55a and to 8% at theblade hub 55b. -
Fig. 14 is a graph showing operational noise of the axial flow fan according to the invention as a function of the rake angle of the axial flow fan. This graph shows that it is possible to accomplish a desired minimum operational noise of 23dB when the rake angle is set to zero. - When such an axial flow fan of this invention and a conventional axial flow fan are used in refrigerators, it is possible to obtain a graph of
Fig. 15 , comparatively showing the operational noise characteristics of the front sections of the refrigerators. In the graph ofFig. 15 , the curve "a" is an operational characteristic curve of a refrigerator having the axial flow fan of this invention, while the curve "b" is an operational characteristic curve of a refrigerator having the conventional axial flow fan. - As shown in the graph of
Fig. 15 , it is possible to desirably reduce operational noise of the front section of the refrigerator using the axial flow fan of this invention by about 4.3dB(A) in comparison with the refrigerator using the conventional axial flow fan. - In a brief description, the shrouds of this invention effectively reduce the operational noise of the axial flow fan by 1.2dB to 2.3dB in comparison with the conventional shroud.
- As described above, the present invention provides an axial flow fan for refrigerators. This axial flow fan is optimally designed in a variety of designing factors, such as the number of blades, hub ratio, sweep angle, pitch angle and maximum camber ratio, thus allowing a smooth flow of cool air agreeable with both the large pressure loss and complex flow passage of refrigerators while accomplishing a reduction in air flow noise of the refrigerators.
- In addition, the axial flow fan of this invention increases the blade passing frequency (BPF), which is the main frequency of fluid noise caused by a collision of the air current against the blades during operation of the fan, at least two times. The doors of a refrigerator typically designed to intercept high frequency noise effectively intercept such a high level BPF. It is thus possible to desirably reduce operational noise of refrigerators.
- In the axial flow fan of this invention, the blade tip of each blade is curved from its pressure surface to its negative pressure surface while forming a predetermined radius of curvature. The blades during rotation are thus less likely to form a vortex stream in their trailing positions and desirably reduce the blade vortex interaction (BVI), in which each trailing blade undesirably confronts a vortex stream formed by a leading blade during operation of a conventional axial flow fan, thus generating fluid noise.
- In addition, a vortex prevention means is provided on the back surface of the shroud's annular rim for preventing an undesirable collision of a discharged air current against the concave back surface of the rim, thus preventing a formation of a vortex stream in back of the rim and reducing air flow loss of the fan, and reducing operational noise of the fan.
- Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the invention as disclosed in the accompanying claims.
Claims (4)
- An axial flow fan for refrigerators, comprising a hub (51) mounted to a rotating shaft of a motor, with at least seven blades (55) regularly fixed around said hub (51),
characterized in that
a hub ratio of a hub diameter (ID) to an outer diameter of said fan is set to 0.45 - 0.55, a pitch angle (Ψ) of each of said blades is 32° ± 2° at a blade tip (55a) and 45°± 2° at a blade hub (55b), a maximum camber ratio of each of the blades (55) is 11.5 ± 0.5% at the blade tip (55a) and 8 ± 0.5% at the blade hub (55b), and a sweep angle (Θ) of each of said blades (55) ranges from 32° to 34°, wherein a rake angle of each of the blades (55) is zero. - The axial flow fan according to claim 1,
wherein the number of said blades (55) is nine. - The axial flow fan according to claim 1,
wherein a maximum camber position of each of said blades (55) is set to 0.65 ± 0.05, with camber positions being uniformly distributed on each of the blades (55) from a blade hub (55b) to a blade tip (55a). - The axial flow fan according to claim 1,
wherein a blade tip (55a) of each of the blades (55) is curved from its pressure surface (55b) to its negative pressure surface (56a) while forming a predetermined radius of curvature.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR9929803 | 1999-07-22 | ||
KR9929802 | 1999-07-22 | ||
KR1019990029802A KR100347048B1 (en) | 1999-07-22 | 1999-07-22 | Axial flow fan for refrigerator |
KR1019990029803A KR100336132B1 (en) | 1999-07-22 | 1999-07-22 | Refrigerator shroud |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1070849A2 EP1070849A2 (en) | 2001-01-24 |
EP1070849A3 EP1070849A3 (en) | 2002-07-17 |
EP1070849B1 true EP1070849B1 (en) | 2010-03-24 |
Family
ID=26635904
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP20000114849 Expired - Lifetime EP1070849B1 (en) | 1999-07-22 | 2000-07-11 | Axial flow fan |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP1070849B1 (en) |
JP (1) | JP3469857B2 (en) |
DE (1) | DE60044049D1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11965522B2 (en) | 2015-12-11 | 2024-04-23 | Delta Electronics, Inc. | Impeller |
Families Citing this family (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100347050B1 (en) * | 1999-11-02 | 2002-08-03 | 엘지전자주식회사 | Axial flow fan of refrigerator |
KR100402477B1 (en) * | 2001-05-17 | 2003-10-22 | 엘지전자 주식회사 | Fan assembly for refrigerator |
KR100420519B1 (en) * | 2001-08-30 | 2004-03-02 | 엘지전자 주식회사 | A multi type blade fan for the refrigerator |
FR2833050B1 (en) * | 2001-12-03 | 2005-11-11 | Abb Solyvent Ventec | HELICOID FAN WITH A NOISE REDUCING MEANS |
US6911636B2 (en) * | 2002-01-03 | 2005-06-28 | Lg Electronics Inc. | Cooling fan for microwave oven |
ES2283746T3 (en) * | 2002-02-28 | 2007-11-01 | Daikin Industries, Ltd. | FAN. |
JP4745626B2 (en) * | 2004-06-29 | 2011-08-10 | ループウイング株式会社 | Axial flow blower |
JP4943817B2 (en) | 2006-10-31 | 2012-05-30 | 日本電産サーボ株式会社 | Axial fan |
CN102947597B (en) * | 2010-02-26 | 2016-10-19 | 罗伯特·博世有限公司 | Free top end type axial fan assembly |
JP6215296B2 (en) * | 2013-02-22 | 2017-10-18 | ジョンソンコントロールズ ヒタチ エア コンディショニング テクノロジー(ホンコン)リミテッド | Propeller fan and air conditioner equipped with the same |
FR3015379B1 (en) * | 2013-12-20 | 2017-06-09 | Valeo Systemes Thermiques | AUTOMOTIVE FAN HAVING A STATOR BEFORE THE PROPELLER |
CN204213047U (en) * | 2014-10-24 | 2015-03-18 | 常州格力博有限公司 | Axial-flow blower fan blade |
FR3032494B1 (en) * | 2015-02-06 | 2018-05-25 | Safran Aircraft Engines | AUBE DE SOUFFLANTE |
CN106870451A (en) * | 2015-12-11 | 2017-06-20 | 台达电子工业股份有限公司 | Impeller and fan |
JP2019056309A (en) * | 2017-09-20 | 2019-04-11 | ミネベアミツミ株式会社 | Axial flow fan |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
IT8353039V0 (en) * | 1982-03-15 | 1983-03-10 | Sueddeutsche Kuehler Behr | AXIAL FAN PARTICULARLY FOR WATER COOLED THERMAL ENGINE COOLING RADIATORS |
EP0174487A1 (en) | 1984-08-16 | 1986-03-19 | Siemens Aktiengesellschaft | Axial ventilator |
IT206701Z2 (en) | 1985-08-02 | 1987-10-01 | Gate Spa | AXIAL FAN PARTICULARLY FOR VEHICLES |
US5244347A (en) * | 1991-10-11 | 1993-09-14 | Siemens Automotive Limited | High efficiency, low noise, axial flow fan |
US5273400A (en) | 1992-02-18 | 1993-12-28 | Carrier Corporation | Axial flow fan and fan orifice |
EP0913584B1 (en) | 1992-05-15 | 2005-07-20 | Siemens VDO Automotive Inc. | Axial flow fan |
US5393199A (en) | 1992-07-22 | 1995-02-28 | Valeo Thermique Moteur | Fan having a blade structure for reducing noise |
DE19631093A1 (en) | 1996-08-01 | 1998-02-05 | Deutsche Forsch Luft Raumfahrt | Process for the aeroacoustic optimization of an axial fan |
-
2000
- 2000-07-11 EP EP20000114849 patent/EP1070849B1/en not_active Expired - Lifetime
- 2000-07-11 DE DE60044049T patent/DE60044049D1/en not_active Expired - Lifetime
- 2000-07-14 JP JP2000218758A patent/JP3469857B2/en not_active Expired - Fee Related
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11965522B2 (en) | 2015-12-11 | 2024-04-23 | Delta Electronics, Inc. | Impeller |
Also Published As
Publication number | Publication date |
---|---|
EP1070849A2 (en) | 2001-01-24 |
JP2001059499A (en) | 2001-03-06 |
JP3469857B2 (en) | 2003-11-25 |
EP1070849A3 (en) | 2002-07-17 |
DE60044049D1 (en) | 2010-05-06 |
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