WO2023199406A1 - 遠心送風機 - Google Patents

遠心送風機 Download PDF

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Publication number
WO2023199406A1
WO2023199406A1 PCT/JP2022/017612 JP2022017612W WO2023199406A1 WO 2023199406 A1 WO2023199406 A1 WO 2023199406A1 JP 2022017612 W JP2022017612 W JP 2022017612W WO 2023199406 A1 WO2023199406 A1 WO 2023199406A1
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WO
WIPO (PCT)
Prior art keywords
impeller
centrifugal blower
protrusion
main plate
outer diameter
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.)
Ceased
Application number
PCT/JP2022/017612
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English (en)
French (fr)
Japanese (ja)
Inventor
勇児 秋場
一輝 岡本
千景 門井
一樹 蓮池
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Priority to PCT/JP2022/017612 priority Critical patent/WO2023199406A1/ja
Priority to JP2024515214A priority patent/JP7665099B2/ja
Publication of WO2023199406A1 publication Critical patent/WO2023199406A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
    • 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
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/44—Fluid-guiding means, e.g. diffusers
    • 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

Definitions

  • the present disclosure relates to a centrifugal blower equipped with an impeller that generates airflow.
  • a centrifugal blower has a scroll casing that houses an impeller.
  • the scroll casing has an air inlet and an air outlet, and forms a flow path for the airflow generated by the rotation of the impeller.
  • Noise generated inside the scroll casing due to the rotation of the impeller is emitted to the outside of the scroll casing from the suction port or the blowout port.
  • the airflow inside the centrifugal blower has the highest velocity immediately after leaving the impeller. Furthermore, since the distance between the impeller and the wall of the scroll casing increases as the direction of rotation advances, fluctuations in airflow are likely to occur.
  • the airflow flowing out of the impeller is roughly divided into main flow and secondary flow.
  • Secondary flow is airflow that flows in a direction perpendicular to the main flow. It is known that secondary flow causes secondary loss and deteriorates air blowing performance.
  • centrifugal blowers generate noise when the blade surface flow undergoes periodic pressure fluctuations due to the rotation of the impeller.
  • similar noise is also generated when the flow around the blades of the impeller changes periodically due to the influence of the above-mentioned airflow fluctuations and the like.
  • Such noise is called discrete frequency noise and deteriorates the acoustic characteristics of the centrifugal blower.
  • Patent Document 1 discloses a technique in which a rectifying block is installed in a bell mouth to rectify the flow within the scroll casing. This aims to improve the blowing performance of the blower.
  • Patent Document 2 discloses that a cylindrical wall is formed on the back surface of the main plate of the impeller, and the outer diameter of the cylindrical wall is made the same as the outer diameter of the blades of the impeller. This prevents the secondary flow formed by the rotation of the impeller from flowing into the back surface of the main plate, reduces secondary loss, and improves air blowing performance.
  • Patent No. 6246434 Japanese Patent Application Publication No. 2008-169826
  • Patent Document 1 proposes a technique in which a shielding portion is provided in the bell mouth in order to reduce such secondary flow, when the technique described in Patent Document 1 is used, it is not possible to provide a shielding portion.
  • the problem is that the flow from the bell mouth side toward the main plate of the impeller becomes stronger, and the flow on the back side of the main plate of the impeller is likely to be disturbed, leading to worsening of noise.
  • the centrifugal blower disclosed in Patent Document 2 can be expected to have the effect of preventing the secondary flow formed by the rotation of the impeller from flowing into the back surface of the main plate and mitigating the loss due to the secondary flow. It is not possible to cope with the flow from the bell mouth side toward the main plate side of the impeller, which increases pressure fluctuations on the back side of the main plate of the impeller, leading to a problem of worsening noise.
  • the distance between the impeller and the scroll casing is close to suppress leakage flow. Therefore, discrete frequency noise is likely to propagate behind the main plate of the impeller, leading to deterioration of the acoustic characteristics of the centrifugal blower.
  • the present disclosure has been made in view of the above, and provides a centrifugal blower that suppresses pressure fluctuations caused by interference between the secondary flow and the impeller, and reduces discrete frequency noise generated from around the blades of the impeller.
  • the purpose is to obtain.
  • a centrifugal blower includes a motor, an inlet, an outlet, a bell mouth that guides the airflow toward the inlet, and a downstream side of the airflow.
  • a scroll portion whose width in the radial direction increases as it goes toward the end, a tongue portion that connects the scroll portion and the air outlet so as to enlarge the opening area of the air outlet, and a flow path between the scroll portion and the air outlet.
  • a scroll casing having a diffuser portion, a disk-shaped main plate fixed to the shaft of a motor and rotating, and a plurality of blades installed in an annular manner around the outer periphery of the main plate, installed in the scroll casing, and an impeller that forms an airflow inside the scroll casing from the suction port to the blowout port.
  • the bell mouth is provided with a shielding portion downstream of the tongue portion in the rotational direction of the impeller for shielding a secondary flow flowing out from the impeller and flowing back into the impeller.
  • the impeller has a cylindrical protrusion that protrudes from the back surface of the main plate. The maximum width of the protrusion is smaller than the outer diameter of the impeller.
  • the centrifugal blower according to the present disclosure has the effect of suppressing pressure fluctuations caused by interference between the secondary flow and the impeller, and reducing discrete frequency noise generated from around the blades of the impeller.
  • FIG. 1 A diagram showing the relationship between the position of the shielding part provided in the bell mouth of the centrifugal blower according to Embodiment 1, the amount of increase in static pressure, and noise.
  • Cross-sectional view of a centrifugal blower according to a second comparative example of Embodiment 1 A diagram showing a flow velocity distribution of a centrifugal blower according to a second comparative example of Embodiment 1.
  • a diagram showing flow velocity distribution of the centrifugal blower according to Embodiment 1 A diagram showing the distribution of effective values of pressure fluctuations of the centrifugal blower according to Embodiment 1
  • Cross-sectional view of a centrifugal blower according to Embodiment 2 A perspective view of an impeller of a centrifugal blower according to Embodiment 3
  • FIG. 1 is a perspective view of a centrifugal blower according to Embodiment 1.
  • FIG. 2 is a sectional view of the centrifugal blower according to the first embodiment.
  • FIG. 3 is a top view of the centrifugal blower according to the first embodiment.
  • FIG. 2 shows a cross section taken along the line II-II in FIGS. 1 and 3. Further, FIG. 3 shows the entire impeller 4 without illustration of the bell mouth 8a.
  • the centrifugal blower 1 according to the first embodiment includes a motor 3, an impeller 4 that is rotationally driven by the motor 3, and a scroll casing 11 that accommodates the impeller 4.
  • the centrifugal blower 1 generates airflow by rotating an impeller 4.
  • the scroll casing 11 has an air inlet 8 and an air outlet 10.
  • the scroll casing 11 forms a flow path for air flow generated by the rotation of the impeller 4.
  • air outside the scroll casing 11 is sucked into the scroll casing 11 through the suction port 8.
  • the air inside the scroll casing 11 is blown out of the scroll casing 11 through the air outlet 10.
  • an air flow Y1 from outside the scroll casing 11 toward the suction port 8 and an air flow Y2 from the air outlet 10 toward the outside of the scroll casing 11 are generated.
  • FIG. 1 an air flow Y1 from outside the scroll casing 11 toward the suction port 8 and an air flow Y2 from the air outlet 10 toward the outside of the scroll casing 11 are generated.
  • a main stream Y3 which is an air flow flowing from the suction port 8 through the impeller 4 and between the impeller 4 and the scroll casing 11, is generated. That is, as the impeller 4 rotates, an air flow from the suction port 8 toward the blowout port 10 is generated inside the scroll casing 11 .
  • the scroll casing 11 has a scroll portion 6, a diffuse portion 7, and a tongue portion 9.
  • the scroll portion 6 is a portion forming a spiral flow path whose width in the radial direction increases toward the downstream side of the air flow.
  • the spiral flow path is, for example, an Archimedean spiral. That is, the distance from the rotation shaft 2 of the impeller 4 to the scroll portion 6 increases as the rotation direction of the impeller 4 advances, as shown in FIG.
  • the diffuse portion 7 is a portion on the downstream side of the scroll portion 6 and constitutes a flow path between the scroll portion 6 and the air outlet 10.
  • the diffuser section 7 efficiently converts the dynamic pressure of the airflow flowing out from the impeller 4 into static pressure while guiding the airflow to the outlet 10 .
  • the tongue portion 9 is a portion that connects the scroll portion 6 and the air outlet 10 so as to expand the opening area of the air outlet 10. The tongue portion 9 guides the airflow swirling inside the scroll casing 11 to the outlet 10 .
  • the scroll casing 11 has a first wall 11a, a second wall 11b, and a third wall 11c.
  • the first wall 11a and the second wall 11b face each other in the axial direction of the scroll casing 11.
  • the third wall 11c connects the first wall 11a and the second wall 11b.
  • the suction port 8 is formed in the first wall 11a.
  • a bell mouth 8a whose diameter increases as it moves away from the second wall 11b is formed on the first wall 11a.
  • the material of the scroll casing 11 is, for example, resin.
  • the bell mouth 8a is provided so as to surround the suction port 8 through which air is sucked.
  • the impeller 4 is a multi-blade impeller.
  • the impeller 4 is fixed to the shaft 3a of the motor 3.
  • the impeller 4 rotates around the shaft 3a.
  • the impeller 4 includes a disc-shaped main plate 4a, a plurality of blades 4b annularly installed on the outer circumference of the front side of the main plate 4a, and a boss portion 4c fixed to the shaft 3a of the motor 3.
  • the number of blades 4b of the impeller 4 is 43.
  • the impeller 4 includes a rib 4d, which is a blade reinforcing member, on the outer diameter edge of the upstream side of the blade 4b.
  • a protrusion 5 for rectifying airflow is provided on the back surface of the main plate 4a of the impeller 4.
  • the impeller 4 has a shape in which a protrusion 5 branches from the middle of the main plate 4a.
  • the protrusion 5 preferably has a rotationally symmetrical or axially symmetrical shape with respect to the rotation axis 2 of the impeller 4 from the viewpoint of preventing leakage flow occurring on the back surface of the main plate 4a and reducing noise.
  • the protrusion 5 has an axially symmetrical cylindrical shape.
  • a portion of the motor 3 is housed in a space surrounded by the cylindrical wall of the protrusion 5.
  • the main plate 4a of the impeller 4 has a flat surface in the area from the outer circumference of the main plate 4a to the portion where the protrusion 5 is provided in the radial direction of the rotating shaft 2.
  • the reason why the area from the outer periphery of the main plate 4a to the part where the protruding part 5 is provided is made into a flat surface is to suppress the sudden turning of the airflow flowing out from the impeller 4, and to maintain the main flow up to the air outlet 10 with as little loss as possible. This is to reach Y3. This effect will be described later.
  • the main plate 4a of the impeller 4 is provided with a plurality of ventilation holes 4e.
  • the ventilation hole 4e is provided for the purpose of suppressing the temperature rise of the motor 3.
  • the ventilation hole 4e is provided to promote the air cooling effect of the motor 3.
  • the ventilation holes 4e may not be provided in the main plate 4a.
  • the number of ventilation holes 4e does not need to be six as shown in FIG. 3, and is not limited to a specific number.
  • the positional relationship and shape of the impeller 4 and the scroll casing 11, the presence or absence of the ventilation hole 4e, and the shape of the ventilation hole 4e are not limited to those shown in FIGS. 1 to 3.
  • the positional relationship of each component and the shape of each component may be appropriately determined at the time of design.
  • the centrifugal blower 1 has a structure that blows air sucked into the scroll casing 11 from the suction port 8 along the axial direction of the rotation shaft 2 of the impeller 4 in the radial direction of the rotation shaft 2 of the impeller 4. , an inertial force acts on the airflow. Therefore, the airflow blown into the scroll casing 11 through the impeller 4 forms a velocity distribution in which the closer it gets to the second wall 11b of the scroll casing 11, the faster the velocity becomes. A part of the air flow blown into the scroll casing 11 then rolls up from the main plate 4a of the impeller 4 toward the tip of the blade 4b or from the tip of the blade 4b toward the main plate 4a along the third wall 11c. A secondary flow Y4 is formed.
  • the bell mouth 8a has a curved surface at a portion around the rotating shaft 2 of the impeller 4 so as to prevent the air flow from the impeller 4 from flowing into the scroll casing 11 instead of flowing into the air outlet 10. It has an outstanding structure.
  • the curved surface of the bell mouth 8a is partially removed so as to block the secondary flow Y4, which is a part of the blowout flow from the impeller 4, so that the secondary flow Y4 and the blowout from the impeller 4 are cut off. Collision or interference with the airflow caused by the centrifugal blower 1 can be suppressed, and the blowing performance of the centrifugal blower 1 can be improved and noise suppressed.
  • the portion where the curved surface of the bell mouth 8a is partially removed will be referred to as a shielding portion 8b.
  • the bell mouth 8a has a rotationally symmetrical shape with respect to the rotation axis 2 of the impeller 4, except for the shielding part 8b, and the shape of the cross section perpendicular to the rotation axis 2 of the impeller 4 is at the shielding part 8b. It has an interrupted arc shape. In a cross section passing through the rotation axis 2 of the impeller 4 shown in FIG. The circular diameter of the opening continuously decreases toward the leeward.
  • the curved surface of the bell mouth 8a is open toward the outside of the scroll casing 11 on the upstream side. Further, the curved surface of the bell mouth 8a is along the axial direction on the downstream side. Therefore, the curved surface of the bell mouth 8a has a convex shape on the air suction port 8 side.
  • the curved surface facing the suction port 8 is a front surface 8f
  • the curved surface not facing the suction port 8 is a back surface 8r.
  • the scroll casing 11 and the bell mouth 8a are integral, and are formed by processing a single metal plate using sheet metal processing. Therefore, a bell mouth back space 82 is formed between the curved surface of the bell mouth 8a and the first wall 11a of the scroll casing 11.
  • the shielding portion 8b divides the bell mouth backside space 82 in the circumferential direction.
  • the shielding part 8b has two shielding part side parts 81a formed on two planes that are parallel to the rotation axis 2 of the impeller 4 and facing each other across the rotation axis 2, and a plane that intersects the rotation axis 2.
  • the shielding part bottom part 81b connects the downstream ends of the two shielding part side parts 81a.
  • the upper end on the upstream side of the shield side surface portion 81a is connected to the bell mouth 8a.
  • the outer circumferential end of the shield side surface portion 81 a is connected to the scroll casing 11 .
  • a downstream lower end portion of the shielding side surface portion 81a is connected to the shielding portion bottom surface portion 81b.
  • An outer peripheral end of the shielding portion bottom surface portion 81b is connected to the scroll casing 11.
  • the shielding part 8b is continuously connected to the bell mouth 8a, the shielding part side part 81a, the shielding part bottom part 81b, the shielding part side part 81a, and the bell mouth 8a without branching.
  • the bell mouth 8a and the shielding part 8b can be integrally molded from one metal plate.
  • the bell mouth back space 82 is divided in the circumferential direction, so that it is possible to suppress the secondary flow Y4 from flowing in the bell mouth back space 82 in the circumferential direction.
  • FIG. 4 is a cross-sectional view of a centrifugal blower according to a first comparative example of the first embodiment.
  • the bell mouth 8a of the centrifugal blower 1 according to the first comparative example shown in FIG. 4 has a structure in which the curved surface is continuous over the entire circumference of the rotation shaft 2 of the impeller 4 without any missing parts. Further, in the centrifugal blower 1 according to the first comparative example, the bell mouth back space 82 is not partially filled, and the bell mouth back space 82 is connected without being separated in the circumferential direction of the rotation shaft 2 of the impeller 4. ing.
  • the structure and shape of components other than the bell mouth 8a are the same as in the first embodiment.
  • the centrifugal blower 1 As shown in FIG. 4, the centrifugal blower 1 according to the first comparative example has a structure in which the bell mouth 8a exists over the entire circumference of the rotation shaft 2 of the impeller 4, so that the secondary flow Y4 Collision or interference between the airflow and the airflow blown out from the impeller 4 causes a decrease in air blowing performance and an increase in noise.
  • FIG. 5 is a diagram showing the results of an actual machine test of the air volume-specific noise characteristics of the centrifugal blower according to the first embodiment and the centrifugal blower according to the first comparative example.
  • the horizontal axis represents the air volume
  • the vertical axis represents the specific noise.
  • black diamonds are plots representing the centrifugal blower 1 according to the first comparative example
  • white circles are plots representing the centrifugal blower 1 according to the first embodiment.
  • the noise value in the operating air volume band of the centrifugal blower 1 is 12.5 dB in the centrifugal blower 1 according to the first comparative example, whereas the centrifugal blower 1 according to the first embodiment In this case, the noise was 11.7 dB, and it can be confirmed that the noise was reduced by 0.8 dB.
  • the difference between the centrifugal blower 1 according to the first embodiment and the centrifugal blower 1 according to the first comparative example is whether or not the bell mouth 8a is provided with the shielding part 8b. It can be determined that noise reduction was achieved because the shielding portion 8b was able to effectively suppress the collision or interference with the airflow blown out from the car 4.
  • the centrifugal blower 1 has a structure in which the curved surface of the bell mouth 8a is partially removed so as to block the secondary flow Y4, which is a part of the blowout flow from the impeller 4. There is. Therefore, collision or interference between the secondary flow Y4 and the airflow blown out from the impeller 4 can be effectively suppressed, and the blowing performance of the centrifugal blower 1 can be improved and noise suppressed.
  • the structure of the bell mouth 8a is not limited to a structure in which a part of the curved surface is partially removed like the centrifugal blower 1 according to the first embodiment, and the structure is not limited to a structure in which a part of the curved surface is partially removed.
  • a structure in which the bell mouth back space 82 is partially filled or a protrusion that projects into the bell mouth back space 82 is partially provided on the back surface 8r of the bell mouth 8a so as to block the secondary flow Y4. It may be replaced by
  • FIG. 6 is a diagram showing the position of the end of the shielding part of the shielding part provided in the bell mouth of the centrifugal blower according to the first embodiment.
  • FIG. 7 is a diagram showing the relationship between the position of the shielding part provided in the bell mouth of the centrifugal blower according to the first embodiment, the amount of increase in static pressure, and the noise. Note that the shielding portion terminal end portion 8c is the downstream end of the shielding portion 8b.
  • FIG. 7 shows the results of verifying the blocking effect of the shielding portion 8b on the secondary flow Y4 of the centrifugal blower 1 according to the first embodiment through an actual machine test.
  • the horizontal axis in FIG. 7 represents the position of the shield end portion 8c.
  • the 7 represents the static pressure increase amount and the noise level of the centrifugal blower 1 according to the first embodiment.
  • the rotation angle up to the position of the shield end portion 8c is shown with the rotation direction of the impeller 4 shown as the forward direction.
  • the centrifugal blower 1 As shown in FIG. 7, in the measurement results when the angle ⁇ from the reference line P to the shield end 8c is 60° to 150°, the larger the angle ⁇ , the more noise increases and the amount of increase in static pressure decreases. There is a tendency to Since the amount of increase in static pressure is a positive value until the angle ⁇ is about 140°, the centrifugal blower 1 according to the first embodiment has the shielding portion terminal portion 8c disposed at a position where the angle ⁇ is 140° or less. In this case, the effect of increasing static pressure can be obtained. Further, even if the shielding portion terminal end portion 8c is set within the angle ⁇ of 60° to 120° in consideration of deterioration of noise, an increase in static pressure of approximately 4% or more can be obtained.
  • the angle ⁇ is 100° or less, static pressure increases and deterioration of noise is suppressed.
  • the angle ⁇ is around 70°, for example when the angle ⁇ is in the range of 60° to 90°, the amount of increase in static pressure is large and the increase in noise is small compared to when the angle ⁇ is outside this range. It is.
  • the angle ⁇ is increased, the influence of the reduction in the cross-sectional area of the flow path increases, and the above-mentioned effect obtained by providing the shielding portion 8b is canceled out.
  • the angle ⁇ which is the rotation angle from the reference line P to the shielding part terminal part 8c, is set to 120 degrees or less; It is preferable that ⁇ is set to 100° or less.
  • FIGS. 2 and 3 also shows a circle 4f connecting the outer diameter side ends of the plurality of ventilation holes 4e, a circle 4g connecting the outer diameter side ends of the plurality of blades 4b of the impeller 4, and a circle 4g connecting the outer diameter side ends of the plurality of blades 4b of the impeller 4.
  • a circle 4h connecting the inner end portions of the blade 4b is shown by a dashed dotted line.
  • the inner diameter of the impeller 4 is defined as D1, the outer diameter of the impeller 4 as D2, the outer diameter of the motor 3 as Dc, and the outer diameter of the protrusion 5 as Da.
  • the outer diameter of the protrusion 5 is the maximum width of the protrusion 5.
  • the diameter of a circle 4h connecting the inner diameter side ends of the plurality of blades 4b of the impeller 4 is defined as the inner diameter D1 of the impeller 4.
  • the diameter of a circle 4g connecting the outer diameter side ends of the plurality of blades 4b of the impeller 4 is defined as the outer diameter D2 of the impeller 4.
  • the diameter of a circle 4f connecting the outer peripheral side ends of the plurality of ventilation holes 4e with the rotation axis 2 of the impeller 4 as the central axis is the outer diameter Db of the ventilation holes 4e.
  • the outer diameter Da of the protrusion 5, which serves as a reference for defining the attachment position of the protrusion 5, satisfies D2>Da>Dc.
  • Da 0.9 ⁇ D2.
  • the secondary flow Y4 Due to the structural cause of inertial force acting on the airflow, the secondary flow Y4 has a larger flow rate toward the second wall 11b side than the bell mouth 8a side, so that the curved surface of the bell mouth 8a partially escapes. Also in the centrifugal blower 1 according to the first embodiment, by ensuring the distance between the protrusion 5 and the scroll casing 11, the effect of suppressing interference between the protrusion 5 and the secondary flow Y4 is further increased.
  • Discrete frequency noise is generated when the suction flow of the impeller 4 changes periodically, or when the impeller 4 sucks in large turbulence and the flow around the blade 4b changes periodically.
  • the discrete frequency noise generated around the blades 4b of the impeller 4 of the centrifugal blower 1 is caused by interference between the secondary flow and the impeller 4 in a portion where the distance between the impeller 4 and the scroll casing 11 is small. It becomes easier.
  • the outer diameter Da of the protrusion 5 is larger than the outer diameter Db of the ventilation hole 4e. Therefore, by installing the protrusion 5 to satisfy the condition D2>Da>Db, it is possible to suppress the noise generated by the collision of the secondary flow Y4 with the protrusion 5, and also to suppress the generation of discrete frequency noise. It can be suppressed.
  • the gap Hb between the protrusion 5 and the scroll casing 11 in the direction along the rotation axis 2 of the impeller 4 should be as small as possible from the viewpoint of preventing leakage of the secondary flow Y4. desirable.
  • the gap Hb is too small, there is a risk that the protrusion 5 and the scroll casing 11 will collide while the impeller 4 is rotating. For this reason, it is necessary to balance prevention of leakage of the secondary flow Y4 and collision avoidance, and it is actually appropriate to provide a gap Hb of about 3 mm to 7 mm.
  • FIG. 8 is a sectional view of a centrifugal blower according to a second comparative example of the first embodiment.
  • the protrusion 20 is provided at the same position as the outer diameter D2 of the impeller 4 on the back surface of the main plate 4a.
  • the protrusion 20 has a cylindrical shape like the protrusion 5 of the centrifugal blower 1 according to the first embodiment. Therefore, in the centrifugal blower 1 according to the second comparative example, the outer diameter Da of the protrusion 20 is the same as the outer diameter D2 of the impeller 4.
  • the structure and shape of the constituent elements other than the protrusion 20 are the same as those of the centrifugal blower 1 according to the first embodiment.
  • the protrusion 20 is provided so as to correspond to 80% of the outer diameter D2 of the impeller 4 on the back surface of the main plate 4a.
  • the structure and shape of the constituent elements other than the protrusion 20 were the same as those of the centrifugal blower 1 according to the first embodiment. Therefore, in the centrifugal blower 1 according to the third comparative example, the outer diameter Da of the protrusion 20 is 0.8 ⁇ (outer diameter D2 of the impeller 4). Note that the centrifugal blower 1 according to the third comparative example is the same as the centrifugal blower 1 according to the second comparative example, except that the outer diameter of the protrusion 20 is different, and therefore illustration thereof is omitted.
  • FIG. 9 is a diagram showing the flow velocity distribution of the centrifugal blower according to the second comparative example of the first embodiment.
  • FIG. 9 shows the flow velocity distribution in a cross section at a position corresponding to the II-II line in FIG. 3 for the centrifugal blower 1 according to the second comparative example.
  • FIG. 9 shows the flow velocity distribution using a monotone image that becomes darker as the flow velocity increases.
  • the region where the flow velocity is high is the region through which the main flow Y3 flowing out from the impeller 4 passes.
  • a secondary flow Y4 is formed that flows perpendicularly to the main flow Y3. If the outer diameter Da of the protrusion 20 is made the same as the outer diameter D2 of the impeller 4 as in the centrifugal blower 1 according to the second comparative example, the distance between the protrusion 20 and the secondary flow Y4 will inevitably become short. As a result, the protrusion 20 and the secondary flow Y4 tend to interfere with each other.
  • FIG. 10 is a diagram showing the distribution of effective values of pressure fluctuations of the centrifugal blower according to the second comparative example of the first embodiment.
  • FIG. 10 shows the distribution of effective values of pressure fluctuations using a monotone image that becomes darker as the pressure fluctuations increase.
  • the pressure fluctuation on the surface of the protrusion 20 provided on the impeller 4 is approximately 30 Pa or more.
  • the cause of the pressure fluctuation is considered to be that the secondary flow Y4 interferes with the protrusion 20 and the airflow around the protrusion 20 is disturbed, as shown in FIG.
  • FIG. 11 is a diagram showing the distribution of pressure fluctuation levels on the bottom surface of the scroll portion of the centrifugal blower according to the second comparative example of the first embodiment.
  • the pressure fluctuation level is a time fluctuation average of pressure expressed by the root mean square (RMS) of pressure.
  • RMS root mean square
  • the pressure fluctuation level near the tongue portion 9 on the bottom surface of the scroll portion 6 is 104 to 112.
  • the reason why the pressure fluctuation level near the tongue portion 9 increases is considered to be that in addition to the pressure fluctuation due to the secondary flow Y4, fluctuations due to the circulation flow generated from the vicinity of the tongue portion 9 are also added.
  • FIG. 12 is a diagram showing the flow velocity distribution of the centrifugal blower according to the first embodiment.
  • FIG. 12 shows a flow velocity distribution in a cross section taken along the line II-II in FIG. 3 for the centrifugal blower 1 according to the first embodiment.
  • FIG. 12 shows the flow velocity distribution using a monotone image that becomes darker as the flow velocity increases.
  • FIG. 13 is a diagram showing a distribution of effective values of pressure fluctuations of the centrifugal blower according to the first embodiment.
  • FIG. 13 shows the distribution of effective values of pressure fluctuations using a monotone image that becomes darker as the pressure fluctuations increase.
  • the outer diameter Da of the protrusion 5 is not the same as the outer diameter D2 of the impeller 4, and the entire cylindrical wall of the protrusion 5 is on the inner diameter side than the outer diameter D2 of the impeller 4. It is set in.
  • the secondary flow Y4 is generated in the centrifugal blower 1 according to the first embodiment as well, as in the centrifugal blower 1 according to the second comparative example.
  • the centrifugal blower 1 according to the first embodiment since the protrusion 5 is provided on the inner diameter side of the outer peripheral end of the impeller 4, the distance between the secondary flow Y4 and the protrusion 5 cannot be secured. Therefore, interference between the secondary flow Y4 and the protrusion 5 is suppressed.
  • the protrusion 5 is installed inside the inner diameter D1 of the impeller 4, it is possible to suppress the collision of the secondary flow Y4 with the protrusion 5, and suppress the generation of noise due to the secondary flow Y4. .
  • the main plate 4a of the impeller 4 has a flat surface from the outer periphery of the main plate 4a where the plurality of blades 4b are arranged to the part where the protrusion 5 is provided, the main flow Y3 is directed against the main plate 4a of the impeller 4. It can be seen that the outflow is almost parallel. By flowing out almost parallel to the main plate 4a, the main flow Y3 can reach the outlet 10 with little loss without causing a sudden turn of the airflow. Furthermore, there is also the effect of effectively separating the secondary flow Y4 and the main flow Y3, and the interference between the main flow Y3 and the secondary flow Y4 can also be effectively suppressed.
  • the magnitude of the pressure fluctuation of the protrusion 5 is reduced by about 15 Pa to 30 Pa when compared with the centrifugal blower 1 according to the second comparative example.
  • the reason for this is thought to be that interference between the secondary flow Y4 and the protrusion 5 was effectively suppressed, as shown in FIG. 12.
  • FIG. 14 is a diagram showing the distribution of pressure fluctuation levels on the bottom surface of the scroll portion of the centrifugal blower according to the first embodiment.
  • the centrifugal blower 1 according to the first embodiment has a smaller area where the pressure fluctuation level is high, especially near the tongue portion 9, compared to the centrifugal blower 1 according to the second comparative example. .
  • FIG. 15 is a diagram showing the results of an actual machine test of the air volume-specific noise characteristics of the centrifugal blower according to the first embodiment, the centrifugal blower according to the second comparative example, and the centrifugal blower according to the third comparative example. .
  • the horizontal axis shows the air volume, and the vertical axis shows the specific noise.
  • black diamonds indicate the plots of the centrifugal blower 1 according to the second comparative example
  • black triangles indicate the plots of the centrifugal blower 1 according to the third comparative example
  • white circles indicate the plots of the centrifugal blower 1 according to the first embodiment. 1 plot is shown.
  • the noise value of the minimum specific noise is 13.1 dB for the centrifugal blower 1 according to the second comparative example and 13.0 dB for the centrifugal blower 1 according to the third comparative example.
  • the centrifugal blower 1 according to Embodiment 1 it is 12.8 dB, and it can be confirmed that the noise is reduced by 0.2 dB or more.
  • the reason why we were able to confirm such low noise is because the protrusion 5 is provided on the inner diameter side of the impeller 4, interference between the protrusion 5 and the secondary flow Y4 can be suppressed, and the impeller 4 This is thought to be due to the fact that it was able to effectively suppress the discrete frequency noise generated from the back of the vehicle.
  • the entire circumference of the protruding part 5 is installed offset to the inner side in the radial direction than the plurality of blades 4b of the impeller 4, the protruding part 5 and Interference with the secondary flow Y4 can be suppressed, and pressure fluctuations on the surface of the protrusion 5 can be effectively reduced. Moreover, due to this influence, discrete frequency noise generated with the rotation of the impeller 4 can be suppressed, and noise reduction can be realized.
  • the centrifugal blower 1 according to the first embodiment can be expected to have the effect of suppressing the generation of discrete frequency noise
  • the second protrusion 20 is provided at the same position as the outer diameter of the impeller 4 on the back surface of the main plate 4a.
  • the number of blades can be expected to be reduced by 10% or more, and material costs and processing costs for the impeller 4 can be reduced.
  • FIG. 16 is a sectional view of a centrifugal blower according to the second embodiment. Note that in FIG. 16, illustration of the scroll casing 11 is omitted.
  • the protrusion 5 of the first embodiment is replaced with a protrusion 30.
  • the centrifugal blower 1 according to Embodiment 2 has the same configuration as the centrifugal blower 1 according to Embodiment 1 except for the protrusion 30, and therefore, duplicate explanation will be omitted.
  • the protruding portion 30 is not branched from the main plate 4a, and is formed by bending the main plate 4a to have a V-shaped cross section.
  • the impeller 4 of the centrifugal blower 1 according to the second embodiment can be formed by resin molding. Unlike the centrifugal blower 1 according to the first embodiment, the protrusion 30 is not branched from the main plate 4a, so the productivity of resin molding is high.
  • the attachment position of the protrusion 30 is within a range that satisfies D2>Da>Dc and D1 ⁇ Da>Db.
  • the impeller 4 can be mass-produced by resin molding. Further, as described above, since the protrusion 5 is provided so as to satisfy the condition D1 ⁇ Da>Db, in addition to the same effect as the centrifugal blower 1 according to the first embodiment, the material cost for the protrusion 5 is reduced. can be suppressed.
  • FIG. 17 is a perspective view of an impeller of a centrifugal blower according to Embodiment 3.
  • the protrusion 5 of the first embodiment is replaced with a protrusion 40.
  • the configuration of Embodiment 3 other than the protrusion 40 is the same as that of Embodiment 1, and redundant explanation will be omitted.
  • the protrusion 40 has a rotationally symmetrical shape, for example, an elliptical cylinder shape.
  • the elliptical cylindrical protrusion 40 has a central axis on the rotation axis 2 of the impeller 4 .
  • the major axis of the elliptical cylinder is equal to or less than the outer diameter D2 of the impeller 4
  • the minor axis of the elliptical cylinder is equal to or greater than the outer diameter Db of the ventilation hole 4e.
  • the major axis of the elliptical cylinder and the minor axis of the elliptical cylinder are measured using the outer diameter of the protrusion 40, for example.
  • the entire elliptical cylindrical protrusion 40 is installed in the range from the outer diameter D2 of the impeller 4 to the outer diameter Db of the ventilation hole 4e.
  • the major axis of the elliptical cylinder is the maximum width of the protrusion 40.
  • the impeller 4 does not need to be provided with the ventilation holes 4e.
  • the protruding part 40 is installed without protruding into a region outside the outer diameter of the impeller 4 in the radial direction over the entire circumference, and At least a portion of the impeller 4 is provided inside the outer diameter of the impeller 4 in the radial direction.
  • the longer diameter portion of the protruding portion 40 is installed on the outer diameter portion of the impeller 4, and the portion other than the longer diameter portion is provided further inside the outer diameter of the impeller 4 in the radial direction.
  • the protrusion 40 is not cylindrical but elliptical. Since the distance from the central axis to the wall surface of the elliptical cylindrical protrusion 40 varies depending on the location, it becomes difficult for sound waves existing inside the protrusion 40 and sound waves of the same frequency propagating in the opposite direction to overlap. Therefore, in the centrifugal blower 1 according to the third embodiment, standing waves are less likely to occur, and resonance noise can be effectively suppressed.
  • the elliptical cylindrical protrusion 40 has a large difference between the major axis and the minor axis.
  • the difference between the major axis and the minor axis is at least half the difference between the outer diameter D2 of the impeller 4 and the outer diameter Db of the ventilation hole 4e. That is, if the major axis of the protrusion 40 is Dx and the minor axis is Dn, it is preferable that (Dx-Dn)>(D2-Db)/2.
  • the protruding portion 40 since the protruding portion 40 has an elliptical cylindrical shape, standing waves are less likely to occur, resonance noise can be effectively suppressed, and noise can be further reduced. can.
  • the protrusion 40 is installed over the entire circumference of the impeller 4 without protruding from the outer diameter of the impeller 4 to a region outside the impeller 4 in the radial direction, and at least a portion of the entire circumference of the protrusion 40 extends beyond the impeller 4.
  • the shape is not limited to an ellipse, but may be any shape as long as it satisfies the condition that the shape is provided radially inside the outer diameter of the shape.
  • the configuration shown in the above embodiments shows an example of the content, and it is also possible to combine it with another known technology, or a part of the configuration can be omitted or changed without departing from the gist. It is also possible.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6411399U (https=) * 1987-07-10 1989-01-20
JP2006090297A (ja) * 2004-09-24 2006-04-06 Samsung Electronics Co Ltd シロッコファン及びこれを備えた空気調和機
WO2008072558A1 (ja) * 2006-12-14 2008-06-19 Panasonic Corporation 遠心羽根車とそれを用いた遠心送風機
WO2021144942A1 (ja) * 2020-01-17 2021-07-22 三菱電機株式会社 遠心送風機及び空気調和装置

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017044133A (ja) * 2015-08-26 2017-03-02 三菱電機株式会社 遠心送風機及び換気扇

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6411399U (https=) * 1987-07-10 1989-01-20
JP2006090297A (ja) * 2004-09-24 2006-04-06 Samsung Electronics Co Ltd シロッコファン及びこれを備えた空気調和機
WO2008072558A1 (ja) * 2006-12-14 2008-06-19 Panasonic Corporation 遠心羽根車とそれを用いた遠心送風機
WO2021144942A1 (ja) * 2020-01-17 2021-07-22 三菱電機株式会社 遠心送風機及び空気調和装置

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