WO1990009524A1 - Centrifugal fan and diffuser with accumulating volute - Google Patents

Centrifugal fan and diffuser with accumulating volute Download PDF

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Publication number
WO1990009524A1
WO1990009524A1 PCT/US1990/000658 US9000658W WO9009524A1 WO 1990009524 A1 WO1990009524 A1 WO 1990009524A1 US 9000658 W US9000658 W US 9000658W WO 9009524 A1 WO9009524 A1 WO 9009524A1
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WIPO (PCT)
Prior art keywords
volute
blower
diffuser
airflow
impeller
Prior art date
Application number
PCT/US1990/000658
Other languages
French (fr)
Inventor
Martin G. Yapp
Original Assignee
Airflow Research & Manufacturing Corporation
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 Airflow Research & Manufacturing Corporation filed Critical Airflow Research & Manufacturing Corporation
Publication of WO1990009524A1 publication Critical patent/WO1990009524A1/en

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Classifications

    • 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
    • F04D29/441—Fluid-guiding means, e.g. diffusers especially adapted for elastic fluid pumps

Definitions

  • This invention relates to centrifugal blowers and fans.
  • Centrifugal blowers and fans generally include an impeller that rotates in a predetermined direction in a housing and is driven by an electric motor.
  • the impeller has curved blades which draw air in axially, along the impeller's axis of rotation, and disch rge air radially outwardly.
  • blowers are used in a variet of applications, and they may feature a variety of blower design points for pressure difference, airflow volume, motor power, motor speed, space constraints, inlet and outlet configuration, noise, and manufacturing tolerances.
  • blade exit angle the angle of the blade tip relative to a tangen to the tip. This angle is called the "blade exit angle”. If the blade exit angle is greater than 90°, the impeller is said to have forwardly curved blades; if the blade exit angle is less than 90°, the impeller is said to have rearwardly curved blades.
  • Centrifugal blowers may include a volute which recaptures dynamic pressure (the kinetic energy inherent in moving fluid) and converts that dynamic pressure to static pressure.
  • GB 2,080,879 discloses a rearwardly curved centrifugal blower with stator vanes to convert radial flow to axial flow.
  • GB 1,483,455 and GB 1,473,919 disclose centrifugal blowers with a volute.
  • GB 1,426,503 discloses a centrifugal blower with dual openings.
  • Canadian 1,157,902 discloses a rearwardly curved centrifugal blower with a curved sheet-metal guide.
  • volute geometry achieves substantially ( ⁇ 20%) constant pressure around the volute, which avoids pressure and velocity gradients inherent in designs which exhibit substantial increases in the radial extent of the volute, or which fail to accomodate increasing airflow volume around the circumference of the volute. Because the volute provides uniform airflow velocity, it is possible to improve the blower's efficiency further by including one or more stator vanes in the diffuser.
  • the stator vanes extend in the general direction of airflow velocity, and the leading edge of at least one vane extends into the volute.
  • the volute does, however, increase in cross-sectional area around its circumference to accomodate increasing air volume as the impeller rotates. Specifically, the volume of air moving through the volute at point B will be far greater than the volume at point A. Failure to increase the cross-sectional area to accomodate this increased volume would cause a velocity increase, which is generally undesirable.
  • the log spiral the cross-sectional area increases as a log function to produce an increase in pressure with radius. Increasing the area too rapidly increases pressure and hinders flow to the heat exchanger.
  • the axial extent of the volute increases around the circumference at a rate which maintains a relatively steady pressure in the volute (e.g. ⁇ 20%).
  • the cross-sectional area of the volute increases substantially linearly with circumferential position.
  • the invention generally features a centrifugal blower having an impeller rotating on an axis in a predetermined direction and a housing surrounding the impeller.
  • the housing is sized, shaped and positioned to define a volute positioned around at least part of the impeller circumference and a diffuser to receiving and control airflow from the volute.
  • the radial extent of the volute remains substantially constant.
  • the cross-sectional area of the volute increases substantially linearly as a function of circumferential position in the direction of impeller rotation. Increasing airflow is accomodated so that airflow pressure around the volute remains substantially constant (e.g. ⁇ 20%).
  • the radius of the volute remains substantially constant (e.g. ⁇ 20%).
  • the axial extent of the volute increases substantially around the circumference of the blower so that the cross sectional area of the volute is a substantially linear function of angular position in the volute.
  • the axial extent of the blower is at last 4X the radial extent of the blower, in the volute region extending from about 160° to 270°.
  • the diffuser (which expands rapidly in the radial direction) includes at least one stator vane (preferably multiple vanes) extending in the general direction of airflow, and the leading edge of at least one vane is positioned in the volute.
  • the airflow velocity is preferably uniform at the leading edge of that vane.
  • the diffuser outlet is adapted to be positioned at a source of air resistance (e.g. a heat exchanger).
  • the impeller preferably has rearwardly curved blades.
  • Fig. 1 is a top view of a centrifugal blower, volute and diffuser, connected to a heat exchanger.
  • Fig. 2 is a section of the blower of Fig. 1 taken along 1-1.
  • Fig. 3 is a graph of volute axial dimension and of volute radial dimension (width) as a function of circumferential position.
  • Fig. 4 is a graph of volute cross-sectional area as a function of circumferential position.
  • centrifugal blower 10 includes a rotating impeller 12 driven by a motor 14.
  • the impeller has rearwardly curved blades 15 which rotate within housing 16 to draw air axially through inlet 18 and then force it radially outward to volute 20.
  • Volute 20 surrounds impeller 12. As best shown in Fig. 1, the radial extent of volute 20 remains substantially constant. For example, the radius of the volute increases less than 20% from point A to point B (an arc of about 160°-270° from the inlet to the volute). At the same time, the cross-sectional area of the volute increases in a linear fashion with circumferential position.
  • the diffuser thus pulls on the airflow radially to recover static pressure from the velocity energy (swirl) of the airflow.
  • swirl velocity decreases as the airflow radius increases; Bernoulli's law requires that static pressure increase as velocity decreases.
  • volute-diffuser geometry avoids energy loss that occurs in a radially extended volute.
  • the large diffuser exit area (5x the volute exit area) reduces the exit losses.
  • the axially extended volute design (the axial/radial dimension of the volute at B is at least 4x) reduces variations in velocity at the outlet by reducing vorticies. Because the outlet flow is organized and its direction is known, it is possible to use vanes, as set forth below, in the pressure-building area of the system (the diffuser) to smooth the flow to the heat exchanger and to increase the effectiveness of the diffuser. At an arc of about 300°-330° from the inlet to the volute, the volute connects to a diffuser 22 which increases cross-sectional area rapidly, by increasing its radial dimensions, and thereby increases pressure.
  • Diffuser 22 includes vanes 24 which serve to maintain attached boundary layer flow as the diffuser increases in area (resulting in increased pressure).
  • One vane 24a extends into the volute to shield the impeller 10 from pressure in the diffuser created by the heat exchanger 26.
  • the passage between any pair of vanes constitutes a diffuser, and, the effectiveness of any diffuser increases as the included angle between the sides decreases.
  • the multi-vaned diffuser is much more effective than one without vanes. The effective use of such a multi-vane diffuser is possible because of the above-mentioned control over area and pressure in the volute to reduce pressure and velocity gradients of airflow entering the diffusion area.

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

Abstract

A centrifugal blower (10) and volute (20) in which the radial extent of the volute is controlled to keep it substantially (e.g., ±20 %) constant up to the connection to the diffuser (22). The cross-sectional area of the volute increases linearly in the direction of impeller (10) rotation to accommodate increasing airflow volume. Airflow exits the volute and enters a diffuser which rapidly opens (increases in cross-sectional area) by increasing its radial extent. The diffuser may be attached to a source of air resistance such as a heat exchanger (26).

Description

Figure imgf000003_0001
- 1 -
CENTRIFUGAL FAN AND DIFFUSER WITH ACCUMULATING VOLUTE
Background of the Invention This invention relates to centrifugal blowers and fans.
Centrifugal blowers and fans generally include an impeller that rotates in a predetermined direction in a housing and is driven by an electric motor. The impeller has curved blades which draw air in axially, along the impeller's axis of rotation, and disch rge air radially outwardly. Such blowers are used in a variet of applications, and they may feature a variety of blower design points for pressure difference, airflow volume, motor power, motor speed, space constraints, inlet and outlet configuration, noise, and manufacturing tolerances.
One important design feature in a centrifugal' fan is the angle of the blade tip relative to a tangen to the tip. This angle is called the "blade exit angle". If the blade exit angle is greater than 90°, the impeller is said to have forwardly curved blades; if the blade exit angle is less than 90°, the impeller is said to have rearwardly curved blades.
Centrifugal blowers (particularly forwardly curved blowers) may include a volute which recaptures dynamic pressure (the kinetic energy inherent in moving fluid) and converts that dynamic pressure to static pressure.
Specific centrifugal blowers described in prior patents are discussed below. Koger et al., U.S. 4,526,506 and DE 2,210,271 disclose rearwardly curved centrifugal blowers with a volute.
GB 2,080,879 discloses a rearwardly curved centrifugal blower with stator vanes to convert radial flow to axial flow.
Zochfeld, U.S. 3,597,117 and GB 2,063,365 disclose forwardly curved centrifugal blowers with a volute. Calabro, U.S. 3,967,874 discloses a blower 16 positioned in a plenum chamber 14. The blade configuration and blower design are not apparent, but opening 46 in the bottom of the plenum chamber is in communication with the blower outlet. GB 2,166,494 discloses a centrifugal impeller in a rotationally symmetrical cone-shaped housing, with guide vanes to produce an axial discharge.
GB 1,483,455 and GB 1,473,919 disclose centrifugal blowers with a volute. GB 1,426,503 discloses a centrifugal blower with dual openings.
Shikatani et al., U.S. 4,269,571 disclose a centripetal blower, which draws air in axial entrance 26 and out of the top periphery of disc 22 and axial exit 27 (3:26-36).
Canadian 1,157,902 discloses a rearwardly curved centrifugal blower with a curved sheet-metal guide.
Summary of the Invention Improved performance for a centrifugal blower is achieved by controlling the radial extent of the volute to keep it substantially (e.g., ±20%) constant up to the connection to the diffuser, as explained in greater detail below; at the same time, the cross-sectional area of the volute increases in the direction of impeller rotation to accomodate increasing airflow volume. Airflow exits the volute and enters a diffuser which rapidly opens (increases in cross-sectional area) by increasing its radial extent. The diffuser may be attached to a source of air resistance such as a heat exchanger.
The above described volute geometry achieves substantially (±20%) constant pressure around the volute, which avoids pressure and velocity gradients inherent in designs which exhibit substantial increases in the radial extent of the volute, or which fail to accomodate increasing airflow volume around the circumference of the volute. Because the volute provides uniform airflow velocity, it is possible to improve the blower's efficiency further by including one or more stator vanes in the diffuser. The stator vanes extend in the general direction of airflow velocity, and the leading edge of at least one vane extends into the volute.
The volute does, however, increase in cross-sectional area around its circumference to accomodate increasing air volume as the impeller rotates. Specifically, the volume of air moving through the volute at point B will be far greater than the volume at point A. Failure to increase the cross-sectional area to accomodate this increased volume would cause a velocity increase, which is generally undesirable. In one common prior art volute design, called the log spiral, the cross-sectional area increases as a log function to produce an increase in pressure with radius. Increasing the area too rapidly increases pressure and hinders flow to the heat exchanger. In contrast to such designs, in blowers according to the invention, the axial extent of the volute (and therefore its cross-sectional area) increases around the circumference at a rate which maintains a relatively steady pressure in the volute (e.g. ± 20%). In other words, the cross-sectional area of the volute increases substantially linearly with circumferential position.
Accordingly, the invention generally features a centrifugal blower having an impeller rotating on an axis in a predetermined direction and a housing surrounding the impeller. The housing is sized, shaped and positioned to define a volute positioned around at least part of the impeller circumference and a diffuser to receiving and control airflow from the volute. The radial extent of the volute remains substantially constant. The cross-sectional area of the volute increases substantially linearly as a function of circumferential position in the direction of impeller rotation. Increasing airflow is accomodated so that airflow pressure around the volute remains substantially constant (e.g. ± 20%).
In preferred embodiments the radius of the volute remains substantially constant (e.g. ± 20%). The axial extent of the volute increases substantially around the circumference of the blower so that the cross sectional area of the volute is a substantially linear function of angular position in the volute. The axial extent of the blower is at last 4X the radial extent of the blower, in the volute region extending from about 160° to 270°. The diffuser (which expands rapidly in the radial direction) includes at least one stator vane (preferably multiple vanes) extending in the general direction of airflow, and the leading edge of at least one vane is positioned in the volute. The airflow velocity is preferably uniform at the leading edge of that vane. The diffuser outlet is adapted to be positioned at a source of air resistance (e.g. a heat exchanger). The impeller preferably has rearwardly curved blades.
Other features and advantages of the invention will be apparent from the following claims.
Description of the Preferred Embodiment
Fig. 1 is a top view of a centrifugal blower, volute and diffuser, connected to a heat exchanger.
Fig. 2 is a section of the blower of Fig. 1 taken along 1-1.
Fig. 3 is a graph of volute axial dimension and of volute radial dimension (width) as a function of circumferential position.
Fig. 4 is a graph of volute cross-sectional area as a function of circumferential position.
In Figs, l and 2, centrifugal blower 10 includes a rotating impeller 12 driven by a motor 14. The impeller has rearwardly curved blades 15 which rotate within housing 16 to draw air axially through inlet 18 and then force it radially outward to volute 20.
Volute 20 surrounds impeller 12. As best shown in Fig. 1, the radial extent of volute 20 remains substantially constant. For example, the radius of the volute increases less than 20% from point A to point B (an arc of about 160°-270° from the inlet to the volute). At the same time, the cross-sectional area of the volute increases in a linear fashion with circumferential position.
The diffuser thus pulls on the airflow radially to recover static pressure from the velocity energy (swirl) of the airflow. Specifically, the swirl velocity decreases as the airflow radius increases; Bernoulli's law requires that static pressure increase as velocity decreases.
The volute-diffuser geometry described above avoids energy loss that occurs in a radially extended volute. The large diffuser exit area (5x the volute exit area) reduces the exit losses. The axially extended volute design (the axial/radial dimension of the volute at B is at least 4x) reduces variations in velocity at the outlet by reducing vorticies. Because the outlet flow is organized and its direction is known, it is possible to use vanes, as set forth below, in the pressure-building area of the system (the diffuser) to smooth the flow to the heat exchanger and to increase the effectiveness of the diffuser. At an arc of about 300°-330° from the inlet to the volute, the volute connects to a diffuser 22 which increases cross-sectional area rapidly, by increasing its radial dimensions, and thereby increases pressure.
Diffuser 22 includes vanes 24 which serve to maintain attached boundary layer flow as the diffuser increases in area (resulting in increased pressure). One vane 24a extends into the volute to shield the impeller 10 from pressure in the diffuser created by the heat exchanger 26. The passage between any pair of vanes constitutes a diffuser, and, the effectiveness of any diffuser increases as the included angle between the sides decreases. Thus, the multi-vaned diffuser is much more effective than one without vanes. The effective use of such a multi-vane diffuser is possible because of the above-mentioned control over area and pressure in the volute to reduce pressure and velocity gradients of airflow entering the diffusion area.
Other embodiments are within the following claims.

Claims

- 7 -
Claims 1. A centrifugal blower comprising an impeller rotating on an axis in a predetermined direction, and" a housing surrounding the impeller, the housing being sized, shaped, and positioned to define: a) a volute around at least part of the circumference of the impeller; and b) a diffuser shaped and positioned to receive airflow from the volute and to control that airflow, the blower being further characterized in that: the radial extent of the volute remains substantially constant; the cross-sectional area of the volute increases substantially linearly as a function of circumferential position in the direction of impeller rotation to accomodate increasing airflow volume, 5 whereby the airflow pressure around the volute 6 remains substantially constant.
2. The blower of claim l in which the radius of the volute remains constant within ±20%.
3. The blower of claim 1 in which the axial extent of the volute increases substantially around the circumference of the blower, whereby the cross-sectional area of the volute is a substantially linear function of angular position in the volute.
i 4. The blower of claim 1 in which the axial
2 extent of the blower is at least four times the radial
3 extent of the blower in the volute region extending from
4 about 160°-270°.
i
5. The blower of claim 1 in which the diffuser
2 comprises at least one stator vane extending in the
3 general direction of airflow, the leading edge of said
4 vane being positioned in the volute.
6. The blower of claim 5 in which the airflow velocity is substantially uniform at the leading edge of the vane.
7. The blower of claim 1 in which the diffuser comprises an outlet adapted to be positioned at a source of air resistance.
8. The blower of claim 7 in which the source of air resistance is a heat exchanger.
9. The blower of claim 1 in which the impeller comprises rearwardly curved blades.
PCT/US1990/000658 1989-02-14 1990-02-05 Centrifugal fan and diffuser with accumulating volute WO1990009524A1 (en)

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US31043089A 1989-02-14 1989-02-14
US310,430 1989-02-14

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0570955A1 (en) * 1992-05-20 1993-11-24 Praxair Technology, Inc. Compressor collector with nonuniform cross section
FR2781531A1 (en) * 1998-07-24 2000-01-28 Valeo Climatisation Centrifugal fan for vehicle air conditioning systems has outlet from voluted case connected to outlet flow pipe via an intermediate flaring section, which gives abrupt increase in cross sectional area of flow.
GB2340550A (en) * 1998-07-13 2000-02-23 Ford Motor Co Centrifugal blower assembly with diffuser
US6499954B1 (en) 2000-08-21 2002-12-31 Textron Automotive Company Inc. Centrifugal impeller and housing
US6604906B2 (en) * 2000-08-04 2003-08-12 Calsonic Kansei Corporation Centrifugal multiblade blower
GB2400168A (en) * 2003-04-03 2004-10-06 Peter Yeung Kitchen range hood motor housing and fan
DE202005004180U1 (en) * 2005-03-14 2006-07-27 Ebm-Papst Landshut Gmbh centrifugal blower
EP1747917A2 (en) 2005-07-28 2007-01-31 ebm-papst St. Georgen GmbH & Co. KG Heating device
EP2068002A1 (en) * 2007-12-07 2009-06-10 ABB Turbo Systems AG Compressor casing
EP2292935A2 (en) * 2009-07-17 2011-03-09 Behr GmbH & Co. KG Radial ventilator housing
CN108700090A (en) * 2016-03-30 2018-10-23 三菱重工发动机和增压器株式会社 Compressor is vortexed and centrifugal compressor
EP3815520A1 (en) * 2019-10-29 2021-05-05 Andreas Stihl AG & Co. KG Hand-held machining apparatus with radial blower
DE102020210330A1 (en) 2020-08-13 2022-02-17 Mahle International Gmbh Air duct housing of a heating, ventilation or air conditioning system

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2042496A (en) * 1934-02-19 1936-06-02 Gen Electric Multistage rotary compressor
US3246834A (en) * 1963-12-18 1966-04-19 Space Conditioning Inc Blower housing
JPS5388205A (en) * 1977-01-14 1978-08-03 Hitachi Ltd Centrifugal type hydraulic machine
JPS5421608A (en) * 1977-07-18 1979-02-19 Sanyo Electric Co Ltd Centrifugal fan
DE3432503A1 (en) * 1984-09-04 1986-03-13 Siemens AG, 1000 Berlin und 8000 München RADIAL FAN
US4712611A (en) * 1985-06-07 1987-12-15 Sueddeutsche Kuehlerfabrik Julius Fr. Behr Gmbh & Co. Kg Heating or air-conditioning ventilation unit for motor vehicles

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2042496A (en) * 1934-02-19 1936-06-02 Gen Electric Multistage rotary compressor
US3246834A (en) * 1963-12-18 1966-04-19 Space Conditioning Inc Blower housing
JPS5388205A (en) * 1977-01-14 1978-08-03 Hitachi Ltd Centrifugal type hydraulic machine
JPS5421608A (en) * 1977-07-18 1979-02-19 Sanyo Electric Co Ltd Centrifugal fan
DE3432503A1 (en) * 1984-09-04 1986-03-13 Siemens AG, 1000 Berlin und 8000 München RADIAL FAN
US4712611A (en) * 1985-06-07 1987-12-15 Sueddeutsche Kuehlerfabrik Julius Fr. Behr Gmbh & Co. Kg Heating or air-conditioning ventilation unit for motor vehicles

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0570955A1 (en) * 1992-05-20 1993-11-24 Praxair Technology, Inc. Compressor collector with nonuniform cross section
GB2340550A (en) * 1998-07-13 2000-02-23 Ford Motor Co Centrifugal blower assembly with diffuser
GB2340550B (en) * 1998-07-13 2002-10-09 Ford Motor Co A centrifugal blower assembly with a diffuser
FR2781531A1 (en) * 1998-07-24 2000-01-28 Valeo Climatisation Centrifugal fan for vehicle air conditioning systems has outlet from voluted case connected to outlet flow pipe via an intermediate flaring section, which gives abrupt increase in cross sectional area of flow.
US6604906B2 (en) * 2000-08-04 2003-08-12 Calsonic Kansei Corporation Centrifugal multiblade blower
US6499954B1 (en) 2000-08-21 2002-12-31 Textron Automotive Company Inc. Centrifugal impeller and housing
GB2400168A (en) * 2003-04-03 2004-10-06 Peter Yeung Kitchen range hood motor housing and fan
GB2400168B (en) * 2003-04-03 2006-09-20 Peter Yeung Range hood motor housing and fan assembly
DE202005004180U1 (en) * 2005-03-14 2006-07-27 Ebm-Papst Landshut Gmbh centrifugal blower
US8257034B2 (en) 2005-03-14 2012-09-04 ERM-Papst Landshut GmbH Radial fan
EP1747917A3 (en) * 2005-07-28 2007-12-26 ebm-papst St. Georgen GmbH & Co. KG Heating device
EP1747917A2 (en) 2005-07-28 2007-01-31 ebm-papst St. Georgen GmbH & Co. KG Heating device
EP2068002A1 (en) * 2007-12-07 2009-06-10 ABB Turbo Systems AG Compressor casing
WO2009071621A1 (en) * 2007-12-07 2009-06-11 Abb Turbo Systems Ag Compressor housing
EP2292935A2 (en) * 2009-07-17 2011-03-09 Behr GmbH & Co. KG Radial ventilator housing
EP2292935A3 (en) * 2009-07-17 2013-01-30 Behr GmbH & Co. KG Radial ventilator housing
CN108700090A (en) * 2016-03-30 2018-10-23 三菱重工发动机和增压器株式会社 Compressor is vortexed and centrifugal compressor
CN108700090B (en) * 2016-03-30 2020-05-15 三菱重工发动机和增压器株式会社 Compressor scroll and centrifugal compressor
EP3815520A1 (en) * 2019-10-29 2021-05-05 Andreas Stihl AG & Co. KG Hand-held machining apparatus with radial blower
US11434926B2 (en) 2019-10-29 2022-09-06 Andreas Stihl Ag & Co. Kg Hand-guided working apparatus having a radial fan
DE102020210330A1 (en) 2020-08-13 2022-02-17 Mahle International Gmbh Air duct housing of a heating, ventilation or air conditioning system

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