CA1218635A - Centrifugal fans - Google Patents
Centrifugal fansInfo
- Publication number
- CA1218635A CA1218635A CA000424692A CA424692A CA1218635A CA 1218635 A CA1218635 A CA 1218635A CA 000424692 A CA000424692 A CA 000424692A CA 424692 A CA424692 A CA 424692A CA 1218635 A CA1218635 A CA 1218635A
- Authority
- CA
- Canada
- Prior art keywords
- blades
- impeller
- centrifugal fan
- actuator
- fan according
- 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
Links
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
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/003—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids by throttling
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Control Of Positive-Displacement Air Blowers (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
Abstract
ABSTRACT
A centrifugal fan having the inner edges of the impeller blades (7) extending parallel to the impeller axis incorporates a circular damper plate (11) supported coaxially within the array of blades with its edge closely adjacent the inner edges of the blades, and movable in an axial direction so as to vary the useful width of the blades and thereby the flow rate.
The damper plate, being separate from the impeller (2), may be supported in a non-rotatable manner and enables the fan to operate at an efficiency comparable with one having a radial vane damper, but is simpler mechanically as it requires only a single primary moving part.
A centrifugal fan having the inner edges of the impeller blades (7) extending parallel to the impeller axis incorporates a circular damper plate (11) supported coaxially within the array of blades with its edge closely adjacent the inner edges of the blades, and movable in an axial direction so as to vary the useful width of the blades and thereby the flow rate.
The damper plate, being separate from the impeller (2), may be supported in a non-rotatable manner and enables the fan to operate at an efficiency comparable with one having a radial vane damper, but is simpler mechanically as it requires only a single primary moving part.
Description
~2~ 3~i ~ he invention relates to centrifugal fans of the kind in which the impeller comprises a back plate carrying an array of blades disposed around a peripheral region of the back plate with their inner 5 edges eaually sp~ced from the axis of rotation to provide an inlet r:egion~ co~!monly known as the i~lpeller eye, into wbich a gas, such as air, is drawn to replace that which is expelled outwards be'ween the blades as the impeller rotates. In such fans the 10 impeller is normally housed within a casing in the form of a volute provided with an inlet opening which communicates with the eye of the impeller, and an outlet opening communicating with the space around the impeller through which the gas is discharged in 15 use of the fan~
~he flowrate of a centrifugal fan can be varied by varying the speed of rotation of the impeller but this is not always desirable or practicable.
~n alternative is to provide dampers, which may be positioned either on the inlet or outlet side of the fan, depending on the nature of the fan and the characteristics required, and although such dampers tend to lower the fan efficiency to some extent 25 depending on the form employed they have the advantage of simplicit~ and low initial cost compared with most methods used for varying the impeller speed.
One form of damper in common use consists of a plurality of parallel pivotable blades, usually 30 disposed across the fan outlet, and providing a greater or lesser resistance to the gas flow depending upon their angular setting~
~ nother form of damper makes use of radially extending pivotable vanes at the fan inlet. In use of 35 a centrifugal fan full pressure is developed by the fan only when ~as enters the impeller eye axially and without swirl. ~he radial vane damper is arranged to develop a degree of pre-rotation of the gas in the direction of impeller rotation, and as a result the pressure developed by the fan is reduced, with a consequential reduction in flowrate and power absorption. Such damper permits the fan to operate at a greater efficiency than the parallel blade dampers referred to above, but the mechanism required to enable the blades to rotate in synchronism is considerably more complicated.
It is known that for a given blade arrangement and speed of impeller rotation the flowrate is a function of the blade width, and this is made use of in providing an alternative form of damper which has advantages over the forms of dampers above described, 15 as will be apparent from the following description.
According to the invention a centrifugal fan of the kind referred to has the inner edges of impeller blades extending parallel to the impeller axis and incorporates a damper plate in the form of a circular 20 disc supported coaxially and non-rotatably within the anray of blades, with its edge closely adjacent the inner edges of the blades, the disc being movable in an axial direction within the array of blades by means of an actuator which is controllable automatically in 25 response to a control signal.
It has been found that such a damper effectively varies the useful width of the impeller blades, and enables the fan to operate at an efficiency which is comparable with one having a radial vane damper, but 30 is considerably simpler mechanically, requiring only a single primary moving part, and moreover, is able to give stable control to almost zero flow, added resistance being virtually negligible.
The axial movement of the damper plate may be 35 achieved by means of a pneumatic, hydraulic or electrically operated actuator, which is controlled automatically in response to a control signal derived B~
.. .
:`
3 Ei3~i in any suitable way, for example in dependence, either directly or indirectly, upon the fan output; or even from manual control means.
~he fan impeller can be driven by an electric motor or by any other suitable drive mean~. A vari~ble speed electric motor may be used in associatio~ with the movable damper plate to give an additional degree of controlO
~he invention is particularly applicable to blowing systems utilising relatively wide impellers of high specific speeds~ a ~ubstantial range o~ control being possible~ With the damper plate acting on width operation is unaffected by blade shape, and the impeller blades can therefore take any of the forms commonly empl~yed in centrifugal fans; for example the blades may be backwardly inclinded, backwardl~ or forwardl~
curved or of aerofoil section, provided their inner edges are para~lel to the impeller axis as above des-cribed~
One centri~ugal fan in accordance with the present invention will now be described by wa~ of example with reference to Figures 1 and 2 of the accompanying schematic drawin~, in which ~igure 1 represe~ts i~ diagrammatic form an axial ~ection through the fan~ and ~igure 2 represents a trans~erse ~ection in the plane indicated by the line II-II of Figure 1.
~he fan comprises, in the usual way, an outer casing 1 in the form of a volute having inlet a~d outlet openi~g~ 10~ 20 and rotatably supporting within it aa impelIer 2, the impeller compriæing a backplate 3 carried b~ a shaft 4 which extends through a bearing 5 mou~ted in the rear wall 6 of the casing for connectio~
to a suitable drive member (not ~hown) such as an ~^~J
'.
~ 2 ~ 5 electric ~otor.
~ he backplate 3 ~upports an array of blfides 7 disposed uniformly around the front faoe of the backplate 9 and ha~ing radially inner edges extending parallel to, and ~paced equidist~ntl~ from, the impeller axi~. ~n annular ~hroud 8 ifi attached to the front edges of the blades 79 it~ i~ner edge curving forwardly and ~urr~unding the Pdjacent end of a Btatio~ary i~let venturi 9 which communicates with the inlet opening 10 in the ~ront wall of the casing in hlowu mPnner.
In accordance with the invention the fan incor-porates a da~per co~prising a circular plate 11 supported coaxially withi~ the array of impeller blades 7~ a~d of a diameter such that its edge lies close to the inner edges of the blades with only a small clearance.
~he plate 11 i8 carried by an axially extending rod 12 which projects outwards through the inlet venturi 99 and iB movable axlally by means of an actuator 13 of any convenient kind9 supported ~rom the ca~ing 1 ~y radially ex*ending tie rods 14.
Movement of the actuatiDg rcd 12 alters the position of the damper plate 11 with respect to the impeller blades 7, a~d it h~s bee~ found that thi~
effectively co~trols the ~lowrate, by varying the u~eful width of the blades~ without an~ substa~tial loss of fan efficiency, and with the minimum of moving part~. ~he fl~wrate can be varied from practically zero with the damper pl~te 11 in a withdrawn position closely adjace~ the iDlet venturi 9~ to a mæ~imum ~alue whe~ it lie~ close to the backplate 3O
~ he actuator 13 ca~ be operated pneumatical~y, hydraulically or electrically or i~ any other co~
venie~t manner, dependiDg on the ~ature of the installation of which the fan forms part.
In one arrangement the fan may be associated with a tèmperature responsive sensor, as at 15 arranged to generate an output signal dependent upon 5 temperature and located in a position at which the temperature is responsive to ch2rlges ln the output of the fan, the output signal controlling the actuator, and hence the position of the damper plate, in the sense which tends to maintain the temperature 10 substantially constant. In an alternative arrangement the temperature sensor may be replaced by another form of sensor responsive to a different condition, for example humidit~, which is variable in response to changes in the fan output. Means may be provided for 15 adjustin~ the output signal, in order to vary the temperature or otber condition obtainable by adjustment of the fan output.
Although the impeller blades 7 are shown as planar and backwardly inclined in ~i~ure 2, it will 20 be understood that they can take any of the forms commonly employed in centrifugal fans of the kind with which the invention is concerned~
~he flowrate of a centrifugal fan can be varied by varying the speed of rotation of the impeller but this is not always desirable or practicable.
~n alternative is to provide dampers, which may be positioned either on the inlet or outlet side of the fan, depending on the nature of the fan and the characteristics required, and although such dampers tend to lower the fan efficiency to some extent 25 depending on the form employed they have the advantage of simplicit~ and low initial cost compared with most methods used for varying the impeller speed.
One form of damper in common use consists of a plurality of parallel pivotable blades, usually 30 disposed across the fan outlet, and providing a greater or lesser resistance to the gas flow depending upon their angular setting~
~ nother form of damper makes use of radially extending pivotable vanes at the fan inlet. In use of 35 a centrifugal fan full pressure is developed by the fan only when ~as enters the impeller eye axially and without swirl. ~he radial vane damper is arranged to develop a degree of pre-rotation of the gas in the direction of impeller rotation, and as a result the pressure developed by the fan is reduced, with a consequential reduction in flowrate and power absorption. Such damper permits the fan to operate at a greater efficiency than the parallel blade dampers referred to above, but the mechanism required to enable the blades to rotate in synchronism is considerably more complicated.
It is known that for a given blade arrangement and speed of impeller rotation the flowrate is a function of the blade width, and this is made use of in providing an alternative form of damper which has advantages over the forms of dampers above described, 15 as will be apparent from the following description.
According to the invention a centrifugal fan of the kind referred to has the inner edges of impeller blades extending parallel to the impeller axis and incorporates a damper plate in the form of a circular 20 disc supported coaxially and non-rotatably within the anray of blades, with its edge closely adjacent the inner edges of the blades, the disc being movable in an axial direction within the array of blades by means of an actuator which is controllable automatically in 25 response to a control signal.
It has been found that such a damper effectively varies the useful width of the impeller blades, and enables the fan to operate at an efficiency which is comparable with one having a radial vane damper, but 30 is considerably simpler mechanically, requiring only a single primary moving part, and moreover, is able to give stable control to almost zero flow, added resistance being virtually negligible.
The axial movement of the damper plate may be 35 achieved by means of a pneumatic, hydraulic or electrically operated actuator, which is controlled automatically in response to a control signal derived B~
.. .
:`
3 Ei3~i in any suitable way, for example in dependence, either directly or indirectly, upon the fan output; or even from manual control means.
~he fan impeller can be driven by an electric motor or by any other suitable drive mean~. A vari~ble speed electric motor may be used in associatio~ with the movable damper plate to give an additional degree of controlO
~he invention is particularly applicable to blowing systems utilising relatively wide impellers of high specific speeds~ a ~ubstantial range o~ control being possible~ With the damper plate acting on width operation is unaffected by blade shape, and the impeller blades can therefore take any of the forms commonly empl~yed in centrifugal fans; for example the blades may be backwardly inclinded, backwardl~ or forwardl~
curved or of aerofoil section, provided their inner edges are para~lel to the impeller axis as above des-cribed~
One centri~ugal fan in accordance with the present invention will now be described by wa~ of example with reference to Figures 1 and 2 of the accompanying schematic drawin~, in which ~igure 1 represe~ts i~ diagrammatic form an axial ~ection through the fan~ and ~igure 2 represents a trans~erse ~ection in the plane indicated by the line II-II of Figure 1.
~he fan comprises, in the usual way, an outer casing 1 in the form of a volute having inlet a~d outlet openi~g~ 10~ 20 and rotatably supporting within it aa impelIer 2, the impeller compriæing a backplate 3 carried b~ a shaft 4 which extends through a bearing 5 mou~ted in the rear wall 6 of the casing for connectio~
to a suitable drive member (not ~hown) such as an ~^~J
'.
~ 2 ~ 5 electric ~otor.
~ he backplate 3 ~upports an array of blfides 7 disposed uniformly around the front faoe of the backplate 9 and ha~ing radially inner edges extending parallel to, and ~paced equidist~ntl~ from, the impeller axi~. ~n annular ~hroud 8 ifi attached to the front edges of the blades 79 it~ i~ner edge curving forwardly and ~urr~unding the Pdjacent end of a Btatio~ary i~let venturi 9 which communicates with the inlet opening 10 in the ~ront wall of the casing in hlowu mPnner.
In accordance with the invention the fan incor-porates a da~per co~prising a circular plate 11 supported coaxially withi~ the array of impeller blades 7~ a~d of a diameter such that its edge lies close to the inner edges of the blades with only a small clearance.
~he plate 11 i8 carried by an axially extending rod 12 which projects outwards through the inlet venturi 99 and iB movable axlally by means of an actuator 13 of any convenient kind9 supported ~rom the ca~ing 1 ~y radially ex*ending tie rods 14.
Movement of the actuatiDg rcd 12 alters the position of the damper plate 11 with respect to the impeller blades 7, a~d it h~s bee~ found that thi~
effectively co~trols the ~lowrate, by varying the u~eful width of the blades~ without an~ substa~tial loss of fan efficiency, and with the minimum of moving part~. ~he fl~wrate can be varied from practically zero with the damper pl~te 11 in a withdrawn position closely adjace~ the iDlet venturi 9~ to a mæ~imum ~alue whe~ it lie~ close to the backplate 3O
~ he actuator 13 ca~ be operated pneumatical~y, hydraulically or electrically or i~ any other co~
venie~t manner, dependiDg on the ~ature of the installation of which the fan forms part.
In one arrangement the fan may be associated with a tèmperature responsive sensor, as at 15 arranged to generate an output signal dependent upon 5 temperature and located in a position at which the temperature is responsive to ch2rlges ln the output of the fan, the output signal controlling the actuator, and hence the position of the damper plate, in the sense which tends to maintain the temperature 10 substantially constant. In an alternative arrangement the temperature sensor may be replaced by another form of sensor responsive to a different condition, for example humidit~, which is variable in response to changes in the fan output. Means may be provided for 15 adjustin~ the output signal, in order to vary the temperature or otber condition obtainable by adjustment of the fan output.
Although the impeller blades 7 are shown as planar and backwardly inclined in ~i~ure 2, it will 20 be understood that they can take any of the forms commonly employed in centrifugal fans of the kind with which the invention is concerned~
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A centrifugal fan of the kind in which the impeller comprises a back plate carrying an array of blades disposed around a peripheral region of the back plate with their inner edges equally spaced from the axis of rotation to provide an inlet region into which a gas is drawn to replace that which is expelled outwards between the blades as the impeller rotates, the inner edges of the impeller blades extending parallel to the impeller axis, a damper plate in the form of a circular disc being supported coaxially and non-rotatably within the array of blades with its edge closely adjacent the inner edges of the blades, the disc being movable in an axial direction within the array of blades by means of an actuator which is controllable automatically in response to a control signal.
2. A centrifugal fan according to claim 1 including a sensor arranged to generate a signal which is dependent upon a condition variable in response to changes in the output of the fan, and means for applying said signal as a control signal for controlling the actuator, and hence the position of the damper plate, in a manner which tends to maintain said condition substantially constant.
3. A centrifugal fan according to claim 2 wherein the sensor is responsive to temperature changes.
4. A centrifugal fan according to claim 1, 2 or 3 wherein the actuator is operable electrically.
5. A centrifugal fan according to claim 1, 2 or 3 wherein the actuator is operable pneumatically or hydraulically.
6. A centrifugal fan according to claim 1 wherein the actuator is controllable in response to a manually produced control signal.
7. A centrifugal fan according to claim 1, 2 or 3 wherein the impeller is driven by a variable speed electric motor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8212312 | 1982-04-28 | ||
| GB8212312 | 1982-04-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1218635A true CA1218635A (en) | 1987-03-03 |
Family
ID=10530035
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000424692A Expired CA1218635A (en) | 1982-04-28 | 1983-03-28 | Centrifugal fans |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0099615A3 (en) |
| JP (1) | JPS58190599A (en) |
| AU (1) | AU555454B2 (en) |
| CA (1) | CA1218635A (en) |
| DK (1) | DK161283A (en) |
| HK (1) | HK70486A (en) |
| MY (1) | MY8700205A (en) |
| NO (1) | NO831256L (en) |
| NZ (1) | NZ203561A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2224076A (en) * | 1988-08-03 | 1990-04-25 | Atomic Energy Authority Uk | Controlling pumps |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1834959A (en) * | 1929-02-14 | 1931-12-08 | Comb Eer Inc | Blower |
| DE2311061A1 (en) * | 1973-03-06 | 1974-09-12 | Maschf Augsburg Nuernberg Ag | DEVICE FOR SEALING AND SECURING A CYLINDER LID |
-
1983
- 1983-03-14 NZ NZ20356183A patent/NZ203561A/en unknown
- 1983-03-16 EP EP83301462A patent/EP0099615A3/en not_active Withdrawn
- 1983-03-28 CA CA000424692A patent/CA1218635A/en not_active Expired
- 1983-04-08 NO NO831256A patent/NO831256L/en unknown
- 1983-04-13 DK DK161283A patent/DK161283A/en not_active IP Right Cessation
- 1983-04-15 JP JP6686183A patent/JPS58190599A/en active Pending
- 1983-04-28 AU AU14031/83A patent/AU555454B2/en not_active Ceased
-
1986
- 1986-09-18 HK HK70486A patent/HK70486A/en not_active IP Right Cessation
-
1987
- 1987-12-30 MY MY8700205A patent/MY8700205A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| HK70486A (en) | 1986-09-26 |
| DK161283D0 (en) | 1983-04-13 |
| EP0099615A3 (en) | 1984-08-08 |
| NO831256L (en) | 1983-10-31 |
| MY8700205A (en) | 1987-12-31 |
| AU1403183A (en) | 1983-11-03 |
| AU555454B2 (en) | 1986-09-25 |
| JPS58190599A (en) | 1983-11-07 |
| EP0099615A2 (en) | 1984-02-01 |
| DK161283A (en) | 1983-10-29 |
| NZ203561A (en) | 1986-04-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |