GB2467354A

GB2467354A - Two fans having a common displaceable fan shroud

Info

Publication number: GB2467354A
Application number: GB0901567A
Authority: GB
Inventors: Colin J Biggs
Original assignee: NU AIRE Ltd
Current assignee: NU AIRE Ltd
Priority date: 2009-01-30
Filing date: 2009-01-30
Publication date: 2010-08-04
Anticipated expiration: 2029-01-30
Also published as: GB0901567D0; EP2213954B1; EP2213954A1; GB2467354B

Abstract

A fan system or method of controlling a fan system comprises a displaceable fan shroud common to both a first (duty) fan 103 and a second (back-up) fan 102. The first and second fans are in-line. The displaceable shroud is pivotally moved to alter the flow characteristics of the fan system so that airflow from an outlet 108 of the system is switched between the first and second fan. The shroud is hinged 109 intermediately between the first and second fans, and in a first position provides an airflow guiding surface for airflow from the first fan and in a second position provides an airflow guiding surface for airflow from the second fan. The shroud may have a concave surface 107 and a convex surface on opposite sides. A pneumatic piston 110 may be used to drive the displaceable shroud. The shroud may be driven intermediate of two extreme positions enabling both fans to operate simultaneously. The fans may be centrifugal fans.

Description

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Ventilation System The present invention relates to a ventilation system.

Ventilation systems are often provided with at least two fan units, one to act as a lead or duty fan' and the other as an idle or standby' fan, ready for operation should the duty fan fail. Conventionally, such a ventilation system comprises two complete fan units located together in a common enclosure, one of the fans arranged to operate continuously until failure, at which point the other fan starts and takes over the ventilating operation.

Such functionality is known as 100% duty and standby operation' and is commonly specified in the UK and elsewhere for toilet extract ventilation systems, for smoke transfer ventilation systems, extract and stairwell pressurisation systems and also for critical process ventilation systems.

In the event of duty fan failure, the standby fan may be turned on by manual control, but more commonly, is turned on automatically by a duty fan failure detection system, linked to the standby fan's control circuit.

Other control enhancements are commonly found, for example, duty sharing', whereby . each fan in turn periodically assumes the role of the duty fan, thus equalising wear and * S.* ensuring that both fans are regularly exercised.

To achieve 100% operation from both fans, it is necessary to arrange the system so that : ** 25 either: 1) two identical fans are used, and the air entry and discharge paths are similar for * U..

* both in terms of resistance to airflow, or 2) the two fans are dissimilar, so that each ** component is rated to achieve the same delivered air flow rate for the unit as a whole.

Currently, there are a number of known systems available on the market.

EP1936291 discloses two prior art systems. Referring to Figure 1 of EP1936291, there is illustrated a known ventilation system I comprising a housing 2 having an air inlet port 3 at one end 2a and an air outlet port 4 at an opposite end 2b. The housing 1 contains a first fan 4 and a second fan 5. The first fan 5 and the second fan 6 are identical and are arranged side by side in parallel between the air inlet port 3 and the air outlet port 4.

The first fan 5 and the second fan 6 are provided with respective non -return shutter or damper arrangements 5a and 6a, each configurable in an open position to enable air to flow through the respective fans 5 and 6 and in a closed position to prevent air flowing thorough the respective fans 5 and 6. In use, the shutter associated with the duty fan is open (the first fan 5 in Figure 1) and the shutter associated with the standby fan is closed (the second fan 6 in Figure 1). The duty fan 5 causes air to flow into the housing I through the air inlet 3 and out from the housing through the air outlet 4. The closed non -return shutter 6a of the standby fan 6 prevents the backflow of air through the standby fan 6, an effect that would de-rate the performance of the duty fan 5.

Typically, the fans 5 and 6 are centrifugal fans, although they may also be axial flow fans, provided that they can overcome the air flow resistance presented by the system's layout.

In such systems, the fans are arranged side by side, so that the air entry and exit paths for both are similar. A disadvantage of such systems is that the width (w) of the housing is at least twice that of an individual fan, and often as much as three times as wide. This is * * 20 necessary to allow for a reasonable clearance around the fans' inlet areas. Additionally, the length (L) of the housing may also be significantly greater than that of an individual fan to make provision for efficient guiding of incoming air and to incorporate the non-return shutters or dampers 5a, 6a. Simply reducing the size of the housing I can cause significant penalties in terms of performance, noise and required fan power.

* ** 25 Figure 2 of EP 1936291 illustrates an alternative known ventilation system 20. The system * 20 comprises a housing 21 having an air inlet port 22 at one end 21a and an air outlet port 23 at an opposite end 21b. The housing 21 contains a first fan 24 and a second fan 25 arranged in series between the air inlet port 22 and the air outlet port 23. In use, one of the fans 24 and 25 acts as the duty fan and the other of the fans 24 and 25 acts as the standby fan. The duty fan causes air to flow into the housing 21 through the air inlet 22 and out from the housing through the air outlet 23, the airflow path running sequential through both of the fans 24 and 25.

This fans in series arrangement is more compact than the fans in parallel arrangement, but has the disadvantage that the duty fan has an additional air resistance load imposed on it by the idling resistance of the standby fan. This additional load can severely limit the overall performance and energy efficiency of the system.

The majority of Duty and Standby ventilation systems are used for toilet ventilation systems or other systems that are generally complex. These systems, for reasons of economy and occupant comfort, are typically ducted systems of high aerodynamic resistance. The use of centrifugal fans is often preferred in such ducted systems due to 1) their efficient and quiet operation against higher resistance and 2) their relative insensitivity to poor inlet and discharge conditions (compared to axial flow fans), as caused by limited space in which to arrange the fan layout. The fans in series arrangement for Run and Standby unit design is preferable due to its relative compactness, but hitherto this has been unachievable with centrifugal fan designs requiring efficient operation.

Figures 3a and 3b of EPl93629ldisclose a centrifugal duty and standby fan ventilation :. 20 system in which centrifugal fans 34, 35 are arranged in series and spaced apart along a longitudinal axis of the housing 31, with the first fan arrangement 34 located upstream of * *** the second fan arrangement 35. In operation, one of the first 34 and second 35 fan * :* arrangements acts as a duty fan arrangement whilst the other acts as a standby fan arrangement. A system controller 38 is connected to the first 34 and second 35 fan * *, 25 arrangements and to the first 36 and second 37 air-flow control arrangements and controls *.::. the first 36 and second 37 air-flow control arrangements such that the first air-flow control S..

arrangement 36 is closed and the second air-flow control arrangement 37 is open when the first fan arrangement 34 acts as the duty fan (Figure 3a), and the first air-flow control arrangement 36 is open and the second air-flow control arrangement 37 is closed when the second fan arrangement 35 acts as the duty fan (Figure 3b). This arrangement requires a relatively complex air control arrangement and also the overall length of the unit must accommodate the combined lengths of each fan unit 34, 35 and a clearance space between.

Additionally the complex airflow path through the unit causes a relatively high pressure drop through the unit requiring high power usage.

An improved arrangement has now been devised.

According to the present invention, there is provided a fan system for a ventilation arrangement, the fan system comprising; a first fan arrangement including a shroud for directing air toward a system air outlet; a second fan arrangement situated in-line with the first fan arrangement and including a shroud for directing air toward the system air outlet; the system including a displaceable fan shroud section common to both the fan arrangements, which displaceable fan shroud section is displaceable to alter the airflow characteristics of the system with respect to the airflow able to pass to the air outlet from the respective fan arrangements.

: 20 It is preferred that the displaceable fan shroud section is displaceable to act to vary or * ** switch airflow mode between the fan arrangements. S. * S *

* * In one embodiment, the displaceable fan shroud section is displaceable between a first position in which airflow from the first fan arrangement is preferentially accommodated ::5:. 25 and a second position in which airflow from the second fan arrangement is preferentially * * accommodated. Beneficially, in the first position the displaceable fan shroud section extends across the airflow outlet from the second fan arrangement shroud to block flow from the second fan arrangement. In the second position the displaceable fan shroud section may extend across the airflow outlet from the first fan arrangement shroud to block flow from the second fan arrangement. Appropriate seals may be provided to ensure that the non-duty fan arrangement is sealed off by the displaceable fan shroud section.

It is preferred that the displaceable fan shroud section is pivotally movable to alter the airflow characteristics of the system. Beneficially the displaceable fan shroud section is mounted at a hinge positioned intermediately between the first and second fan arrangements. The displaceable fan shroud section extends from the hinge to a free end which moves in an arcuate path in the region of the system air outlet.

The displaceable fan shroud section is common to the airflow guide shrouds of both the fan arrangements, preferably such that the displaceable fan shroud section has a first surface providing an airflow guiding surface for the airflow from the first fan arrangement when orientated appropriately and also preferably, a second surface, obverse to the first surface which provides an airflow guiding surface for the airflow from the second fan arrangement when orientated appropriately.

Beneficially, the displaceable fan shroud section has a generally concave surface profile.

The displaceable fan shroud section preferably has a generally convex surface profile on the opposite side to the concave surface profile.

The displaceable fan shroud is preferably provided immediately upstream of the system air outlet. * * a

The system preferably includes control means for controlling operation of the displaceable ***.

fan shroud section to alter the airflow characteristics of the system. S. S. * a a * S

The system is preferably provided with drive means for driving the displaceable fan shroud * *, 25 to alter the airflow characteristics of the system with respect to the airflow distribution * :.. from the respective fan arrangements.

SS *

Beneficially, the fan arrangements comprise centrifugal fan arrangements.

According to a second aspect, the invention provides a method of controlling operation of a fan system comprising a duty fan and a back-up fan wherein operational airflow mode is switched between the duty fan and back-up fan by means of movement of a displaceable fan shroud section which is common to the airflow shroud arrangement of both fans.

According to a further aspect, the invention provides a fan system for a ventilation arrangement, the fan system comprising a duty fan and a back-up fan wherein operational airflow mode is switched between the duty fan and back-up fan by means of movement of a displaceable fan shroud section which is common to the airflow shroud arrangement of both fans The invention will no be further described in a specific embodiment, by way of example only and with reference to the accompanying drawings, in which; Figures 1A and lB are is a schematic side and plan views respectively of a prior art fan for use in a ventilation system.

Figure 2 is a schematic view of a dual fan ventilation system in accordance with the present invention, in a first operational configuration; *.. : Figure 3 is a schematic view of the ventilation system of figure 2 in an alternative S...

operational configuration; S. * . * * . Referring to the drawings and initially to figures 1A and 2A, there is shown a fan unit I for * use in a ventilation system. The fan unit 1 comprises a metal housing 2 having an air inlet side 3 and air outlet side 4. The fan 5 comprises a centrifugal fan in which air is drawn into the fan via the side (arrows A in figure 1A) and exits the scroll shroud casing 6 of the fan 5 in the direction of arrow B. The impeller 7 of the fan 5 is driven by a belt drive 8 driven by a motor 9. Alternatively a direct drive may be used. The air is caused to flow radially about the scroll shroud casing 6 to be discharged via the discharge orifice 10 in the direction of arrow B. In use, the air inlet 3 may, for example be connected to incoming duct work (not shown) and the air outlet 4 may be connected to outgoing duct work (not shown) and the ventilating system used to ventilate one or more enclosed areas of a building, for example a lavatory.

Referring now to figures 2 and 3, in accordance with the present invention, the ventilation unit 101 comprises an upstream fan 102 and a downstream fan 103. The fans are provided in-line within a metal housing 104. The fans are generally of a type similar to that known in the art and described in figures 1A and lB. For ease of reference, in figures 2 and 3 the detail operating components such as the drive motors and belt drive are not shown.

The fan shroud scroll 106 of the downstream fan 103 includes a concavely curved displaceable section 107 leading towards the fan outlet orifice 108. This section is pivotably mounted at a hinge mounting 109 and can be moved from the position shown in figure 2 to the position shown in figure 3. In figure 3 the original position of the fan shroud section 107 is shown in dashed line detail. Movement of the fan shroud section is controlled by a controller (as will be described in greater detail later). The movement may be effected by any convenient means such as a pneumatic or hydraulic piston or a motor lead screw and follower arrangement. In figures 2 an 3 a pneumatic piston arrangement is shown as being operable to move the fan shroud the limits of the extreme positions for the fan shroud scroll section 107 as shown in figures 2 and 3. * S

In the first operational configuration shown in figure 3, the downstream fan is the duty fan * * and the upstream fan 102 remains in-operative (idle). In such a configuration the fan *.* operates as a generally conventional fan arrangement such as that shown in figures 1 A and * lB. The air is drawn into the fan side on (in a direction into the paper in the drawings) and * 25 the air passes radially through the fan and circumferentially around the shroud scroll 106 in the direction shown by the arrows in figure 2. The shroud scroll section 7 is held in the position shown in figure 2 where it defines a generally concave curved surface over which the air flows out through the outlet orifice 108. In the position shown in figure 2 the shroud scroll section 107 extends across the outlet of the upstream fan 102.

In the event that the duty fan is to be swapped to the upstream fan 102 and the downstream fan 103 is to become inoperative (idle), the controller controls operation of the pneumatic piston arrangement 110 to move and hold the displaceable fan shroud section 107 to the position shown in figure 3 in which airflow is directed from the upstream fan 102 to the air outlet orifice 108 of the unit. In the position shown in figure 3 the airflow out of the fan is circumferentially around the shroud scroll 106 in the direction shown by the arrows in figure 3 and then through the space defined between the convex outer surface of the displaceable fan shroud section 107 and the outer housing 104. The displaceable fan shroud section 107 is therefore common to the airflow shrouds of both the upstream and the downstream fans.

In both modes of operation the displaceable fan shroud section 107 acts as an airflow guide surface for airflow from a different fan. The displaceable fan shroud section 107 is displaceable from one extreme position in which the airflow outlet area from one fan is maximised to a second extreme position in which the airflow outlet area from the other fan is maximised.

It is possible that the system could be operated with the displaceable fan shroud section 107 positioned intermediately between the extreme positions in which case the two fans could potentially be operated simultaneously to discharge air simultaneously via the outlet * *s* orifice 108. ** S. * S * * S

S *.*

* Because the fans are in-line and use the same outlet orifice 108, the overall width of the * : unit is minimised and no grater than the width required for a single fan unit. Additionally * . 25 and advantageously, because the spacing in the in-line direction between the fans is minimised, the overall length of the unit is kept to a realisable minimum. This is achieved by means of the special relationship between the upstream and downstream fans in which the displaceable fan shroud section 107 has the ability to selectively act as an airflow guide surface for airflow from both of the different fans 102, 103.

The system controller is arranged to monitor for malfunction of the duty fan arid if a malfunction is detected, to close the duty fan down and to activate the standby (or back-up) fan to act as the new duty fan. The controller also changes the orientation of the displaceable fan shroud section 107 from that illustrated in Figure 2 to that illustrated in Figure 3 or vice versa, depending upon which of the fan arrangements 102 and 103 is the new duty fan. The controller may also be arranged to periodically change which of the fan arrangements is acting as the duty fan and to configure the displaceable fan shroud section 107 accordingly.

Having thus described the present invention by reference to a preferred embodiment it is to be well understood that the embodiment in question is exemplary only and that modifications and variations such as will occur to those possessed of appropriate knowledge and skills may be made without departure from the spirit and scope of the invention as set forth in the appended claims and equivalents thereof. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims. The word "comprising" and "comprises", and the like, does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements. * S S 5 **** * * **** ** S. * S 5 * *

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Claims

Claims: I. A fan system for a ventilation arrangement, the fan system comprising; a first fan arrangement including a shroud for directing air toward a system air outlet; a second fan arrangement situated in-line with the first fan arrangement and including a shroud for directing air toward the system air outlet; the system including a displaceable fan shroud section common to both the fan arrangements, which displaceable fan shroud section is displaceable to alter the airflow characteristics of the system with respect to the airflow able to pass to the air outlet from the respective fan arrangements.
2. A fan system according to claim 1, wherein the displaceable fan shroud section is displaceable to act to vary or switch airflow mode between the fan arrangements.
3. A fan system according to claim I or claim 2, wherein the displaceable fan shroud section is displaceable between a first position in which airflow from the first fan arrangement is preferentially accommodated and a second position in which airflow from the second fan arrangement is preferentially accommodated. S. ** * * * * *
4. A fan system according to claim 3, wherein in the first position the displaceable fan shroud section extend across the airflow outlet from the second fan * S. arrangement shroud to block flow from the second fan arrangement.S
5. A fan system according to claim 3 or claim 4, wherein in the second position the displaceable fan shroud section extend across the airflow outlet from the first fan arrangement shroud to block flow from the second fan arrangement.
6. A fan system according to any preceding claim, wherein the displaceable fan shroud section is pivotally movable to alter the airflow characteristics of the system.
7. A fan system according to claim 6, wherein the displaceable fan shroud section is mounted at a hinge positioned intermediately between the first and second fan arrangements.
8. A fan system according to any preceding claim, wherein the displaceable fan shroud section has a first surface providing an airflow guiding surface for the airflow from the first fan arrangement when orientated appropriately.
9. A fan system according to claim 8, wherein the displaceable fan shroud section has a second surface, obverse to the first surface which provides an airflow guiding surface for the airflow from the second fan arrangement when orientated appropriately.
10. A fan system according to any preceding claim, wherein the displaceable fan shroud section has a generally concave surface profile. * * **::::
11. A fan system according to any preceding claim, wherein the displaceable fan shroud section has a generally convex surface profile on the opposite side to the concave surface profile. * *.*S

* ** 25
12. A fan system according to any preceding claim, wherein the displaceable fan shroud is provided immediately upstream of the system air outlet. S..

S
13. A fan system according to any preceding claim, wherein the system includes control means for controlling operation of the displaceable fan shroud section to alter the airflow characteristics of the system.
14. A fan system according to any preceding claim, including drive means for driving the displaceable fan shroud to alter the airflow characteristics of the system with respect to the airflow distribution from the respective fan arrangements.
15. A fan system according to any preceding claim, wherein the fan arrangements comprise centriffigal fan arrangements.
16. A method of controlling operation of a fan system comprising a duty fan and a back-up fan wherein operational airflow mode is switched between the duty fan and back-up fan by means of movement of a displaceable fan shroud section which is common to the airflow shroud arrangement of both fans.
17. A fan system for a ventilation arrangement, the fan system comprising a duty fan and a back-up fan wherein operational airflow mode is switched between the duty fan and back-up fan by means of movement of a displaceable fan shroud section which is common to the airflow shroud arrangement of both fans. * . aS a. * a a.-. a. * a a * . a,. * S. * p * *S. a *e. *