GB1560684A - Fans having air flow guide arrangements - Google Patents

Description

(54) FANS HAVING AIRFLOW GUIDE ARRANGEMENTS (71) We, PITSTOCK PTY. LIMITED., an Australian Company of 157 Kent Street, Sydney 2000, Australia, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention is concerned with inlet and outlet aspects of fans, particularly centrifugal fans and axial flow fans.

Axially directed fan ports occur in systems such as air-conditioning systems, and hitherto it has generally been the accepted rule that to avoid power loss, a spacing approximately equal to the port diameter should be provided between the port and any confronting obstruction.

In the case of a centrifugal fan, it is well known that air passing into the inlet port adopts a spiralling path and the clear space in front of the inlet port should be at least equal to the diameter of the impeller of the fan. This rule has been widely accepted as necessary for reasonably efficient airflow into the inlet port. Data has been widely published by fan manufactures showing that the effect of reducing the clear space at the inlet is to use much more power to operate the fan for the same airflow output. Taking the data of one typical centrifugal fan, for a typical application the motor driving the fan requires an output of 9.23 b.h.p. and operates at 1304 r.p.m. where 1.0 rotor diameter (Rd) spacing is provided in front of the inlet port but when this distance is reduced to 0.5 Rd it is found that 10.10 b.h.p. is required but the motor speed is increased to 1356 r.p.m.Thus, a penalty of power consumption approaching 10% is incurred and furthermore, the fan has to operate at greater speed, this resulting in greater problems for acoustic treatment, and greater wear and strain on parts due to the higher speed.

Since the cost of energy for running a fan during its normal working life is enormously greater than the initial capital cost of the fan, a penalty approaching 10% on energy consumption is a very great disadvantage.

Frequently, space available in a building for the installation of a fan is limited and it would be greatly advantageous to provide a structure which would permit smaller spacings, without large energy consumption penalties, between the confronting wall and the inlet to a centrifugal fan. Hitherto, there have been no effective proposals which deal with this problem.

According to one aspect of the invention, there is provided a fan having an airflow guide member mounted in spaced confronting relation with an axially directed port thereby providing a duct extending around the guide member and communicating with said port, the guide member having a body member for location with its axia substantially coaxial with said port and having a discontinuous profile in the circumferential direction such that spiralling of the airflow around the body member as air flows through said port is opposed, and the body member being shaped to deflect the airflow smoothly between the atmosphere and said port. Thus the air will be deflected through a substantial angle.

The invention may be applied to different types of fans including centrifugal fans and axial flow fans. The ports may be circular or of other shape such as square.

Use of this invention can permit the port to be located very close to an obstruction such as a wall of a plant room. In preferred embodiments of the invention, the port can be located from an obstruction as close as about 30% or approximately one third of the diameter (Rd) of the port or fan impeller if the port is of a centrifugal fan.

This close spacing may in some cases permit even significant power savings and more generally the arrangement can be used without incurring substantial power penalties. A further major advantage of this invention is that embodiments may incorporate an acoustic treatment. The guide member is in the form of an acoustic panel member, the acoustic treatment being for example as described hereinafter, with reference to the drawings. This acoustic treatment is the subject of copending patent application No. 25129/76 (Serial No.

1554286) in United Kingdom by Louis A.

Challis.

Preferably, the guide member has elongated shoulders extending generally in spaced radial planes relative to its axis for the purpose of reducing or tending to reduce the normal spiralling airflow which would otherwise tend to occur, particularly when the airflow is into a centrifugal fan.

Furthermore, divider plates may be included in the guide member, the plates extending in substantially radial planes relative to the axis of the body member so that in use they extend from the surfaces of the body member across towards and optionally to engage in the port of the conduit.

Optionally a portion of the body member may extend into the port to provide a smooth substantially non-whirling airflow.

Preferably said body member extends in a plane normal to the aims of said port to an extent greater than said port.

The divider plates may be curved or have curved portions at least in the portions thereof remote from the surface of the body member, the direction of curving being opposite to the direction in which the impeller of the centrifugal fan will rotate thereby tending to further oppose the natural tendency of a spiral airflow into fan.

Furthermore, the divider plates may have hinged flaps which are adjustable to an optimum setting.

Preferably the body member has generally the shape of a pyramid extending from a backing panel member, especially preferred is the shape of a truncated pyramid, the four sides of which being provided by concave panels whereby adjacent panels are jointed together to form ridges extending in radial planes for the purpose of opposing spiralling airflow around the body member.

The present invention can be applied not only by inclusion in new centrifugal fans or panel members therefore but also existing installations can be modified with advantage.

When the invention is applied to an airconditioning system such as in a building, new arrangements for installation can be advantageously utilised resulting in attrac tive economics of both the operation of the installation as well as the sace required for the plant. Furthermore, the effective acous tic treatment can be applied and this can obviate objectionable noise emission as well as the use of alternative acoustic treatments which may be inefficient from a power point of view as well as expensive to instal.

Embodiments of the invention will now be described with reference to the accompanying drawings: Figure I is a perspective partially brokenaway view of a double ended centrifugal fan embodying the present invention; Figure 2 is an isometric view of a further embodiment of inlet guide member; Figure 3 is a side elevation of the guide member of Figure 2 and showing an optional addition to a guide blade; Figure 4 is an elevation of an alternative blade for the guide member; Figure 5 is a plan view of the blade of Figure 4; Figure 6 is an elevation of a further embodiment of blade, and Figure 7 is a plan view of the blade of Figure 6, Figure 8 shows an axial flow fan embodying the invention.

The double end centrifugal fan of Figure 1 embodies both the present invention and acoustic treatment according to an invention which is the subject of a pending patent application No. 25129/76 (Serial No.

1554286) by Louis A. Challis.

Figure 1 will now be described in detail.

The centrifugal fan comprises an outer casing 1 of rectangular panels fixed to a rigid framework 2, an outlet port 3 being located in the top panel la and each end panel 4 having a circular inlet port 5. An electric motor 6 is mounted on the top of the casing and by means of belts 7 drives the impeller 8, an inlet cone 9 guiding the air from the inlet port to the impeller.

Figure 1 shows the arrangement at one end only, a similar arrangement being provided at the other end, the illustrated fan being a double width, double inlet fan. The impeller 8 is mounted on a shaft which extends through the fan and is in bearings 10 at each end.

For the purpose of guiding airflow into the inlet ports a panel member 11 is provided at each end. In this embodiment each panel member is to be secured to the framework 2 at a fixed position, the spacing between each panel member and adjacent end panel 4 being approximately 30% of the diameter of the impeller.

Each panel member 11 has a rigid steel backing 12 and an acoustically permeable facing 13 which in this embodiment is formed from closely perforated metal sheet.

The panel includes a guide member 14 also formed from perforated metal sheets, each guide member being formed from four curved sheets which concave and join one another along welded ridges or hips 15, a square centre panel 16 providing a flat nose.

The hips 15 act to reduce substantially the whirling effect which otherwise would occur and this reduction in the whirling effect can be substantially advantageous from a power point of view.

The panel member 11 which is broken away shows the interior structure as comprising fibreglass or mineral infill 17 between the permeable sheet 13 and the backing 12 and between the guide member 14 and the permeable sheet 13. In this embodiment the panel member is not shown as having a plurality of Helmholtz cavities but partition walls are included to provide such cavities.

Acoustic absorption is also provided in the fan between the fan scroll 18 and the outer casing 1, acoustic infill 17 also being provided. Figure 1 shows partition walls 19 extending between the casing and the scroll to divide the casing into a plurality of Helmholtz absorption cavities having respective different centres to their absorption frequency bands. The acoustic infill broadens each acoustic absorption band.

The cavities are connected acoustically to the interior of the scroll by bands of perforations 20 extending across the scroll in a direction parallel to the axis of the fan.

This can permit effective acoustic coupling without extensive performation and thus without excessive aerodynamic drag. Typically the area of perforation may be as small as 10% of the scroll area.

Comparison data will now be given to one embodiment of the invention, the data concerning a standard double width double inlet air foil fan fitted with inlet vane control and having a rotor diameter of 26", an inlet diameter of 27" and an outlet of 23 and one-eighth inch by 391/2". The fan was operated firstly with the panel and acoustic treatment of the type shown in Figure 1 with the inlet guide panel mounted such that the distance between the rear of the panel member and the periphery of the inlet port was about one-third of the impeller of rotor diameter of the fan. The fan was operated to produce 16,500 cubic feet per minute at 1500 r.p.m. and 14.1 b.h.p.

However, when the fan was operated without the acoustic inlet member, in order to produce 16,500 cubic feet per minute, it was necessary to operate the fan at 1542 r.p.m. and 15.4 b.h.p.

The guide member of Figures 2 and 3 comprises a rectangular back member 30 and a curved body member 31 fabricated suitably from sheet steel with a curved shoulder 32 providing a transition between the back member and the body member.

The body member is fabricated from four curved qualdrilateral sheets 33 steel terminating in a square nose 34 which faces the inlet port of the fan. Each of the sheets 33 is fixed at its longest edge to a side of the backing member 30 and dishes in a concave manner towards the nose 34. The sheets are joined to one another along ribs or hips 35 which extend radially and provide means for tending to oppose the spiralling air path which would otherwise occur. Figures 2 and 3 show optional feature which may be provided, namely a blade 36 which is conveniently welded across the centre of each of the sheets 33, although these Figures show only one such blade in position. Optionally this blade may include a projection 37 which extends towards and into the inlet port of the fan.

The alternative blade of Figures 4 and 5 has a planar portion 38 which has a curved edge profiled to the shape of the panel 33.

The blade can be welded to the panel. The blade has a projecting portion 39 which is curved in a direction which will be opposite to the direction of rotation of the impeller of the fan, the portion 39 projecting beyond the nose of the guide member. Optionally the blade may include an extension portion 40 which is shown in dotted lines for extending into the inlet port of the fan.

Another model of blade is shown in Figures 6 and 7, this blade having a similar planar portion 38 but provided with a hinged flap 41 which is capable of being angled towards either of the positions shown in dotted lines in Figure 7 so that the airflow may be deflected either towards or against the direction of rotation of the rotor of the fan.

Reference will also be made to Figure 8 of the accompanying drawings which illustrates schematically an axial flow fan having axial discharge.

Figure 8 shows the application of a panel member embodying the invention spaced from the inlet port by about one-third of the rotor diameter of the fan and where the fan is to disperse air extensively into a zone rather than to discharge air into a conduit, a panel member as shown in dotted lined may also be used at the discharge port. This can permit efficient airflow at both inlet and discharge and when the panel is acoustically treated, unwanted noise emission can be effectively reduced.

WHAT WE CLAIM IS: 1. A fan having an airflow guide member mounted in spaced confronting relation with an axially directed port, the guide member having a body member for location with its axis substantially coaxial with said port and having a discontinuous profile in the circumferential direction such that spiralling of the airflow around the body member as air flows through said port is opposed, and the body member being shaped to deflect airflow smoothly between

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. square centre panel 16 providing a flat nose. The hips 15 act to reduce substantially the whirling effect which otherwise would occur and this reduction in the whirling effect can be substantially advantageous from a power point of view. The panel member 11 which is broken away shows the interior structure as comprising fibreglass or mineral infill 17 between the permeable sheet 13 and the backing 12 and between the guide member 14 and the permeable sheet 13. In this embodiment the panel member is not shown as having a plurality of Helmholtz cavities but partition walls are included to provide such cavities. Acoustic absorption is also provided in the fan between the fan scroll 18 and the outer casing 1, acoustic infill 17 also being provided. Figure 1 shows partition walls 19 extending between the casing and the scroll to divide the casing into a plurality of Helmholtz absorption cavities having respective different centres to their absorption frequency bands. The acoustic infill broadens each acoustic absorption band. The cavities are connected acoustically to the interior of the scroll by bands of perforations 20 extending across the scroll in a direction parallel to the axis of the fan. This can permit effective acoustic coupling without extensive performation and thus without excessive aerodynamic drag. Typically the area of perforation may be as small as 10% of the scroll area. Comparison data will now be given to one embodiment of the invention, the data concerning a standard double width double inlet air foil fan fitted with inlet vane control and having a rotor diameter of 26", an inlet diameter of 27" and an outlet of 23 and one-eighth inch by 391/2". The fan was operated firstly with the panel and acoustic treatment of the type shown in Figure 1 with the inlet guide panel mounted such that the distance between the rear of the panel member and the periphery of the inlet port was about one-third of the impeller of rotor diameter of the fan. The fan was operated to produce 16,500 cubic feet per minute at 1500 r.p.m. and 14.1 b.h.p. However, when the fan was operated without the acoustic inlet member, in order to produce 16,500 cubic feet per minute, it was necessary to operate the fan at 1542 r.p.m. and 15.4 b.h.p. The guide member of Figures 2 and 3 comprises a rectangular back member 30 and a curved body member 31 fabricated suitably from sheet steel with a curved shoulder 32 providing a transition between the back member and the body member. The body member is fabricated from four curved qualdrilateral sheets 33 steel terminating in a square nose 34 which faces the inlet port of the fan. Each of the sheets 33 is fixed at its longest edge to a side of the backing member 30 and dishes in a concave manner towards the nose 34. The sheets are joined to one another along ribs or hips 35 which extend radially and provide means for tending to oppose the spiralling air path which would otherwise occur. Figures 2 and 3 show optional feature which may be provided, namely a blade 36 which is conveniently welded across the centre of each of the sheets 33, although these Figures show only one such blade in position. Optionally this blade may include a projection 37 which extends towards and into the inlet port of the fan. The alternative blade of Figures 4 and 5 has a planar portion 38 which has a curved edge profiled to the shape of the panel 33. The blade can be welded to the panel. The blade has a projecting portion 39 which is curved in a direction which will be opposite to the direction of rotation of the impeller of the fan, the portion 39 projecting beyond the nose of the guide member. Optionally the blade may include an extension portion 40 which is shown in dotted lines for extending into the inlet port of the fan. Another model of blade is shown in Figures 6 and 7, this blade having a similar planar portion 38 but provided with a hinged flap 41 which is capable of being angled towards either of the positions shown in dotted lines in Figure 7 so that the airflow may be deflected either towards or against the direction of rotation of the rotor of the fan. Reference will also be made to Figure 8 of the accompanying drawings which illustrates schematically an axial flow fan having axial discharge. Figure 8 shows the application of a panel member embodying the invention spaced from the inlet port by about one-third of the rotor diameter of the fan and where the fan is to disperse air extensively into a zone rather than to discharge air into a conduit, a panel member as shown in dotted lined may also be used at the discharge port. This can permit efficient airflow at both inlet and discharge and when the panel is acoustically treated, unwanted noise emission can be effectively reduced. WHAT WE CLAIM IS:

1. A fan having an airflow guide member mounted in spaced confronting relation with an axially directed port, the guide member having a body member for location with its axis substantially coaxial with said port and having a discontinuous profile in the circumferential direction such that spiralling of the airflow around the body member as air flows through said port is opposed, and the body member being shaped to deflect airflow smoothly between

the atmosphere and said port.

2. A fan as claimed in claim 1, wherein said body members extends in a plane normal to the axis of said port to an extent greater than said port.

3. A fan as claimed in claim 1 or claim 2 wherein said discontinuous profile is provided by a plurality of shoulders spaced from one another around the axis of the body member.

4. A fan member as claimed in any of the preceding claims and having a plurality of spaced plate members disposed in respective radial planes and extending from the body member whereby spiralling of the airflow is reduced.

5. A fan as claimed in claim 4 wherein said plate members have extension portions for projecting towards said port when mounted in position for use.

6. A fan as claimed in claim 4 or 5, for use at the inlet port to a centrifugal fan wherein said plate members are curved in a direction which will be opposed to the direction of rotation of the impeller of the fan.

7. A fan as claimed in claim 4 or claim 5, wherein said plate members have a hinged flap adjustable to an angled setting relative to the plane of the plate member.

8. A fan as claimed in any one of the preceding claims, wherein said body member has generally the shape of a pyramid extending from a backing panel member.

9. A fan as claimed in claim 8, wherein said body member has the shape of a truncated pyramid, the four sides of which are provided by concave panels whereby adjacent panels are joined together to form ridges extending in radial planes for the purpose of opposing spiralling airflow around the body member.

10. A fan as claimed in any one of claims 1 to 9. wherein the spacing, in a direction perpendicular to the plane of said port, between the periphery of the port and the confronting portion of the guide member is substantially less than the diameter of the impeller of the fan or said port.

11. A fan as claimed in claim 10, wherein said spacing is approximately one-third of the diameter of said fan impeller or port.

12. A fan as claimed in any preceding claim, wherein said fan is a centrifugal fan.

13. A fan having an airflow member substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings or modified by the additional inclusion of a plurality of blades substantially as herein described with reference to Figures 2 and 3, Figures 4 and 5 or Figures 6 and 7 of the accompanying drawings.