GB2126652A

GB2126652A - Peripheral toroidal blowers

Info

Publication number: GB2126652A
Application number: GB08225418A
Authority: GB
Inventors: Andrew Henry Middleton; Anthony Graham Herbert
Original assignee: British Gas Corp
Current assignee: British Gas Corp
Priority date: 1982-09-07
Filing date: 1982-09-07
Publication date: 1984-03-28
Also published as: GB2126652B

Abstract

The blower has a toroidal chamber 1 divided along a plane at right angles to its axis into a first chamber part bounded by a stator housing 2 having adjacent inlet and outlet ports with a stripper between them and a second chamber part bounded by a rotor housing 6 containing a series of impeller blades 7. A channel 19 extends circumferentially around the toroidal chamber 1 and communicates with the toroidal chamber through the peripheral clearance 20 between the rotor and stator housings. Droplets of condensate produced when hot flue gases are pumped by the blower collect in the channel 19 and are removed by way of a drain pipe 21. The rotor and stator housings are preferably of die cast aluminium. A plurality of relatively small air bleed holes 25 act to ventilate a space 24 in which a motor 23 driving the rotor housing 6 is accommodated and thus prevent the entry of hot flue gases. <IMAGE>

Description

SPECIFICATION Improvements in peripheral toroidal blowers This invention relates to a peripheral toroidal blower of a kind comprising a toroidal chamber divided along a plane at right angles to its axis into a first part bounded by a stator housing having adjacent inlet and outlets ports with a stripper between them and a second part bounded by a rotor housing containing a series of impeller blades. The impeller blades and the stripper are arranged in such a way that when the rotor housing is rotated a flow of air is induced into the chamber through the inlet port, along a substantially helical path the axis of which extends around the toroidal chamber and out of the chamber through the outlet port.

When such a peripheral toroidal blower is used in circumstances involving the handling of a vapour with a dew point above ambient temperature droplets of condensate tend to form in or enter the toroidal chamber. This is disadvantageous in that the centrifugal force acting on the droplets rotating with the rotor housing will throw the droplets outwards towards the periphery of the toroidal chamber.

Consequently, there is a build up of fluid in the peripheral clearance between the rotor and stator housings which slows down and may stop the rotation of the rotor housing.

An object of this invention is to provide a peripheral toroidal blower in which the abovementioned disadvantage is alleviated.

According to one aspect of the present invention a peripheral toroidal blower comprises a toroidal chamber divided along a plane at right angles to its axis into a first part bounded by a stator housing having adjacent inlet and outlet ports with a stripper between them and a second part bounded by a rotor housing containing a series of impeller blades, and a channel extending circumferentially around the toroidal chamber and communicating with the toroidal chamber through the peripheral clearance between the stator and rotor housings.

Preferably the cross-sectional area of the channel is between 1% and 10% of the crosssectional area of the toroidal chamber. The channel may be substantially rectangular in crosssection.

The peripheral toroidal blower may include a drain pipe for the condensate communicating with the channel and extending out of the stator housing.

The stator housing and the rotor housing may be formed from die cast aluminium and the stator housing may be provided with one or more relatively small air bleed holes for ventilating a space in which a motor driving the rotor housing is accommodated. The or each relatively small air bleed hole may be substantially 1.0 mm in diameter.

The stator housing may be provided with a spiral groove communicating with an air bleed hole and arranged to induce air into the space in which the motor driving the rotor housing is accommodated.

When peripheral toroidal blowers are incorporated in central heating systems any noise produced by the blower tends to be transmitted into the living spaces which are heated. It is therefore important that the noise produced by the blower should be reduced to a minimum.

A further object of the invention is to reduce the noise produced by a peripheral toroidal blower.

According to another aspect of the invention a peripheral toroidal blower comprises a toroidal chamber divided along a plane at right angles to its axis into a first part bounded by a stator housing having adjacent inlet and outlet ports with a stripper between them and a second part bounded by a rotor housing containing a series of impeller blades, the inlet port being located immediately adjacent to the stripper and the outlet port being spaced from the stripper by a predetermined distance which reduces the noise produced at blade passing frequency by between 5 to 8 dB.

Preferably the predetermined distance is substantially 12 mm for a blower having a throughput of source volume of 120 cubic feet per hour.

The invention wiil now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is an end elevation, partly broken away, of a peripheral toroidal blower in accordance with the invention; Figure 2 is a sectional plan view of the peripheral toroidal blower shown in figure 1: Figure 3 is a sectional plan view of another peripheral toroidal blower in accordance with the invention; and Figure 4 is a fragmentary sectional plan view showing a modification of the peripheral toroidal blower shown in Figure 3.

Referring in the first instance to Figures 1 and 2, the peripheral toroidal blower, which is suitable for use in a central space heating system, comprises a toroidal chamber 1 divided on a plane at right angles to its axis into a first chamber part bounded by a stator housing 2 having adjacent inlet and outlet ports 3 and 4 respectively with a stripper 5 located between them, and a second chamber part bounded by a rotor housing 6 containing a plurality of radially extending impeller blades 7. The stripper 5 and the impeller blades 7 are arranged so that, upon rotation of the rotor housing 6 by a drive shaft 8, a flow of air is induced into the toroidal chamber 1 through the inlet port 3, along a substantially helical path (the axis of which extends around the toroidal chamber) and out of the toroidal chamber through the outlet port 4, the stripper 5 preventing recirculation.

The stripper 5 is formed by a central block 1 3 arranged to be a snug fit in the stator housing 2 and two curved vanes 14 extending one from each end of the block 13 so as to almost cover the inlet and outlet ports 3 and 4 respectively.

Each vane 14 is shaped so that its width in a radial direction and its thickness in an axial direction gradually diminish from its root connection with the block 1 3 towards its radiused tip.

As shown in Figure 1 the inlet port 3 is located immediately adjacent to the central block 1 3 of the stripper 5 and the outlet port 4 is spaced from the central block 1 3 by a predetermined distance 10 such as to reduce the noise produced at blade passing frequency by between 5 to 8 dB. Typcially the predetermined distance 10 is substantially 12 mm for a blower having a throughput of source volume of 120 cubic feet per hour. The stator housing 2 is provided with an inlet passage in the form of a duct (not shown) communicating with the inlet port 3 and an outlet passage in the form of a duct (not shown) communicating with the outlet port 4. Both the inlet duct and the outlet duct extend from the stator housing 2 in a direction away from the rotor housing 6 for ease of connection.

A channel 1 9 extends circumferentially around the toroidal chamber 1 and communicates with the toroidal chamber through the peripheral clearance 20 between the stator and rotor housings 2 and 6. The channel 1 9 is substantially rectangular in cross-section and has a crosssectional area which is between 1% and 10% of the cross-sectional area of the toroidal chamber.

A drain pipe 21, which communicates with the channel 19 through a bore 22, extends out of the stator housing 2. The drain pipe 21 may be connected directly or indirectly to the source volume (not shown) from which the vapour is being drawn, e.g. the heat exchanger of a gas appliance. An electric motor 23 is coupled to the drive shaft 8 so as to rotate the rotor housing 6.

When the peripheral blower is used in circumstances involving the handling of a vapour with a dew point above ambient temperature droplets of condensate tend to enter or form in the toroidal chamber 1. Centrifugal force acting on the droplets of condensate rotating with the rotor housing 6 causes the droplets to be thrown outwards towards the periphery of the toroidal chamber 1. The droplets of condensate in the region of the peripheral clearance 20 between the stator housing 2 and the rotor housing 6 are drawn into the channel 1 9 and flow through the bore 22 to the drain pipe 21.Measurements show that whilst there is a variation of pressure around the circumference of the channel 1 9 dependent on the position relative to the central block 13, the pressure may be everywhere higher than that in the space from which the vapour is being drawn e.g. the heat exchanger of a gas appliance. Therefore the gaseous part of any substance being pumped may tend to flow along the drain pipe 21 connecting the channel to the source volume and any droplets of condensate collecting in the channel 1 9 may be conveyed along with the gas flow. In practice a gas flow along the drain pipe of 1% of the total gas flow is sufficient to expel any droplets of condensate produced by the heat exdhanger of a gas appliance.

Referring now to Figure 3, the peripheral blower is simiiar to that shown in Figures 1 and 2 but is intended for prolonged use in hot flue gases and the stator housing 2 and rotor housing 6 which bound with toroidal chamber 1 are die cast aluminium components. The electric motor 23 which drives the rotor housing through the shaft 8 is not in the flue gas stream, but since it is difficult to seal the space 24 in which the electric motor 23 is accommodated the stator casing near the end of the shaft 8 remote from the rotor housing 6 is provided with a plurality of relatively small air bleed holes 25. Typically the air bleed hoix's 25 are 1.0 mm in diameter so that they present a high impedance to sound produced in the motor space 24 and hence to not significantly reduce the noise insulation of the peripheral blower.When the electric motor 23 is running air is induced into the motor space 24 through the air bleed holes 25 and flows to the circumferentially extending channel 1 9 which is connected to the source volume by way of the drain pipe 21. An alternative orientation of the drain pipe 21 is shown in broken line.

Instead of or in addition to the air bleed holes 25 shown in Figure 3, a plurality of further relatively small air bleed holes 26 as shown in Figure 4 may be provided in the stator housing 2 near the end of the shaft 8 adjacent to the rotor housing 6. The stator housing 2 is provided with a spiral groove 28 communicating with the air bleed holes 26 through the clearance 29 between the rotor and stator housings. When the electric motor 23 is running the spiral groove 28 provides a pumping action which induces air into the motor space through the air bleed holes 26. The pumped air flows to the circumferentially extending channel 1 9 which is connected to the source volume by way of the drain pipe 21.

Claims

1. A peripheral toroidal blower comprising a toroidal chamber divided along a plane at right angles to its axis into a first part bounded by a stator housing having adjacent inlet and outlet ports with a stripper between them and a second part bounded by a rotor housing containing a series of impeller blades, and a channel extending circumferentially around the toroidal chamber and communicating with the toroidal chamber through the peripheral clearance between the stator and rotor housings.

2. A peripheral toroidal blower as claimed in Claim 1, wherein the cross-sectional area of the channel is between 1% and 10% of the crosssectional area of the toroidal chamber.

3. A peripheral toroidal blower as claimed in Claim 1 or Claim 2, wherein the channel is substantially rectangular in cross-section.

4. A peripheral toroidal blower as claimed in any preceding claim, including a drain pipe communicating with the channel and extending out of the stator housing.

5. A peripheral toroidal blower as claimed in Claim 4, wherein the drain pipe communicates with the channel through a bore.

6. A peripheral toroidal blower as claimed in any preceding claim, wherein the stator housing and the rotor housing are formed from die cast aluminium.

7. A peripheral toroidal blower as claimed in any preceding claim, wherein the stator housing is provided with one or more relatively small air bleed holes for ventilating a space in which a motor driving the rotor housing is accommodated.

8. A peripheral toroidal blower as claimed in Claim 7, wherein the or each relatively small air bleed hole is substantially 1.0 mm in diameter.

9. A peripheral toroidal blower as claimed in Claim 7 or Claim 8, wherein the stator casing is provided with a spiral groove communicating with an air bleed hole and arranged to induce air into the space in which the motor driving the rotor housing is accommodated.

1 0. A peripheral toroidal blower as claimed in any one of Claims 7 to 9, wherein the air bleed holes are located adjacent bearings of the motor driving the rotor housing.

11. A peripheral toroidal blower comprising a toroidal chamber divided along a plane at right angles to its axis into a first part bounded by a stator housing having adjacent inlet and outlet ports with a stripper between them and a second part bounded by a rotor housing containing a series of impeller blades, the inlet port being located immediately adjacent to the stripper and the outlet port being spaced from the stripper by a predetermined distance which reduces the noise produced at blade passing frequency by between 5 to 8 dB.

12. A peripheral toroidal blower as claimed in Claim 11, wherein the predetermined distance is substantially 12 mm for a blower having a throughput of source volume of 120 cubic feet per hour.

1 3. A peripheral toroidal blower constructed and arranged to operate substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

1 4. A peripheral toroidal blower constructed and arranged to operate substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings, with or without the modification substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.