Fan

Abstract

A radial fan comprising: a plurality of blades rotatable about an axis of rotation and extending radially from the axis of rotation; characterised in that each of the blades has a transverse profile that is symmetrical about a radial line of symmetry extending through the blade, at least a portion of the profile of each blade being curved.

Claims

1. A hydroelectric machine comprising: an electric motor-generator; a radial fan disposed to cool the electric motor-generator, the radial fan further comprising: a plurality of blades rotatable about an axis of rotation and extending radially from the axis of rotation; each of the blades comprising a transverse profile that is symmetrical about a radial line of symmetry extending through the blade, and wherein at least a portion of the transverse profile is curved; a lower sealing component; an upper sealing component; the blades disposed between the upper and lower sealing components; and the upper sealing component comprising an upper flange that curves towards the axis of rotation and extends radially inward towards the axis of rotation beyond a leading axial end portion of the blades, the upper flange defining an air inlet to the leading axial end portions of the blades such that incoming air changes direction at the air inlet from axial flow to radial flow through the blades at a location radially inward the leading axial end portions of the blades.

2. The hydraulic machine as claimed in claim 1, wherein the radial fan has a diameter equal to or in excess of three metres.

3. The hydraulic machine as claimed in claim 1, wherein the transverse blade defines one of a tear-drop shape, a stadium shape, or a rectangle having rounded ends.

4. The hydraulic machine as claimed in claim 1, wherein the upper flange is rounded at a radially inward surface thereof towards the axial flow of the incoming air.

5. The hydraulic machine as claimed in claim 1, wherein the lower sealing component comprises a lower flange defining the air inlet.

6. The hydraulic machine as claimed in claim 5, wherein the lower flange is rounded.

7. The hydraulic machine as claimed in claim 1, wherein an axial thickness of each blade varies radially along the blade.

8. The hydraulic machine as claimed in claim 1, wherein an axial thickness of each blade decreases with increasing distance from the axis of rotation.

9. The hydraulic machine as claimed in claim 1, wherein the radial fan is mountable on a rotational shaft of the hydroelectric machine to cool the hydroelectric machine in pump mode or in turbine mode.

10. The hydraulic machine as claimed in claim 9, wherein the radial fan cools the hydroelectric machine in pump mode when the fan rotates in a first direction and cools the hydroelectric machine in turbine mode when the fan rotates in a second direction.

11. The hydraulic machine according to claim 10, wherein the first direction is opposite to the second direction.

12. The hydraulic machine according to claim 1, comprising two of the radial fans at either end of the rotor.

Description

(1) The invention will now be further described by way of example only with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic representation of a machine according to an embodiment of the second aspect of the invention incorporating a fan according to an embodiment of the first aspect of the invention;

(3) FIG. 2 is a schematic representation of a portion of the machine of FIG. 1 showing the fan and a rotor of the machine in more detail;

(4) FIG. 3 is a detailed representation of one of the blades forming the fan shown in FIG. 2;

(5) FIG. 4 is a detailed schematic representation of a portion of the fan of FIG. 2;

(6) FIG. 5 is a schematic representation comprising the cross-sectional shape of the blades of the fan of FIG. 2 with straight blades from a conventional fan;

(7) FIG. 6 is a schematic representation showing the shape of the blade of a fan according to embodiments of the invention in more detail;

(8) FIG. 7 is a schematic representation showing the shape of known blades in more detail;

(9) FIG. 8 is a schematic representation showing the upper and lower sealing portions of the fan of FIG. 2;

(10) FIG. 9 is a table showing the parameters of a conventional radial fan having straight blades compared to the parameters of a radial fan according to an embodiment of the invention;

(11) FIG. 10 is a graph showing how both the static generation and the efficiency of a fan according to embodiments of the invention are improved compared to known fans having straight blades;

(12) FIG. 11 is a graph showing a reduced power consumption for a given flow rate for a fan shown in FIG. 2 compared to that of a known fan; and

(13) FIG. 12 is a schematic diagram showing how the improved performance of the radial fan according to embodiments of the invention can be explained in terms of flow behaviour around the blades which is shown in FIG. 10 for a flow rate of 30 m.sup.3/s.

(14) Referring initially to FIGS. 1, 2, 3 and 4, the rotor of a machine in the form of an electric motor-generator is designated generally by the reference numeral 2. The rotor 2 rotates about a shaft 4. In this embodiment, the motor is a bi-directional motor and thus can rotate in both directions around the shaft 4. In other embodiments, the motor may be one-directional.

(15) The machine further comprises a fan designated generally by the reference numeral 6. In this embodiment of the invention the fan comprises a plurality of blades 8 which extend radially from an axis of rotation that is co axial with the shaft 4. In this embodiment of the invention the fan 6 is positioned within components of the rotor 2 in order to cool the electric motor-generator during use of the motor.

(16) Because the motor-generator is a bi-directional motor generator, in this embodiment, the fan 6 according to embodiments of the first aspect of the invention must also be able to operate bi-directionally. In other embodiments of the invention the motor generator may be one directional and therefore the fan 6 may also be one directional.

(17) In some embodiments of the invention, the electric motor-generator 2 will comprise two fans 6 positioned at opposite ends of the rotor 2.

(18) The fan 6 further comprises an upper sealing component 10 and a lower sealing component 12 shown in more detail in FIG. 8. The edge of the upper sealing component 10 is designed to provide a flange that partially defines an air inlet 14 as shown in FIG. 8. The air inlet 14 serves to reduce the pressure loss at entry into the radial fan 6. In an alternative embodiment of the invention, in order to further facilitate this reduction in pressure loss, both the upper and lower sealing components 10, 12 are rounded.

(19) The lower sealing component 12 is, in this embodiment, mounted directly onto the rotor 4 of the electric motor-generator.

(20) The lower sealing component 12 is, in this embodiment, connected directly onto the rotor 2.

(21) The purpose of the upper sealing component 10 is to reduce or prevent leakage air flows. In this respect the upper sealing component 10 is, in this embodiment, part of a sealing system (not shown) that seals the rotating parts of the fan 6 against stationary air guides.

(22) The fan blades 8 are located between the upper sealing component 10 and the lower sealing component 12. The upper sealing component 10 and/or the lower sealing component 12 may be used to mount the fan blades 8 between the two components 10, 12 and to thus fix them in position between the two sealing components 10, 12.

(23) The shape of the blades 8 will now be discussed in more detail.

(24) As can be seen from FIGS. 2, 3, 4, 5 and 6, each of the blades 10 has a rounded symmetrical transverse profile. More specifically, each blade is symmetrical about an axis of symmetry S which extends radially from the shaft 4. This is shown in more detail in FIG. 4.

(25) A further feature of the shape of each blade is that the profile is rounded at least in parts of the profile, as well as being symmetrical about the axis of symmetry S.

(26) In the illustrated embodiment, the shape of each blade is tear-drop shaped, although other shapes would be possible. For example, each blade could be substantially rectangular in shape having opposite rounded ends.

(27) The shape of the blade 8 according to aspects of the present invention is contrasted with the shape of known blades 50 shown in FIGS. 5, 6 and 7.

(28) It can be readily seen that known blades are substantially straight, having two edges 52, 54 which are parallel to one another.

(29) Turning back to the blades 8 forming part of the present invention, each blade has a thickness 16 extending in an axial direction. In this embodiment of the invention a thickness 16 decreases with the radial distance from the shaft 4.

(30) In other words, the thickness 16 at the rounded end portion 18 of each blade 8 is greater than at the narrower end 20 of each blade.

(31) The symmetrical transverse shape of the blades 8 results in a superior fan performance regarding pressure generation and efficiency compared to fans with radially straight blades.

(32) The performance of a fan according to embodiments of the invention will now be discussed with reference to a similar known fan having straight blades.

(33) FIG. 9 sets out the parameters of the fans which were tested. The parameters set out in this table are exemplary only, and different parameters could prevail.

(34) It can be seen that the dimensions of the prior art fan shown in the second column of the table are the same as the parameters of fan 6 according to an embodiment of the invention.

(35) The performance of the two fans will be compared with Computational Fluid Dynamics (CFD). Both fans can be used with a bi-directional air cooled electrical motor-generator.

(36) For both fans, the fan performance was calculated with CFD. This study revealed that the symmetrical profiles of the blades 8 in fan 6 have a considerably higher static pressure generation in wide volume flow range. As shown in FIG. 10, the bi-directional radial fan according to embodiments of the invention generates around 3.4 times higher static pressure for a volume flow of 30 m.sup.3 s.sup.−1.

(37) The fan 6 according to the invention facilitates a much higher cooling air flow than a fan according to the prior art. The fan according to the invention can be used to reduce the temperature of the electric motor-generator or to increase the power of the motor-generator. In addition to the improvement in the static pressure generation, the efficiency is also considerably higher. The higher static efficiency leads to a lower power consumption of the fan according to embodiments of the invention which is shown in FIG. 11.

(38) The superior performance of the fan 6 according to aspects of the present invention can be explained by considering the behaviour of flow around the blades. This is shown in FIG. 12 for a flow rate of 30 m.sup.3 s.sup.−1.

(39) The left-hand portion of FIG. 12 shows the flow behaviour around the straight blades of a known fan, and the right-hand portion of FIG. 12 shows the flow behaviour around the symmetrically profiled blades 8 of the fan 6 according to the invention. This shows that the fan 6 has considerably less delamination compared to the known fan. This explains the superior fan performance of the fan according to the invention.