GB2585707A

GB2585707A - Variable radial inlet guide vane assembly

Info

Publication number: GB2585707A
Application number: GB1910095.7A
Authority: GB
Inventors: Harley Peter; James Kyle Robert; John Collison Michael
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2019-07-15
Filing date: 2019-07-15
Publication date: 2021-01-20
Anticipated expiration: 2039-07-15
Also published as: WO2021009478A1; GB201910095D0; GB2585707B; CN114144587A

Abstract

An air moving device 300, such as a fan, comprises a radial air inlet 104, an air outlet 106, and a cavity 103 therebetween which has a central axis 105 passing through the outlet. The device also comprises an airflow generator 200, such as a motor driven impeller, and a plurality of guide vanes 110 spaced around the cavity axis, wherein at least a part of each vane is located in the cavity. Each of the vanes has an end portion 118 and a second portion 119 with the end portion between the second portion and the outlet. Each of the vanes is movable relative to the radial inlet to at least one position where the end portion of the respective vane overlaps the outlet less than the second portion of the respective vane does. The vanes may be at least partially tapered to their respective end portions. The vanes may be pivotable about axes parallel to the cavity axis.

Description

VARIABLE RADIAL INLET GUIDE VANE ASSEMBLY

Technical Field

The present invention relates to variable radial inlet guide vane assemblies. Particularly, but not exclusively, the present invention relates to variable radial inlet guide vane assemblies for air moving devices, such as may be comprised in fan assemblies.

Background

Radial inlet guide vanes are typically employed to affect the direction of a flow entering a system or device through a radial inlet. Particularly, but not exclusively, the vanes impart swirl into the flow. The direction of the inflow may be affected by varying the angle of attack of the vanes relative to the initial flow direction.

Fan assemblies are known which draw air through a radial inlet using an air-moving device, such as an impeller located within the fan assembly, before outputting the accelerated air through an air outlet

Summary

According to a first aspect of the present invention, there is provided an air moving device, comprising: a radial air inlet, an air outlet, and a cavity between the radial air inlet and the air outlet, wherein the cavity has a central axis that passes through the air outlet; an airflow generator configured to receive air from the air outlet in use; and a plurality of guide vanes spaced around the central axis, wherein at least a part of each vane is located in the cavity; wherein each of the vanes has an end portion nearest to the air outlet, and a second portion arranged so that the end portion is between the second portion and the air outlet in a direction parallel to the central axis, and wherein each of the vanes is movable relative to the radial air inlet to at least one position at which the end portion of the respective vane, when viewed along the central axis, overlaps the air outlet less than the second portion of the respective vane overlaps the air outlet.

In an exemplary embodiment, at the at least one position, when viewed along the central axis the end portion does not overlap the air outlet In an exemplary embodiment, at the at least one position, when viewed along the central axis, the second portion overlaps the air outlet and the end portion does not overlap the air outlet.

In an exemplary embodiment, at the at least one position, when viewed along the central axis the second portion overlaps the air outlet over a majority of a span of the vane parallel to the central axis In an exemplary embodiment, over a full range of movement of the vane, when viewed along the central axis the end portion does not overlap the air outlet.

In an exemplary embodiment, the vanes are at least partially tapered to their respective end portions In an exemplary embodiment, the vanes are pivotable about respective pivot axes parallel to the central axis so as to vary respective angles of attack of the vanes relative to a direction of air flow from the radial air inlet.

In an exemplary embodiment, each of the vanes is pivotable over between 50 and 70 degrees from a position radial to the central axis. In an exemplary embodiment, each of the vanes is pivotable over between 55 and 65 degrees from a position radial to the central axis.

In an exemplary embodiment, in each of the vanes, a span of the vane parallel to the central axis is greater than an average width of the vane perpendicular to the span In an exemplary embodiment, wherein the cavity comprises a first boundary and a second boundary, the second boundary being spaced from the first boundary in the direction of the central axis and having an aperture therethrough defining the air outlet, and wherein a span of each of the vanes parallel to the central axis is at least 50% of a distance between the first and second boundaries.

In an exemplary embodiment, the air moving device has one or more openings at an exterior of the device, and the device is configured so that air is drawn radially through the one or more openings to the radial air inlet in use.

In an exemplary embodiment, the airflow generator comprises a motor-driven impeller.

In an exemplary embodiment, the air moving device comprises at least one air filter upstream of the radial air inlet.

According to a second aspect of the present invention, there is provided a fan assembly, comprising an air moving device according to the first aspect of the present invention, and an air outlet for emitting an air flow generated by the airflow generator of the air moving device In an exemplary embodiment, the air outlet may be a nozzle.

According to a third aspect of the present invention, there is provided a variable radial inlet guide vane assembly for conditioning air upstream of an airflow generator of an air moving device, the assembly comprising: a radial air inlet, an air outlet through which air is to flow from the assembly to the airflow generator in use, and a cavity between the radial air inlet and the air outlet, wherein the cavity has a central axis that passes through the air outlet; and a plurality of guide vanes spaced around the central axis, wherein at least a part of each vane is located in the cavity; wherein each of the vanes has an end portion nearest to the air outlet, and a second portion arranged so that the end portion is between the second portion and the air outlet in a direction parallel to the central axis, and wherein each of the vanes is movable relative to the radial air inlet to at least one position at which the end portion of the respective vane, when viewed along the central axis, overlaps the air outlet less than the second portion of the respective vane overlaps the air outlet.

In an exemplary embodiment, at the at least one position, when viewed along the central axis the second portion overlaps the air outlet over a majority of a span of the vane parallel to the central axis.

In an exemplary embodiment, over a full range of movement of the vane, when viewed along the central axis the end portion does not overlap the air outlet.

In an exemplary embodiment, the vanes are at least partially tapered to their respective end portions.

In an exemplary embodiment, the vanes are pivotable about respective pivot axes parallel to the central axis so as to vary respective angles of attack of the vanes relative to a direction of air flow from the radial air inlet In an exemplary embodiment, in each of the vanes, a span of the vane parallel to the central axis is greater than an average width of the vane perpendicular to the span.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings

Brief Description of the Drawings

Figure 1 shows a cross-sectional schematic view of an example air moving device.

Figure 2 shows an isometric view of an example variable radial inlet guide vane assembly.

Figure 3 shows a top-down view of the example variable radial inlet guide vane assembly of Figure 2 Figure 4 shows a top-down schematic view of the example variable radial inlet guide vane assembly of Figures 2 and 3.

Figures 5 and 6 show an example fan assembly.

Figure 7 shows a cross-sectional view of the example fan assembly of Figures 5 and 6, showing an example air moving device according to Figure 1.

Detailed Description

There will now be described an air moving device comprising a variable radial inlet guide vane assembly and an airflow generator. Such an air moving device is suitable for use as part of a fan assembly. The term "fan assembly" as used herein refers to a fan assembly configured to generate and deliver an airflow for the purposes of thermal comfort and/or environmental or climate control. Such a fan assembly may be capable of generating one or more of a dehumidified airflow, a humidified airflow, a purified airflow, a filtered airflow, a cooled airflow, and a heated airflow. However, the fan assembly could equally be suitable for generating an airflow for other purposes, such as in a hair dryer or other hair care appliance.

Figure 1 shows a cross-sectional schematic view of an exemplary air moving device 300 comprising a variable radial inlet guide vane assembly 100 and an airflow generator 200. Figures 2, 3 and 4 show an isometric view, a top-down view, and a top-down schematic view, respectively, of the variable radial inlet guide vane assembly 100. The variable radial inlet guide vane assembly 100 comprises a body 101 comprising a substantially radial air inlet 104, an air outlet 106, and a cavity 103 located between the radial air inlet 104 and the air outlet 106. The body 101 may be unitary or assembled from plural pieces. The cavity 103 has a central axis 105 that passes through the air outlet 106 of the assembly 100. The assembly 100 is disposed within a body (not shown) of the air moving device 300, the body of the air moving device 300 comprising an air outlet through which air is emitted from the body of the air moving device 300 (e.g. into the surrounding environment, into a nozzle mounted on the body etc.). The airflow generator 200 is mounted between the air outlet 106 of the assembly 100 and the air outlet of the body of the air moving device 300. The airflow generator 200 has an inlet 206 to receive air from the air outlet 106 of the assembly 100. That is, in use, air is to flow through the air outlet 106 of the assembly 100 to the airflow generator 200. In this example, the airflow generator inlet 206 and the air outlet 106 are circular.

In other examples, the airflow generator inlet 206 and/or the air outlet 106 may be non-circular, such as elliptical or polygonal.

The assembly 100 comprises a plurality of guide vanes 110 spaced around the central axis 105 of the cavity 103. At least a part of each vane 110 is located in the cavity 103.

In this example, all of each vane 110 is located in the cavity 103. In other examples, some or all of the vanes 110 may protrude from the cavity 103, so that only a part of each protruding vane 110 actually is in the cavity 103. In this example, the cavity 103 has a circular cross-section, so the vanes 110 are circumferentially spaced around the central axis 105. In other examples, the cross-section of the cavity 103 may be other than circular, such as elliptical, annular, or polygonal. In the present example, the cavity 103 is non-annular and is devoid of any obstruction between the vanes 110 on opposite sides of the central axis 105.

In this example, the air moving device 300 has openings 304 at an exterior of the device 300, and the device 300 is configured so that air is drawn radially through the openings 304 to the radial air inlet 104 in use. In other examples, there may be only one such opening 304. In the present example, the air moving device 300 comprises a filter 301 located upstream of the radial air inlet 104, so that incoming air passes through the filter 301 before passing through the radial air inlet 104 and entering the cavity 103. In other examples, there may be more than one filter upstream of the air inlet 104 or there may be no such filter.

Each vane 110 is movable relative to the radial air inlet 104 to vary how the vane 110 acts on air passing from the radial air inlet 104 and into the cavity 103 in use. In this, but not all, examples, the vanes 110 are pivotable about respective pivot axes 115 parallel to the central axis 105. In some examples, the pivot axis 115 of a given vane 110 may pass through any portion of the vane 110, such as substantially along an edge or through a central portion of the vane 110. In other examples, the pivot axis 115 may be distanced from the vane 110. Movement of each of the vanes 110 is configured to affect the direction of a radial inflow 107 impinging on the vanes 110 from outside the assembly 100 via the radial air inlet 104 (and, in this example, via the openings 304 and the filter 301). For example, changing an angle of attack a of each of the vanes 110 relative to the radial inflow 107 from the radial air inlet 104 may induce a tangential velocity, or 'swirl', into the radial inflow 107. If a given vane 1_10 is aligned with the radial inflow 107, the angle of attack a is zero, and no such swirl is induced by that vane 110. In some examples, it may be desirable to induce swirl to increase the operating range of the air moving device 300. Such pre-swirling of flow in an air moving device 300 prior to the air reaching the airflow generator 200 mounted downstream of the assembly 100 may provide, for instance, higher efficiency or lower acoustics of the air moving device 300. It should be understood that the substantially radial air inlet 104 may permit a radial inflow 107 at angles other than strictly orthogonal to the central axis 105, but still in a generally radial direction. Such a radial air inlet 104 may itself be so inclined to the central axis 105.

Each of the guide vanes 110 of Figures 1 to 4 has a span 113 parallel to the central axis 105. Each of the vanes 110 also has a trailing edge 114 facing into the cavity 103 and an opposite leading edge 117. In this example, the leading edge 117 faces the radial air inlet 104. Each of the guide vanes 110 has an end portion 118 nearest to the air outlet 106, and a second portion 119 arranged so that the end portion 118 is between the second portion 119 and the air outlet 106 in a direction parallel to the central axis 105. The end portion 118 has a first width 111, and the second portion 119 has a second width 112. The first and second widths 111, 112 are each perpendicular to the span 113. Each of the vanes 110 of the present example has an aspect ratio (AR) greater than unity. The AR is defined as the ratio between the span 113 and the average width of the vane 110. In some examples, the AR may be between 1 and 4, such as approximately 3. In some examples, the AR may be greater than 4.

The present inventor realised that a large vane width may be desirable for achieving high swirl angles, but that a turbulent wake from a vane having a large width may undesirably interact with a downstream airflow generator, particularly if limited space is available within the air moving device. Such an interaction may create additional vibration or noise. Alternatively, or in addition, the efficiency of the air moving device may be degraded. The present invention attempts to mitigate the interaction of a turbulent wake with the air flow generator 200 while still imparting high swirl angles.

This effect is achieved by ensuring that each of the vanes 110 is movable, relative to the radial air inlet 104, to at least one position at which the end portion 118 nearest to the air outlet 106, and thus nearest to the air-moving device 200, overlaps the air outlet 106 less than the second portion 119 when viewed along the central axis 105. In this example, this is as a result of the first width 111 being less than the second width 112. Indeed, in this example, when viewed along the central axis 105 the end portion 118 does not overlap the air outlet 106 at all when the vane 110 is at the at least one position. Moreover, in this example, at the at least one position, the second portion 119 overlaps the air outlet 106 and the end portion 118 does not overlap the air outlet 106 In this example, the second width 112 of each of the vanes 110 is greater than the first width 111 along a majority of the span 113 of the vane 110 such that, at the at least one position, when viewed along the central axis the second portion 119 overlaps the air outlet 106 over a majority of the span 113 of the vane. In this example, the second width 112 is also constant along a majority of the span 113 of the vane 110. In other examples, the second width 112 may vary, such as by less than 10%, along a majority of the span 113 of the vane 110. In this example, the first width 111 is non-zero. In other examples, the first width 111 is zero, such that the end of the vane 110 nearest to the air outlet 106 is pointed (e.g. tapers to a point).

In the present example, the vanes 110 are tapered to their respective end portions 118, as indicated by reference numeral 116. That is, a portion of the trailing edge 114 of the vane 110 is tapered. In each vane 110, the tapering 116 reduces the intensity of the wake leaving the trailing edge 114 of the vane 110 and entering the air moving device 200, while still permitting the vane 110 to impart high swirl angles due to a relatively long width along another portion, in this case a majority portion, of the span 113 of the vane 110. In other examples, a width of each of the vanes 110 may reduce towards the end portion 118 by way of any one or a combination of: a convex fillet; a concave fillet; a chamfer; and at least one step. In the present example, except for the taper 116, the leading edge 117 and the trailing edge 114 of each of the vanes 110 are substantially parallel to the central axis 105.

As noted above, in this example, the guide vanes 110 are pivotably mounted relative to the cavity 103, the radial air inlet 104, and the central axis 105. In other examples, the vanes 110 may be movable relative to the cavity 103, the radial air inlet 104, and the central axis 105 as a translation or a combination of a translation and a rotation. The assembly 100 may comprise any suitable actuator (not shown) for causing movement of the vanes 110 relative to the cavity 103, the radial air inlet 104, and the central axis 105.

In this example, the airflow generator 200 has an axis of rotation which is aligned with the central axis 105 of the cavity 103 That is, the central axis 105 of the cavity 103 and the axis of rotation of the airflow generator 200 are coincident. In other examples, the central axis 105 of the cavity 103 and the axis of rotation of the airflow generator 200 may be offset, such as parallel to each other.

As discussed above, the swirl is induced by varying the angle of attack a of the vanes 110 relative to the incoming air. If the vanes 110 were to be aligned with the incoming air 107, the angle of attack a would be zero. If the angle of attack a is zero, the inflowing air 107 may enter the device 300 or the assembly 100 substantially radially (such as perpendicular to the central axis 105), change direction within the cavity 103, and pass through the air outlet 106 substantially axially (such as parallel to the central axis 105). In this case, the vanes 110 may not impart a tangential component of velocity into the flow, but they may still produce a wake. If the vanes 110 are instead disposed at an angle of attack a of greater than zero degrees, the inflowing air 107 will enter the device substantially radially, impinge on surfaces of the vanes 110 and proceed to pass tangentially, as well as axially, through the cavity 103. The airflow generator 200 would thereby receive pre-swirled air, potentially improving the performance characteristics of the air moving device as described hereinbefore As noted hereinbefore, the present inventor realised that increasing the width of each vane 110 may generate more swirl and thus improve the characteristics of the air moving device 300. However, the inventor also realised that the wake emanating from a vane 110 having a long width may negatively impact the operation of the air moving device 300 at low angles of attack a. This may be particularly pertinent in devices having a limited space envelope, such as the example shown in Figures 1 to 4, wherein a vane 110 having a long width when viewed along the central axis 105 at low angles of attack a may overlap the air outlet 106. Providing that the end portion 118 of each of the vanes 110 overlaps the air outlet 106 less than the second portion 119 when viewed along the central axis 105 as described hereinbefore provides the advantage of a reduced wake intensity leaving the vane 110 and entering the airflow generating device 200, whilst still providing high swirl angles elsewhere along the vane 110. In the present example, over a full range of movement of each of the vanes 110, the end portion 118 of each of the vanes 110 does not overlap the air outlet 106 when viewed along the central axis 105. This results in the advantage being obtained regardless as to the angle of attack a at which the vanes 110 are positioned. In some other examples, in each of the vanes 110 the end portion 118 of the vane 110 may somewhat overlap the air outlet 106 (albeit less than the second portion 119 of the vane overlaps the air outlet 106) yet still provide a similar advantage.

In some examples, the vanes 110 may be pivoted relative to the cavity 103, the radial air inlet 104, and the central axis 105 between an angle a of zero degrees (at which the vane 110 is radially aligned with the central axis 105) and an angle a of about 60 degrees from a direction radial to the central axis 105. In some examples, the upper limit on this range of movement of the vanes 110 may be another angle between 50 and 70 degrees, optionally between 55 and 65 degrees. The upper limit may be more than 40 degrees, more than 50 degrees, or more than 55 degrees, for example. The upper limit may be less than 80 degrees, less than 70 degrees, or less than 65 degrees, for example.

Figure 4 shows one of the vanes 110 in two states: at an angle of attack a of zero degrees, and at an angle of attack a of 60 degrees. In the present example, when viewed along the central axis 105 the second portion 119 of the vane 110 does not overlap the air outlet 106 when the vane 110 is at an angle of attack a of 60 degrees. Preferably, the trailing edge 114 of the vane 110 is incident with a boundary of the air outlet 106 or the airflow generator inlet 206 when the vane 110 is positioned at an angle of attack a of 60 degrees. In other examples, when viewed along the central axis 105, the trailing edge 114 of the vane 110 may be incident with the boundary of the air outlet 106 or the airflow generator inlet 206 at other angles of attack a, such as 30 degrees, 40 degrees, 50 degrees, or greater than 60 degrees. In other examples, the trailing edge 114 of the vane 110 may overlap the air outlet 106 or the airflow generator inlet 206 at all angles of attack a, or may not so overlap at angles of attack greater than a predetermined size, such as 60 degrees. Nevertheless, since the second portion 119 of the vane 110 is spaced from the air outlet 106 in a direction parallel to the central axis 105, such overlap may have negligible or no impact on performance of the assembly 100 or the device 300.

Figures 5 and 6 show an example fan assembly 500 comprising an air moving device 300 as shown in Figure 1, and a nozzle 400 for emitting the airflow generated by the air moving device 300. In some examples, the nozzle 400 may define an opening through which air from outside the fan assembly is drawn by air flow emitted from the nozzle 400 in use. In other examples, the air may be emitted through an air outlet of the fan assembly 500 that is other than a nozzle. Figure 7 shows a cross-sectional view across section A-A of the example fan assembly 500 of Figure 6, highlighting the air moving device 300 of Figure 1, and the variable radial inlet guide vane assembly 100 of Figures Ito 4 thereof It will be appreciated that individual items described above may be used on their own or in combination with other items shown in the drawings or described in the description and that items mentioned in the same passage as each other or the same drawing as each other need not be used in combination with each other. In addition, the expression "means" may be replaced by actuator or system or device as may be desirable. In addition, any reference to "comprising" or "consisting" is not intended to be limiting in any way whatsoever and the reader should interpret the description and claims accordingly.

Furthermore, although the invention has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. For example, those skilled in the art will appreciate that the above-described inventions might be equally applicable to other types of environmental control fan assemblies, and not just free standing fan assemblies. By way of example, such a fan assembly could be any of a freestanding fan assembly, a ceiling or wall mounted fan assembly and an in-vehicle fan assembly. In addition, the above-described inventions might be equally applicable to other types of air flow generating devices, or blowers, such as a hairdryer or other hair care appliance.

Moreover, in the example illustrated in Figure 7, the airflow generator comprises a motor-driven impeller. However, the airflow generator may be of a different form. In addition, in the example illustrated in Figure 7, the impeller is in the form of a mixed flow impeller that comprises a generally conical hub, a plurality of impeller blades connected to the hub, and a generally fnisto-conical shroud connected to the blades so as to surround the hub and the blades. However, the impeller could equally be of a different form, such as an axial or radial impeller.

Claims

CLAIMSI. An air moving device, comprising: a radial air inlet, an air outlet, and a cavity between the radial air inlet and the air outlet, wherein the cavity has a central axis that passes through the air outlet; an airflow generator configured to receive air from the air outlet in use; and a plurality of guide vanes spaced around the central axis, wherein at least a part of each vane is located in the cavity; wherein each of the vanes has an end portion nearest to the air outlet, and a second portion arranged so that the end portion is between the second portion and the air outlet in a direction parallel to the central axis, and wherein each of the vanes is movable relative to the radial air inlet to at least one position at which the end portion of the respective vane, when viewed along the central axis, overlaps the air outlet less than the second portion of the respective vane overlaps the air outlet.
2. The device according to claim 1, wherein, at the at least one position, when viewed along the central axis the end portion does not overlap the air outlet.
3. The device according either claim 1 or claim 2, wherein, at the at least one position, when viewed along the central axis the second portion overlaps the air outlet over a majority of a span of the vane parallel to the central axis
4. The device according to any one of claims 1 to 3, wherein, over a full range of movement of the vane, when viewed along the central axis the end portion does not overlap the air outlet.
5. The device according to any one of claim 1 to 4, wherein the vanes are at least partially tapered to their respective end portions.
6. The device according to any one of claims 1 to 5, wherein the vanes are pivotable about respective pivot axes parallel to the central axis so as to vary respective angles of attack of the vanes relative to a direction of air flow from the radial air inlet.
7. The device according to any one of claims 1 to 6, wherein each of the vanes is pivotable over between 50 and 70 degrees from a position radial to the central axis
8 The device according to any one of claims Ito 7, wherein in each of the vanes, a span of the vane parallel to the central axis is greater than an average width of the vane perpendicular to the span.
9. The device according to any one of claims 1 to 8, wherein the cavity comprises a first boundary and a second boundary, wherein the second boundary is spaced from the first boundary in the direction of the central axis and has an aperture therethrough defining the air outlet, and wherein a span of each of the varies parallel to the central axis is at least 50% of a distance between the first and second boundaries.
10. The device according to any one of claims Ito 9, wherein the device has one or more openings at an exterior of the device, and the device is configured so that air is drawn radially through the one or more openings to the radial air inlet in use.
11. The device according to any one of claims 1 to 10, wherein the airflow generator comprises a motor-driven impeller.
12. The device according to any one of the preceding claims, wherein the device comprises at least one filter upstream of the radial air inlet.
13 A fan assembly, comprising an air moving device according to any one of claims Ito 12, and an air outlet for emitting an air flow generated by the airflow generator of the air moving device.
14. A variable radial inlet guide vane assembly for conditioning air upstream of an airflow generator of an air moving device, the assembly comprising: a radial air inlet, an air outlet through which air is to flow from the assembly to the airflow generator in use, and a cavity between the radial air inlet and the air outlet, wherein the cavity has a central axis that passes through the air outlet; and a plurality of guide vanes spaced around the central axis, wherein at least a part of each vane is located in the cavity; wherein each of the vanes has an end portion nearest to the air outlet, and a second portion arranged so that the end portion is between the second portion and the air outlet in a direction parallel to the central axis, and wherein each of the vanes is movable relative to the radial air inlet to at least one position at which the end portion of the respective vane, when viewed along the central axis, overlaps the air outlet less than the second portion of the respective vane overlaps the air outlet.
15. The assembly according to claim 14, wherein, at the at least one position, when viewed along the central axis the end portion does not overlap the air outlet.
16 The assembly according to any one of claims 14 and 15, wherein, at the at least one position, when viewed along the central axis the second portion overlaps the air outlet over a majority of a span of the vane parallel to the central axis
17. The assembly according to any one of claims 14 to 16, wherein, over a full range of movement of the vane, when viewed along the central axis the end portion does not overlap the air outlet.
18. The assembly according to any one of claims 14 to 17, wherein the vanes are at least partially tapered to their respective end portions.
19. The assembly according to any one of claims 14 to 18, wherein the vanes are pivotable about respective pivot axes parallel to the central axis so as to vary respective angles of attack of the vanes relative to a direction of air flow from the radial air inlet.
20. The assembly according to any one of claims 14 to 19, wherein in each of the vanes, a span of the vane parallel to the central axis is greater than an average width of the vane perpendicular to the span