WO2014096344A1

WO2014096344A1 - A modular mixed flow fan

Info

Publication number: WO2014096344A1
Application number: PCT/EP2013/077654
Authority: WO
Inventors: Victor SILBERMANN
Original assignee: Multi-Wing International A/S
Priority date: 2012-12-21
Filing date: 2013-12-20
Publication date: 2014-06-26

Abstract

A modular mixed flow fan (1) comprising a hub (2) being configured for rotation about an axis and a plurality of fan blades (3). A retention part (4) of each blade is received in openings (5) in an outer surface (6) of the hub, and each blade extending radially between opposite ends, one end forming a tip edge (7) and the other one forming a hub edge (8) from which the retention part protrudes. The hub edge is arch-shaped, and the outer surface of the hub is formed as a section of a sphere having a sphere centre (13). The section of the sphere is defined between a first plane (10) and a second plane (11) being parallel. Furthermore, a first diameter (L1) of the hub along the first plane is smaller than a second diameter (L2) of the hub along the second plane.

Description

A MODULAR MIXED FLOW FAN Field of the invention

The present invention relates to a modular mixed flow fan comprising a hub and a plurality of fan blades. Each blade comprises a retention part which is received in openings in an outer surface of the hub.

Background of the invention

Traditionally, mixed flow fans are provided for cooling of an engine, such as a combustion engine or an electrical motor. A mixed flow, i.e. a flow comprising both an axial component and a radial component, is typically provided by a hub having a conical shape. To optimise the flow of air provided by the fan, the shape of the root end of the blades should match the conical shape of the hub, as gaps between the root end of the blades and the hub create turbulence which lowers the performance of the fan.

In axial fans where the hub is not conical, it is often possible to rotate the blades around their longitudinal length axis to change the performance for specific conditions. This is referred to as pitching.

Due to the conical shape of the hub, pitching of the fan blades are not carried out in mixed flow fans, as such pitching would create gaps between the root ends of the blades at the leading edge or the trailing edge depended on the direction of the pitching. At the opposite edge, the root end of the blade will instead collide with the hub. To enable pitching and avoid collision, a large gap should be provided at the root end of the blades at both the leading edge and the trailing edge, thereby lowering the performance of the fan.

Description of the invention

It is an object of embodiments of the invention to provide an improved mixed flow fan.

It is a further object of embodiments of the invention to provide a mixed flow fan which allow pitching of the fan blades.

According to a first aspect, the invention provides a modular mixed flow fan comprising a hub being configured for rotation about an axis and a plurality of fan blades, a retention part of each blade being received in openings in an outer surface of the hub, each blade extending radially between opposite ends, one end forming a tip edge and the other one forming a hub edge from which the retention part protrudes, wherein the hub edge is arch-shaped, and the outer surface of the hub is formed as a section of a sphere having a sphere centre, the section of the sphere being defined between a first plane and a second plane being parallel, and wherein a first diameter of the hub along the first plane is smaller than a second diameter of the hub along the second plane.

In the context of the present invention, the term 'mixed flow fan' should be understood as, a fan which is adapted to move gas, typically air, in a direction parallel with the rotation axis of the fan and radially relatively to the rotation axis, i.e. a fan having an air flow with an axial and a radial component. Herein 'air' should be understood as covering any gas, so that an 'airflow' in the present context covers a flow of gas.

The mixed flow fan according to the present invention may be used for cooling of a combustion engine. The combustion engine may e.g. form part of a tractor, or a combine harvester or any similar kind of agricultural machinery, or an excavator, a bulldozer, a crane, or any similar kind of construction equipment for on-highway or off-highway usage.

The hub will typically be connected to an axle which is rotated by the combustion engine via a belt or driven by an electrical driven motor or a hydraulic driven motor. The rotation causes rotation of the hub and thereby movement of air. In air cooled combustion engines the air cools an outer surface of the combustion engine, and in water cooled engines, the air is blown through a radiator which cools the cooling liquid. This axle may be an axle which forms an extension of the axle of the combustion engine.

Each blade may define a retention part and an air moving part, where the retention part is that part of the blade which is attached to the hub and retained in the openings of the hub. Thus, each blade is formed as separate components which are attached to a hub by insertion of the retention part into openings in the hub. One opening may be provided for each fan blade. The separate blades and the hub define the modularity of the fan, thereby allowing for use of a hub with different sets of fan blades.

The hub and/or the blades may as an example be made from a metal material, plastic material, or from a composite material comprising fibres e.g. of glass or carbon. Different examples are iron, aluminium, polycarbonate, polystyrene, polyamide, polypropylene, or vinyl, etc. It will be appreciated that other metals or plastic materials may be used. The fan comprises a plurality of fan blades such as four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, etc. The length of the blades may be in the range 100-750 millimetres, such as 100 millimetres, such as 250 millimetres, such as 500 millimetres, such as 750 millimetres. The size of the mixed flow fan along the axial direction may be in the range of 30-400 millimetres.

By providing the blades with a hub edge being arch-shaped, and the outer surface of the hub being formed as a section of a sphere, the root end of the blades and the hub may match each other even during pitching of the blades. Due to the arch-shaped edges, the gap resulting from pitching is minimized and the arch-shape therefore facilitates pitching of blades on mixed flow fans without decreasing the performance of the fan.

The section of the sphere is defined between a first plane and a second plane being parallel, and a first diameter of the hub along the first plan is smaller than a second diameter of the hub along the second plane, whereby the diameter of the hub at one end is larger than at the other end. As the hub is formed as a section of a sphere, the diameter of the hub increases from the first plane to the second plane.

The first and second plane may extend perpendicular to the rotation axis, whereby the first diameter and second diameter of the hub can be measured perpendicular to the rotation axis. The second plane may be positioned closer to the sphere centre, the first diameter may be smaller than the second diameter. In one embodiment, a first distance from the sphere centre to the first plane is in the range of 65-80 percent of the radius of the sphere, whereas a second distance from the sphere centre to the second plane is in the range of 40-65 percent of the radius of the sphere.

To facilitate pitching of the blades, the hub edge may have a larger radius than the sphere or a radius being at least equal to the radius of the sphere, as a smaller radius would create a gap between the hub edge and the sphere-shaped hub, and may cause collision between the hub edge and the hub, which would lead to loss of performance compared to the

performance when having a radius of the hub edge being at least equal to the radius of the sphere.

The openings for the retention parts of the blades may be substantially circular. However, the openings may also have other shapes, such as oval-shaped, square-shaped, etc.

Furthermore, the openings may comprise notches, indentations, recesses, or protrusions, etc. of different shape along the inner circumference. Each opening may have a centre point, and pitching of the fan blade may be facilitated by arranging all the centre point in a common plane having identical distance to a centre of the sphere. The centre point of each opening may be the geometric centre point.

The common plane may be arranged between the first plane and the second plane, and may be parallel to both the first and second planes. In one embodiment, the common plane may be arranged centrally between the first and the second plane. The common plane may however in different embodiments be arranged closer to one of the first and second plane.

In one embodiment, the hub and the blades are designed such that the pitch of the blade may be set in connection with the attachment of the blade to the hub. In this embodiment, the pitch of the blades may be changed by disconnecting the blades from the hub or by loosening the joint between the hub and the blades, and subsequently attaching or fastening the blades to the hub at a new pitch angle.

To provide pitching at different rotational positions of the fan blades, the retention part may be rotationally lockable in multiple positions in the openings, whereby each position correspond to a different pitching angle of the fan blade. The number of positions may depended on the size of the hub, the size of the fan blades, the number of blades, the type of appliance in which the fan is to be incorporated, etc.

The locking may be provided by engagement of a first cooperating structure at the retention parts and a second cooperating structure in the openings. As an example, the first cooperation structure of the retention part may comprise one or more protrusions extending radially from the retention part. The second cooperating structure in the openings may be indentations along the inner surface of the openings, so that a protrusion may be inserted in an indentation of the opening. The pitch angle may be changed by inserting the retention part into the opening with the protrusion in another indentation. It should be understood, that the indentations may also be provided at the retention parts, whereas the protrusion(s) may be provided at the inner surface of the opening.

Alternatively, the locking may be provided by use of a separate element adapted for engagement with the first and second structure, i.e. the fan may comprise a third separate structure for cooperation with the first and second cooperating structures. As an example, both the first cooperating structure at the retention parts and the second cooperating structure in the openings may comprise at least two indentations. The third separate structure may be inserted in one of the indentations of the retention part and one of the indentations of the opening, thereby locking the retention part relative to the opening to provide a specific pitching angle of the blade. If another combination of indentations is chosen, the blade can be locked at another pitching angle.

In one embodiment, the indentations may in a cross-section be provided as semi-circles. When an indentation at the retention part is positioned opposite an indentation in the opening, the two oppositely positioned indentations may form a tubular shape which in a cross-section is circular. A third separate structure having a tubular shape which in a cross- section is circular may consequently lock the retention part relative to the opening, thereby providing a specific pitching angle of the blade. By changing at least one of the indentations, i.e. at least one of the first cooperating structure and the second cooperating structure, the pitching angle can be changed.

It should be understood, that the circular cross-section is just an example. The cross- sectional shape of the third structure and thus the first and second cooperating structures in combination may be different from a circle, as the important feature is that the cross- sectional shape of the third structure matches the combined cross-sectional structure of the first and second cooperating structures in combination. Thus, the cross-sectional shape may e.g. be square-shaped, oval, triangular, etc.

In one embodiment, the third separate structure may have a cross-sectional shape corresponding to a symmetrically shape being halved and the two halves being displaced perpendicularly to the centre axis of the structure, so that the resulting cross-sectional shape e.g. is two semi-circles being displaced sideward relative to each other, or two squares being displaced sideward relative to each other, thereby defining a non-symmetrical cross-sectional shape.

An advantage of the non-symmetrically shape, is that one of semi-circles may be inserted in an indentation in an opening, and the other semi-circle may be inserted in an indentation in a retention part, whereby the two indentations can be displaced relative to each other. As the third structure may also be oppositely positioned, the displacement may also be in the other direction, thereby allowing for a more fine adjustment of the pitch.

It should be understood, that the above example of a third structure having a cross-sectional shape comprising two semi-circles displaced relative to each other is for illustration only. The third structure may have a cross-sectional shape comprising two squares, two semi-ovals, etc. displaced relative to each other.

As the blades typically will be equidistantly spaced circumferentially along an outer surface of the hub, the openings may be equidistantly arranged circumferentially along the outer surface. The blades may, however, also be arranged asymmetrically along an outer surface of the hub.

According to a second aspect, the invention provides a hub for a modular mixed flow fan, the hub being configured for rotation about an axis and comprising a plurality of openings in an outer surface in which openings a blade can be received, each blade extending radially between opposite ends, one end forming a tip edge and the other one forming a hub edge from which the retention part protrudes, wherein the hub edge is arch-shaped, and the outer surface of the hub is formed as a section of a sphere having a sphere centre, the section of the sphere being defined between a first plane and a second plane being parallel, and wherein a first diameter of the hub along the first plane is smaller than a second diameter of the hub along the second plane.

Each opening may have a centre point, and all centre points may be arranged in a common plane and may have identical distance to a centre of the sphere.

It should be understood, that a skilled person would readily recognise that any feature described in combination with the first aspect of the invention could also be combined with the second aspect of the invention, and vice versa.

The hub according to the second aspect of the invention is very suitable for the mixed flow fan according to the first aspect of the invention. The remarks set forth above in relation to the mixed flow fan are therefore equally applicable in relation to the hub according to the second aspect of the invention.

Brief description of the drawings

Embodiments of the invention will now be further described with reference to the drawings, in which:

Fig. 1 illustrates an embodiment of a mixed flow fan, Fig. 2 illustrates an embodiment of a mixed flow fan with indication of the sphere and planes, Fig. 3 illustrates another view of the mixed flow fan of Figs. 1 and 2. Figs. 4a and 4b illustrate a first and a second cooperating structure, and Figs. 5a, 5b, and 5c illustrate different embodiment of a third separate locking structure. Detailed description of the drawings

It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Fig. 1 illustrates an embodiment of a modular mixed flow fan 1 comprising a hub 2 and a plurality of fan blades 3 of which only one is shown. The blades 3 comprise a retention part 4 which is received in openings 5 in an outer surface 6 of the hub 2, as illustrated by the dotted line. Each blade 3 extends radially between opposite ends, one end forming a tip edge 7 and the other one forming a hub edge 8 from which the retention part 4 protrudes.

The hub edge 8 is arch-shaped, and the outer surface 6 of the hub is formed as a section of a sphere 9 (see Fig. 2). Due to the arch-shaped edges 8, a gap resulting from pitching of the blade 3 can be minimized and the arch-shape therefore facilitates pitching of blades 3 on mix flow fans 1 without decreasing the performance of the fan.

The outer surface 6 of the hub 2 is formed as a section of a sphere 9. In Fig. 2 the sphere 9 is illustrated. The section has a width w and is defined between a first plane 10 and a second plane 11. The planes 10 and 11 are parallel and extend perpendicular to the rotation axis (not shown). In the illustrated embodiment, the openings 5 for the retention parts 4 of the blades 3 are substantially circular. Each opening 5 has a centre point, and pitching of the fan blades 3 are facilitated by arranging all the centre point in a common plane 12 indicated by the dotted line 12. The centre points have identical distance to the sphere centre 13.

The section of the sphere is defined between the first plane 10 and the second plane 11 being parallel, whereby the diameter L2 of the hub at one end is larger than the diameter LI at the first plane. The common plane 12 is arranged between the first and second planes 10, 11, and is parallel to both the first and second planes 10, 11.

To facilitate pitching of the blades 3, the hub edge 8 has a larger radius than the sphere 9, as a radius being smaller than the radius of the sphere would create a gap between the hub 8 edge and outer surface 6 of the hub 2. This is illustrated by at Fig. 2 by indicating the radius of the hub edge as RXXX+1, whereas the radius of the sphere 9 is indicated as RXXX.

Fig. 3 illustrates another view of the mixed flow fan 1 of Figs. 1 and 2, where the retention part is inserted in the opening and therefore not visible. To provide pitching at different rotational positions of the fan blades 3, the retention part 4 is rotationally lockable in multiple positions in the openings 5, whereby each position correspond to a different pitching angle of the fan blade 3. The locking is provided by engagement of a first cooperating structure 14 at the retention parts 4 and a second cooperating structure 15 in the openings in cooperation with a third separate structure 16, which are illustrated in Figs. 4a and 4b.

In the illustrated embodiment, the first cooperation structure 14 of the retention part 4 comprises a plurality of indentations along the circumference of the retention part. The second cooperating structure in the openings 5 comprises a plurality of indentations 15 along the inner surface of the openings. The retention part 4 and thus the blade 3 can be rotationally locked to the hub 2 by aligning an indentation of 14 with an indentation 15 and inserting a third separate locking structure 16 in a tubular cavity defined by the two indentations in common, thereby locking the retention part 4 relative to the opening 5 to provide a specific pitching angle of the blade 3. If another combination of indentations is chosen, the blade can be locked at another pitching angle. In Fig. 4a, the third separate locking structure 16 has a tubular shape which in a cross- section is circular.

Figs. 5a illustrates the locking structure 16 in cross-section. In Figs. 5b and 5c an alternative embodiment of a locking structure 16' is illustrated. The third separate structure 16' has a cross-sectional shape corresponding to two semi-circles being displaced sideward relative to each other thereby providing a locking structure 16' with a non-symmetrically shape.

An advantage of the non-symmetrically shape, is that one of semi-circles may be inserted in an indentation 15 in an opening 5, and the other semi-circle may be inserted in an indentation 14 in a retention part 4, whereby the two indentations can be displaced relative to each other. As the third structure 16' may also be oppositely positioned (illustrated by Fig. 5b and 5c), the displacement may also be in the other direction, thereby allowing for a more fine adjustment of the pitch.

Claims

1. A modular mixed flow fan comprising a hub being configured for rotation about an axis and a plurality of fan blades, a retention part of each blade being received in openings in an outer surface of the hub, each blade extending radially between opposite ends, one end forming a tip edge and the other one forming a hub edge from which the retention part protrudes, wherein the hub edge is arch-shaped, and the outer surface of the hub is formed as a section of a sphere having a sphere centre, the section of the sphere being defined between a first plane and a second plane being parallel, and wherein a first diameter of the hub along the first plane is smaller than a second diameter of the hub along the second plane.

2. A fan according to claim 1, wherein each opening has a centre point and wherein all centre points are arranged in a common plane and having identical distance to the sphere centre.

3. A fan according to claim 1 or 2, wherein the common plane is arranged between the first and second planes.

4. A fan according to any of the preceding claims, wherein a first distance from the sphere centre to the first plane is in the range of 65-80 percent of the radius of the sphere.

5. A fan according to any of the preceding claims, wherein a second distance from the sphere centre to the second plane is in the range of 40-65 percent of the radius of the sphere.

6. A fan according to according to any of the preceding claims, wherein the hub edge has a larger radius than the sphere.

7. A fan according to any of the preceding claims, wherein the retention part is rotationally lockable in multiple positions in the openings.

8. A fan according to claim 7, wherein the locking is provided by engagement of a first cooperating structure at the retention parts and a second cooperating structure in the openings.

9. A fan according to claim 8, further comprising a third separate structure for cooperation with the first and second cooperating structures.

10. A fan according to any of the preceding claims, wherein the openings are equidistantly arranged circumferentially along the outer surface.

11. A hub for a modular mixed flow fan, the hub being configured for rotation about an axis and comprising a plurality of openings in an outer surface in which openings a blade can be received, each blade extending radially between opposite ends, one end forming a tip edge and the other one forming a hub edge from which the retention part protrudes, wherein the hub edge is arch-shaped, and the outer surface of the hub is formed as a section of a sphere having a sphere centre, the section of the sphere being defined between a first plane and a second plane being parallel, and wherein a first diameter of the hub along the first plane is smaller than a second diameter of the hub along the second plane.

12. A hub according to claim 11, wherein each opening has a centre point and wherein all centre points are arranged in a common plane and having identical distance to the sphere centre.