GB2345094A

GB2345094A - Axial fan blades

Info

Publication number: GB2345094A
Application number: GB9923751A
Authority: GB
Inventors: Andrea Giribaldi; Antonio Cicirello
Original assignee: Gate SRL
Current assignee: Gate SRL
Priority date: 1998-10-08
Filing date: 1999-10-07
Publication date: 2000-06-28
Anticipated expiration: 2019-10-07
Also published as: ITTO980852A1; GB9923751D0; FR2784421B1; GB2345094B; FR2784421A1; IT1303114B1; DE19948075A1

Abstract

Each blade 3 extends from a hub 2 with a forward angle of inclination and has a leading edge 5, which exhibits a forward angle of inclination that is positive and decreasing from the hub to a point between 30% and 70% of the radial extent of the blade from the hub, and is positive and increasing at least in the portion between 70% and 85% of the radial extent. Beyond 90% the inclination may be negative (fig. 4). The set angle of the blade may decrease as the radial distance from the hub increases.

Description

1 2345094 AXIAL FAN The present invention relates to a fan, particularly a

cooling fan associated with a heat exchanger in a motor vehicle.

More specifically, the subject of the invention is an axial fan of the type comprising a central hub and a plurality of blades which extend from the hub and the leading edges of which have a positive, forward angle of inclination in the direction of rotation of the fan in the vicinity of the hub and are inclined predominantly forwards from the hub to the periphery.

An object of the present invention is to provide an axial fan of the aforementioned type which achieves a considerable reduction in operating noise.

A further object of the invention is to provide an axial fan of the type defined above which has improved performance from a flow-dynamics point of view.

These and other objects are achieved, according to the invention, by an axial fan the main characteristics of which are defined in appended Claim 1.

Further characteristics and advantages of the invention will become clear from the following detailed description given purely by way of nonlimiting example, with reference to the appended drawings, in which:

Figure 1 is a front view of a fan according to the invention, Figure 2 shows a detail of Figure 1 on an enlarged scale, 2 Figure 3 is a section taken on the cylindrical surface IIIIII of Figure 1 and developed in a plane, and Figure 4 is a view similar to that of Figure 2 and shows a variant.

In the drawings, an axial fan according to the invention is generally indicated 1. The fan comprises a hub 2, for example, a substantially cylindrical hub, the axis 0 of which coincides with the axis of rotation of the fan.

The fan 1 of Figure 1 comprises an outer ring 4 coaxial with the hub 2.

A plurality of blades, indicated 3, extends between the hub 2 and the ring 4.

However, the invention is not limited to fans having outer rings, and is also not intended to be limited to fans with six blades such as that shown in Figure 1.

With reference to Figure 2, in the following description, the radius of the hub 2 will be indicated Ri and the radial distance between the distal ends of the blades 3 and the axis 0 will be indicated R,. In the case of the fan according to Figures 1 and 2, the distance Re corresponds to the internal radius of the ring 4.

The direction of rotation of the fan 1 is indicated F in Figures 1, 2 and 4. - Each blade 3 of the fan 1 has a leading edge 5 and a trailing edge 6.

3 The angle of inclination of the leading edge 5 of each blade 3 of the fan will be indicated T below. For a generic point on the leading edge 5 of a blade, the angle of inclination T is defined as the angle which is formed, in the plane of the axial projection of the fan, between the tangent to the leading edge at this point and the radial line which passes through this point and the projection of the axis 0.

By way of example, in Figure 2, the angles of inclination To, Tly T2 and T3 Of the leading edge 5 of a blade 3 are shown at points indicated Po, P1, P2 and P3 of this edge, re spectively. In particular, the point Po is disposed at the root of the blade 3 of Figure 2, that is, on the periphery of the hub 2.

The angle To of the inclination of the leading edge 5 at the point PO, measured from the radius RO to the tangent TO at the point PO, is positive, that is, the leading edge 5 at the point PO is inclined forwards in the direction of rotation F of the fan 1.

In a first embodiment shown in Figures 1 and 2, the leading edge 5 of each blade 3 has an angle of inclination T which is positive in the vicinity of the periphery of the hub 2 and is then positive but with a value which decreases gradually as the radial distance f rom the hub 2 increases, up to a point of inflection Pf beyond which the angle of inclination z is still positive but its values increase as the radial distance from the hub increases.

The leading edge 5 of the blade 3 shown in Figure 2 thus has a sinuous characteristic curve and is convex up to the point Pf and then concave from this point towards the periphery.

4 The point of inflection Pf is advantageously situated within a range of from 30% and 70% of the radial distance (R,,-Rj_) along the blade 3. The point of inflection Pf is preferably situated about 50% of the radial distance along the blade 3.

Moreover, the angle of inclination T of the leading edge 5 of each blade is preferably between +20' and +60' at at least one point of the portion of the leading edge disposed between the point Po and a point 30% of the radial distance along the blade. The angle of inclination T is also preferably between +20' and +60' at at least one point of the portion of the leading edge disposed between 70% and 85% of the radial distance along the blade.

In Figure 3, the set angle of a generic blade 3 of the fan is indicated y and is defined as the angle between a line M passing through the leading edge 5 and the trailing edge 6 and the line N of the plane of rotation of the fan.

In a fan according to the invention, the set angle 1 of each blade 3 advantageously but not necessarily decreases as the radial distance from the hub 2 increases, at least in the portion of the blade disposed between 70% and 100% of the radial distance (Re - Ri) along the blade. Moreover, the set ---angley of each blade preferably decreases as the radial distance from the hub increases throughout the radial extent of the blade.

Figure 4 shows a variant which has substantially all of the characteristics defined above with reference to the preceding drawings except that the leading edge 5 of each blade 3, from a point P, situated at a radial distance D, from the periphery of the hub 2 and up to a point P2 situated at a radial distance D2 from the periphery of the hub, has a positive angle of inclination z which decreases to 0' at the point P2. Between the point P2 and the peripheral end of each blade 3, the angle of inclination T of the leading edge 5 is negative and its absolute value preferably increases as the radial distance from the hub decreases.

The distance D, between the point P, and the periphery of the hub 2 is preferably about 85% of the radial extent (R, - Ri) of the blade, and the distance D2 is preferably about 90% of the radial extent of the blade.

Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention as defined in the appended claims.

6

Claims

1. An axial fan, particularly for motor vehicles, comprising a central hub and a plurality of blades which extend from the hub and the leading edges of which have a positive, forward angle of inclination in the direction of rotation of the fan in the vicinity of the hub and are then inclined predominantly forwards from the hub to the periphery, wherein the angle of inclination of the leading edge of each blade is positive and decreasing from the hub to a point on the edge disposed between 30% and 70% of the radial distance along the blade, and is positive and increasing as the radial distance from the hub increases, at least in the portion disposed between 70% and 85% of the radial distance along the blade.

2. An axial fan according to claim 1, wherein the angle of inclination of the leading edge of each blade is positive and decreasing from the hub to a point situated at a radial distance from the hub substantially equal to 50% of the radial extent of the blade.

3. An axial fan according to either preceding claim, wherein the angle of inclination of the leading edge of each blade is positive and increasing as the radial distance from the hub increases, starting from a point situated at a radial distance from the hub substantially equal to 50% of the radial extent of the blade.

4. An axial fan according to any one of claims 1 to 3, wherein the angle of inclination of the leading edge of each blade is positive and increasing as the radial distance from the hub increases, at least in the portion comprised between 70% of the radial extent of the blade and the periphery of the blade.

7

5. An axial fan according to any one of claims 1 to 3, wherein the angle of inclination of the leading edge of each blade is negative, that is, rearward relative to the sense of rotation of the blade in the portion disposed substantially between 85% and 100% of the radial distance along the blade.

6. An axial fan according to any one of the preceding claims, wherein the angle of inclination of the leading edge is between +200 and +600 at at least one point of the portion disposed between 0 and 30% of the radial distance along the blade.

7. An axial fan according to any one of the preceding claims, wherein the angle of inclination of the leading edge is between + 20' and +60 at at least one point of the portion disposed between 70% and 85% of the radial distance along the blade.

8. An axial fan according to any one of the preceding claims, wherein the set angle of each blade decreases as the radial distance from the hub increases, at least in the portion disposed between 70% and 100% of the radial distance along the blade.

9. An axial fan according to any one of the preceding claims, wherein the set angle of each blade decreases as the radial distance from the hub increases, throughout the radial extent of the blade.

10. An axial f an according to any one of the preceding claims, wherein an outer ring is provided which is coaxial with the hub and to which the radially outer ends of the blades are connected.

8

11. An axial fan substantially as hereinbefore described with reference to Figures 1, 2 and 3, or Figure 4, of the accompanying drawings.