ES2561717T3 - An axial fan - Google Patents

Abstract

An axial fan comprising a motor (38) and an impeller (34) housed inside an outer casing (30), the fan further comprising a mounting assembly (40) for mounting said motor inside said casing, said comprising assembly assembly at least one elongated vane (40a) that extends between the inner wall of said housing (30) and said motor and that is connected to said motor (38) by means of a set of connectors (40), characterized by the set of connectors comprising means (40b) for connecting said vane (40a) to said motor (38) at a selected distance from a plurality of distances from said impeller.

Description

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DESCRIPTION

An axial fan

The present invention relates generally to an axial fan and, more particularly, to an improved mounting arrangement for mounting the motor of an axial fan inside an outer housing.

Axial fans are generally used to move high volumes of air with low static pressure. With reference to Figure 1 of the drawings, an axial fan typically comprises an outer cylindrical housing 10 within which a motor 12 is mounted, with stamped or fabricated steel brackets 14 that are used to connect and maintain the motor within the housing 10. An impeller 16 is also provided within the housing 10, which comprises a plurality of blades 18 extending from a central hub, and connecting to the motor shaft for propulsion therethrough.

It is known to a person skilled in the art that, in order to maximize aerodynamic performance and efficiency, while minimizing noise generation, it is desirable to maximize the distance between the rotary impeller 16, 18 and the support arrangement 14. In fact, if the support arrangement could be omitted completely then the turbulence would be eliminated along with any losses caused by it. In practice, however, there are significant limitations in this regard, for example, there may be narrow limitations on the overall product size or design limitations on the length of the motor shaft on which the impeller is mounted.

Similar axial fans are known, for example, from US2003 / 133815A1 or US3790114A.

It is therefore an object of the present invention to provide an improved mounting arrangement for mounting the motor of an axial fan within its outer housing, which allows the aerodynamic performance of the axial fan to be significantly increased without a corresponding increase in power. or input speed.

This object is achieved by the invention as described in the appended claims. A support arm is provided for a mounting arrangement for mounting the motor of an axial fan within an outer housing, the support arm comprising an elongated vane arranged and configured to extend between said motor and the inner wall of said housing, and a connection part for the connection of said vane to said motor, said connection part comprising means for varying the angle of the surface of said vane relative to the direction of the air flow through said axial fan.

The pallet of the support arm will be designed to be fixed to the motor and not be varied in angular position during service. The angle is preselected as a specific service angle and set in place. The invention allows arm vanes to be used at specific angles in varying angular orientations depending on the "service" requirements and the specific fan structure and size. Accordingly, it is preferred that the vane be secured with respect to the motor in a specific "service" angular orientation and not subsequently varied. Beneficially the vane is secured to the engine by means of a mechanical tightening fixation so that the orientation of the vane cannot be varied (once fixed) without releasing the mechanical fastening by loosening it.

Preferably, said connecting part comprises an arcuate groove defining a plurality of selectable angular orientations in which said elongated vane can be mounted. In an exemplary embodiment, the arcuate groove is provided with a connection plate that is substantially perpendicular to, and integrally formed with, said elongated vane. The arcuate groove is arranged and beneficially configured to receive a connector so that it extends through said groove into a mounting hole provided in said motor. In a preferred embodiment, the angle of the surface of the vane, measured between a first axis perpendicular to the longitudinal axis of said elongated blade and a second axis parallel to the longitudinal axis of said axial fan, is between 80 ° and 50 °, and more preferably between 70 ° and 55 °. In a preferred embodiment, the angle is between 65 ° and 60 °.

Beneficially, the angle of the profile of the elongated blade varies along its length. In one embodiment, the elongated vane could be rotated by approximately 15 ° along its length. Alternatively, the vane could be curved at about 15 ° to about 3/3 of its total length.

In fact, a support arm is provided for a mounting arrangement for mounting an axial fan motor inside an outer housing, the support arm comprising an elongated vane arranged and configured to extend between said motor and the inner wall. of said housing, and a connecting part for connecting said vane to said motor, in which the angle of the profile of the elongated vane varies along its

length.

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Again, in one embodiment, the elongated vane could be rotated approximately 15 ° along its length. Alternatively, the vane could be curved at about 15 ° to about 3/3 of its total length.

The present invention extends to an axial fan comprising a motor and impeller housed within an outer housing, the fan further comprising a mounting assembly for mounting said motor within said housing, the mounting assembly comprising one or more support arms as defined above connected between said motor and the inner wall of said outer housing.

Preferably, the support arms are connected between the motor and the inner walls of said outer housing by means of a set of connectors comprising means for connecting said vane to said motor to a selected one of a plurality of longitudinal distances from said impeller . Preferably, the motor can be provided with a plurality of discrete mounting holes, beneficially substantially equidistant, defining the respective distances.

In accordance with one aspect of the present invention, an axial fan is provided comprising a motor and impeller housed within an outer casing, the fan further comprising a mounting assembly for mounting said motor within said casing, said comprising assembly assembly at least one elongated vane extending between the inner wall of said housing and said motor and said motor being connected by means of a set of connectors comprising means for connecting said vane to said motor to a selected one of a plurality of distances from said impeller.

It has been determined that by providing mounting brackets that are manufactured in a section of aerodynamic profile and rotated along its length, a significant improvement in aerodynamic performance can be achieved (i.e. the movement of larger volumes of air to a higher pressure). Further improvement can be achieved by making the brackets adjustable, so that their distance from the impeller can be varied and the angle thereof can be adjusted to the direction of the air flow, depending on the type of impeller being used.

These and other aspects of the present invention will be apparent from, and elucidated with reference to, the embodiments described herein.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a perspective view of an axial fan according to the prior art;

Figure 2 is a perspective view of an axial fan that includes a mounting arrangement in accordance with an exemplary embodiment of the present invention;

Figure 3 is a perspective view of a mounting arm of a mounting arrangement according to a first exemplary embodiment of the present invention;

Figure 4 is a perspective view of a mounting arm of a mounting arrangement according to a second exemplary embodiment of the present invention;

Figure 5 is an enlarged view of a motor connection part of one of the mounting arms of the mounting arrangement of Figure 2;

Figure 6 is a schematic illustration showing the support arm at various angles in relation to the direction of the air flow;

Figures 7 and 8 are illustrative of the ratio of the speeds of an axial fan blade at two respective points;

Figures 9, 10, 11 and 12 are illustrative of the air flow as a result of the variation of the angle of the support arms by 90 °, the ideal position, under the rotation of the support arms, and the over-rotation of the support arms, respectively;

Figure 13 illustrates the force applied to the impeller blade during use; Y

Figure 14 illustrates the variation in the direction of the air flow along the length of an impeller blade.

With reference to Figure 2 of the drawings, an axial fan according to an exemplary embodiment of the present invention comprises a cylindrical outer shell 30 having a circumferential flange 32 at each end thereof, each flange extending upwardly relative to the outer wall of the housing 30 and

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substantially perpendicular to it. The fan further comprises an impeller 34 consisting of a plurality of blades 36 extending from a central hub. The impeller 34 is housed inside the housing 30 and connected to the motor shaft 38 for propulsion therein. The motor 38 is mounted inside the housing 30 by means of four substantially equidistant arms 40 that are connected between the outer circumference of the motor 38 and the inner wall of the cylindrical housing 30.

With reference to Figure 5 of the drawings, each arm 40 comprises an elongated part 40a and an assembly part 40b. The elongated part 40a is substantially of aerodynamic section and of a length sufficient to extend between the outer circumference of the motor housing and the inner wall of the cylindrical housing. The mounting part 40b extends substantially perpendicular to the elongated part 40a and is provided with an arcuate groove 42. During use, the arm 40 is connected to the motor by means of a screw or pin that extends through the arcuate groove. 42 and inside a mounting hole in the motor housing. As shown, a plurality of mounting holes 46 can be provided along a part of the length of the motor housing, so that the arm 40 can be mounted on a selected one of a certain number of distances from the impeller .

The arched groove 42 allows the angle of the elongated part 40a of the arm 40 to be varied, as can be seen more clearly in Figure 6 of the drawings. The angle referred to in this case is the angle between a first axis (X) that is perpendicular to the length of the elongated part 40a of the arm and a second axis (Y) that is perpendicular to the flange 32 of the cylindrical housing 30. Thus, in Figure 6a, the arm mounting portion 40 is connected to the motor housing at the end of the arcuate groove 42 closest to the elongated portion 40a of the arm 40 and the arm 40 is at 90 °. In Figure 6b the connection point between the mounting part 40b of the arm and the motor housing has moved along the arcuate groove 42 in a direction of separation from the elongated part 40a of the arm 40 and the arm 40 is at 75 °. In Figure 6c, the connection point has been moved even further along the arcuate groove 42 in a separation direction from the elongated part 40a of the arm 40 and the arm 40 is at 60 °.

This ability to vary the angle of the arm 40 in relation to the air flow caused by the impeller results in significant advantages in terms of increased aerodynamic performance, because the arm angle can be set to adapt to the direction of the air flow , depending on the type of impeller used, as will now be described in more detail.

Consider first the basic theory in relation to an axial fan. Figure 7 shows the ratio of the speeds for an axial fan blade at a working point, and the three speeds to be considered

They are:

• Absolute airflow velocity (local airflow velocity / fixed coordinates (x, y)):

S

Q „: Air flow volume (m3 / s)

S: Air flow section considered (m2)

At the fan inlet, this speed is axial with respect to the impeller.

• Blade speed:

U = Ru>

R: Blade radius (m)

oj: Blade angular velocity (rad / s)

• Relative air flow velocity (air flow velocity / rotation coordinates at the point considered):

V-U = W

At the fan outlet, the air flow shows a helical movement and the triangle of the velocities at the point to be considered later in this document is represented in Figure 8. An evaluation of the motor support arms and the effect on the air flow of different angular orientations thereof in relation to the air flow is illustrated in Figures 9, 10, 11 and 12.

With reference to Figure 9, when the arm is set at 90 ° (Figure 3a), the angle formed by the direction of the fluid and the surface of the arm is significant. As a consequence of the illustrated arrangement, with a high speed of

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air flow, turbulence takes place (represented by 50) due to a separation of the air flow, which results in a consequent decrease in performance.

On the contrary, if the arm is oriented to coincide with the direction of the air flow, better performance can be achieved. In an ideal case (a "laminar flow" situation), in which the support arm is oriented precisely in relation to the direction of the air flow, the velocity profile can be considered as shown in Figure 10. If, on the other hand, the support arm is at an angle relative to the air flow, but in an insufficient amount, the turbulence will appear again (as illustrated in Figure 11), but still in a degree less than if the arms are set at 90 °. Thus even if the ideal case is reached, the turbulence is relatively low compared to the provisions of the prior art.

Finally, and to complete it, if the support arms are turned too much in relation to the direction of the air flow, a case similar to the previous one takes place and a turbulence is created accordingly due to the separation of the flow (air trail), as illustrated in Figure 12, but again to a lesser extent than in the case where the arms are set at 90 °.

Depending on the angle of the impeller blade (which is a significant contribution factor to the direction of the air flow), it is possible to estimate the ideal angular rotation of the support arms to optimize aerodynamic performance. Figure 13 shows the force applied to the impeller blade. Consider that the air pressure is perpendicular to the impeller blade surface and creates a dynamic force oriented by an angle "a". To achieve optimum performance, the support arms should be oriented at the same angle a. However, the air fluctuation is constant, while the direction is variable, so that the angle a can only be estimated by using the relationship:

A = 90 - (3;

where p is the angle of the impeller blade.

Experimental results have shown that the total efficiency of the fan can be increased by adjusting the angle of the support arms to match the direction of the air flow, depending on the type of impeller and the angle of the impeller blades. It has also been observed that the total efficiency of the fan can be increased by changing the angle of the arms from 90 ° (prior art) to 60 ° as explained above in relation to Figures 9 and 10 respectively. It has also been observed that, at least in some applications, efficiency may begin to fall again from an arm angle of approximately 55 °. From these results, it is considered that, at least for some applications, the optimum arm angle can be from 65 ° to 60 °.

Another significant consideration is that there is a variation in the direction of the air flow along the length of the blades the impeller. This variation can be located within a range of approximately 15 °. For example, at the tip of the blade, the direction of air flow could be approximately 45 ° and the direction could change to approximately 60 ° further along the blade towards the engine. As illustrated in Figure 14. Thus, in a preferred embodiment, it is desirable to have a variation, preferably progressive, of the angle of the support arm within the housing, as well as having the arm oriented in accordance with the direction of the air flow.

With reference to Figure 3, in an exemplary embodiment, arm 40 could be rotated approximately 15 ° along its length. Alternatively, as shown in the Figure, the arm 40 could be curved in approximately 15 ° to approximately 3/3 of its total length. While it is believed that the first embodiment (Figure 3) could provide a solution closer to the ideal, the second embodiment (Figure 4) may be more practical in terms of manufacturing.

It should be noted that the aforementioned embodiments illustrate instead of limiting the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parentheses should not be construed as limiting the claims. The word "comprising" and "comprises", and the like, do not exclude the presence of elements or stages other than those listed in any claim or in the specification as a whole. The singular reference to an element does not exclude the plural reference to said elements and vice versa. The invention can be implemented by means of a hardware comprising several different elements. In a claim of the device that lists several means, several of these means can be realized by one and the same hardware article. The mere fact that certain measures are listed in mutually different dependent claims does not indicate that a combination of these measures cannot be used with advantage.

Claims (13)

5 10 fifteen twenty 25 30 35 40 Four. Five 1. An axial fan comprising a motor (38) and an impeller (34) housed within an outer casing (30), the fan further comprising a mounting assembly (40) for mounting said motor inside said casing, said mounting assembly comprising at least one elongated vane (40a) extending between the inner wall of said housing (30) and said motor and connecting to said motor (38) by means of a set of connectors (40), characterized by the set of connectors comprising means (40b) for connecting said vane (40a) to said motor (38) at a selected distance of a plurality of distances from said impeller. 2. An axial fan according to claim 1, wherein the motor housing is provided with a plurality of discrete mounting holes (46) defining the respective distances. 3. An axial fan according to claim 1 or claim 2, wherein the set of connectors for connecting the vane (40a) to the motor (38) comprises a connecting part (40b), said part comprising connection means (42) for the variation of the surface angle of said vane in relation to the direction of the air flow through said axial fan. 4. An axial fan according to any preceding claim, wherein the vane (40a) is secured with respect to the motor (38) by means of a mechanical fixation so that the orientation of the vane cannot be varied once fixed, without releasing the mechanical fixation. 5. An axial fan according to any preceding claim, wherein said connecting part comprises an arcuate groove (42) defining a plurality of selectable angular orientations in which said elongated vane (40a) can be mounted. An axial fan according to claim 5, wherein the arcuate groove (42) is provided in a connection plate that is substantially perpendicular to, and integrally formed with, said elongated vane. 7. An axial fan according to claim 5 or claim 6, wherein the arcuate groove (42) is arranged and configured to receive a connector so that said connector extends through said groove into an orifice of assembly (46) provided in the housing of said motor. 8. An axial fan according to any one of the preceding claims, wherein the angle of the surface of the blade, measured between a first axis perpendicular to the longitudinal axis of said elongated blade (40a) and a second axis parallel to the axis longitudinal of said axial fan, is between 80 ° and 50 °. 9. An axial fan according to claim 8, wherein said angle is between 70 ° and 55 °. 10. An axial fan according to claim 9, wherein said angle is between 65 ° and 60 °. 11. An axial fan according to any of the preceding claims, wherein the angle of the profile of the elongated vane (40a) varies along its length. 12. An axial fan according to claim 11, wherein the elongated vane (40a) is rotated along its length. 13. An axial fan according to claim 12, wherein the vane (40a) is curved at an angle at a point along its entire length.