EP1156224A2

EP1156224A2 - Double entry fan

Info

Publication number: EP1156224A2
Application number: EP00830825A
Authority: EP
Inventors: Ignazio Giacalone
Original assignee: Faber SpA
Current assignee: Faber SpA
Priority date: 2000-05-11
Filing date: 2000-12-15
Publication date: 2001-11-21
Also published as: IT250953Y1; ITAN20000012U1; EP1156224A3

Abstract

The present invention relates to a high-efficiency low-noise electrical aspirating fan unit obtained thanks to the innovative design of its constructive elements.

Description

The present patent application for industrial invention relates to a high-efficiency low-noise electrical aspirating fan unit obtained thanks to the innovative design of its constructive elements.
The unit according to the present invention is normally used in modern hoods installed over kitchen cookers. More precisely, it comprises a centrifugal wheel, provided with two parallel series of blades, housed inside a scroll with two parallel diffusing ducts, one for each series of blades.
The scroll has two opposed circular aspirating openings closed with two grilles, of which one features a reinforced central plate supporting the electrical motor used to drive the wheel.
The scroll has a single delivery opening where the two diffusing ducts end.
The purpose of the present invention is to improve the efficiency of this type of electrical aspirating fan units by simply modifying the design of their constructive elements in order to minimise aerodynamic load losses.
To this end the elements in contact with the air flow aspirated by the wheel have been redesigned in order to avoid the creation of turbulent motions that, as it is known, result in higher energy dispersion compared to laminar motions.
The achievement of this objective indirectly involves another advantage, that is the reduction of noise during the operation of the unit, since turbulent motions are always associated with higher noise compared to laminar motions.
First of all, it must be noted that the aspirating fan unit according to the present invention has an annular separator between the two diffusing ducts of the scroll, in order to avoid any interference between the two air flows entering the two aspirating openings of the scroll in opposite direction.
Then, the external edge of the wheel blades has been redesigned in order to follow the internal profile of the diffusing ducts, while the wheel hub has been redesigned in order to improve its aerodynamic profile.
Finally, the grilles used to close the aspirating openings have been provided with inclined partitions capable of offering the minimum impact surface possible to the air flows aspirated by the wheel.
These morphological modifications result in the elimination of all turbulence sources in the air route, from the two aspirating openings to the single delivery opening.
For major clarity the description of the electrical aspirating fan unit according to the present invention continues with reference to the enclosed drawings, which are intended for purposes of illustration and not in a limiting sense, whereby:

Fig. 1 is a view of the unit seen from the aspirating opening closed with the grille provided with the central plate used to support the motor;
Fig. 2 is a view of the unit seen from the opposite direction with respect to Fig. 1;
Fig. 3 is the orthogonal projection of Fig. 2 according to direction III-III;
Fig. 4 is the orthogonal projection of Fig. 1 according to direction IV-IV;
Fig. 5 is the orthogonal projection of Fig. 4 according to direction V-V;
Fig. 6 is a section of the scroll with plane VI-VI of Fig. 1;
Fig. 7 is a section of the scroll with a plane perpendicular to the rotation axis of the wheel and tangent to the annular separator between the two diffusing ducts.

With reference to the aforementioned figures, the electrical aspirating fan unit according to the present invention comprises a centrifugal wheel (1) provided with two parallel series of blades (1a), housed in a scroll (2) with two parallel diffusing ducts (3), one for each series of blades (1a).
The scroll (2) has two opposed circular aspirating openings (4 and 5) closed with two grilles (6 and 7), of which one (6) features a reinforced central plate (6a) supporting the electrical motor (8) used to drive the wheel (1).
The scroll (2) has a single delivery opening (9) where the two diffusing ducts end.
First of all, it must be noted that in the electrical aspirating fan unit according to the present invention an annular separator (10) is located between the two diffusing ducts (3) of the scroll (2), in order to avoid any interference between the two air flows entering the two aspirating openings (4 and 5) of the scroll (2) in opposite directions.
As shown in Fig. 7, the annular separator (10) has a variable height, since its internal circumference (10a) must circumscribe the external circumference of the wheel (1) closely, in order to avoid that, after passing by the wheel (1), the air flow aspirated through the opening (4) interferes with the air flow aspirated through the opening (5) and vice versa.
As shown in Figs. 5 and 6, the external edge (1b) of the blades (1a) of the wheel (1) has been designed in order to follow the internal profile of the diffusing ducts (3) so that the distance between the internal wall (3a) of the ducts (3) and the external edge (1b) of the blades (1a) remains constant in each axial section of the unit.
As shown in Fig. 6, the hub (1c) of the wheel (1) is aerodynamically designed on the side facing the grille (7), so that the air aspirated through the opening (5) is guided and conveyed towards the opening of the blades (1a) of the wheel.
Finally, the radial partitions of the grilles (6 and 7) have been especially designed, being formed by a concentric series of rings (11) crossed by radial partitions (12), with suitable inclination in order to avoid the abrupt impact of the air aspirated through the grilles. In the currently existing units radial planes are situated on planes passing by the rotation axis of the wheel.
In other words, after identifying the direction of the air flow in entering the blades (1a) of the wheel (1), the radial partitions (12) were given an inclination close to the value of this direction, so that the partitions do not represent the first obstacle along the route of the aspirated air flow which would cause the first load loss for the air flow through the electrical aspirating fan unit.
It has been shown that load losses are irrelevant if inclination ranges between 15° and 40° with respect to a plane passing by the rotation axis of the wheel.
Finally, attention is drawn to another device used to reduce the noise level of the electrical aspirating fan unit according to the present invention, that is a pair of inclined planes (13) located immediately before the delivery opening (9).
As shown in Fig. 7, the planes (13) feature an inclination angle (α) with respect to the section of the delivery opening (9), as well as an inclination angle (β) with respect to the symmetrical axis A-A of the scroll (2).
Thanks to their special design, the inclined planes (13) can intercept the air flow passing through the delivery opening (9) and fractionate the intensity of the acoustic wave, thus considerably reducing the noise level compared to the traditional electrical aspirating fan units of known type.

Claims

High-efficiency low-noise electrical aspirating fan unit, of the type comprising a centrifugal wheel (1) provided with two parallel series of blades (1a), housed in a scroll (2) with two parallel diffusing ducts (3) ending in a single delivery opening (9) and two opposed circular aspirating openings (4 and 5) closed with two grilles (6 and 7), of which one (6) features a reinforced central plate (6a) supporting the electrical motor (8) used to drive the wheel (1);
the unit being characterised by the fact that:

an annular separator (10) is located between the two diffusing ducts (3) of the scroll (2) with variable height since its internal circumference (10a) closely circumscribes the external circumference of the wheel (1);

the external edge (1b) of the blades (1a) of the wheel (1) has been designed in order to follow the internal profile of the diffusing ducts (3) so that the distance between the internal wall (3a) of the ducts (3) and the external edge (1b) of the blades (1a) remains constant in each axial section of the unit;

the hub (1c) of the wheel (1) is aerodynamically designed on the side facing the grille (7), so that the air aspirated through the opening (5) is guided and conveyed through the opening (5) towards the opening of the blades (1a) of the wheel;

the radial partitions (12) of the grilles (6 and 7) are not situated on planes passing by the rotation axis of the wheel.
High-efficiency low-noise electrical aspirating fan unit according to the previous claim, characterised by the fact that the radial partitions (12) of the grilles (6 and 7) have an inclination ranging between 15° and 40° with respect to a plane passing by the rotation axis of the wheel.
High-efficiency low-noise electrical aspirating fan unit according to the previous claims, characterised by the fact that the a pair of inclined planes (13) is located immediately before the delivery opening (9), with an inclination angle (α) with respect to the section of the delivery opening (9), as well as an inclination angle (β) with respect to the symmetrical axis A-A of the scroll (2).