WO2012130437A1

WO2012130437A1 - Extractor hood with improved air mixing

Info

Publication number: WO2012130437A1
Application number: PCT/EP2012/001350
Authority: WO
Inventors: Udo Berling
Original assignee: Berling Gmbh
Priority date: 2011-03-28
Filing date: 2012-03-28
Publication date: 2012-10-04
Also published as: DE102011015361A1

Abstract

The invention relates to an extractor hood (2) comprising a housing and a radial fan (6) which is arranged therein and which suctions an air flow through a suction opening, accelerates and expels through openings between the air blades (12) in a circular air guiding channel (16) surrounding the radial fan (6). The aim of the invention is to improve the separation effect of the extractor hood. As such the lateral wall (10) of the radial fan (6) arranged opposite the suction opening comprises a projection (38) which projects with respect to the peripheral edge thereof, said edge reducing the free flowing cross-section upstream of the projection (38) in the air chambers between the air blades (12) in the direction of the projection (38), and as a result, the air flow flowing along the lateral wall (10) is deflected in a direction which is opposite to the deflection direction in the air guiding channel (16) upstream of the projection (3).

Description

EXTRACTOR HOOD WITH INCREASED AIR MIXING

The present invention relates to an extractor hood with a housing and a radial fan disposed therein, which sucks an air flow through an intake opening, accelerated and blows out at orifices between the air blades in a radial duct surrounding the radial fan duct.

A generic extractor hood is disclosed in the document PCT / EP 2008/008401. The air stream flowing through this extractor hood is initially sucked in by the radial fan in the middle in the axial direction, deflected by the fan fins, accelerated and blown out in the radial direction and then redirected back to a substantially axial direction. The hood of this type is able to separate from a sucked cooking fume or other polluted air, such as occurs in industrial plants, increased amounts of fats and oils in the air, which are accumulated in the hood.

Experiments have shown that it is not possible with the disclosed configuration, the air flow completely under all conditions of suspended in the air flow suspended particulates, especially light oils to clean.

Accordingly, it is the object of the present invention to improve the separation efficiency of the extractor hood.

The object is achieved for a generic extractor hood in that the side wall of the radial fan opposite the intake opening has a projection towards its peripheral edge, through which the free flow cross section present upstream of the projection is lowered in the air chambers between the air blades in the direction of the projection and thereby the air flow flowing along the side wall is deflected in a direction which counteracts the directional deflection in the air duct downstream of the projection.

CONFIRMATION COPY The first in an approximately axial direction in the radial fan incoming air flow must first be deflected in a radial direction, so that the air flow can flow through the radial fan. As a result, the air flow from the intake port to the outer edge of the radial fan towards an arcuate course, towards the end of the air flow continues to approach as laminar flow of the intake port opposite side wall of the radial fan and flows to this to a considerable extent along. In addition to this main flow course, however, there are also slower secondary flows within the flow chambers formed between the air blades which are not directed precisely to the peripheral outer edge of the side wall of the radial fan facing the intake opening, but exit at a distance from the outlet openings of the flow chambers.

If the air flow at the peripheral outer edge of the suction side opposite side wall of the radial fan in the air duct is deflected sharply, without the projection of the invention is present, the laminar main flow breaks abruptly at the outer edge, and the air flow turns directly into the new flow direction. In this diversion, the slower side streams are taken, without there being a more intensive mixing of the air streams and collisions of the entrained in the air streams particles. However, if the projection according to the invention is present, then the main flow before reaching the outer edge through the projection once again receives a steering pulse, through which the main flow is directed to the side of the sidewall more remote streams. Due to the steering impulse, the main and secondary flows do not mix in a parallel flow, but the main flow is directed into the secondary flows, so that there is a more intensive mixing of the air streams.

For the separation of particles moved in the air flow, intensive mixing, in particular with regard to the very small particles, is important. While fat molecules are comparatively large and heavy, oily ones in particular Particles often have an extremely small particle size. Owing to the small size and the low weight, oily particles are very difficult to completely separate out only by a directional reversal of the air flow, since they can join the direction of the air flow because of their low weight. The invention now aims to allow the particles floating in the air streams to collide with one another by intensively mixing different speed air streams, thereby bringing about an agglomeration of a plurality of very small particles into a larger particle. In a collision, especially oily particles tend to form a new larger particle. Since this larger particle is then heavier and has a larger mass, such a particle can be deposited more easily at a directional deflection of an air flow.

Due to the projection on the outer edge of the side wall of the faster, moving along the side wall main air flow is directed obliquely into the slower secondary air flows. The floating in the main air flow oil particles meet in slower secondary air flow to slower oil particles with which they connect. The collision of the air streams also creates turbulent flows, which disturb the laminar flow of the main air flow. As a result of the turbulences, the particles moving in the air flows are thrown in directions which run transversely to the main flow direction. These transverse movements also lead to further collisions of particles moving in the air currents. This additionally promotes the formation of larger drops. If then immediately after the deflection of the air flow in a new conveying direction, as the downstream takes place behind the outer edge of the side wall, so far the previously very small oily particles have come together to larger drops that can not reorient themselves so quickly in a new flow direction , These larger drops can then impinge on the outer wall in the deflection region and adhere there; in this way they are finally separated from the air stream.

An important aspect of the invention is to be seen in that is deflected with the projection of the faster main air flow against the later deflection direction. The faster main air flow has the higher energy density due to the higher flow velocity. If this main air flow meets the crossing slower secondary air flow, it is slowed down less than the secondary air flow is accelerated. However, since the faster main air flow through the projection receives a steering impulse in a direction pointing away from the subsequent deflection direction, this increases the radius of the turning arc that the oily particles moving in the air flow must move in order to move in the new flow direction to be able to. Due to the larger radius of the turning arc but increases the probability that the turning arc in its course collides with the outer wall.

However, it should be noted that the projection must not be too large, in order not to slow down the main air flow too much. Too sharp a deflection slows down the air flow too much, and too much turbulence develops in the deflection area, as a result of which the particles moving in the air flow do not occupy a clear turning arc more than trajectory. However, without a clear turn arc as a trajectory, there is the danger that these particles will no longer collide with the outer wall and therefore will no longer be separated from the air flow. The measure of the projection must be selected so that at the prevailing flow velocities of the main and secondary air flow and the available space in the air duct in the area in which the air flow is redirected in an approximately axial direction, a satisfactory separation effect for in the air stream with moving airborne particles, in particular the oily particles adjusts.

The term of the side wall of the radial fan opposite the intake opening does not only mean the side wall, which is directly connected to the air blades and is driven in rotation, in the narrower sense. Also encompassed by the term sidewall is a rigid sidewall which is not directly connected to the airfoils and which forms part or all of the lateral boundary of the rotatably driven airfoils opposite the aspiration opening or continues the lateral boundary in the radial direction. The lowering of the free Flow cross-section in the air chambers means a downstream height offset by the amount of the projection.

According to one embodiment of the invention, the projection projects in an inwardly curved curvature toward the outer edge of the side wall. Due to the rounded, arcuate, continuously slightly rising course of the curvature, the laminar flow of the main air flow along the side wall remains undisturbed, a stall before reaching the outer edge of the side wall is avoided. As a result, the main air flow in this area retains its velocity and energy, and thereby can strike the side air flows more effectively obliquely, thereby achieving a good mixing of the air flows and the particles moved therein.

According to one embodiment of the invention, the outer edge of the side wall has a rounded contour. Due to the rounded contour, the deflection of the air flow in the air duct is supported in the approximately axial direction.

According to one embodiment of the invention, the projection in the side wall in the flow direction of the air flow through the air duct is arranged in front of the projection of the outer wall. This longitudinal offset between the two projections ensures that initially the main air flow can collide with the secondary air flows before the mixed air flow reaches the projection of the outer wall, by means of which the free cross section of the air duct is additionally narrowed in relation to the upstream section , The constriction caused by the protrusion on the outer wall causes the portion of the air flow striking this projection to be redirected once more inwardly into an even narrower radius of the flow path. The constriction in this section also leads to a deceleration of the air flow and an increase in pressure in this area. Since the particles that are specifically heavier than air are more likely to move on the outer side of the airflow, and these very particles are barely able to track both the deceleration of the airflow and its additional deflection on the shortness of the available distance - These particles inevitably collide with the projection on the outer wall and are deposited in this way. Since the projection in this area slows down the flow velocity of the air flow, the risk that the particles that have hit the projection will be taken back by the air flow is low. The oily and greasy particles clump together to larger and smaller drops and then run downwards along the outer wall, following the principle of gravity.

According to one embodiment of the invention, the radial fan on a side wall facing the suction opening, which is designed in an arcuate manner in its upstream region to the intake opening. By the arcuately tapered to the suction port shape of the suction port facing side wall, the formation of a broader flow band of the incoming air flow is promoted in a faster main air flow and slower secondary air streams within the radial fan. By avoiding a sharp inflow edge around which the inflowing air flow has to flow around, owing to the curved course of the side wall in the inflow region, airflow zones with different flow rates are retained even in the inflow region of the radial fan.

According to one embodiment of the invention, the suction side facing the opposite side wall protrudes with the projection formed thereon and the outer edge on the enveloping circle of the air blades. Due to the projection of the projection in the side wall beyond the enveloping circle of the air blades, an immediate deflection of the air flow emerging from the radial fan in the approximately axial direction is avoided. The supernatant gives the main and secondary airflow the opportunity to initially cross before being deflected in the approximately axial direction.

According to one embodiment of the invention, the outer wall over the height of the air blades on an increasing in the flow direction of the air flow distance to the enveloping circle of the air blades. Due to the widening outward The volume of space and thus the ability to swallow the air duct in this area increases in the downstream direction. By increasing the height of the air blades width of the air duct dead spaces in the lower area are avoided, while in the upper part of the entire air flow can be collected and deflected in the approximately axial direction.

According to one embodiment of the invention, the curvature of the outer wall decreases over the height of the air blades in the flow direction. The degressive curvature forces the air flow increasingly in the approximately axial direction. This causes a deceleration of the air flow and an increase in pressure in this area.

According to one embodiment of the invention, the projection on the outer wall on its upstream side has a rounded cross-sectional contour. The rounded cross-sectional contour avoids a stall with corresponding turbulence in this area.

According to one embodiment of the invention, the distance between the outer edge, the collar and / or the inner wall to the highest elevation of the projection on the outer wall is less than the height of the air blades at its outer circle. As a result of this configuration, the air flow in the area of the outflow from the radial fan can reach its highest speed, while it is first deflected in front of the projection on the outer wall and then braked by the constriction. Both effects - deflection and deceleration - lead to an effective separation of entrained in the air flow suspended particles on the outer wall.

It is expressly understood that the above-described embodiments of the inventions can be combined individually with the subject matter of the main claim and other embodiments, as far as this description and the claims is not otherwise. This also applies to individual features that are named for the individual configurations. Further modifications and details can be taken from the following description and the accompanying drawings.

The invention will now be described with reference to an embodiment. Show it:

1 is a cross-sectional view of an extractor hood,

Fig. 2: an enlarged view of the zone of the projection according to the invention, and

3 shows a further illustration of the projection shown in FIG. 2.

FIG. 1 shows an extractor hood 2 in which a drive motor 4 rotatably drives a radial fan 6. The drive motor 4 is arranged in an installation space 8.

The radial fan 6 is arranged coaxially to the output shaft of the drive motor 4 and has a side wall 10 facing the drive motor 4 and a number of air blades 12. In a rapid rotating movement of the radial fan 6, the air blades 12 generate an air flow in the axial direction of the radial fan 6 centrally sucked, then transported into the spaces between the air blades 12, accelerated there and is deflected in a substantially radial direction. Then, the air flow exits the outlet openings between the air blades 12 from the radial fan 6 and in the annular air duct 16, which surrounds the radial fan 6 and the installation space 8 in a ring, a. In order to avoid an intervention of persons in the current radial fan 6, an engagement protection 14 is arranged in the region of the suction opening of the extractor hood 2, which can be configured like a lattice. In the air duct 16, the air flow is deflected again in a substantially axial direction to the central axis of the hood 2. The air duct 16 is bounded laterally by an outer wall 18 and an inner wall 20. A portion of the outer wall 18 is formed by a trough 22, which surrounds the radial fan 6 at a distance substantially laterally, but also at least partially downwards. Below the radial fan 6, the trough 22 forms a collecting trough, in which on the outer wall 18 from the air stream deposited oils and fats can accumulate. The upper part of the outer wall 18 is formed by a wall which is part of an upper support bell.

The two parts of the outer wall 18 are connected in the embodiment by a circumferential seal 24. The air duct 16 toward the seal 24 forms a projection 26 which protrudes in proportion to the surface of the adjacent upstream wall of the trough 22 by a dimension. The projection 26 has on its upstream side a rounded cross-sectional contour, whereby the flow of air through the projection 26 is facilitated without unnecessary turbulence. Notwithstanding the embodiment, the projection 26 may also be formed on the walls of the trough 22 or the support bell.

The air flow enters upstream and downstream of the projection 26 from the outflow openings of the radial fan 6 in the air duct 16 and is deflected by the outer wall 18 in the region of the trough 22 upwards. In this case, the air flow must flow around the outer edge 40 of the side wall 10 around. Diagonally opposite to the outer edge 40 of the side wall 10 is the projection 26, which forms a bottleneck in the air duct 16 together with the collar 28 located on the opposite side. The collar 28 is circumferentially attached to the outer edge 40 of the side wall 10 at its outer periphery and extends in the flow direction of the air flow, it is thus turned over to the E- bene of the rotating side wall 10 driven. At the end of the collar 28 on the inside of the air duct 16 closes the Trennfu 30 years old. The parting line 30 separates the collar 28 from the inner wall 20, which is a part of the support bell.

The parting line 30 runs around the circumference of the collar 28 and forms an opening through which the installation space 8 and the air flow flowing through the air duct 16 are interconnected.

The upper edge of the collar 28 and the seal 24 are arranged in the exemplary embodiment on a plane. This results in a reduction of the radial fan 6 and the trough 22 of the hood 2, the possibility that the radial fan 6, including the collar 28 may be set in the tub 22, for example in a dishwasher for cleaning purposes, without one of the two components opposite protruding from the other component.

In the air duct 16 close to the parting line 30 rectifier flow surfaces 32, through which the flowing through the air duct 16 air rollers are made uniform. By equalizing the air flow in a stream with the same laminar flow, the recording and line capacity of the adjoining the extractor hood exhaust pipes can be fully utilized.

The extractor hood 2 has an intake opening 34, through which the sucked-in air flow flows into the extractor hood 2 and in particular into the radial fan. The radial fan 6 has at its upstream end via an inflow edge 36, which engages behind the guard 14. The air flow can flow into the centrifugal fan 6 without turbulence.

The air flow entering the radial fan 6 passes into the air chambers between the air blades 12. The rotational movement and the specific shape of the air blades 12 accelerate the air flow in the air chambers and deflect them in a radial direction. The air flow occurs at the outer edges of the air blades 12, which in the rotational movement of the radial fan 6 an enveloping circle form, in the air duct 16 from. The course of the air flow through the radial fan 6 and the air duct 16 is shown in FIG. 2 based on the curves for the main air flow 46 and the secondary air flow 48 is illustrated in more detail. The side wall 10 forms outwardly a projection 38 which rises in an inwardly curved curvature to the outer edge 40 of the side wall 10 out. The main air flow 46 follows the contour of the side wall 10 in the region of the projection 38. The outer edge 40 is rounded so that it can be better flowed around by the air flow.

On the outer wall 18 is a projection 26 which is integrated in the embodiment in the seal 24. The projection 26 may also be formed in the outer wall 18 itself. By the projection 26 narrows the free cross section of the air duct 16. Viewed in the flow direction of the air duct 16, the projection 26 is the projection 38 by the longitudinal offset 42 downstream.

In the exemplary embodiment shown, the radial fan 6 also has a side wall 44 facing the intake opening 34, which in its upstream area is designed to taper to the intake opening 34 and the inflow edge 36. The air flow flowing into the radial fan 6 can easily follow the arcuate course of the side wall 44 in the inflow region, turbulences in the air flow caused by sharp deflections being reduced or completely prevented in this way.

The main air flow 46 extends starting from the intake opening 34 and coming from an approximately axial direction arcuately increasingly in a radial direction, wherein the main air flow in the air chambers increasingly approaches the side wall 10 and laminar flows in the downstream region of the radial fan 6 along the side wall 10 , In the region in which the projection 38 begins to rise, the main air flow 46 changes its flow direction, following the contour of the side wall 10, until the tip of the projection 38 is reached. There, the main air stream 46 crosses the slower secondary air streams 48. In this area, moving particles can be present in the main and secondary air streams. collide with each other and together form larger droplets, which are better deposited on the outer wall 18.

In Fig. 3 it is shown that the projection 38 protrudes by the dimension 50 over the upstream upper boundary of the flow chamber. The height dimension 52 of the free flow cross section in the air chambers between the air blades 12 is reduced by the projection 38 to the height 54. In the embodiment, although the highest point of the projection 38 is slightly outside the outer circle of the outer edges of the air blades 12, but also this position of the projection 38 still forms part of the side wall 10. The projection 38 can also deviating from the embodiment inwardly on the shaft of the radial fan 6 to be offset. The projection 38 may also form part of a fixed side wall deviating from the embodiment, when the parting line 30 is laid in a portion of the side wall 10 between the projection 38 and the shaft of the radial fan 6 and the projection 38 together with the outer edge 40 and the collar 28th is formed fixed.

The invention is not limited to the present subject description based on an embodiment. It is not difficult for the person skilled in the art, while maintaining the teaching according to the invention, to modify components or to replace them with alternatives having the same effect if this makes sense on the basis of concrete installation conditions.

Claims

claims

1. Extractor hood (2) with a housing and a radial fan (6) disposed therein, which sucks an air flow through a suction, accelerated and at mouth openings between the air blades (12) in a radial fan (6) annularly enclosing air duct (16) blows out , characterized in that the suction opening opposite side wall (10) of the radial fan (6) to its peripheral edge has a projection (38) through which the upstream of the projection (38) existing free flow cross-section in the air chambers between the air blades (12 ) is lowered in the direction of the projection (38) and thereby the air flow flowing along the side wall (10) is deflected in a direction which counteracts the directional deflection in the air duct (16) downstream of the projection (38).

2. Extractor hood (2) according to claim 1, characterized in that the projection (38) in an inwardly curved curvature to the outer edge of the side wall (10) protrudes out.

3. extractor hood (2) according to claim 1 or 2, characterized in that the outer edge (40) of the side wall (10) has a rounded contour.

4. extractor hood (2) according to any one of the preceding claims, characterized in that the projection (38) in the side wall (10) arranged in the flow direction of the air flow through the air duct (16) in front of the projection (26) of the outer wall (18) is.

5. extractor hood (2) according to any one of the preceding claims, characterized in that the radial fan (6) has a suction opening (34) facing side wall (44), which is designed in its upstream area arcuately on the suction port (34) tapered ,

6. extractor hood (2) according to any one of the preceding claims, characterized in that the suction opening opposite side wall (10) protrudes with the projection (38) and the outer edge (40) over the enveloping circle of the air blades (12).

7. Extractor hood (2) according to one of the preceding claims, characterized in that the outer wall (18) over the height of the air blades (12) has an increasing in the flow direction of the air flow distance to the enveloping circle of the air blades (12).

8. Extractor hood (2) according to one of the preceding claims, characterized in that the curvature of the outer wall (18) decreases over the height of the air blades (12) in the flow direction.

9. extractor hood (2) according to any one of the preceding claims, characterized in that the projection (26) on the outer wall (18) on its upstream side has a rounded cross-sectional contour.

10. Extractor hood (2) according to one of the preceding claims, characterized in that the distance between the outer edge (40), the collar (28) and / or the inner wall (20) to the highest elevation of the projection (26) on the outer Wall (18) is less than the height of the air blades (12) at its outer circle.