Air extraction device and method for separating particles moving in an airflow

Abstract

Air extraction device (2) with an intake opening (4), an adjoining air guide channel for an airflow (L) which in a first section passes through a rotatably driven fan wheel (6) in a radial direction outwards and which in a second section extends to the outlet openings (5) of the fan wheel (6) in an approximately axial direction towards the fan wheel (6), deflecting the airflow (L) and terminating in an outlet opening (8), wherein the fan wheel (6) is designed such that the flow velocity of an airflow (L) flowing through the fan wheel (6) is increased and the second section has a lateral wall (10) which is arranged at the level of and at a distance from the outlet openings (5) of the fan wheel (6), characterized in that the second section has a flow passage (12) arranged at the level of the fan wheel (6),which is directly connected to the outlet openings (5) of the fan wheel (6), which is limited in the radial direction by the side wall (10) and in which no air guide devices are arranged, and wherein rectifier flow surfaces (22) are arranged in the air guide channel downstream to the flow space (12).

Description

The present invention relates to an air suction device having a suction opening, an adjoining air guide duct for an air flow which extends in a radial direction outwards in a first section through a fan wheel which can be driven in rotation, and which extends in an approximately axial direction to the fan wheel in a second section adjoining the outflow openings of the fan wheel, deflecting the air flow, and is designed to open out in an outflow opening, wherein the fan wheel is designed such that the flow speed of an air flow flowing through the fan wheel increases and the second section has a lateral wall which is arranged at the level of and at a distance from the outflow openings of the fan wheel.The invention also relates to a method for separating particles moved in an air flow, in which the air flow is conveyed and accelerated in the radial direction by a fan wheel, exits from outflow openings from the fan wheel and is subsequently deflected in an axial direction.A generic air suction device and a generic method are known from the document WO 2009 / 056 207 A2. In this document, guide blades arranged directly downstream of a fan wheel are disclosed, by means of which the air flow emerging from the fan wheel is decelerated and as a result a separation of the particles moved in the air flow takes place in that these impinge on the surfaces of the guide blades and adhere there. This device leads to acceptable deposition results, but an even comparatively high blower output is required and the running noise is clearly tolerable. U.S. Pat. No. 3,865,022 A discloses an air exhaust device having an intake opening, an adjoining air guide duct for an air stream, which in a first section extends through a fan wheel that can be driven in rotation in the radial direction and which, adjoining the outflow openings of the fan wheel, in a second section extends with deflection in an approximately axial direction to the shaker wheel and is designed to open out in an exhaust opening.It is the object of the present invention to improve the previously known air suction device and the previously known method.The object is achieved by a generic air suction device in that the second section has a flow space arranged at the height of the fan wheel, which flow space directly adjoins the outflow openings of the fan wheel, which is bounded in the radial direction by the lateral wall and in which no air guiding devices are arranged, and wherein rectifier flow surfaces are arranged in the air guide channel downstream of the flow space.The object is achieved for a method of the generic type in that the deflection in an axial direction takes place in a flow space which directly adjoins the outflow openings, which is bounded in the radial direction by a lateral wall arranged at a distance from the outflow openings and in which no air guiding devices are arranged, and wherein rectifier flow surfaces are arranged in the air guide channel downstream of the flow space, so that helical swirl flows of the air flow are converted into a more uniform flow.Due to the configuration according to the invention, the air flow flowing out of the fan wheel is not decelerated, but can flow unimpeded at full speed into the flow space. As a result of the deflection of the air flow in the flow space from the radial direction into the approximately axial direction along the lateral wall, by means of which the deflection is effected, separation of the particles floating in the air flow, such as oils, fats, condensates and the like, from the air moved in the air flow occurs. For the invention, the air flow does not necessarily have to be deflected in an exactly axial direction; a deflection in an approximately axial direction is sufficient. According to the invention, the air flow does not have to be directed into a single exhaust opening either; a plurality of exhaust openings can also be present. It is also pointed out that the air suction device does not necessarily have to be arranged like an extractor hood or a suction device for an air conditioning system at one end of a ventilation duct, but rather the air suction device can also be integrated into a section of a pipe system and inserted into a pipe section, for example.While the specifically lighter air can align itself with the new direction of movement at a smaller radius, the particles moved in the air stream require a larger radius because of their specifically higher weight. The greater the flow velocity of the air stream exiting the fan wheel, the greater the difference in the radius of the air and the particles moved in the air stream. Due to the larger radius and the increased flow velocity, most of the particles moved in the air flow collide with the surface of the lateral wall and adhere there. As a result, these particles are separated out of the air stream. Due to the higher flow velocity in the region of the flow space, even better separation performances can be achieved. In this case, the power consumption during operation of the air suction device according to the invention is lower than in the device known from the prior art, and the noise generation is lower. Likewise, a lower volumetric flow of air is required.For the purposes of the invention, it is sufficient to use an impeller optimized for the application case, in which the rotational speed and the shape and ejection direction of the air blades and the size and shape of the flow chamber are matched to one another such that a large constant power range of the air extraction device results. If axial or radial direction is mentioned in this description, these details always relate to the axis of rotation of the fan wheel.According to one embodiment of the invention, the lateral wall has one or more openings through which substances sliding and / or flowing along the wall can reach the rear side of the wall. As a result, the substances sliding and / or flowing along the wall are completely separated out of the flow space and cannot be entrained again by the air flow or pass into the downstream air-guiding channels, where these represent a fire risk, can trigger malodors or can attract vermins. The openings can be arranged transversely to the flow direction of the air flow flowing through the passage space, in this way the air flow forcibly drives the substances into the region of the openings. A single opening can be provided in the flow direction, but it is also possible to arrange a plurality of openings in a staggered manner one behind the other in the flow direction in order to thereby increase the separation efficiency if this appears to be necessary depending on the application. The opening can be designed as a narrow slot with which satisfactory separation performances can already be achieved. The opening can be designed in such a way that a capillary action is established, so that the substances are suctioned off from the surface of the lateral wall by the capillary action. The openings represent a type of trap through which the substances can be removed from the flow space.According to one embodiment of the invention, a projection is arranged downstream of an opening, by means of which projection materials which slide and / or flow along the wall can be collected and can be diverted through the opening into the space on the rear side of the wall. The separation performance can be improved by a projection, wherein the projection also results in a shading effect with respect to the air flow flowing past. If the protrusion is configured to direct the flow of air past the opening, the fabrics can more easily enter the opening without being easily entrained by the flow of air.According to one embodiment of the invention, a collecting reservoir for collecting the sliding and / or flowing substances separated from the second section through the opening is arranged on the rear side of the wall. By collecting the substances separated by the opening on the rear side of the lateral wall, the substances no longer have to be transported far. On the rear side of the lateral wall there is also sufficient installation space in which the substances can be collected.According to one embodiment of the invention, the lateral wall can be cooled completely or at least in regions by a cooling device and / or heated by a heating device. By cooling the lateral wall, substances deposited thereon can adhere better to the surface of the wall if the viscosity of the deposited substances is temperature-dependent, as is the case, for example, with oils and fats. Depending on the dew point and evaporation point and the current temperature of the respective substance, particles moved in the air stream can change the aggregate state by the cooling effect of the lateral wall and, for example, condense on the latter, or liquid substances become at least viscous due to the cooling. By later heating of the lateral wall, which can be carried out passively by switching off the cooling and slow heating to the ambient temperature or in a targeted and active manner by heating the lateral wall, it is possible to mobilize the substances adhering in a cooled manner, which are likewise heated in the process, and to deposit them in a targeted manner. This can be done, for example, by liquifying grease by the heating, draining on the lateral wall following gravity and supplying it to a collecting container via a drain line. In this way, the lateral wall can be cleaned by brief heating. The heating of the lateral wall can also be realized without cooling.According to the invention, rectifier flow surfaces are arranged in the air guide duct downstream of the flow space. The rectifier flow surfaces can convert the helical swirl flows of the air flow which exits from the fan wheel back into a more uniform flow. As a result, the pipeline cross sections of the fan pipes arranged downstream can be better utilized. Since the rectifier flow surfaces are arranged downstream of the flow space, the speed loss associated with rectification does not adversely affect the separation performance in the flow space.According to one embodiment of the invention, the flow space is configured annularly encircling the fan wheel. However, the flow space does not necessarily have to be round and ring-shaped; geometries with 4, 5, 6 or more outer corners or uniform or non-uniform geometries can also be used.According to one embodiment of the invention, the fan wheel and / or the lateral wall are connected to the air suction device via a connection which can be released without tools. Since the particles moved in the air flow adhere to the lateral wall, but also in the fan wheel, it is advantageous if at least one or also both components can be removed quickly and easily from the air suction device in order to clean it. A connection that can be released without tools can be produced, for example, by clamping or latching connection techniques or comparable solutions.According to one embodiment of the invention, the lateral wall extends in the axial direction as far as into a region behind the fan wheel and in this region at least one opening is present in the lateral wall. As a result of the deflection of the air flow emerging from the fan wheel, the latter does not continue to flow in an axial direction, but rather the flow direction is offset in the axial direction. In order to be able to fully utilize the separating effect of the lateral wall in this case, it is expedient to guide it into a region behind the fan wheel. If particles still adhere there, it is expedient to deposit these via an opening.According to one embodiment of the invention, the opening is designed as a circumferential gap, in particular as an annularly circumferential gap. A gap running circumferential in the shape of a ring can be realized, for example, in a simple manner via an enlarged parting line between different components, for example a parting line between the lateral wall and a connecting component.According to one embodiment of the invention, the shape of the lateral wall is adapted to the flow profile of the air flow through the flow space and has a widening in the flow direction of the air flow.According to one embodiment of the invention, the air suction device can be used as a pipe fan module in an existing ventilation device. As a module, the air suction device can be produced in large numbers with corresponding cost advantages. The air suction device can be used as a technical component in extractor hoods. The manufacturers of the extractor hood can refer to the air extraction device as a single ventilation component from the supplier and focus on adapting the outer components of the extractor hood to their design requirements. As a module, however, the air suction device can also be used in any ventilation lines, for example in industrial or industrial plants.It is expressly pointed out that the above-described advantageous embodiments can each be combined with the features of the main claim, but also with one another in any combination.Further modifications and preferred embodiments of the invention will become apparent from the following physical description and the drawings. The invention is described in more detail below with reference to an exemplary embodiment.FIG. 1 shows a sketch-like cross section through an air suction device 2, through which an air stream L flows through an air guide duct formed in the air suction device 2. In a first section, the air guide duct leads, starting from a suction opening 4, through a fan wheel 6, which can be driven by a motor 9. The fan wheel 6 is provided with a number of air blades 7. The rotational movement of the fan wheel 6 accelerates the air flow L in the interspace between the air blades 7 in a radial direction outwards and reaches its highest speed when it exits the fan wheel 6. The rear edges, as seen in the direction of flow, of adjacent air vanes 7 each laterally delimit an outflow opening 5, through which the air flow L exits the fan wheel 6.Directly adjoining the outflow opening 5 is the throughflow space 12 as a component of a second section of the air duct. The flow space 12 is delimited upstream by the outflow openings 5 and in the radial direction outwards by the lateral wall 10 arranged at a distance from the outflow openings 5. In the downstream direction, the flow space 12 is open so that the air flow L can freely flow therethrough. No air guiding devices are arranged in the flow chamber 12, by means of which the air flow L could be decelerated or redirected. As a result, the air flow L can emerge from the fan wheel 6 at the highest possible speed and enter the flow space 12, in which the air flow L is then diverted in a more axial flow direction in relation to the axis of rotation of the fan wheel 6. The directional indications 'radial and 'axial' are not to be understood as sharp, but rather merely approximate directional indications which can be exactly or at least approximately adhered to. The deflection of the flow direction of the air flow L in the flow space 12 is influenced in particular by the course of the air guide duct adjoining the flow space 12. The direction deflection in the flow chamber 12 is however also brought about by the lateral wall 10. Because it is located at the height of and at a distance from the outflow openings 5 and extends in the transverse direction to the air flow L, the air flow L is likewise deflected in the flow space 12.In FIG. 1, the air flow L is indicated by a dashed line. In the region of the flow space 12, dotted lines indicate the trajectory of particles moved in the air flow in the flow space 12. It can be seen from the dotted lines, which indicate the possible flight paths of the particles, that the particles do not follow the sharp deflection of the air flow L in the flow space 12. Although the trajectories of the particles also have a more or less strongly curved, arc-shaped course, owing to the larger radius of the trajectories of the particles they strike the lateral wall 10 and adhere there to their surface. In this way, the particles are separated from the air flow L.In the cross-sectional view in FIG. 1, it can be seen that, viewed in the direction of flow, at the end of the lateral wall 10, there is an opening 14, through which substances which slide and / or flow along the lateral wall 10 can reach the rear side 16 of the wall 10. By removing the corresponding substances from the flow space 12, they cannot mix again with the air stream L and be carried away from it. In the exemplary embodiment shown in FIG. 1, the opening 14 is located offset behind the fan wheel 6, as seen in the direction of flow of the air stream L, in a region axially with respect to the axis of rotation of the fan wheel 6, wherein the distance between the fan wheel 6 and the opening 14 corresponds to the distance dimension A in the exemplary embodiment shown. The lateral wall 10 is likewise guided by the distance A in the axial direction as far as into the region behind the fan wheel 6. In the exemplary embodiment, only a single opening 14 is provided between the lateral wall 10 and the lateral wall 10 a, which opening can circulate annularly, but a plurality of openings 14 can also be provided.In the exemplary embodiment, a projection 18 is shown which rises above the surface of the adjacent lateral wall 10 by a suitable amount. The projection 18 deflects the air flow L from the opening 14. Droplets of particles reaching the opening 14 are thus prevented from being entrained by the air flow L by the protrusion 18. The particles that reach the opening 14 can thus reach the rear side 16 of the lateral wall 10 and drop there into a collection reservoir 20.If particles are deposited in the region of the lateral wall 10 a, the particles deposited there can run down to the projection 18 on the lateral wall 10 a, following the force of gravity. At the projection 18, the particles thus discharged can then likewise pass into the region of the opening 14 and in this way be separated out of the flow space 12. The running off of the particles along the lateral wall 10 ais indicated by a small arrow.Downstream of the flow space 12, there are rectifier flow surfaces 22 in the air guide duct, by means of which flow surfaces the air flow L is equalized.The cross-sectional view of the air suction device shown in FIG. 1 can relate to a device having a circular basic shape; in this case, it is advantageous if the flow chamber 12 is configured annularly around the fan wheel 6. In contrast to this exemplary embodiment, it is also possible, however, to configure the air suction devices according to the invention to be rectangular or in some other way in their basic shape. However, in the case of a circumferential ring shape of the flow chamber 12, particularly uniform flow conditions are obtained in the flow chamber 12 because of the circular shape of the fan wheel, and corresponding air suction devices 2 having a circular basic shape also have a relatively large range at different rotational speeds of the motor 9, in which uniform separation powers are achieved.In the exemplary embodiment shown in FIG. 1, it can be seen that the shape of the lateral wall 10 is adapted to the flow profile of the air flow L through the flow chamber 12. Since the air flow L in the flow chamber 12 has an arcuate course towards the outflow opening 8, the flow chamber 12 can be made narrower in its lower region than in its upper region. As a result of the oblique wall profile of the lateral wall 10, the latter has an expansion, as seen in the flow direction of the air flow L, and the free cross section of the flow chamber 12 through which the air flow L can flow increases downstream.The invention is not limited to the exemplary embodiment described above, which serves only as an example for describing the invention. The skilled person is free from any difficulties in adapting the above-described exemplary embodiment to a specific application by corresponding modifications in a manner which appears suitable for him.

Claims

Air suction device (2) having a suction opening (4), an air guide duct for an air stream (L) which adjoins the latter and extends outwards in the radial direction in a first section through a fan wheel (6) which can be driven in rotation, and which extends towards the fan wheel (6) in a second section, adjoining the outflow openings (5) of the fan wheel (6), while diverting the air stream (L) in an approximately axial direction towards the fan wheel (6) and is designed to open out in an outflow opening (8), wherein the fan wheel (6) is designed such that the flow speed of an air stream (L) flowing through the fan wheel (6) increases and the second section has a lateral wall (10) which is arranged at the height of and at a distance from the outflow openings (5) of the fan wheel (6), characterized in that, the second section has a flow space (12) arranged at the height of the fan wheel (6) and immediately adjoining the outflow openings (5) of the fan wheel (6), which is bounded in the radial direction by the lateral wall (10) and in which no air guiding devices are arranged, and wherein rectifier flow surfaces (22) are arranged in the air guide channel downstream of the flow space (12).Air suction device (2) according to claim 1, characterised in that the lateral wall (10) has one or more openings (14) through which substances sliding and / or flowing along the wall (10) can reach the rear side (16) of the wall (10).Air suction device (2) according to claim 2, characterised in that a projection (18) is arranged downstream of an opening (14), by means of which projection materials sliding and / or flowing along the wall (10) can be collected and diverted through the opening (14) into the space on the rear side (16) of the wall (10).Air suction device (2) according to one of the preceding claims, characterized in that a collecting reservoir (20) for collecting the sliding and / or flowing substances separated from the second section by the opening (14) is arranged on the rear side (16) of the wall (10).Air suction device (2) according to one of the preceding claims, characterized in that the lateral wall (10) can be cooled completely or at least in regions by means of a cooling device and / or heated by means of a heating device.Air suction device (2) according to one of the preceding claims, characterized in that the flow space (12) is configured annularly encircling the fan wheel (6).Air suction device (2) according to one of the preceding claims, characterized in that the fan wheel (6) and / or the lateral wall (10) are connected to the air suction device (2) via a connection which can be released without tools.Air suction device (2) according to one of the preceding claims, characterized in that the lateral wall (10) extends in the axial direction as far as a region behind the fan wheel (6) and in this region at least one opening (14) is present in the lateral wall (10).Air suction device (2) according to one of the preceding claims, characterized in that the opening (14) is designed as a circumferential gap.Air suction device (2) according to one of the preceding claims, characterized in that the shape of the lateral wall (10) is adapted to the flow profile of the air flow (L) through the flow space (12) and has an expansion in the flow direction of the air flow (L).Air suction device (2) according to one of the preceding claims, characterized in that the air suction device (2) can be inserted as a tube fan module into an existing ventilation device.Method for separating particles moved in an air flow (L), in which the air flow (L) is conveyed and accelerated in the radial direction by a fan wheel (6), exits from outflow openings (5) from the fan wheel (6) and is subsequently deflected in an axial direction, characterized in that the deflection takes place in an axial direction in a flow space (12) which directly adjoins the outflow openings (5) which is bounded in the radial direction by a lateral wall (10) and in which no air guiding devices are arranged, and wherein rectifier flow surfaces (22) are arranged in the air guide channel downstream of the flow space (12), so that helical swirl flows of the air flow (L) are converted into a more uniform flow.

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