MXPA00009419A - Cyclonic separation apparatus - Google Patents

Abstract

The invention provides cyclonic separation apparatus (10) comprising a cyclone body (14) having at least one fluid inlet (18) and a fluid outlet, the fluid outlet being concentric with the longitudinal axis of the cyclone body (14) and comprising a vortex finder (26) projecting from an end surface (24) of the cyclone body (14) into the interior thereof, and a proboscis (30) located partially within the vortex finder (26) and projecting beyond the distal edge thereof so that the distance between the end surface (24) of the cyclone body (14) and the furthermost end of the proboscis (30) is at least twice the smallest diameter of the vortex finder (26), wherein the cross-sectional area of the proboscis (30) is circular at any point along its length.

Description

CYCLONE SEPARATION APPARATUS The invention relates to the cyclonic separation apparatus, particularly but not exclusively to the cyclonic separation apparatus for use in a vacuum cleaner. The cyclonic separation apparatus generally consists of a truncated-conical cyclone body having a tangential inlet at its longer, usually higher end and a cone opening at its smaller, usually lower, end. A fluid that transports particles entrained within it enters through the tangential inlet and follows a helical path around the cyclone body. The particles are separated from the fluid during this movement and transported or deposited through the cone opening in a collector from which they can be eliminated in an appropriate manner. The cleaned fluid, usually air, travels through the central axis of the cyclone body to form a vortex and exits the cyclone separator by means of a vortex finder which is positioned at the larger (upper) end of the cyclone body and is aligned with the central axis of it. The vortex finder usually takes the form of a simple tube that extends down into the cyclone body so that the vortex of the existing fluid is reliably directed out of the cyclone. However, the vortex finder has a number of inherent disadvantages. One of these disadvantages is the fact that there is a significant pressure drop within the vortex finder due to the high angular velocity of the existing fluid. In an attempt to overcome this problem, the central bodies have been introduced into the known vortex seekers in combination with tangential exit holes in order to reinforce the flow passing through and out of the cyclone. Some attempts have been made to reduce the turbulence of the flow using asparcijas. A variety of such attempts are illustrated in the document entitled "The use of tangential offtakes for energy savinges in process industries" (T O'Doherty, M Biffin, N Syred: Journal of Process Mechanicai Engineering 1992, Vol. 206). Other arrangements incorporating central bodies or vanes are illustrated in WO 97/46323, WO 91/06750 and US 5,444,982. In all those documents of the prior art, the central body is completely contained within the vortex seeker or, otherwise, is projected only to a very small degree within the body of the cyclone. This is because the only intention of the central body or blade is to remove the turbulence of the flow within the vortex seeker, instead of stabilizing it. The central bodies have also been introduced into cyclone separators for other reasons. One such reason, illustrated in US 4,278,452, is to expand the exit fluid so that the outermost annulus of the fluid containing any entrained permanent particles is recirculated through the separator. However, by necessity, most of the central body must remain outside the vortex seeker and therefore is unable to stabilize the fluid flow within the vortex seeker. Another use of a central body is to support an electrode by means of which a corona discharge occurs within the separation zone of the separator. This improves the efficiency of the separation within the separation zone but, because the electrode must incorporate angular or indicated areas from which the corona will discharge, there may be no stabilization of the exit fluid. In CH 388267, use is made of a central body projecting out of the vortex finder to prevent gas bubbles from escaping from the main outlet of the apparatus to separate the solid particles and gas bubbles from a slurry of gas. liquid. The central body has an essentially flat end, the gas bubbles, which migrate towards the vortex core during the operation, they are caused to come out of the apparatus by means of the cone opening, which forms an opening of the cyclone. Another problem associated with vortex seekers is the fact that, during the operation of the cyclonic separation apparatus, the vortex core presses around the vortex seeker causing a significant amount of noise. The prohibition of a central body completely within the vortex seeker has been recognized as a contributor to the reduction of noise associated with the fluid that exits to a certain degree although no attempts have been made to make use of a central body to reduce noise even more. In household appliances such as vacuum cleaners, noise is also undesirable and there is a constant desire to reduce the noise associated with the appliance as much as possible. It is therefore an object of the present invention to provide a cyclonic separation apparatus, suitable for incorporation in a household appliance, in which the noise level is improved. It is a further object of the present invention to provide the cyclonic separation apparatus in which the pressure drop appears through the vortex finder which is as small as possible. It is a further object of the invention to provide the cyclonic separation apparatus suitable for use in domestic vacuum cleaners. The invention provides the cyclonic separation apparatus as set forth in claim 1. The invention also provides a vacuum incorporating the cyclonic separation apparatus. Additional and preferred features are set forth in the dependent claims. The provision of a central body having a circular cross-section and a hemispherical or trunco-conical conical end projecting beyond the lowermost end of the vortex seeker to a distance in which the most anterior end of the central body is at least twice the smallest diameter of the vortex finder from the extreme surface of the cyclone body reduces the noise associated with the exit vortex to an appreciable extent. The reduction has been found to be significantly better than in the case with the vertex finder not protruding out of the vortex finder to a significant degree. It is considered that the precedence of the vortex core when confined by the walls of the vortex seeker causes pressure alterations within the air flow that manifest as noise. Therefore, it is desirable to stabilize this rotation completely before the exhaust air enters the vortex seeker. The extension of the central body within the low pressure area of the core before it reaches the vortex seeker causes the core to stabilize before it reaches the vortex seeker. The noise level is therefore reduced. Experimentation with the specific apparatus has shown that, for specific dimensions of the cyclone, the vortex seeker and the central body, there are optimal distances from the upper surface of the cyclone towards which the central body should extend. It will be clear from the description and examples that follow that it is not necessary for the central body to extend the entire distance towards the vortex seeker towards the upper surface of the cyclone. The embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows, in cross-section, the cyclonic separation apparatus according to the present invention and suitable for use in a vacuum cleaner; Figure 2a shows on a larger scale, the central body that forms part of the apparatus shown in Figure 1; Figure 2b shows a first alternative configuration of the central body of Figure 2a; Figure 2c shows a second alternative configuration of the central body of Figure 2a; Figure 3 is a cross-section through parts of the alternative cyclonic separation apparatus according to the present invention; Figure 4 is a schematic drawing of the test apparatus used to determine the results of the experiments described below; Figure 5 is a graph showing a comparison in cyclone noise with and without a center body of vortex finder optimized in place. Figure 1 shows the cyclonic separation apparatus 10 suitable for use in a cyclonic vacuum. In fact, in this example, the cyclonic separation apparatus consists of two concentric cyclones 12, 14 for sequential cleaning of an air flow. The remaining features of the vacuum cleaner (such as the vacuum head or hose, motor, motor filters, handle, support wheels, etc.) are not shown in the drawing because they are not part of this invention will be further described herein. In fact, it is only the most internal high efficiency cyclone 14 that incorporates a vortex finder in this embodiment and therefore it is only the innermost cyclone 14 that is of interest in the context of this invention. However, it will be understood that the invention is applicable to the cyclonic separation apparatus different from that which is suitable for use in vacuum cleaners and also for the cyclonic separation apparatus incorporating only a single cyclone. The innermost cyclone 14 comprises a central cyclone body 16 which is generally truncated-conical in shape and has a fluid inlet 18 at its upper end and a cone opening 20 at its lower end. The cone opening 20 is surrounded by a closed collection chamber 22 in which the particles carried by the cyclone 14 via the fluid inlet 18 and separated from the air fluid within the cyclone body 16 are collected. The cyclone body 16 has an upper surface 24 at the center of which is located a vortex finder 26. The vortex finder is generally tubular in shape and has a lower cylindrical portion 26a that fuses into a trunco-conical portion. upper 26b leading outside the cyclone body 16 towards an outlet duct. The operation of the cyclonic separation apparatus of the type described is known and documented elsewhere and will not be further described in detail herein. The invention takes the form of a central vortex finder body 30 which is located within the vortex finder 26 and is shown in position in Figure 1. The central body 30 is also shown on a remote scale in Figure 2a. The central body 30 comprises a central elongate member 32 which is cylindrical along most of its length and has hemispherical ends 32a, 32b. The hemispherical shape of the ends 32a, 32b reduces the risk of turbulence that is introduced to the air flow as a result of the presence of the central body 30. The elongated member 32 carries two diametrically opposed tongues 34 that are generally rectangular in shape and extends radially outwardly from the elongate member 32 sufficiently apart to abut against the inner walls of the vortex finder 26 within the cylindrical portion 26a. The edges downstream of the tabs 34 have rounded outer corners to reduce the risk of turbulence being introduced. Also, the notches or grooves 36a are formed on the outer edges of the tabs 34 as they correspond to spikes or projections 36b that are formed in the walls interiors of the cylindrical portion 26a of the vortex finder 26. The ears or projections 36b are also diametrically opposed and are designed and positioned to cooperate with the notches or slots 36a in the tabs 34 and to thereby hold the central body 30 in position. in the vortex finder 26. It will be understood that the exact method of retention of the central body in position is not material of the invention and the notches / grooves 36a and the spikes / projections 36b can be replaced by suitable alternative means to sustain reliably the central body 30 within the vortex finder 26 so that the central body 30 will not be dislodged by the likely velocity of fluid flow through the cyclonic separation apparatus, nor will it be subjected to unacceptable vibrations. A method of rapid adjustment is considered particularly desirable because of its ease of manufacture and use. The length of the central body 30 and its placement are sufficient to ensure that the end 32a of the central body 30 from the upper surface 24 is located at a point whose distance below the upper surface 24 equals at least twice the diameter more small of the vortex finder 26. Thus, the length of the projection of the central body 30 beyond the lower end of the vortex finder 26 added to the total length of the vortex finder 26 (below the upper surface 24) must be at least twice the diameter of the vortex finder 26. If this criterion is met, the noise reduction that is achieved is improved. In the embodiment shown in Figure 1, the lowermost point of the central body 30 is located below the upper surface 24 at a distance that is equal to approximately 2.58 times the smallest diameter of the vortex seeker 26. Specifically, the most under the central leather 30 is located at 82.5 mm below the upper surface 24 and the smallest diameter of the vortex finder 26 is 32 mm. In addition, the length of the central body 30 is 60 mm and its diameter is 6 mm. The central body 30 projects below the lowermost edge of the vortex seeker to a distance of 16.5mm. this placement succeeds in achieving a reduction in the overall sound pressure level (noise) emitted from the full 1.5 dBA vacuum cleaner product. In order for the central body 30 to function properly, the cross-section of the central body 30 is made to circulate at any point along its length. The main body of the central body 30 is cylindrical, as mentioned above, although the upstream and downstream ends 32a, 32b may take various forms. In the embodiment shown in Figure 2a, both ends 32a, 32b are hemispherical. However, one or the other of the ends could be, for example, conical or truncated conical, although a conical end will be preferable because this reduces the pressure drop and / or the energy losses within the apparatus. An alternative center body 50 is shown in Figure 2b in which the central portion of the elongate body 52 of the central body 50 is again cylindrical and the downstream end 52b is hemispherical, although the upstream end 52a is conical in shape. An additional difference between the central body 50 shown in Figure 2a and the alternative center body shown in Figure 2b is the number of tabs 54 provided in the elongated body 52 for support purposes. In the embodiment shown in Figure 2b, four equiangular separate tabs 54 are provided. The corresponding pins are then provided on the wall of the vortex finder 26 in order to support the central body 50 therein.

An additional alternative embodiment is shown from two different angles in Figure 2c. In the Figure, the central body 70 is shown from two different perspective views so that the helical shape of the tabs 74 can be clearly observed. The helical shape is present so that the tongues 74 do not interfere with the rotational movement of the air exiting via the vortex finder. As in the embodiment shown in Figure 2a, the elongated body 72 is generally cylindrical in shape and the upstream end 72a is hemispherical. The downstream end 72b is planar. Each tab 74 is formed at its distal end to include slots 74a which cooperate with molded projections in the vortex seeker so that the central body 70 is held firmly in the correct position in the vortex seeker. An alternative configuration of the separation apparatus is shown in part in Figure 3. The figure shows only the upper portion of the separation apparatus 80 which, as before, comprises a low efficiency cyclone upstream 82 and a current high efficiency cyclone. down 84. The low efficiency cyclone 84 has a cyclone body 86 having an inlet 88 that communicates with the upper end of the cyclone 84 and a cone opening (not shown) at the opposite end thereof surrounded by a collector (also not shown). shown) in the same manner as shown in Figure 1. Cyclone 84 is closed at its upper end by an upper surface 90 from which hangs a vortex seeker 92 extending within the interior of cyclone 84 to along a central axis of it. The vortex finder 92 is cylindrical in shape for most of its length although it widens outwardly at its upper end so that it fuses uniformly with the upper surface 90. A central body 94 is immovably mounted within the vortex finder 92 and extends from the point on the level of the upper surface 90 directly through the vortex finder 92 so that the central body 94 projects beyond the lower edge of the vortex finder 92. The body of the body central 94 is generally cylindrical with a slight taper towards the upstream end 94b. The upstream end 94a is hemispherical in shape, although at its current end 94b it is simply flat. The central body 94 has three equi-angularly spaced tabs or tabs 96 which extend outwardly from the upper end of the central body 94 towards the inner wall of the vortex finder 92. The more extreme edges of the tabs or tabs 96 are formed to follow the shape of the inner wall of the vortex finder 92 to assist with the correct positioning of the central body 94. In this embodiment, the diameter of the central body 94 is 10mm and the diameter D1 of the vortex finder 92 is 30.3mm. The length L1 of the vortex finder is 50mm and the distance L2 between the lower end 94a of the center body 94 and the upper surface 90 is 64.4mm. Therefore, the lowest point of the central body 94 is located below the upper surface 90 at a distance of 2.13 times the diameter (smaller) of the vortex finder 92. The central body 94 projects below the vortex seeker 92 to a distance of 14.4 mm. Tests to determine the optimal placement of the lowermost end of the central body in the apparatus shown in Figure 1 have been executed. The test method and the apparatus will now be described with reference to Figure 4 of the accompanying drawings. A transparent cyclone 10 with a variable length vortex seeker 120 and a variable length center body 140 was mounted in a vertical position using appropriate fasteners and mounting devices (not shown). The cyclone 10 has a maximum diameter of 140mm and a height of 360mm. The suction was provided to the cyclone 100 by a source connected by means of a first flexible hose 102 to ensure the minimum interference of the engine noise. A second flexible hose 104 connected to the inlet of the cyclone 106 takes the inlet air from a remote chamber (not shown) to avoid interference from the noise associated with the air entering from the hose opening. At the inlet 106 the cyclone 100 a flow rate mediator 108 was joined to allow the inflow velocity to move accurately. The variable length vortex finder 120 consists of a tube 122 of fixed length and a fixed diameter connected to the first flexible hose 102 and slidably mounted to the upper plate 110 of the cyclone 100 by means of a clamping and sealing ring 124. In this case, the diameter of the tube was 32mm. By holding the tube 122 in different positions so that it projects into the cyclone 100 by different amounts, the length S of the vortex finder 120 can be varied. The variable length central body 140 consisted of an elongated member 142 mounted on a ball 126 at the upper end of the vortex finder 120. The elongated member 142 was slidably mounted on the ball 126 by means of a sealing and holding block 144. Additional support was provided to the elongated member 142 by means of two tabs 146 extending from the elongated member 142 towards the inner wall of the vortex finder 122. The tabs 146 prevented the elongated member 142 from oscillating during the test procedure. By holding the elongated member 142 so that it projects beyond the lower end 128 of the tube 122 by different amounts, the length L of the central body 140 can be varied. In order to execute the experiment, the vortex finder length S was set to the required value and the end of the elongated member 142 was flush with the lower end 128 of the tube 122 (ie, L = 0). The suction source was activated and the flow velocity measured and set to the required level by proper adjustment. The central body 140 moved down in 5mm steps and sound measurements were taken at each stage. The central body 140 was moved down in 5mm steps and sound measurements were taken at each stage. The optimal length of the central body that was sought was the length at which the noise level was reduced to a minimum. When an appropriate location of the optimum length of the central body 140 has been located, increments of 2mm in the length L of the central body were used to more accurately indicate the optimum length. Having determined the optimum length of the central body 140 for a given flow velocity and a determined vortex finder length S, the flow velocity was varied by adjusting the suction source and varying the length of the central body. L was repeated to determine the optimal central body length for that flow velocity. Having determined the optimal length of the central body for each required flow velocity and a determined vortex finder length, the vortex finder length was adjusted and a second series of experiments were performed using the same set of flow velocities to produce results comparable. The results obtained are established below.

The optimal length was further defined as the length of the central body in which the noise reduction reverted to a slight gain in the noise level. The optimal length was therefore observed as a minimum general disunited pressure level, a point where no significant reduction is obtained by continuing to extend the central body or a point where the tonal quality begins to deteriorate. In particular, the fundamental frequency, identified using narrow band analysis, of the vortex accuracy was considered to be minimal at the optimal length. Additional tests revealed that, in a cyclone body that has a diameter of 140mm, a height of 300mm, a vortex finder diameter of 32mm and a vortex finder length of 66mm, the optimum protrusion of the central body 30 beyond The lower end of the vortex finder is 16.5 mm. This gives a distance between the lowermost end of the central body 30 and the upper surface 24 of 82.5 mm, which is 2.58 the diameter of the vortex seeker 26. The additional tests were carried out using an apparatus similar to that described above but with replaceable vortex finders that have different diameters. In each case, the length of the vortex finder was 46mm and a fixed flow rate of 27 liters / second was used. The central body used was similar to that described above but had a diameter of 10mm. A method similar to that described above was used to find the optimal central body length for each diameter of the vortex finder. The results obtained are as follows: This clearly demonstrates that the optimum central body length for a given flow velocity and a given central body diameter generally decreases with the diameter of the vortex finder. The central body 30 is preferably made from plastic material and must be sufficiently rigid so as not to flex or oscillate when exposed to flow velocities similar to those passing through the separation apparatus. For a central body suitable for use in the vacuum cleaner, a suitable material is polypropylene and this allows the central body to be molded simply and economically using one of a variety of common techniques, for example, injection molding. The test and research have shown that, depending on the specific configuration of the cyclone, the optimization of the central body length can result in a reduction of between 2 to 6 dB of the overall sound pressure level of a cyclone. This is sufficient to achieve an audible difference in the overall noise levels of a domestic vacuum cleaner. Figure 5 illustrates the difference in noise (sound pressure level) produced by the cyclone of a specific vacuum with and without an optimized central body in place. As can be clearly seen, the presence of the central body (noise level shown in dark lines) eliminates a significant tone that is present when the central body is absent (the noise level shown in dotted lines). The advantages of reducing the noise level of a domestic vacuum cleaner are to improve consumer satisfaction and allow a user to hear other sounds and noises within the environment in which the vacuum cleaner is being used. This can improve user safety when using the vacuum cleaner.

Claims (23)

1. CLAIMS 1. Cyclone separation apparatus comprising a cyclone body having at least one fluid inlet and one fluid outlet, the fluid outlet being concentric with a longitudinal axis of the cyclone body and comprising a vortex seeker which projects from an end surface of the cyclone body within it, and a central body located partially within the vortex seeker and projecting beyond the end thereof away from the end surface so that the distance from the end surface of the cyclone body and the far end of the central body is at least twice the smallest diameter of the vortex seeker, the cross-sectional area of the central body which is circular at any point along its length, characterized in which the central body tapers inward toward its far end and is hemispherical, conical or truncated-conical in shape. Cyclonic separation apparatus according to claim 1, characterized in that the distance between the end surface of the cyclone body and the most anterior end of the central body is at least 2.3 times the smallest diameter of the vortex finder. 3. Cyclonic separation apparatus according to claim 2, characterized in that the distance between the end surface of the cyclone body and the most anterior end of the central body is at least 2.3 times the smallest diameter of the vortex finder. Cyclonic separation apparatus according to any of the preceding claims, characterized in that the central body is generally cylindrical with at least one hemispherical end. 5. Cyclonic separation apparatus according to any of the preceding claims, characterized in that the central body is generally cylindrical with at least one conical end. 6. Cyclonic separation apparatus according to any of the preceding claims, characterized in that the diameter of the central body is no more than half the smallest diameter of the vortex seeker. Cyclonic separation apparatus according to claim 6, characterized in that the diameter of the central body is not more than one third of the smallest diameter of the vortex finder. Cyclonic separation apparatus according to claim 7, characterized in that the smallest diameter of the vortex finder is substantially 32mm and the diameter of the central body is substantially 6mm. 9. Cyclonic separation apparatus according to claim 8, characterized in that the distance of the most anterior end of the central body is between 80mm and 110mm from the end surface of the cyclone body. 10. Cyclonic separation apparatus according to claim 9, characterized in that the distance from the most anterior end of the central body is between 85mm and 95mm from the end surface of the cyclone body. Cyclonic separation apparatus according to claim 7, characterized in that the smallest diameter of the vortex finder is substantially 30mm and the diameter of the central body is substantially 10mm. 12. Cyclonic separation apparatus according to claim 11, characterized in that the distance from the most anterior end of the central body is between 50mm and 90mm from the end surface of the cyclone body. Cyclone separation apparatus according to claim 12, characterized in that the distance from the most anterior end of the central body is between 60mm and 70mm from the end surface of the cyclone body. 14. Cyclonic separation apparatus according to any of the preceding claims, characterized in that the central body projects beyond the lower edge of the vortex seeker to a distance of at least 10mm. A cyclonic separation apparatus according to claim 14 and any of claims 11 to 13, characterized in that the central body projects beyond the lower edge of the vortex finder to a distance of substantially 14.4mm. 16. Cyclonic separation apparatus according to claim 14 and any one of claims 8 to 10, characterized in that the central body projects beyond the lower edge of the vortex finder to a distance of substantially 16.5mm. 17. Cyclonic separation apparatus according to any one of the preceding claims, characterized in that the central body is supported in the vortex finder by means of support tabs extending to the inner wall of the vortex finder. 18. Cyclonic separation apparatus according to claim 17, characterized in that the tabs are diametrically opposed. 19. Cyclonic separation apparatus according to claim 17 or 18, characterized in that the tongues comprise helical blades. The cyclonic separation apparatus according to one of claims 17 to 19, characterized in that the tabs and the internal wall of the vortex finder incorporate retaining means for retaining the central body in position within the vortex finder. 21. Cyclonic separation apparatus according to claim 20, characterized in that the retaining means comprise engageable elastic tabs with corresponding grooves. 22. A vacuum incorporating a cyclonic separation apparatus according to any of the preceding claims. 23. Cyclonic separation apparatus substantially as described so far with reference to Figure 1 of the accompanying drawings.