Untitled record

A 54,336 g Pall Corporation

g - 202 2200 Northern Boulevard

27th January 1998 East Hills, NY 11548-1289

USA

separating

The invention relates to a separation device and in particular an inertia or impact separation device.

A Trägiieitsabscheidevorrichtung removes particles from a fluid flowing through the device. Such devices can be used in the air intake of engines of all kinds, for example in engines for military purposes or engines for off-road vehicles. The engines may be gasoline engines or diesel engines and may be turbocharged. In this case, the fluid is air, and the particles are dust and other waste materials, such as coarse sand, sand and rocks. The pros ^r direction includes a number of centrifugal separators. Each separator applies to the fluid passing through a central passage a torque component which causes the particles to migrate to the periphery of the flow from which the particles are removed. An example of such a separator is shown in GB-A-1207028 in which the separator is a vortex separator. Similar separators are shown in GB-A-1278488 and GB-A-1236941.

The separators in such a device can be arranged in various ways. In one embodiment, a first and a second stage are present, which are spaced apart in the flow direction of the fluid. Each stage has a number of separators which are arranged in a side-by-side arrangement, with their inlets and outlets in alignment, the passages being arranged parallel to one another. The two stages are identical, so that each separator

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in one stage has a corresponding separator in the other stage. The effect of this is that the passage of a separator in the first stage is coaxial with the axis of the passage of the corresponding separator in the second stage.

As a result, all particulate matter exiting a separator in the first stage is directed to a corresponding separator in the second stage. This is especially true for larger particles which can be accelerated as they pass through a first stage separator, and this can cause such particles to pass through the corresponding second stage separator without being separated. Of course this is not desirable.

In a first embodiment of the present invention, there is provided a separation apparatus comprising a first stage having a plurality of centrifugal separators through which fluid flows along a first axial path and a second stage downstream of the first stage comprising a plurality of centrifugal separators contains, through which the fluid flows along a second axial path, wherein each of the first and second stage separators has a passage of diameter, the apparatus being characterized in that the first stage axial paths are offset from the second stage axial paths by between 10% and 90% of that diameter ,

In the following, a more detailed description of an embodiment of the invention will be given by way of example, with reference to the accompanying drawing, which is a schematic sectional view of a two-stage centrifugal separation apparatus for a turbocharger of a turbocharged diesel engine.

The drawing shows a separating device comprising a housing 10, which has a first separating stage 11 and a second

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Separation stage 12 contains. Each of the stages 11, 12 is formed of a plurality of separators 13. The two stages 11, 12 are separated by a chamber.

The separators themselves are known per se, and one of these separators 13 will now be briefly described. For more details of separators of this general type, reference is made, for example, to GB-A-1207028.

Each separator comprises a tubular body 14 having a central passage or passage 15, an inlet 16 and an outlet 17. A vortex generator 18 is disposed within the central passage 15. The vortex generator 18 may be made of nylon or polypropylene and molded or glued into the passage 15 in the assembly. The vortex generator 18 has helical guide surfaces which surround a cylindrical hub 20. The body 14, the vortex generator 18, and the hub 20 may be molded as a single article.

A substantially conical tubular outlet member has an inlet 22 and an outlet 23. The outlet member 21 is coaxial with the passage 15 and has the inlet 22 which extends to the outlet end 17 of the passage 15. The outer diameter of the inlet 22 of the outlet 21 is less than the inner diameter of the passage 15 at the passage outlet 17th Thereby, an annular space 24 is formed between the outlet 17 of the passage 15 and the outer surface of the inlet end 22 of the outlet 21.

The separator may be made of nylon or thermoplastic materials as well as metal and may be made by assembling a number of components or by molding more complex subunits.

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As can be seen from the drawing, each separator 13 is mounted between a pair of plates 25, 26 and 27, 28, respectively. One plate 25, 27 abuts around the inlet 16 of each passage 15 and the other plate 26, 28 abuts around the outlet 23 of the outlet 21.

In each stage, the separators 13 are arranged in rows, wherein the separators 13 of the one row are arranged offset by half the passage diameter with respect to the separators 13 of the adjacent row. This is shown in the figure in this way. The axes 29 of the separators in the first stage 11 are all parallel and the axes 30 of the separators 13 in the second stage are also all arranged parallel to each other. However, as can be seen from the drawing, the first stage shafts 29 are offset from the second stage shafts 12 by half the passage diameter. This offset is always present, but may be more or less than half the diameter of the passage to optimize the properties for different sizes of particulate material.

As a result, none of the separators 13 in the first stage 11 with its axis 29 coaxial with the axis 30 of a separator 13 in the second stage 12. This means that no outlet 23 of an outlet 21 with an inlet 16 of a passage 15 of a separator 13th in the second stage 12 is aligned.

The second stage 12 may be followed by a filter (not shown) and may lead to an engine intake. This engine may be a gasoline engine or a diesel engine and may include a turbo blower.

In operation, air enters the housing 10 at the housing inlet 31. The air may carry particles such as dust or other waste materials including coarse sand, sand and rocks. The air enters the inlet 16 of the separator 13 in the first stage 11. In the air flow through each

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the vortex generators 18, a vortex is generated and the particles are forced to the edge of each passage 15, the air in the middle becoming relatively clean. The marginal portions of the air flow, which carry the particles with it, pass through the annular space 24 between the passages 15 and the outlet 21. The core or center of clean air exits through the outlet member 21 into the space within the housing 10 between the first stage 11 and the second stage 12. The particles passing through the annular spaces 24 become between the downstream in that space The first stage plate 26 and the second stage upstream plate 27 are collected and discharged from this space.

Although the separators 13 of the type described above may have separation efficiencies greater than 95%, particles may still be contained in the air leaving the first stage separators 13.

The torque component of the velocity imparted to the air as it passes through the vortex generators 18 and the acceleration of the flow in the outlet members 21 may also transfer significant energy to the particles entrained in the air.

The displacement of the axes 29 of the first stage separators 13 with respect to the axes 30 of the second stage separators 13 reduces the ballistic velocity of any dust or other solid particles passing through the first stage separators 11. As a result, air passing through the first stage 11 is deflected before entering the inlet 16 of the separators 13 in the second stage 12.

The second stage separators operate in the same manner as the first stage separators in terms of particulate separation, as previously described. This allows the second stage a much higher separation efficiency

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otherwise this would be the case. This prevents large particles, such as stones in particular, from being transmitted significant energy in the first stage 11 and passing straight through the second stage under the influence of this energy. This increases the efficiency of the second stage 12 and prevents large particles from passing through the second stage and damaging downstream equipment.

The distance between the first stage 11 and the second stage 12 may be varied to optimize the efficiency of the second stage in terms of likely operating conditions.

It will be understood that a number of variations can be made. Although the arrangement described above has a number of rows of separators 13, it is to be understood that only a single row may be present. In fact, only a single separator 13 can be present in each stage. The rows are laterally offset from each other in each stage to achieve the largest packing density of separators in each stage 11, 12. However, such an offset is not necessary.

As mentioned above, the offset between the stages can be varied to optimize the particle separation efficiency with respect to the particular particle sizes as a whole. For example, the offset may be between 10 and 90% of the tube diameter.

The effect achieved by the arrangement as described above with reference to the drawing can also be achieved by using a different number of separators 13 in the first stage 11 and in the second stage 12. There may be more separators 13 in the first stage 11 than in the second stage 12 or vice versa. Additionally or alternatively, the separators in the first

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Stage 11 have a different diameter than the separator in the second stage 12.

The vortex-type separators 13 described above with reference to the drawings may be replaced by any other suitable centrifugal separator.

Although the axes 29, 30 of the passages 15 in the two stages 11, 12 are offset from one another as described above, this need not necessarily be the case. Alternatively, baffles may be present in the space between the first and second stages 11, 12 to ensure that air and particles exiting the separators 13 of the first stage 11 take a path having a non-axially directed component.

Further, although the first and second stages 11, 12 are shown as separate assemblies separated by an air chamber, this need not necessarily be the case.

It may be provided a common tubular body having a first and a second portion whose axes are offset from each other. A first stage separator 13 is received in the first portion of the common tubular body while a second stage separator 13 is disposed in the second portion of the tubular body. Thereby, the axis of the vortex generator 18 of the first stage separator 13 is offset from the axis of the vortex generator 18 of the second stage separator 13 by the same amount that the first and second portions of the tubular body are axially offset from one another are.