WO2011031192A1

WO2011031192A1 - Particle trap and filter device comprising a particle trap

Info

Publication number: WO2011031192A1
Application number: PCT/SE2009/000408
Authority: WO
Inventors: Sassan Etemad; Reimer Ryrholm
Original assignee: Volvo Lastvagnar AB
Current assignee: Volvo Truck Corp
Priority date: 2009-09-14
Filing date: 2009-09-14
Publication date: 2011-03-17
Anticipated expiration: 2012-03-14
Also published as: EP2478206A1; EP2478206B1; BR112012005669B1; EP2478206A4; WO2011031205A1; AU2010293115B2; CN102575624A; AU2010293115A1; ZA201201655B; BR112012005669A2

Abstract

The invention relates to a particle trap (100) for removing particles from a fluid (90), comprising a conduit (10), the conduit (10) comprising a wall (16); a bend (20) with an upstream side (20a) and a downstream side (20b) with respect to a flow direction (70) of the fluid (90); - an inlet (12) at the upstream side (20a) of the bend (20); at least one first outlet (40) at the downstream side (20b) of the bend (20); at least one second outlet (50) at the downstream side (20b) of the bend (20); - wherein the least one first outlet (40) is arranged in a first region (26), at a distance from the wall (16), where the concentration of particles in the fluid (90) is lower than in the vicinity of the wall (16) during operation; and wherein the least one second outlet (50) is arranged in the vicinity of the wall (16) where the concentration of particles is higher than where the first outlet (40) is arranged.

Description

D E S C R I P T I O N

Particle Trap and Filter Device comprising a Particle Trap

TECHNICAL FIELD

The invention relates to the field of removing particles form a fluid. More specifically, the invention relates to a particle trap and a filter device comprising a particle trap.

BACKGROUND OF THE INVENTION

It is known in the art that many kinds of fluids are contaminated with particles and have to be purified before the fluid can be used. For instance, air used in combustion engines is sucked from the ambient so that particles such as dust or water droplets carried in the fresh air have to be filtered out before the air is transported into the combustion engine. US-A-5,034,036 discloses a water separation device configured to be mounted to a housing of an air cleaner in an air intake system of an internal combustion engine. The housing has an air inlet opening, an air outlet opening having an internal bellmouth section which feeds an air intake port of the air cleaner and which defines a circuitous air flow path, including a section with a 180° turn. The circuitous air flow path causes multiple directional changes to air flowing through the flow path. As a result, water particles in the air are thrown off during the directional changes by centrifugal force.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an economic and compact particle trap with a high efficiency and reduced fuel consumption.

Another object is to provide a filter device comprising a particle trap. The objects are achieved by the features of the independent claims. The other claims, the drawing and the description disclose advantageous embodiments of the invention.

A particle trap for removing particles from a fluid is proposed, comprising a conduit, the conduit comprising (i) a wall; (ii) a bend with an upstream side and a downstream side with respect to a flow direction of the fluid; (iii) an inlet at the upstream side of the bend; (iv) at least one first outlet at the downstream side of the bend; (v) at least one second outlet at the downstream side of the bend, wherein the least one first outlet is arranged in a first region, at a distance from the wall, where the concentration of particles in the fluid is lower than in the vicinity of the wall during operation; and wherein the least one second outlet is arranged in the vicinity of the wall where the concentration of particles is higher than where the first outlet is arranged.

Favourably, an effective separation of particles from the fluid can be achieved. The particle reduction in the first region can be as high as 90% or higher compared to the particle content in the fluid upstream of the bend. Favourably, the filter element can be used a longer time before it is congested and needs to be replaced.

Favourably, it might not be necessary to provide a filter material for filtering the particles out of the fluid. Consequently, costs for a filter element and costs for replacing or cleaning congested filter elements can be saved as well as space for such filter elements in the conduit. An inlet of a conduit can extend into the first region for guiding away the purified fluid, additionally or alternatively, the second region can be separated by a wall or conduit from the first region for guiding away the particles. A particle trap can be arranged in at least one bend of the conduit. The invention can make use of swirls which form in bends when a fluid flows through the bend, which swirls separate particles from the fluid. The particles accumulate in a narrow zone near the wall of the conduit and can be removed from the near wall zone easily. Removing the particles can be improved by adding an assisting suction. Particularly, use can be made of one or more already existing bends in a curved conduit without virtually changing the overall layout of the conduit. It is expedient if a long duct is provided at the upstream side of the bend, as the effect of separating the particles from the fluid is enhanced.

According to a favourable embodiment of the invention, the at least one second outlet can be arranged in a portion of the bend downstream of a bend mid-point or in the second half of the bend. For instance the at least one second outlet can be arranged in the rearmost third portion of the bend. Favourably, the at least second outlet can be arranged in a region where the particles accumulate and the particle concentration is high. For instance, the second outlet can be a hole in the wall to which a conduit is attached.

According to a favourable embodiment of the invention, the at least one second outlet can be arranged at an outer wall portion of the conduit with respect to a centre of curvature of the bend. At the outer wall portion, in the middle, i.e. near a symmetry plane if the shape is symmetrical, the particle concentration can be higher than at an inner wall portion. According to a favourable embodiment of the invention, the at least one second outlet can have a cross-sectional area of at least 1 %o of a cross-sectional area of the conduit at the location of the at least one second outlet and at most 25%, preferably at most 20%, of a cross-sectional, area of the conduit at the location of ^" the at least one second outlet. Expediently, a loss of fluid flow can be restricted so not to loose more than about 15%, preferably not more than about 10%, more preferably not more than about 5% of the flow.

According to a favourable embodiment of the invention, the bend can turn the flow of the fluid by at least 30°, particularly by at least 60°, preferably by at least 90°. Such a deflection provides an effective generation of swirls, particularly a pair of counter rotating swirls arranged side by side, and, hence, an effective separation of particles from the fluid. A turn of the flow can also be achieved for instance by arranging several bends in series with less than 90° in series. In the bend, the centrifugal force acting on the fluid and hence the particles therein is in equilibrium with the opposing pressure force. However, in the friction dominated layer near the wall, known as boundary layer, due to the lower velocity, the centrifugal force becomes weaker and thereby its opposing pressure force starts a secondary motion. This motion is known as secondary flow in the field of fluid mechanics. The secondary flow character and strength may depend on parameters such as the bend curvature and aspect ratio of the cross section. In a favourable design the secondary flow may comprise a pair of gradually growing counter rotating swirls. Favourably, if the boundary layer is thick the swirls grow faster and stronger. If the bend cross section is not appropriate, there will be at least a second pair of counter rotating swirls (but smaller) between the first pair of swirls rotating in harmony with the first pair. In such a case there may be more positions where the particles accumulate near the wall.

According to a favourable embodiment of the invention, a reflector element can be provided at least partially at or downstream of the at least one second outlet.

Expediently, the reflector element can be arranged in the second region where the particle concentration is high and where swirls generated by the bend have a high particle concentration. The reflector element can be arranged completely at or downstream of the second outlet. Alternatively, the reflector element can also start at the downstream side of the second outlet and extend towards the upstream side of the second outlet. The reflector element can efficiently support the separation of the particles from the fluid by forcing the particles in the second region to enter a region where they cannot mix again with the purified fluid.

Particularly, the reflector element can comprise at least one of a downstream edge portion of the at least one second outlet protruding farther inside the conduit than an upstream edge portion of the at least one second outlet. This allows for a simple construction of the reflector element without additional components for the reflector element. Expediently, a baffle can be provided which is inclined against the flow direction in the conduit. The baffle can be arranged at the downstream edge portion of the at least one second outlet. Alternatively, the baffle can be extending essentially parallel to an adjoining wall portion of the conduit wall, with a closed end close to the downstream end and an open end close to the upstream side of the bend in the conduit. The particles in the fluid can easily enter in the space between the baffle and the wall of the conduit. The closed end of the baffle prevents the particles from contaminating the purified fluid in the conduit. For allowing the fluid with a high particle concentration to enter the space between the baffle and the adjoining wall portion, the baffle can be provided with one or more openings, e.g. slits, where the particle rich fluid can pass through. The one or more slits are expediently arranged in a proper geometrical relation to the size of the bend, the curvature of the bend, the cross section of the bend and the like in order to maximize the particle separation from the primary flow of the cleaned fluid. If the geometrical constraints are such that more than one pair of swirls are generated, the proper location of such slits or openings can be estimated by model simulations, for instance. In such a case there can also be more than one second opening which can be arranged appropriately. However, if the geometrical constraints are chosen properly so that only one pair of swirls is generated by the bend, an expedient position where the particles accumulate can be easily determined as it is on or near the symmetry plane between the pair of swirls.

According to a favourable development of the last-mentioned alternative

embodiment of the invention, the baffle can have a clearance to the adjoining wall portion of at most 20%, preferably at most 15%, more preferably at most 10% of a distance between the adjoining wall portion and an opposing wall portion of the conduit. The size of the bend remains virtually unchanged for the fluid which can pass the bend virtually undisturbed.

According to another favourable development of the last-mentioned alternative embodiment the baffle can have at least one opening which is at least partially transparent for the fluid. Preferably, the baffle may have a slit along its longitudinal extension. The baffle can be arranged inside the conduit. However, it is also possible to arrange a compartment at the outside of the conduit, wherein the wall of the conduit constitutes the baffle and provides the at least one opening for the particles at the respective region. In this case, the compartment can be easily removed for cleaning and removing the particles from the compartment.

According to a favourable embodiment of the invention, at least one first outlet can be arranged in a substantially central region of a swirl generated in the fluid. For instance, a tube or conduit can extend with its opening into the central region of the swirl.

According to a favourable embodiment of the invention, two first outlets can be arranged side by side, each first outlet assigned to a central region of a swirl generated in the fluid. As two swirls are generated by the bend a high output of purified fluid can be achieved.

According to a favourable embodiment of the invention, a cross section of the inlet of the conduit has an aspect ratio of a maximum extension in a principal direction divided by an extension in a direction perpendicular to the principal direction of not more than 4, preferably not more than 3 and of not less than 1/5, preferably not less than 1/2. Expediently, conduits with cross sections other than circular cross sections can be used, for instance rectangular cross sections or ellipsoid cross sections with different extensions of a main and a minor axis.

According to another aspect of the invention, an air filter device is proposed comprising a particle trap according to any of the features described above.

Favourably the air filter device can be used for cleaning air for a vehicle, for instance for a combustion engine, or for cleaning air for a ventilation device in buildings, tunnels or the like. Advantageously, as the particle trap is associated with a bend of a conduit of the air filter, the layout of the conduit can easily be adapted to the requirements of the application area of the air filter. According to another aspect of the invention, an air supply for an engine

comprises such a particle trap. The engine can be an engine of a stationary power source or a vehicle engine, particularly the engine of a truck. According to another aspect of the invention, an air condition device comprises such a particle trap. Expediently, bends in the air conduit can be used for providing the particle trap described above.

According to another aspect of the invention, a vehicle is proposed which comprises such a particle trap. Preferably, the vehicle can be a truck.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention together with the above-mentioned and other objects and advantages may best be understood from the following detailed description of the embodiment(s), but not restricted to the embodiments, wherein is shown schematically:

Fig. 1 an example embodiment of a particle trap according to the invention in a perspective top view of a conduit comprising the particle trap; Fig. 2a, 2b a perspective view on a bend illustrating a first outlet of the particle trap (Fig. 2a), and a cut through the bend illustrating the first and a second outlet (Fig.^2b);

Fig. 3a, 3b a perspective oblique view of an example embodiment of a particle trap from above (Fig. 3a) and in a side view (Fig. 3b);

Fig. 4a-4c side cut views through example embodiments of particle traps

displaying different reflector elements;

Fig. 5 a top view on a baffle of a particle trap inside a conduit; and

Fig. 6 a particle trap with a conduit with a favourable aspect ratio;

Fig. 7 an example embodiment of a vehicle comprising a particle trap in an air supply according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.

Fig. 1 depicts schematically an example embodiment of a particle trap 100 according to the invention in a perspective top view of a conduit 10 comprising the particle trap 100 for purifying a fluid 90.

The conduit 10 comprises a wall 16, an inlet 12 and a main outlet 14. In between, a bend 20 is arranged with an upstream side 20a and a downstream side 20b with respect to a flow direction 70 of the fluid 90. The bend 20 is arranged between a straight upstream duct 18 and a straight downstream duct 22. The particle trap 100 is employed for removing particles from the fluid 90 entering the inlet 12 of the conduit 10. The purified fluid 90 leaves the conduit 10 at the main outlet 14.

The inlet 12 may have for instance an oval cross section 12a with a long main axis and a much smaller minor axis providing a flat cross section and the outlet 14 may have another shape of a cross section 14a, for instance an oval shape with main and minor axes comparable in size. In this example embodiment, the bend 20 deflects the fluid flow by more than 90°, here by 180°. The bend 20 has an inner side 16a closer to a centre of curvature 20c and an outer side 16b farther away from the centre of curvature 20c.

A first outlet 40 (Fig. 2a, 2b) is arranged in a first region 26, at a distance from the wall 16, where the concentration of particles in the fluid 90 is lower than in the vicinity of the wall 16 during operation. A second outlet 50 is arranged in the vicinity of the wall 16 where the

concentration of particles is higher than at the first outlet 40 at the downstream side 20b of the bend 20. A conduit 54 is arranged at the second outlet 50. The particles can be removed from the conduit 10 through the second outlet 50. For an efficient removal of the particles, the at least one second outlet 40 is arranged in a portion 30a of the bend 20 downstream of a mid-point 30 of the bend 20, for instance in the last third portion of the bend 20. The second outlet 50 has a cross- sectional area 52 of at least 1 %o of a cross-sectional area 34 of the conduit 10 at the location 32 of the at least one second outlet 50 and at most 25%, preferably at most 20%, of a cross-sectional area 34 of the conduit 10 at the location 32 of the at least one second outlet 50.

Figs. 2a and 2b illustrate the way of action of the particle trap 100 of Fig. 1 in more detail, wherein Fig. 2a shows in a simplified way a perspective view on the bend 20 with the first outlet 40 of the particle trap 100 consisting of two tubes 40a, 40b and Fig. 2b shows a cut through the bend 20 illustrating the first outlet 40a, 40b and the second outlet 50.

When the fluid 90 enters the bend 20, the main flow of the fluid passes the bend 20 as a primary flow. Due to the interaction between the acting pressure force and centrifugal force in the fluid 90 a secondary flow is generated the character of which varies from case to case. With the proper geometrical conditions, such as a reasonable cross section of the bend, a reasonable length of the upstream duct 18 of the bend, the curvature of the bend 20, the secondary flow comprises two counter rotating swirls 80a, 80b or vortices.

The counter rotating swirls 80a, 80b are arranged side by side in the fluid 90. In a central region 82a, 82b of each of the swirls 80a, 80b the fluid 90 is depleted from particles and thus purified from particles. The particles accumulate at the outer region of the swirls 80a, 80b in a narrow region at the inside of the outer wall portion 16b.

The second outlet 50 is arranged at the downstream side 20b of the bend 20 in the outer wall portion 16b of the conduit 10.

Particle-rich fluid leaves the conduit 10 through the second outlet 50 and purified fluid 90 leaves the bend through the first outlet 40, e.g. through tubes 40a, 40b arranged side by side. However, it is also possible to avoid the tubes 40a, 40b and use the downstream duct 22 for transporting the purified fluid 90 from the first outlet 40 to the main outlet 14 of the conduit 10. In this case the outlet 40 can be considered as the region where the particle-rich fluid is separated from the particle-depleted fluid by the second outlet 50. Figs. 3a and 3b illustrate the effect of the swirls 80a, 80b shown in Figs. 2a, 2b on a local particle concentration in the fluid 90 and show a perspective oblique view of an example embodiment of a particle trap 100 from above (Fig. 3a) and in a side view (Fig. 3b) according to Fig. 1 based on a model calculation. The upstream duct 18 has a high particle concentration (indicated by a dark shading) in the fluid 90 and the fluid 90 in the downstream duct 22 has only less than 10% of the particle concentration in the upstream duct 18 concentration (indicated by a light shading). The particles are forced by the swirls 80a, 80b generated by the bend 20 to the outer wall portion 16b. The particle-rich fluid flow can be kept there by a reflector element, for instance a baffle, and discharged through the second outlet 50.

Typically, the particles are multiply reflected at the reflector element before they enter then the outlet 50. The reflector element prevents the particles from re- entering the purified fluid flow.

In the bend 20, reference numeral 10a denotes a distance between the outer wall portion 16b and the inner wall portion 16a. Figs. 4a, 4b and 4c display side cut views through example embodiments of particle traps displaying different reflector elements 60. The reflector element 60 is provided at or downstream of the second outlet 50 but can extend from

downstream to upstream the second outlet 50. Fig. 4a shows a reflector element 60 which is a step in the outer wall portion 16b. Particularly the step is a downstream edge portion 58 of the second outlet 50 which is protruding farther inside the conduit 10 than an upstream edge portion 56 of the second outlet 50. Particles impinging on the edge portion 58 are deflected towards the second opening 50. Fig. 4b depicts a reflector element 60 which is a baffle 62. The baffle 62 is inclined against the flow direction 70 in the conduit 10 and arranged at or downstream of the second outlet 50. Particles impinging on the baffle 62 are reflected towards the second opening 50.

Fig. 4c illustrates a reflector element 60 formed of a baffle 62 extending essentially from a closed end 68 downstream the second outlet 50 to the upstream side of the second outlet 50 parallel to the adjoining wall portion 16c at the outer wall portion 16b of the conduit wall 16 in a direction opposite to the flow direction 70 in the conduit 10. A clearance 64 is established between the baffle 62 and the inside of the adjoining wall portion 16c. Particle-rich fluid 90 can enter the clearance through an opening 66 in the baffle 62, e.g. a slit. Fig. 5 shows an example embodiment of a baffle 62 according to Fig. 4c as a top view on the bend 20 cut away from the upstream and downstream ducts 18, 20. The view reveals the baffle 62 which covers the outer wall portion 16b of the bend 20. The baffle 62 extends from a closed end 68 parallel to the adjoining wall portion 16c at the outer wall portion 16b of the conduit wall 16 in a direction opposite to the flow direction 70 in the conduit 10.

The clearance 64 between the baffle 62 and the adjoining wall portion 16c is at most 20%, preferably at most 15%, more preferably at most 10% of a distance 10a between the adjoining wall portion 16c and a wall portion 16d of the inner wall portion 16a opposite to the adjoining wall portion 16c in the bend 20.

Particle-rich fluid can enter the slit-like opening 66 of the baffle 62 so that particles remain in the clearance 64 between the baffle 62 and the adjoining wall portion 16c. The second opening is arranged between the end of the slit-like opening 66 in the baffle 62 and the closed end 68 of the baffle 62 so that the particle-rich fluid can be discharged through the second opening 50. The slit-like opening 66 is arranged in or near the symmetry plane of the generated pair of swirls. In case of geometrical constraints where more than one pair of swirls is created, there can be more than one sit-like opening provided. As already mentioned, it is expedient for enhancing the effect of the swirl generation if the upstream duct 18 is long compared to the bend 20. The downstream duct 22 may be shorter than the upstream duct 18.

Fig. 6 depicts a particle trap 100 with a conduit comprising a favourable aspect ratio. A cross section 12a of the inlet 12 of the conduit 10 can have an aspect ratio of a maximum extension of a main axis 46 divided by an extension of a minor axis 48 in a direction perpendicular to the principal direction of not more than 4, preferably not more than 3 and of not less than 1/5, preferably not less than 1/2.

In this range the aspect ratio is favourably enhancing the effect of the swirls generated in the bend 20 with respect to separation of the particles from the fluid. Particularly, the aspect ratio impacts the swirl strength which in turn impacts separation efficiency. The pair of swirls may be created at the same radius with respect to the centre of curvature 20c, wherein particularly the swirls are generated gradually, not at a given position.

Fig. 7 displays an example embodiment of a vehicle 120, for instance a truck, with an air supply 1 12 for a combustion engine 1 14 comprising a particle trap 100 in a conduit 10. The air supply 1 12 is connected to the combustion engine 1 14 of the vehicle 120. The particle trap 100 is arranged in a bend 20 of the conduit 10 which has to be arranged to couple the conduit 10 to the combustion engine 1 14 in a space efficient way. At an inlet 12b of the conduit a filter 1 16 is placed which may retain larger contaminants such as leaves and the like from entering the air supply 1 12. The inlet 12b is an air intake chamber which may also comprise a particle trap as described above.

Of course, the air supply 1 12 can be arranged at other positions of the vehicle 120. By way of example, the position can be chosen according to an actual design of the air supply 1 12 or vehicle 120, external requirements and the like.

Claims

C L A I M S

A particle trap ( 00) for removing particles from a fluid (90), comprising a conduit (10), the conduit (10) comprising

a wall (16);

a bend (20) with an upstream side (20a) and a downstream side

(20b) with respect to a flow direction (70) of the fluid (90);

an inlet (12) at the upstream side (20a) of the bend (20);

at least one first outlet (40) at the downstream side (20b) of the bend

(20);

at least one second outlet (50) at the downstream side (20b) of the bend (20);

wherein the least one first outlet (40) is arranged in a first region (26), at a distance from the wall (16), where the concentration of particles in the fluid (90) is lower than in the vicinity of the wall (16) during operation; and

wherein the least one second outlet (50) is arranged in the vicinity of the wall (16) where the concentration of particles is higher than where the first outlet (40) is arranged.

The particle trap according to claim 1 , wherein the at least one second outlet (40) is arranged in a portion (30a) of the bend (20) downstream of a bend mid-point (30) or in the second half of the bend (20).

The particle trap according to claim 1 or 2, wherein the at least one second outlet (50) is arranged at an outer wall portion (16b) of the conduit (10) with respect to a centre (20c) of curvature of the bend (20).

The particle trap according to any preceding claim, wherein the at least one second outlet (50) has a cross-sectional area (52) of at least 1 %o of a cross-sectional area (34) of the conduit (10) at the location (32) of the at least one second outlet (50) and at most 25%, preferably at most 20%, of a cross-sectional area (34) of the conduit (10) at the location (32) of the at least one second outlet (50).

The particle trap according to any preceding claim, wherein the bend (20) or a series of bends turns the flow of the fluid (90) by at least 30°, particularly by at least 60°, more particularly by at least 90°.

The particle trap according to any preceding claim, wherein a reflector element (60) is provided at least partially at or downstream of the at least one second outlet (50).

The particle trap according to claim 6, wherein the reflector element (60) comprises at least one of

a downstream edge portion (58) of the at least one second outlet

(50) protruding farther inside the conduit (10) than an upstream edge portion (56) of the at least one second outlet (50);

a baffle (62) which is inclined against the flow direction (70) in the conduit (10);

a baffle (62) extending essentially parallel to an adjoining wall portion (16c) of the conduit wall (16) with a closed end (68) close to the downstream end (22) and an open end close to the upstream side (18) of the bend (20) wherein one or more openings (66) are provided for fluid (90) with a high particle concentration to enter a space between the adjoining wall portion (16c) and the baffle (62).

The particle trap according to claim 7, wherein the baffle (62) has a clearance (64) to the adjoining wall portion (16c) of at most 20%, preferably at most 15%, more preferably at most 10% of a distance (10a) of the ... adjoining wall portion (16c) and an opposing wall portion (16d) of the conduit (10).

The particle trap according to claim 7 or 8, wherein the baffle (62) has at least one opening (66) which is at least partially transparent for the fluid (90).

10. The particle trap according to any preceding claim, wherein at least one first outlet (40) is arranged in a substantially central region (82a, 82b) of a swirl (80a, 80b) generated in the fluid (90).

1 1. The particle trap according to any preceding claim, wherein two first outlets (40a, 40b) are arranged side by side, each first outlet (40a, 40b) assigned to a central region (82a, 82b) of a swirl (80a, 80b) generated in the fluid (90).

12. The particle trap according to any preceding claim, wherein a cross section (12a) of the inlet (12) of the conduit (10) has an aspect ratio of a maximum extension of a principal axis (46) divided by an extension of a minor axis (48) perpendicular to the principal axis (46) of not more than 4, preferably not more than 3 and of not less than 1/5, preferably not less than 1/2.

13. An air filter device (1 10) comprising a particle trap (100) according to any preceding claim. 14. An air supply (1 12) for an engine (1 14) comprising a particle trap (100)

according to anyone of the claims 1 to 12.

15. An air condition device comprising a particle trap (100) according to anyone of the claims 1 to 12.

16. A vehicle (120) comprising a particle trap (100) according to anyone of the claims 1 to 12.

17. A particle trap for removing particles from a fluid, comprising a conduit, the conduit comprising

a wall;

a bend with an upstream side and a downstream side with respect to a flow direction of the fluid;

an inlet at the upstream side of the bend; at least one first outlet at the downstream side of the bend;

at least one second outlet at the downstream side of the bend;

wherein the least one first outlet is arranged in a first region, at a distance from the wall, where the concentration of particles in the fluid is lower than in the vicinity of the wall during operation; and wherein the least one second outlet is arranged in the vicinity of the wall where the concentration of particles is higher than where the first outlet is arranged. 18. The particle trap according to claim 17, wherein the at least one second ^s outlet is arranged in a portion of the bend downstream of a bend mid-point (30) or in the second half of the bend.

19. The particle trap according to claim 17 or 18, wherein the at least one

second outlet is arranged at an outer wall portion of the conduit with respect to a centre of curvature of the bend.

20. The particle trap according to claim 17, wherein the at least one second outlet has a cross-sectional area of at least 1 %o of a cross-sectional area of the conduit at the location of the at least one second outlet and at most

25%, preferably at most 20%, of a cross-sectional area (34) of the conduit at the location of the at least one second outlet.

21. The particle trap according to claim 17, wherein the bend or a series of bends turns the flow of the fluid by at least 30°, particularly by at least 60°, more particularly by at least 90°:

22. The particle trap according to claim 17, wherein a reflector element is

provided at least partially at or downstream of the at least one second outlet.

23. The particle trap according to claim 22, wherein the reflector element

comprises at least one of a downstream edge portion of the at least one second outlet protruding farther inside the conduit than an upstream edge portion of the at least one second outlet;

a baffle which is inclined against the flow direction in the conduit; a baffle extending essentially parallel to an adjoining wall portion of the conduit wall with a closed end close to the downstream end and an open end close to the upstream side of the bend wherein one or more openings are provided for fluid with a high particle concentration to enter a space between the adjoining wall portion and the baffle.

24. The particle trap according to claim 23, wherein the baffle has a clearance to the adjoining wall portion of at most 20%, preferably at most 15%, more preferably at most 10% of a distance of the adjoining wall portion and an opposing wall portion of the conduit.

25. The particle trap according to claim 23 or 24, wherein the baffle has at least one opening which is at least partially transparent for the fluid.

26. The particle trap according to claim 17, wherein at least one first outlet is arranged in a substantially central region of a swirl generated in the fluid.

27. The particle trap according to claim 17, wherein two first outlets are

arranged side by side, each first outlet assigned to a central region of a swirl generated in the fluid.

28. The particle trap according to claim 17, wherein a cross section of the inlet of the conduit has an aspect ratio of a maximum extension of a principal axis divided by an extension of a minor axis perpendicular to the principal axis of not more than 4, preferably not more than 3 and of not less than 1/5, preferably not less than 1/2.

29. An air filter device comprising a particle trap according to any preceding claim.

30. An air supply for an engine comprising a particle trap according to claim 1.

31. An air condition device comprising a particle trap according to claim 1.

32. A vehicle comprising a particle trap according to claim 1.