WO2020126512A1

WO2020126512A1 - Radial compressor inlet recirculation with porous material

Info

Publication number: WO2020126512A1
Application number: PCT/EP2019/083722
Authority: WO
Inventors: Mathias BOGNER
Original assignee: Vitesco Technologies GmbH
Priority date: 2018-12-19
Filing date: 2019-12-04
Publication date: 2020-06-25
Also published as: DE102018222289B3

Abstract

The invention relates to a radial compressor (30) for a charging device (100) of an internal combustion engine and to a corresponding charging device (100) comprising such a radial compressor (30). The radial compressor (30) has a compressor wheel (13) mounted in a compressor housing (31) in a rotatable manner about a compressor axis (2), comprising a compressor wheel inlet plane (14), an air supply channel (35) for supplying the compressor wheel (13) with an air mass flow (LM), and a recirculation device (50) which is arranged in the air supply channel (35) in the region of the compressor wheel inlet plane (14) for stabilizing the compressor characteristic field. The recirculation device (50) is characterized by having a circular arrangement (51) of an air-permeable porous material (52) on the inner circumference of the air supply channel (35). The charging device is designed as a turbocharger or an electric motor-driven compressor.

Description

description

RADIAL COMPRESSOR INLET RECIRCULATION WITH POROUS MATERIAL

The invention relates to a radial compressor for a charging device of an internal combustion engine, which in the air supply channel of the compressor housing

Has device for map stabilization, and a charging device, which as an exhaust gas turbocharger or as an electric compressor with a corresponding

Radial compressor is formed.

Chargers are increasingly used to increase performance

Internal combustion engines, particularly used in motor vehicle internal combustion engines. This is happening more and more frequently with the aim of reducing the size and weight of the internal combustion engine with the same or even increased output, and at the same time reducing consumption and thus C02 emissions, in view of increasingly stringent legal requirements in this regard. The principle of action is to increase the pressure in the intake tract of the internal combustion engine and thus better fill a combustion chamber

To effect internal combustion engine with air-oxygen. This means that more fuel, such as petrol or diesel, can be converted per combustion process, i.e. the performance of the internal combustion engine can be increased.

Frequently, these charging devices have a radial compressor which has a compressor housing and a compressor wheel which is accommodated therein and has a blading and is rotatably mounted about the compressor axis. The

Compressor housing has an air supply duct, which in the direction of

Compressor axis runs towards the axial end of the compressor wheel. An air mass flow is drawn in by the compressor wheel via this air supply duct.

Furthermore, the compressor housing generally has a spiral channel which is arranged in a ring around the compressor wheel and extends in a helical fashion away from the compressor wheel. This spiral channel has a gap opening which extends at least over part of the inner circumference and has a defined gap width, the so-called diffuser, which extends in the radial direction from the outer circumference of the

Compressor wheel directed away into the spiral duct and through which the air mass flow flows away from the compressor wheel under increased pressure into the spiral duct. The radial inner contour of the air supply duct or the compressor housing follows the area between the air supply duct and the diffuser Outer contour of the compressor wheel accommodated in it. This area of the inner contour of the compressor housing is referred to as the compressor sealing contour and causes the air mass flow to flow through the air as completely as possible

Blading of the compressor wheel flows and does not pass it.

A specific example of such a supercharger with a radial compressor is an exhaust gas turbocharger that uses the energy contained in the exhaust gas stream to generate the pressure in the intake tract. For this purpose, the exhaust gas turbocharger has an exhaust gas turbine arranged in the exhaust gas tract of the internal combustion engine, one in the intake tract

arranged radial compressor and an intermediate rotor bearing. The exhaust gas turbine has a turbine housing and a turbine impeller arranged therein and driven by the exhaust gas mass flow. The turbine impeller and the compressor wheel are arranged on the opposite ends of a common shaft, the so-called rotor shaft, in a rotationally fixed manner and thus form the so-called turbocharger rotor, the rotor shaft being rotatably and radially axially supported in the rotor bearing with respect to the rotor shaft axis. According to this construction, the turbine impeller driven by the exhaust gas mass flow drives the compressor wheel via the rotor shaft, as a result of which the pressure in the intake tract of the

Internal combustion engine, based on the fresh air mass flow behind the

Radial compressor, increased and thereby a better filling of the combustion chamber with air-oxygen is effected.

Alternatively, in such a charging device for driving the

Radial compressor instead of an exhaust gas turbine, for example one

electromotive drive unit can be used. Such

Charging device is also referred to as a so-called e-booster, e-charger, electrically driven compressor (EAV) or electric compressor for short. A mechanical coupling to the internal combustion engine, for example via an intermediate gear, can also be used to drive the radial compressor.

The radial compressor is characterized in its operating behavior by a so-called compressor map, which shows the pressure build-up over the mass flow rate for different compressor speeds or peripheral speeds

describes. A stable and usable characteristic map of the radial compressor is limited by the so-called surge limit to low throughputs, by the so-called stuffing limit to higher throughputs, and structurally by the maximum speed limit. When adapting an exhaust gas turbocharger to an internal combustion engine, a radial compressor is also used for the internal combustion engine compressor map selected as cheap as possible. The fulfillment of the

The desired operating parameters often lead to conflicting goals, as these sometimes have opposite effects.

The conflicting goals mentioned could be solved by a compressor design that has a wide map with minimum moment of inertia and maximum

Efficiency on the full load line of the engine.

Various measures known from the prior art are available for expanding or temporarily shifting the compressor map. These exist with restriction to the compressor inlet

Measures, for example, in the use of adjustable blade guiding devices, in variable devices for reducing the inlet cross-section or in the fixed arrangement of recirculation channels, also known as "ported shroud" or "map stabilizing measure".

A recirculation channel, as is known, for example, from DE 10 2008 047 506 A1, is a passive channel, ie one that cannot be changed during operation

Measure that does not require additional actuation. It widens and stabilizes the usable map area of the centrifugal compressor without fundamentally shifting its map and represents a significantly cheaper, if less efficient, solution in comparison to the variable flow control devices and the variable devices for reducing the cross-section, which is nevertheless sufficient in many cases.

Such a recirculation channel consists of an annular one in the region of the air supply channel of the compressor housing, which runs in a ring shape

Compressor wheel inlet arranged and in the direction of the compressor axis over the compressor wheel inlet plane, which is in the area of the inlet edge of the

Impeller blading lies, extending bypass channel, which has a circumferential, so-called recirculation slot and a circumferential, so-called blow-off slot. With respect to the air mass flow, the bypass channel opens via the recirculation slot, upstream of the

Compressor wheel entry level, in the air supply channel and via the blow-off slot is the bypass channel with an area of the air supply channel, downstream of the compressor wheel entry level, that is, already in the area of the sealing contour of the

Air supply channel or in the area of the blading of the compressor wheel, connected. When the compressor is operating near the surge limit, air can flow back from the area of the sealing contour via the recirculation channel into the air supply channel upstream of the compressor wheel entry level. As a result, the effective mass flow at the compressor wheel inlet increases, the flow to the blades improves and the compressor flow stabilizes.

When the compressor is operating at the best point, i.e. in the middle of the compressor map, no air flows through the recirculation channel. During compressor operation at the stuffing limit, the compressor wheel sucks additional air through the

Recirculation duct from the air supply duct upstream of the

Compressor wheel entry level in the area of the sealing contour. As a result, the so-called “throat area” at the compressor wheel inlet is covered by part of the

Bypassed air mass flow and the maximum mass flow through the

Compressor rises. The proportion of the air mass flow that flows through the recirculation channel in operation, no matter in which direction, is also referred to as

Recirculated air mass flow.

The recirculation channel is constructed externally through the wall of the

Air supply duct of the compressor housing is limited and usually internally by an annular or tubular wall, which is supported or connected to the wall of the air supply duct via radial webs. The webs can be streamlined in order not to negatively influence the recirculating flow or even to specifically influence the swirl angle of the flow. Along with the arrangement of recirculation slot and

Exhaust slot results in a complex internal geometry of the

Compressor housing, the production of which usually causes a not inconsiderable additional effort.

The present invention is therefore based on the object

Specify radial compressor and a charging device for an internal combustion engine, which a map-stabilizing device like a

Show recirculation channel, but, compared to existing solutions, are structurally simpler and less expensive to implement.

This object is achieved by a radial compressor and a charging device with the features according to the independent claims

solved. Advantageous training and further education, which individually or in combination can be used together, provided they are not mutually exclusive

exclude are the subject of the dependent claims.

According to the invention, a radial compressor is specified for a supercharging device of an internal combustion engine, the radial compressor having at least the following components:

- A compressor wheel mounted in a compressor housing, rotatable about a compressor axis, with a compressor wheel inlet cross section arranged perpendicular to the compressor axis and lying in a compressor wheel inlet plane, the compressor wheel inlet plane being the plane perpendicular to the compressor wheel axis, in which the radially outer regions of the inlet edges of the blading of the compressor wheel lie ;

- An air supply channel for loading the compressor wheel with one

Air mass flow in the direction of the compressor axis, which has an inner circumference and adjoins the compressor wheel on the compressor housing in relation to the air mass flow upstream, the above-mentioned compressor wheel inlet cross section being provided, through the projection area of the compressor wheel circumference in the region of the radially outer ends of the inlet edges of the blading the compressor wheel on the compressor wheel inlet plane; and

- A recirculation device arranged in the air supply duct in the area of the compressor wheel inlet plane.

The recirculation device according to the invention is characterized in that it has a material arrangement of an air-permeable, porous material that runs around the inside of the air supply channel and extends in the direction of flow of the air mass flow (LM) from an area upstream to an area downstream of the compressor wheel inlet plane.

The charging device according to the invention for an internal combustion engine is characterized in that the charging device as an exhaust gas turbocharger with an exhaust gas turbine as a drive unit or as an electric compressor with a

Electric motor motor is designed as a drive unit, which has a radial compressor with at least the features according to the aforementioned configuration and, if appropriate, further features of the embodiments described below

Has radial compressor.

The embodiment of the recirculation channel according to the invention has particular advantages with regard to the manufacture and assembly of the components required for the design. This can be done on the inner circumference of the air supply duct Circumferential material arrangement of an air-permeable, porous material as a simple sleeve or tubular component made of an air-permeable, porous material separately and inserted into the air supply channel. A simple press, adhesive or welded connection is available for fixation. Furthermore, there are advantages due to the simple design of the

Compressor housing in the area of the air supply duct, since, for example, no complex casting cores for designing the cavities in the duct wall and no complicated reworking are required. There are also advantages in terms of acoustics, since there is no need for webs, ribs, blades, etc., which may be required for support at the edge of the channel and which, in conjunction with the air flow, can cause noise.

Advantageous refinements and developments of the invention are disclosed in the subclaims and are explained below with reference to the figures.

A selection of exemplary embodiments of the invention and various possible combinations of features of different designs, according to the claims, are explained in more detail below with reference to the illustrations in the drawing.

Show it:

Fig. 1 An inventive design of a radial compressor in

simplified representation of an axial quarter section;

FIGS. 2 to 4, further designs of radial compressors according to the invention in the same representation as FIG. 1; such as

5 shows two representations of possible structures of a porous, air-permeable

Materials and

Fig. 6 is an illustration of a charging device according to the invention.

Parts with the same function and designation are identified in the figures with the same reference symbols.

FIG. 1 shows a radial compressor 30 in schematically simplified

Sectional view, in a quarter section, cut along the

Compressor axis 2.

The radial compressor 30 shown has a compressor housing 31 and a compressor wheel 13, which is accommodated therein and is rotatably mounted about the compressor axis 2 by means of a rotor shaft 10 and has a compressor blading 131. The compressor wheel 13 has a compressor wheel inlet cross section 15, which is arranged perpendicular to the compressor axis 2 and lies in a compressor wheel inlet plane 14 and characterizes the compressor wheel inlet 16. The compressor wheel inlet plane 14 is the plane lying perpendicular to the compressor wheel axis 2, in which the radially outer regions or the outer corners of the inlet edges 132 of the compressor blades 131 of the compressor wheel 13 lie.

The compressor housing has an air supply duct 35 with an intake manifold connecting piece 37, the air supply duct 35 having an inner circumference 35a and in the direction of the compressor axis 2 towards the axial end of the

Compressor wheel 13 runs and connects upstream of the compressor housing 31 with respect to the air mass flow (LM) to the compressor wheel (13).

Furthermore, the compressor housing 31 generally has a spiral channel 32 which is arranged in a ring around the compressor wheel 13 and widens away from the compressor wheel 13 in a helical manner. This spiral channel 32 has an at least part of its inner circumference running annular channel opening with a defined channel width, the so-called diffuser 33, which in the radial direction from

The outer periphery of the compressor wheel 13 extends away into the spiral channel 32 and through which the air mass flow LM flows away from the compressor wheel 13 under increased pressure into the spiral channel 32. Over the area between

Air supply channel 35 and diffuser 33 away, the radial inner contour of the air supply channel 35 and the compressor housing 31 follows the outer contour of the compressor wheel 13 received therein. This area of the inner contour of the

Compressor housing 31 is referred to as a compressor sealing contour 34 and causes the air mass flow LM to flow as completely as possible through the compressor blades 13a of the compressor wheel 13 and not past it.

The compressor housing 31 is on its back facing away from the air supply duct 35 (on the right in the illustration in FIG. 1) with a compressor housing rear wall 31 a, which can at the same time be part of a connected bearing or drive housing.

An air mass flow LM is sucked in by the compressor wheel 13 via the air supply channel 35, which flows from the air supply channel 35 via the compressor wheel inlet 16, through the compressor blading 13a and the diffuser 33 into the spiral channel 32 and is thereby compressed to a higher pressure. In the air supply channel 35, a recirculation device 50 is arranged in the area and upstream of the compressor wheel entry plane 14 of the compressor wheel 13 or in the area of the compressor wheel inlet 16. The recirculation device 50 is characterized in that it comprises a material arrangement 51 which runs in a ring on the inner circumference 35a of the air supply channel 35

has air-permeable, porous material 52, which extends in the flow direction of the air mass flow LM from an area upstream to an area downstream of the compressor wheel inlet plane 14.

When viewed in isolation from the compressor housing 31, the material arrangement 51 represents a simple sleeve-shaped or tubular component which can be prefabricated in this form and inserted into the air supply duct.

In the embodiment shown in FIG. 1, the radial compressor 30 is further characterized in that the recirculation device 50 is a clear one

Tube inner cross section 50a is formed, which corresponds to the compressor wheel inlet cross section 15. As a result, the cross-sectional area of the

Compressor wheel inlet cross section 15 and the air mass flow LM flowing through it are not restricted and the entire compressor wheel inlet cross section 15 is flowed evenly by the sucked air mass, which has a positive effect on the swallowing capacity of the compressor wheel 13.

1 that this embodiment of the radial compressor 30 is characterized in that the inner circumference 35a of the air supply duct 35 corresponds to the outer circumference 50b of the recirculation device 50. It is thereby achieved that the assembly of the material arrangement 51 can be carried out in a simple manner by pushing it into the air supply duct 35.

2 shows a further embodiment of the invention

Radial compressor 30, in a representation analogous to FIG. 1, which thereby

is characterized in that, to form a blow-off slot 54 in the area, in the flow direction of the air mass flow LM behind the compressor wheel step 14, between the material arrangement 51 of the porous material 52 and an air gap 54a is formed in a connection shoulder 38 of the compressor housing 31. This can be achieved, for example, in that a preformed tubular component made of the porous, air-permeable material 52 is not inserted into the air supply channel 35 as far as the stop on the connection shoulder 38, but is already fixed in a position in front of it, so that the said one Air gap is formed. This enables a targeted introduction or

Discharging the recirculation air mass flow through the porous material 52 thus increases the throughput and improves the effectiveness of the map-stabilizing measure.

A further embodiment of the radial compressor 30 according to the invention is shown in FIG. 3, in a representation analogous to FIG. 1 and FIG. 2. The one shown

Radial compressor 30 is a further development of the aforementioned

Embodiments characterized in that the material arrangement 51 of the air-permeable, porous material 52 radially inwards, that is to say

Compressor axis 2 out, is delimited by a tube wall 58, which consists of a non-porous material, here a clear tube inner cross section 50a is formed by the tube wall 58, which corresponds to the compressor wheel inlet cross section 15. The tube wall 58 can be designed, for example, as a tube sleeve made of sheet metal, which is connected to the porous material 52, for example by an interference fit, an adhesive connection or also by direct pressing or foaming of the porous material onto the sheet metal sleeve as a support component. It is also within the scope of the invention if the tube wall 58 is formed by the porous material itself, a closed skin being formed, for example, in the edge region of the porous material in the manufacturing process, as is the case with various foamed materials.

The tube wall 58 initially has a stabilizing effect for the tubular component consisting of the porous material 52 and brings about a flow of the recirculation air mass flow through the porous material 52 which is better directed in the axial direction by an air outlet from the porous material 52 into the Air intake duct 35, in the radial direction and possibly over a larger part of the axial component extension, is prevented.

A further development of the previously described embodiment of the radial compressor 30 is characterized in that the tube wall 58 is carried solely by the porous material 52. A component consisting of the porous material 52 and the tube wall 58 can be designed as a composite component, in which the tube wall 58 and the porous material 52 are firmly connected to one another. In such an embodiment, there is no need for fastening webs for fastening or supporting the tube wall 58 on the compressor housing 31. This results in a structurally simplified structure and at the same time one

Low-loss flow through the formed by the porous material 52

Recirculation channel.

A further development of the radial compressor 30 with tube wall 58 on the inside, as can be seen in FIG. 3, as previously described with reference to FIG. 3, is characterized in that the tube wall 58, in order to form a blow-off slot 54, in the area , in the flow direction of the air mass flow LM downstream, ie behind the compressor wheel inlet plane 14, is shortened compared to the porous material arrangement or at least has a recess. In addition to the axially guided flow of the recirculation air mass flow carried in the recirculation device 50, this results in a locally defined inflow or outflow of the recirculation air mass flow into or out of the recirculation device 50.

A further development of the radial compressor 30 with tube wall 58 on the inside, as can be seen in FIG. 3, as previously described with reference to FIG. 3, is characterized in that the tube wall 58, in order to form a recirculation slot 56, in one facing away from the compressor wheel 13

End region, an axial end face of the material arrangement 51 of the porous material 52 not or not completely limited. In the example shown in FIG. 3, the axial end face is only partially, ie not completely, covered by the tube wall 58. On the other hand, an embodiment of the radial compressor is shown in FIG. 4, in which to form a recirculation slot 56, in an end region of the recirculation device 50 facing away from the compressor wheel 13, the tube wall 58 into an axial region of the inner circumference of the porous material arrangement 51 over the inner circumference has circumferential recess 56a

The formation of a recirculation slot 56 in the end region of the recirculation device 50 facing away from the compressor wheel 13 also results in addition to the axially guided flow of the flow in the recirculation device 50

Recirculation air mass flow, a locally defined inflow or

Outflow of the recirculation air mass flow into or out of

Recirculation device 50 and brings about a further improvement in the flow-stabilizing effect.

In a further embodiment of the embodiments described above, a further embodiment of the radial compressor 30 according to the invention is characterized in that the air-permeable, porous material 52 has anisotropic properties with respect to its air-permeability, such that the

Air permeability is only given in the direction of the compressor axis 2 or is at least greater in the direction of the compressor axis 2 than in the circumferential direction of the rotating material arrangement 51. This is the case, for example, if the air-permeable porous material 52 has a honeycomb structure 60 with in

Honeycomb channels 60a which run in the axial direction and are open at the end. This results in an axially directed flow of the recirculation air mass flow and an improved stabilization of the compressor map.

In a further development of the aforementioned embodiments of the invention

Radial compressor 30 has an air-permeable, porous material 52

Sintered structure, a honeycomb structure 60, a wire mesh structure or an open-pore foam structure 62, the foam structure 62 being a

Foamed metallic material, such as an aluminum foam, or a thermoplastic or thermosetting plastic foam. All of these structures are shown in FIGS. 1 to 4 by the cross hatching Material arrangement 51 symbolizes. 5 shows a honeycomb structure 60 with open honeycomb channels 60a (view a)) and an open-pore one

Foam structure 62 (view b)) shown. Materials in the above

Structures are readily available on the market and can be formed into preformed workpieces. This enables a structurally simple and inexpensive design.

Finally, FIG. 6 shows, highly schematized, a supercharging device 100 for an internal combustion engine (not shown), which is characterized in that the supercharging device 100 as an exhaust gas turbocharger with an exhaust gas turbine 22

Drive unit 20 or as an electric compressor with an electric motor 23 as drive unit 20, which has a radial compressor 30, the radial compressor 30 having the features of one of the embodiments according to the invention described above. The basic structure of a radial compressor 30 according to the invention with a compressor housing 31 and a compressor wheel 13, as well as a recirculation device 50 with a

Material arrangement 51 of an air-permeable, porous material 52 in

Air supply channel 35, which extends in the flow direction of the air mass flow LM from an area upstream to an area downstream of the

Compressor wheel entry plane 14 extends. A drive unit 20 is connected via the compressor housing rear wall 31 a. The drive unit 20 generally has a bearing unit 21 for the rotor shaft 10, which is only indicated here. Furthermore, the drive unit 20 optionally has an exhaust gas turbine 22 or an electric motor 23, also only shown here, which are connected to the rotor shaft and via this the compressor wheel 13 of the

Drive the radial compressor 30.

In summary, a radial compressor 30 for a supercharging device 100 of an internal combustion engine and a corresponding one

Charging device 100 described with such a radial compressor 30. The radial compressor 30 has a compressor wheel 13 rotatably mounted in a compressor housing 31 about a compressor axis 2, with a compressor wheel inlet plane 14, an air supply channel 35 for supplying the compressor wheel 13 with an air mass flow LM and one in the air supply channel 35 in the area of the ver - Dichterradeinschlußebene 14 arranged recirculation device 50, for

Stabilization of the compressor map, on. The recirculation device 50 is characterized in that it has an annular shape on the inner circumference of the

Air supply channel 35 surrounding material arrangement 51 of an air-permeable, porous material 52. The charging device is designed as an exhaust gas turbocharger or as an electric motor-driven compressor.

Claims

1. Radial compressor (30) for a charging device (100)

Internal combustion engine, the radial compressor (30) having at least the following components:

- A compressor wheel (13) rotatably mounted in a compressor housing (31) about a compressor axis (2), with a compressor wheel (13) arranged perpendicular to the compressor axis (2) and lying in a compressor wheel entry plane (14)

Compressor wheel inlet cross section (15);

- An air supply channel (35) for loading the compressor wheel (13) with an air mass flow (LM) in the direction of the compressor axis (2), which has an inner circumference (35a) and on the compressor housing (31), in relation to the air mass flow (LM ) upstream, connects to the compressor wheel (13); and

- One in the air supply channel (35) in the area and upstream of the

Compressor wheel inlet plane (14) of the compressor wheel (13) arranged recirculation device (50),

wherein the recirculation device (50) is characterized in that it has an annular arrangement of material (51) of an air-permeable, porous material (52) which runs around the inner circumference of the air supply channel (35) and which extends from a region in the flow direction of the air mass flow (LM) upstream to a region downstream of the

Compressor wheel inlet plane (14) extends.

2. Radial compressor (30) according to claim 1, characterized in that by means of the recirculation device (50) a clear tube inner cross section (50a) is formed, which corresponds to the compressor wheel inlet cross section (15).

3. Radial compressor (30) according to claim 1, characterized in that the inner circumference (35a) of the air supply channel (35) corresponds to an outer circumference (50b) of the recirculation device (50).

4. Radial compressor (30) according to one of the preceding claims, characterized in that, to form a blow-off slot (54), in the region in the flow direction behind the compressor wheel inlet plane (14), between the material arrangement (51) of the air-permeable, porous material (52) and a connecting shoulder (38) of the compressor housing (31) is formed with an air gap (54a).

5. Radial compressor (30) according to any one of the preceding claims, characterized in that the material arrangement (51) of the air-permeable, porous material (52) is limited radially inwardly by a tube wall (58) made of a non-porous material (52) exists.

6. Radial compressor (30) according to claim 4, characterized in that the tube wall (58) is carried solely by the air-permeable, porous material (52).

7. Radial compressor (30), according to claim 4 or 5, characterized in that the tube wall (58), to form a blow-off slot (54), in

Area in the flow direction behind the compressor wheel inlet plane (14), in relation to the material arrangement (51) is shortened or at least has a recess.

8. Radial compressor (5) according to one of claims 4 to 6, characterized

characterized that the tube wall, to form a

Recirculation slot (56), in an end region facing away from the compressor wheel (13), an axial end face and / or a region of the inner circumference of the material arrangement (51) not or not completely limited or at least in an axial region of the inner circumference of the porous

Material arrangement (51) has a recess (56a) running around the inner circumference.

9. Radial compressor (30) according to any one of the preceding claims, characterized in that the air-permeable, porous material (52) has anisotropic properties with respect to its air permeability, such that the Air permeability is only given in the direction of the compressor axis (2) or at least in the direction of the compressor axis (2) is greater than in

Circumferential direction of the circulating material arrangement (51).

10. Radial compressor (30) according to one of the preceding claims, characterized in that the air-permeable, porous material (52) a

Sintered structure, a honeycomb structure (60), a wire mesh structure or an open-pore foam structure (62).

11. Charging device (100) for an internal combustion engine, thereby

characterized in that the charging device (100) is designed as an exhaust gas turbocharger with an exhaust gas turbine (22) as a drive unit (20) or as an electric compressor with an electric motor motor (23) as a drive unit (20), which has a radial compressor (30) with at least the features one of the preceding claims.