EP2181268B1 - Radial compressor with a diffuser for use in a turbocharger - Google Patents

Description

The invention relates to a centrifugal compressor with a diffuser which is used for example in an exhaust gas turbocharger for a motor vehicle.

Turbochargers generally consist of an exhaust gas turbine in an exhaust gas flow, which is connected via a turbo shaft with a compressor in the intake tract. For this purpose, for example, a turbine wheel and a compressor wheel are rotatably mounted on the turbo shaft, wherein the turbine wheel is arranged in a turbine housing and the compressor wheel in a compressor housing with a diffuser. In operation, the exhaust gas flow passing through the turbine housing drives the turbine wheel. The turbine wheel in turn drives the compressor wheel, causing the compressor to increase the pressure in the intake tract of the engine, so that a larger amount of air enters the cylinder during the intake stroke. This means that more oxygen is available and a correspondingly larger amount of fuel can be burned. As a result, the power output of the engine can be increased.

Decisive for the noise emission of the turbocharger here is the compressor. In particular, the compressor discharge radiates a lot of noise to the outside.

Radial compressors for exhaust gas turbochargers are known from the prior art, which have a diffuser, which converts the built-up speed in pressure. Such a diffuser ends in a so-called spiral which discharges the compressed air to the consumer. The geometry of the transition of the spiral, ie the so-called tongue, is in this case a critical embodiment element, since pressure pulsations often arise at this point. According to the prior art, the problem of the formation of such pressure pulsations has hitherto been fluidic favorable shape of the tongue with a constant diffuser diameter or radius solved.

Such a radial compressor is for example off US 2005/232762 A1 known. Disclosed is a compressor housing that achieves a reduced weight and reduced number of parts with the task of maximizing performance while still withstanding the high operating stresses imposed by the pressure and external structural loadings. For this purpose, an arrangement of guide vanes, which are formed integrated on the screw housing wall are proposed, on the one hand direct the flow of fluid and on the other hand support the housing stabilizing.

Furthermore, from the document DE 318 837 C a two-part diffuser for a centrifugal fan with increasing in the direction of rotation radial height is known in which the straight walls of the inner diffuser diverge outwards. As a result, a uniform over the cross section of the exhaust opening outflow velocity of the air flow is achieved.

In order to reduce the intake noise or in the case of large noise pollution, upstream silencers are frequently used. These silencers may have channel-like or backdrop-like elements, which in turn are lined, for example, with sound-absorbing material. In addition to such absorption mufflers, it is also possible to use acoustic resonators and acoustic filters for soundproofing.

However, such mufflers have the disadvantage that they require additional space. Furthermore, the production and installation of the muffler are costly and associated with considerable effort.

Accordingly, it is the object of the present invention to provide a centrifugal compressor with a diffuser and a turbocharger with a centrifugal compressor, designed in such a way are that the occurrence of pressure pulsations can at least be reduced or substantially prevented.

This object is achieved by a centrifugal compressor and a turbocharger with the features of the respective independent claim.

• einem Spiralgehäuse und
• einem Diffusor,

wobei der Diffusor derart ausgebildet ist, dass ein Unterdruckgebiet im Bereich des Übergangs des Spiralgehäuses, also im Bereich der Zunge zumindest reduziert ist. Dazu ist der Querschnitt des Diffusors (12) im Bereich der Zunge (20), derart variiert, dass die Bildung eines Unterdruckgebiets in diesem Bereich zumindest reduziert ist. Dazu weist der Diffusor im Bereich der Zunge eine größere Breite auf und der Radius des Diffusors ist im Bereich der Zunge derart vergrößert, dass er eine Auswölbung nach Art eines Ovals aufweist.Accordingly, according to the invention a radial compressor, in particular for a turbocharger and a turbocharger with such a radial compressor, provided, wherein the radial compressor is designed with:

• a spiral housing and
• a diffuser,

wherein the diffuser is designed such that a negative pressure area in the region of the transition of the spiral housing, ie in the region of the tongue is at least reduced. For this purpose, the cross section of the diffuser (12) in the region of the tongue (20) is varied in such a way that the formation of a negative pressure region in this region is at least reduced. For this purpose, the diffuser in the region of the tongue has a greater width and the radius of the diffuser is increased in the region of the tongue such that it has a bulge in the manner of an oval.

Characterized that the diffuser in the region of the transition of the spiral housing, ie in the region of the tongue has a larger or larger width and such an increased radius that it has a bulge in the manner of an oval, the formation of a negative pressure area is prevented or at least reduced , so that disturbing pulsations can be contained and thus the occurrence of corresponding noise.

The radial compressor has the advantage that disturbing pressure pulsations can be prevented by reducing or suppressing a negative pressure area, which arises above all in the region of the transition of the spiral housing in the diffuser. As a result, for example, the use of additional silencers at least partially or completely be waived. This results in a significant saving in terms of manufacturing and assembly costs. Furthermore, a more compact design can be achieved, for example, when used in a turbocharger. This has the further advantage that the cross-section of a diffuser can be relatively easily adapted or changed and is therefore less expensive and requires no additional space compared to the use of mufflers in the prior art.

Advantageous embodiments and modifications of the invention will become apparent from the dependent claims and the description with reference to the drawings.

In the embodiment according to the invention, the cross section of the diffuser is varied by increasing the width and the radius or the diameter of the diffuser in the region of the transition of the spiral housing, ie in the region of the tongue. This has the advantage that the diffuser can thereby produce a further delay of the gas velocity and thus a larger pressure build-up. The larger pressure build-up allows a discharge substantially without or at least with a reduced pulsation. The region of the diffuser with the enlarged diameter or radius can be designed in the form of a bulge outwards or in the form of an oval.

In a further embodiment according to the invention, to increase the width of the diffuser, at least one wall or both opposing walls of the diffuser are outwardly inclined and / or arched. The respective wall can form a wedge shape, whereby the wedge shape increases towards the outside. The walls can be identical or different in shape, inclination and / or curvature. This has the advantage that, depending on the function and intended use, the width of the diffuser can be easily achieved in at least one area by adapting both walls or even just one wall.

Fig. 1

eine stark vereinfachte, schematische Schnittansicht eines Radialverdichters und seines Diffusors gemäß dem Stand der Technik;

Fig. 2

eine stark vereinfachte Schnittansicht durch das Verdichterrad und einen Diffusor gemäß Fig. 1;

Fig. 3

eine stark vereinfachte, schematische Schnittansicht eines Radialverdichters und seines Diffusors bei dem der Radius bzw. der Durchmesser des Diffusors im Bereich der Zunge vergrößert ist;

Fig. 4

eine stark vereinfachte Schnittansicht durch das Verdichterrad und einen Diffusor gemäß Fig. 3;

Fig. 5

eine stark vereinfachte, schematische Schnittansicht eines Radialverdichters und seines Diffusors, zur Erläuterung eines Teilaspekts der Erfindung; und

Fig. 6

eine stark vereinfachte Schnittansicht durch das Verdichterrad und einen Diffusor gemäß Fig. 5.

The invention will be explained in more detail with reference to the exemplary embodiments indicated in the schematic figures of the drawings. Show it:

Fig. 1

a highly simplified, schematic sectional view of a radial compressor and its diffuser according to the prior art;

Fig. 2

a greatly simplified sectional view through the compressor wheel and a diffuser according to Fig. 1 ;

Fig. 3

a greatly simplified, schematic sectional view of a radial compressor and its diffuser in which the radius and the diameter of the diffuser in the region of the tongue is increased;

Fig. 4

a greatly simplified sectional view through the compressor wheel and a diffuser according to Fig. 3 ;

Fig. 5

a highly simplified, schematic sectional view of a centrifugal compressor and its diffuser, for explaining a partial aspect of the invention; and

Fig. 6

a greatly simplified sectional view through the compressor wheel and a diffuser according to Fig. 5 ,

In all figures, identical or functionally identical elements and devices are - unless otherwise indicated - marked with the same reference numerals.

In Fig. 1 a radial compressor 10 is shown with a diffuser 12 according to the prior art, which is part of a turbocharger (not shown). The radial compressor 10 is shown simplified from the front in a sectional view.

The radial compressor 10 in this case has a volute casing 14 and the diffuser 12. The radius r1 or the diameter of the diffuser 12 is constant. Furthermore, the width b1 of the diffuser 12 is constant as in the following Fig. 2 is shown. The diffuser 12 therefore has a substantially constant cross section.

In the housing of the radial compressor 10, a turbo shaft 16 is arranged, on which a compressor wheel 18 is provided. The compressor wheel 18 is driven via a corresponding turbine wheel (not shown) on the turbo shaft 16. In operation, 18 air is sucked axially by the speed of the compressor wheel and accelerated in the compressor 18 to high speeds. The air leaves the compressor wheel 18 while in the radial direction.

In the diffuser 12, the velocity of the air is reduced. The consequence of this is that pressure and temperature increase. The diffuser 12 is formed, for example, from a compressor rear wall and a part of the spiral housing 14. In the volute 14, the air is collected and the speed up to the compressor outlet further reduced. In this case, the geometry of the transition of the spiral 13 of the volute 14, ie the so-called. Tongue 20, forms a critical execution element, since at this point often pressure pulsations arise because here can form a negative pressure area. As previously stated, therefore, among the radial compressors 10 according to the prior art, inter alia, mufflers (not shown) are provided to prevent or at least reduce disturbing noises as a result of such pressure pulsations.

In Fig. 2 is a sectional view through the diffuser 12 and the compressor 18 according to Fig. 1 shown. The width b1 of the diffuser 12 is kept substantially constant.

Furthermore, in Fig. 3 now a radial compressor 10 is shown, which is part of a turbocharger (not shown). The radial compressor 10 also has a volute casing 14 and a diffuser 12. On a turbo shaft 16 is, as previously with reference to Fig. 1 a compressor wheel 18 and, for example, a turbine wheel (not shown). In this case, the diffuser 12 converts the built-up speed of the air sucked in via the compressor wheel 18 into pressure. The diffuser 12 terminates in the spiral 13 of the spiral housing 14, which discharges the compressed air to the consumer.

To counteract pressure pulsations that arise in the region of the transition of the spiral 13, the so-called tongue 20, the cross section of the diffuser 12 is changed here. In other words, the cross section of the diffuser 12 is varied and is therefore not constant, in contrast to the previously indicated prior art. For this purpose, the radius r or the diameter of the diffuser 12 is designed or changed as follows. The radius r or the diameter of the diffuser 12 is designed such that the formation of a negative pressure area is reduced or substantially no negative pressure area in the region of the tongue 20, ie in the region of the Transition of the spiral, arises. This is achieved, for example, by increasing the radius r or the diameter of the diffuser 12 in at least one predetermined area, in order to reduce or substantially prevent the formation of a negative pressure area. A radius r2 of the diffuser is therefore chosen to be larger in the region of the tongue 20 than a radius r1 of the diffuser 12 outside this range.

It has been found that, for example, it is also advantageous to use a constant width r and / or diameter in a diffuser 12 having a constant width, as is the case in the previously shown example. Instead, it proves to be advantageous if the diffuser 12 is varied in its diameter or radius r. This means that the diffuser 12 has a slightly larger diameter or radius r 2 in at least one region, for example in a region of the transition of the spiral 13.

This increased diameter or radius r2 of the diffuser 12 produces a further delay of the gas velocity and a larger pressure build-up, which allows a discharge substantially without or at least with a reduced pulsation. This has the consequence that an undesirable noise can be counteracted, so that no additional sound-absorbing elements must be installed, which lead to additional costs and installation costs.

For this purpose, as already mentioned above, the diffuser 12, as in Fig. 3 is shown, for example, in the region of the tongue 20 and the transition of the spiral 13 are carried out with a larger radius r2 or larger diameter. In this case, the diffuser 12 is formed, for example, in the region of the tongue 20 with a curvature 30 to the outside or forms an oval in this area. The representation in Fig. 3 is greatly simplified.

In Fig. 4 is further a sectional view through the compressor wheel 18 and the diffuser 12 according to Fig. 3 shown. The diffuser 12 has a substantially constant width b1.

In Fig. 5 Now another embodiment of the radial compressor 10 is shown. The radial compressor 10 has a constant diameter or radius r1. In order to vary the cross section of the diffuser 12 accordingly, the width b of the diffuser 12 is changed here.

According to the invention, in addition to the increased radius r2, the width b of the diffuser 12 is varied in at least one range in order to counteract the previously described pressure pulsations which occur, for example, in the region of the transition of the spiral 13. The width b of the diffuser 12 is here, for example, increased, as in Fig. 6 is shown. The width b1 is increased in the illustrated area to a width b2. For this purpose, a first wall 22 of the diffuser 12 is formed in this area, for example, slightly inclined by an angle γ outwards. Alternatively, however, the first wall 22 can also be curved, for example. In principle, however, an opposite second wall 24 of the diffuser 12 can be adjusted accordingly.

In this case, the width b of the diffuser 12 in the region of the transition of the spiral 13 or in the region of the tongue 20 is varied or increased to a width b 2 in order to counteract the formation of a negative pressure region in this region. The diffuser 12 may in this case have a type of depression 26 in the form of a wedge 28, as in FIG Fig. 5 is shown in a front sectional view and in Fig. 6 in a side sectional view. The wedge 28 expands outward, for example, in the direction of the tongue 20.

Although the present invention has been described above with reference to the preferred embodiment, it is not limited thereto, but modifiable in many ways. The embodiments described above can be combined with each other, in particular individual features thereof, the scope of the invention being defined by the appended claims.

In this case, at least one region or a plurality of regions of the diffuser 12 is varied with respect to its width b. In this case, the regions are selected, for example, from the point of view where undesired pressure pulsations arise in order to adapt the selected regions in such a way that in each case no or at most a small negative pressure region is created in order to counteract these pressure pulsations.

In addition, a diffuser 12 according to the invention additionally has a varied diameter or radius r in each of the at least one region, as described with reference to FIGS 3 and 4 previously described in detail. In other words, the cross section of the diffuser 12 is varied over the width b and the diameter or radius r.

Furthermore, in this case at least the first and / or second wall 22, 24 of the diffuser 12 can be outwardly inclined and / or arched in order to increase the width b of the diffuser 12. The two walls 22, 24 may be identical or differently shaped, i. for example, with different inclinations or vaults. The walls 22, 24 may also have different shapes in this area. Thus, one wall 22, 24 inclined and the other wall 22, 24 may be curved, depending on the function and purpose.

Claims (6)

1. Radial compressor (10), in particular for a turbocharger, comprising

   - a spiral housing (14) and

   - a diffuser (12), the cross section of the diffuser (12) in the region of the transition of the spiral housing (14), therefore in the region of the tongue (20), being varied in such a way that the formation of a negative pressure area in this region is at least reduced, characterized

   in that the diffuser (12) has a greater width (b) in the region of the tongue (20), and
   in that the radius (r) of the diffuser (12) in the region of the tongue (20) is enlarged in such a way that it has a bulge (30) in the manner of an oval.
2. Radial compressor according to Claim 1,
   characterized in that
   at least one wall (22, 24) or both opposite walls (22, 24) of the diffuser (12) is/are inclined and/or curved outwards.
3. Radial compressor according to Claim 2,
   characterized in that
   the walls (22, 24) are formed identically or differently with regard to their shape, inclination and/or curvature.
4. Radial compressor according to either of Claims 2 and 3,
   characterized in that
   the respective wall (22, 24) forms a wedge shape.
5. Radial compressor according to Claim 4,
   characterized in that
   the wedge shape enlarges outwards.
6. Turbocharger having a radial compressor (10) according to at least one of Claims 1 to 5.

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