EP3008292B1 - Turbocharger with a radial/axial turbine wheel - Google Patents

Description

The invention relates to an exhaust gas turbocharger having a radial-axial turbine wheel.

From the DE 10 2009 056 632 A1 An exhaust gas turbocharger is known, which contains such a radial-axial turbine wheel. In this known exhaust gas turbocharger, the turbine housing has a guide element which forms at least part of the rear wall of an inclined or obliquely formed spiral.

Furthermore, the document discloses WO 2005/119030 A1 an exhaust gas turbine with a turbine housing and arranged in the turbine housing turbine wheel, wherein the turbine wheel has a hub. The turbine housing with a gas inlet-side housing part to the left of the turbine wheel and the gas outlet side housing part together with the hub of the turbine wheel forms a flow channel in which flow through hot exhaust gases during operation of the exhaust gas turbocharger. In this case, a cooling channel for cooling the hub of the turbine wheel in the turbine housing is arranged opposite a rear wall of the hub of the turbine wheel facing away from the flow channel.

The FIG. 1 shows a sectional view of this known exhaust gas turbocharger. In this sectional view, the inflow direction and the outflow direction of the exhaust gas with an arrow are shown schematically and greatly simplified. The known exhaust gas turbocharger 1 has a turbine housing 10 with a spiral 16. Within the turbine housing 10, a radial-axial turbine wheel 12 is disposed on a shaft 30. The shaft 30 is mounted in a bearing housing 20. Furthermore, a guide element 24 is provided, which is a heat shield. This is designed such that it forms a rear wall 26 or a portion 28 of the rear wall of the spiral 16, wherein the part the rear wall or the rear wall is inclined at an inclination angle β in the direction of the bearing housing. The region of the guide element 24, which is formed as a rear wall 26 or as part of the rear wall of the spiral 16 or of the turbine housing 10, forms a substantially seamless transition with the spiral 16 or the turbine housing 10, so that the flow guidance of the exhaust gas is so little is affected as much as possible. The guide element 24 may be pushed or plugged in an end region 32 on a shoulder 34 of the bearing housing. Furthermore, the known exhaust-gas turbocharger has a tongue element 14, which is preferably pulled close to the leading edge 18 of the turbine wheel 12, so that the distance a between the tongue element 14 and the leading edge 18 of the turbine wheel 12 is small. By using the described guide element 24 as a flow-guiding component of the turbine housing, the axial space of the turbine housing can be made compact. Due to the small distance from the tongue element 14 to the leading edge 18 of the turbine wheel 10 and the preferably parallel or substantially parallel arrangement of tongue angle and Radeintrittskante the efficiency of the exhaust gas turbocharger is increased.

The heat shield 24 of the exhaust gas turbocharger described above is usually made of sheet metal. This has the disadvantage that the heat shield is additionally subject to deformation during installation due to pressure influences and during operation of the exhaust gas turbocharger due to thermal influences. These can adversely affect the flow of the turbine wheel and thus its thermodynamics. Furthermore, due to these deformations, an undesired collision of the heat shield with the turbine wheel may occur. Furthermore, thermomechanical disadvantages with respect to the functionality and the service life of the exhaust-gas turbocharger occur as a result of the aforementioned deformations. Due to the manufacturing process, a corner radius, which negatively influences the flow of the turbine wheel and thus the thermodynamics of the exhaust-gas turbocharger, arises at the point of the heat shield closest to the turbine wheel back, since the exhaust gas flow does not detach or break cleanly. Furthermore, it comes in practice to an undesirable flow through the cavity between the back of the turbine wheel and the heat shield, which is also associated with losses. Furthermore, due to the temperature-related deformations of the heat shield occurring during operation, a comparatively large wheel back space must be provided. This also leads to a strong and unfavorable flow with hot exhaust gas during operation.

The object of the invention is to provide an equipped with a radial-axial turbine exhaust gas turbocharger, in which the disadvantages mentioned above do not occur.

This object is achieved by an exhaust gas turbocharger with the features specified in claim 1. Advantageous embodiments and further developments of the invention are specified in the dependent claims.

An exhaust gas turbocharger with the features specified in claim 1 includes a shaft having an axis of rotation, a arranged in a turbine housing and rotatably connected to the shaft radial-axial turbine wheel and a turbine housing adjacent bearing housing, which has a side facing the turbine housing side wall. The radial-axial turbine wheel has a back wall with a corner disposed at the radially outer end of the rear wall, with an upper surface of the turbine wheel extending obliquely radially outwardly from the corner of the rear wall. In this case, a partial region of the turbine housing facing side wall of the bearing housing forms a portion of the rear wall of the turbine housing. The partial region of the bearing housing which forms a partial region of the rear wall of the turbine housing has two subsections, of which the first subsection extends obliquely to the axis of rotation of the shaft in the inflow direction of an exhaust gas stream guided into the turbine housing, and the second subsection extends in the radial direction to the axis of rotation of the shaft and parallel to the rear wall of the shaft Turbine wheel runs. The two sections are connected to each other via an exhaust flow separation edge of the bearing housing, wherein the exhaust gas flow-off edge has a corner connected to the second section via a flank. In this case, the first section and the flank includes a corner angle and between the second section and the flank a curved transition region is provided. Furthermore, the top of the turbine wheel, from the corner of the exhaust gas flow-off edge in the inflow direction of the exhaust gas flow, at a distance and the flank is parallel to the top of the turbine wheel.

Such an exhaust gas turbocharger requires no heat shield, which could deform during assembly and operation of the exhaust gas turbocharger by pressure influences and thermal influences in an undesirable manner. This favors the flow of the turbine wheel and improves its thermodynamics. Furthermore, in an exhaust-gas turbocharger with the features according to the invention in its operation, no undesired collisions with the turbine wheel rotating at high speed can occur. This improves the functionality of the exhaust gas turbocharger and increases its service life. Further, in an exhaust gas turbocharger with the features according to the invention, the cavity between the rear wall of the turbine wheel and the adjacent portion of the side wall of the bearing housing, d. H. the Radrückenraum be kept small, so that even in this area an occurrence of an undesirable flow with the exhaust stream can be at least greatly reduced.

Figur 2

eine Schnittansicht eines Teils eines Abgasturboladers gemäß einem Ausführungsbeispiel für die Erfindung,

Figur 3

eine Skizze zur Veranschaulichung der Anströmung des Turbinenrades mit dem Abgasstrom und

Figur 4

eine vergrößerte Darstellung des Detail Z von Figur 3.

Further advantageous features of the invention will become apparent from the following exemplary explanation with reference to FIG Figures 2-4 , It shows

FIG. 2

a sectional view of a portion of an exhaust gas turbocharger according to an embodiment of the invention,

FIG. 3

a sketch illustrating the flow of the turbine wheel with the exhaust stream and

FIG. 4

an enlarged view of detail Z of FIG. 3 ,

The FIG. 2 shows a sectional view of a portion of an exhaust gas turbocharger according to an embodiment of the invention. This exhaust gas turbocharger has a turbine housing 10 with a spiral 16, which encloses an inflow region 17 for the exhaust gas flow. Within the turbine housing 10, a radial-axial turbine wheel 12 connected to the shaft in a rotationally fixed manner is arranged on a shaft 30. The shaft 30 is mounted in a bearing housing 20 which is adjacent to the turbine housing 10. The bearing housing 20 has a turbine housing 10 facing side wall. The turbine wheel 12 has a rear wall 13 and an upper side OS.

A portion of the turbine housing facing side wall of the bearing housing forms a portion of the rear wall of the turbine housing. The partial region of the bearing housing which forms a partial region of the rear wall of the turbine housing has two partial sections TA1 and TA2. The first portion TA1 extends obliquely to the axis of rotation 30a of the shaft 30 in the inflow ZR of the guided into the turbine housing hot exhaust gas stream. The second subsection TA2 extends in the radial direction R to the axis of rotation 30a of the shaft 30 and also parallel to the rear wall 13 of the turbine wheel 12. The two subsections TA1 and TA2 are connected to one another via an exhaust gas flow separation edge 35 of the bearing housing 20. Between the rear wall 13 of the turbine wheel 12 and the second partial section TA2 extending parallel thereto, there is the Radrückenraum 29th

Within the bearing housing 20, a water core 36 is disposed, which is the exhaust gas flow edge 35 adjacent. This advantageously has the effect that, during operation of the exhaust-gas turbocharger, the region of the exhaust gas flow-off edge 35 is cooled by a water flow conducted through the water core 36.

Furthermore, the turbine housing facing side wall of the bearing housing in the region of the first section TA1 and the second section TA2 is coated with a protective layer. This protective layer preferably consists of a high temperature, oxidation and corrosion resistant material, such as nickel. Because of this protective layer, said subsections TA1 and TA2 and in particular also the exhaust gas flow tearing edge 35 of the bearing housing connecting the two subsections are protected against the high temperatures occurring in these regions during operation of the exhaust gas turbocharger, so that the probability of deformation of these regions is reduced.

Furthermore, in the FIG. 2 the axial direction A of the rotation axis 30a of the shaft 30 and the radial direction R of the rotation axis 30a of the shaft 30 are illustrated.

The provided on the bearing housing 20 Abgasströmungsabrisskante 35 is designed such that it withstands the high loads occurring during operation of the exhaust gas turbocharger and that occurring in the region of this Abgasströmungsabrisskante turbulence of the supplied hot exhaust gas flow are kept small, so that the hydrodynamic efficiency of the exhaust gas turbocharger can be increased. This will be explained below with reference to FIGS. 3 and 4 explained in more detail.

The FIG. 3 shows a sketch to illustrate the flow of the turbine wheel of the exhaust gas turbocharger with the hot exhaust gas flow. In the illustrated embodiment, the hot exhaust gas stream enters the nozzle formed between the side wall of the bearing housing 20 and the turbine housing, not shown, and is supplied along the section TA1 to the turbine wheel 12 and its vanes. Thereby, the turbine wheel is rotated together with the shaft 30, wherein this rotation takes place about the rotation axis 30a. The bearing housing 20 has an exhaust gas flow separation edge 35 between the first subsection TA1 and the second subsection TA2.

This exhaust gas flow edge 35 and the adjacent turbine wheel 12 are designed and arranged relative to one another in such a way that the turbulences of the exhaust gas flow which occur in the region of the exhaust gas flow separation edge 35 be kept small and that the Abgasströmungsabrisskante 35 withstand the loads occurring during operation of the exhaust gas turbocharger. Also contributing to this is the water core 36 positioned near the exhaust gas flow tearing edge 35, through which cooling water is passed during operation of the exhaust gas turbocharger which cools the region of the exhaust gas flow tearing edge 35.

The Indian FIG. 3 highlighted portion Z, within which the exhaust gas flow edge 35 and those of these adjacent components of the turbine wheel 12 are included in the FIG. 4 shown on an enlarged scale.

From the FIG. 4 It can be seen that the turbine wheel 12 at the radially upper end of its rear wall 13 has a corner E2, from which the top OS of the turbine wheel or the top of its blades obliquely, with respect to the axis of rotation 30a in the radial direction (R) to the outside , ie in the presentation of the FIG. 2 up, runs. The corner E2 of the rear wall 13 of the turbine wheel 12 has a distance b in the radial direction from a radially arranged above corner E1 of the Abgasströmungsabrisskante 35 of the bearing housing 20 in the radial direction. The upper side OS of the turbine wheel 12 has a distance c from the corner E1 of the exhaust gas flow separation edge 35 of the bearing housing in the inflow direction ZR of the exhaust gas flow. The rear wall 13 of the turbine wheel 12 has a distance a from the second partial section TA2 running parallel thereto. The first section TA1 of the bearing housing 20 also extends in the inflow ZR of the exhaust stream, has an angle β relative to the radial direction R and ends at the corner E1 of the exhaust flow separation edge 35 of the bearing housing.

Between the corner E1 of the Abgasströmungsabrisskante 35 and the second portion TA2 is an outgoing of the corner E1 edge F is provided which is connected to the second portion TA2 via a bent transition region U formed. The flank F runs parallel to the top side OS of the turbine wheel 12. The first section TA1 and the flank F At the corner E1 of the exhaust gas flow edge 35, a corner angle α is included.

The water core 36, through which cooling water flows during operation of the exhaust gas turbocharger, extends into the immediate vicinity of the Abgasströmungsabrisskante 35, so that it is cooled by the cooling water in operation and can not be destroyed by overheating.

In order to prevent overheating of the exhaust gas flow tear-off edge 35, furthermore, the side wall of the bearing housing 20 facing the turbine housing 10 is provided with a protective layer in the region of the first part section TA1, the second part section TA2 and the flank F. This protective layer is preferably made of a high temperature, oxidation and corrosion resistant material, such as nickel.

The distance b of the corner E1 of the Abgasströmungsabrisskante 35 from the corner E2 of the upper end portion of the rear wall 13 of the turbine wheel 12 in the radial direction is in a defined ratio to the measured in the radial direction R diameter DTR of the rear wall 13 of the turbine wheel 12. It is preferably: $$0.005\le \mathrm{b}/\mathrm{DTR}\le \mathrm{0.025.}$$

The distance a between the rear wall 13 of the turbine wheel 12 and the second portion TA2 is also in a defined ratio to the diameter measured in the radial direction DTR of the rear wall 13 of the turbine wheel 12. It also applies here preferably the following relationship: $$0.005\le \mathrm{a}/\mathrm{DTR}\le \mathrm{0.025.}$$

The invention provides after all an exhaust gas turbocharger, which is equipped with an axial-radial turbine wheel, in which the exhaust gas flow in the turbine housing without use of a separate guide element is guided through a nozzle to the turbine wheel. A side wall of this nozzle is from a first Part of the section of the turbine housing facing side wall of the bearing housing formed, which extends in the inflow direction of the exhaust stream. The other side wall of the nozzle is formed by a wall of the turbine housing. The first section TA1 of the turbine housing facing side wall of the bearing housing is connected via an exhaust gas flow edge 35 with a second portion TA2, which runs parallel to the rear wall of the turbine wheel.

Such a design of the side facing the turbine housing side wall of the bearing housing creates the conditions that the Abgasströmungsabrisskante the bearing housing withstand the high loads occurring during operation of the exhaust gas turbocharger, so that the thermodynamic efficiency of the exhaust gas turbocharger can be increased. If, in addition to this embodiment of the turbine housing facing side wall of the bearing housing one or more of the features specified in the dependent claims used, then the functionality of the exhaust gas turbocharger is further increased during operation. Contributing in particular the shape of the bearing housing in the region of the Abgasstromabrißkante, the positioning of the water core, the use of a protective layer and the dimensioning of the distances a and b described above at.

Studies have shown that the functionality of an exhaust gas turbocharger according to the invention in operation is given even in the presence of high exhaust gas inlet temperatures which are greater than 1050 ° C.

Claims (11)

1. Exhaust-gas turbocharger having a shaft (30) which has an axis of rotation (30a), having a radial-axial turbine wheel (12) which is arranged in a turbine housing (10) and which is connected rotationally conjointly to the shaft (30), and having a bearing housing (20) which is arranged adjacent to the turbine housing and which comprises a side wall facing toward the turbine housing, characterized in that

   - the radial-axial turbine wheel (12) has a rear wall (13) with a corner (E2) arranged at the outer end of the rear wall (13) in a radial direction, wherein a top side (OS) of the turbine wheel runs obliquely outward in the radial direction proceeding from the corner (E2) of the rear wall (13),

   - a sub-region of that side wall of the bearing housing (20) which faces toward the turbine housing forms a sub-region of the rear wall of the turbine housing (10),

   - that sub-region of the bearing housing which forms a sub-region of the rear wall of the turbine housing has two sub-portions (TA1, TA2), of which

   - the first sub-portion (TA1) runs obliquely with respect to the axis of rotation (30a) of the shaft (30) in the inflow direction (ZR) of an exhaust-gas flow conducted into the turbine housing,

   - the second sub-portion (TA2) runs in a radial direction (R) with respect to the axis of rotation (30a) of the shaft (30) and parallel to the rear wall (13) of the turbine wheel (12), and

   - the two sub-portions (TA1, TA2) are connected to one another via an exhaust-gas flow separation edge (35) of the bearing housing (20),

   - wherein the exhaust-gas flow separation edge (35) has a corner (E1) which is connected to the second sub-portion (TA2) via a flank (F), wherein the first sub-portion (TA1) and the flank (F) enclose a corner angle (α) and a curved transition region (U) is provided between the second sub-portion (TA2) and the flank (F),

   - wherein the top side (OS) of the turbine wheel (12) has a spacing (c) to the corner (E1) of the exhaust-gas flow separation edge (35) in the inflow direction (ZR) of the exhaust-gas flow and the flank (F) runs parallel to the top side (OS) of the turbine wheel (12).
2. Exhaust-gas turbocharger according to Claim 1, characterized in that the first sub-portion (TA1) ends at the corner (E1).
3. Exhaust-gas turbocharger according to Claim 2, characterized in that the first sub-portion (TA1) is of rectilinear form.
4. Exhaust-gas turbocharger according to Claim 2, characterized in that the first sub-portion (TA1) is of curved form.
5. Exhaust-gas turbocharger according to one of Claims 1 to 4, characterized in that the rear wall (13) of the turbine wheel (12) has, in its upper end region, a corner (E2) which has a first spacing (b) to the corner (E1) of the exhaust-gas flow separation edge (35) in a radial direction (R).
6. Exhaust-gas turbocharger according to one of the preceding claims, characterized in that the rear wall (13) of the turbine wheel (12) has a third spacing (a) to the second sub-portion (TA2).
7. Exhaust-gas turbocharger according to Claim 6, characterized in that the ratio of the third spacing (a) to the diameter (DTR) of the rear wall (13) of the turbine wheel (12) lies in the range between 0.005 and 0.025.
8. Exhaust-gas turbocharger according to one of Claims 5 to 7, characterized in that the ratio of the second spacing (b) to the diameter (DTR) of the rear wall (13) of the turbine wheel (12) lies in the range between 0.005 and 0.025.
9. Exhaust-gas turbocharger according to one of the preceding claims, characterized in that the bearing housing (20) has a water core (36) which is arranged adjacent to the exhaust-gas flow separation edge (35).
10. Exhaust-gas turbocharger according to one of Claims 1-9, characterized in that that side wall of the bearing housing (20) which faces toward the turbine housing (10) is provided with a protective layer in the region of the first sub-portion (TA1), of the second sub-portion (TA2) and of the flank (F).
11. Exhaust-gas turbocharger according to Claim 10, characterized in that the protective layer is composed of a material which is resistant to high temperatures, to oxidation and to corrosion.

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