Radial turbine, turbocharger and insert for a turbine housing of the radial turbine

Abstract

Radial turbine (11) for a turbocharger (10), comprising a turbine housing and a turbine rotor (19), wherein the turbine housing has a turbine inlet housing (23), a turbine outlet housing (24) and an insert (26) mounted on the turbine inlet housing (23), wherein the insert (26) adjoins radially outside the rotor blades (20) of the turbine rotor (19) and sectionally delimits a flow channel of the radial turbine (11) in the region of the rotor blades (20), characterized in that a wall (35) of the insert (26) delimiting the flow channel is drawn radially outwards at a defined circumferential section (36) having a circumferential extent of 120°±40°, with sectionally increasing a nominal radial gap between the rotor blades (20) and the insert (26) when the turbine rotor is stationary.

Description

The invention relates to a radial turbine for a turbocharger according to the preamble of claim 1. Furthermore, the invention relates to a turbocharger with a radial turbine and an insert for a turbine housing of the radial turbine. A turbocharger consists of a turbine and a compressor. In the turbine, a first process gas is expanded, and the energy gained is used to compress a second process gas in the compressor. Both the turbine and the compressor of a turbocharger have a housing and a rotor, with the rotors of the compressor and turbine connected by a shaft supported in a bearing housing. A turbocharger turbine has an inlet housing and an outlet housing. If the turbine is a radial turbine, a so-called insert is mounted on the inlet housing. This insert, located radially outside the turbine rotor blades, partially delimits the flow channel of the radial turbine in the area of ​​the rotor blades. The radial gap between the radially outer ends of the rotor blades and the insert must be large enough to prevent the rotor blades from rubbing against the insert, but small enough to ensure the highest possible efficiency of the radial turbine. US 2014 / 0 000 256 A1 discloses a radial turbine for a turbocharger according to the preamble of claim 1. DE 10 2010 064 047 A1 , DE 10 2009 007 735 A1 , DE 10 2008 000 849 A1 and DE 10 2010 000 222 A1 disclose further state of the art. Starting from this, the present invention is based on the objective of creating a novel radial turbine, a turbocharger with such a radial turbine and an insert for a turbine housing of the radial turbine. This problem is solved by a radial turbine according to claim 1. According to the invention, a wall of the insert, which limits the flow channel, is drawn radially outwards at a defined circumferential section having a circumferential extent of 120°±40°, with a section-by-section enlargement of a nominal radial gap between the rotor blades and the insert when the turbine rotor is stationary. According to the invention, the wall of the insert, which delimits the flow channel, is drawn radially outwards in a defined circumferential section and is thereby formed eccentrically in order to increase the nominal radial gap between the outer ends of the rotor blades and the insert in this circumferential section when the turbine rotor is stationary. This prevents the rotor blades from running into the insert in a defined, particularly critical circumferential section during operation with the turbine rotor rotating, especially during a heating and cooling phase of the turbine inlet casing. Furthermore, it ensures a good efficiency of the radial turbine. The invention is based on the understanding that during the operation of a radial turbine, particularly during heating and cooling phases, the turbine inlet casing undergoes uneven deformation in its circumferential direction. Consequently, the radial gap between the radially outer ends of the rotor blades and the insert changes unevenly across the circumference of the turbine inlet casing and thus across the circumference of the insert. This uneven deformation inherently results in an uneven change in the radial gap. The invention compensates for this uneven change in the radial gap such that a uniform radial gap exists between the rotor blades and the insert of the turbine inlet casing during operation. According to an advantageous further development, the circumferential section in which the wall of the insert is drawn radially outwards, thereby increasing the nominal radial gap between the rotor blades and the insert, has a circumferential extent of 120°±30°, preferably 120°±20°, and particularly preferably 120°±10°. This reliably prevents the rotor blades of the radial turbine from running into the insert of the turbine housing while maintaining high efficiency. According to an alternative advantageous embodiment, the turbine inlet casing has an inlet flange and an inlet channel circumferentially arranged in a worm-like manner, wherein the inlet channel, viewed in the direction of flow through it, has an upstream end adjacent to the inlet flange and a downstream end viewed in the direction of flow through it, and wherein the circumferential section, in which the wall of the insert is drawn radially outwards with an increase in the nominal radial gap between the rotor blades and the insert, is bounded at a first end by the upstream end or the downstream end of the inlet channel and extends from this first end, relative to the direction of flow through the inlet channel, in the opposite direction to the direction of flow through the inlet channel towards its second end.This arrangement of the circumferential section with respect to the flow direction of the inlet channel is particularly preferred, since it has been shown that in this circumferential section, due to the different deformation of the inlet housing over the circumference, there is a higher probability of the rotor blades running into the insert than in other circumferential sections of the turbine inlet housing and thus insert. The turbocharger according to the invention is defined in claim 7. The insert according to the invention is defined in claim 9. Preferred embodiments of the invention are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being limited thereto. These show: Fig. 1: a turbocharger with a compressor and a radial turbine; Fig. 2: a detail of the turbocharger in the area of ​​the radial turbine; Fig. 3: a further detail of the turbocharger in the area of ​​the radial turbine together with debris; Fig. 4: an axial view of the turbine inlet housing of the radial turbine; and Fig. 5: a perspective view of an insert of the radial turbine alone. Fig. 1 shows details of a turbocharger 10 comprising a turbine 11 designed as a radial turbine and a compressor 12 designed as a radial compressor. The compressor 12, designed as a radial compressor, includes a compressor rotor 13 with a shaft 14 and impeller blades 15. Also shown are a compressor spiral casing 16, which serves as an exhaust casing, and an intake casing 17, which serves as an inlet casing. An insert 18 of the compressor 12 is mounted on the compressor spiral casing 16, which serves as the exhaust casing. This insert section, radially adjacent to the impeller blades 15 of the compressor rotor 13, partially delimits a flow channel of the compressor 12. A turbine rotor 19 of the radial turbine 11 is shown, comprising rotor blades 20 and a shaft 21. The shaft 14 of the compressor rotor 13 and the shaft 21 of the turbine rotor 19 are coupled together, with these shafts 14 and 21 being supported in a bearing housing 22. The turbine 11, designed as a radial turbine, also includes a turbine housing comprising a turbine inlet housing 23 and a turbine outlet housing 24. The turbine inlet housing 23 has a spiral or worm-like contour and provides an inlet channel 25 for the radial turbine 11. An insert 26 is mounted on the turbine inlet housing 23 of the turbine housing of the radial turbine 11, wherein this insert 26 radially outside adjacent to the outer ends of the rotor blades 20 of the turbine rotor 19, sectionally delimits a flow channel of the radial turbine 11 in the area of ​​the rotor blades 20. Fig. 3 shows a section of the exhaust gas turbocharger 10 in the area of ​​the turbine 11, where in Fig. 3 both the turbine inlet housing 23 and the turbine outlet housing 24 are surrounded by protective coverings 27, 28. Furthermore, Fig. 3 shows a protective covering 29 in the area of ​​the compressor spiral housing 16. The contaminants 27, 28 of the turbine housing of the radial turbine 11 leave an inlet flange 30 free in the area of ​​the turbine inlet housing 23 and an outlet flange 31 free in the area of ​​the turbine outlet housing 24. As already explained, the turbine inlet housing of a radial turbine 11 has a spiral or worm-like contour, wherein the inlet channel 25 of the inlet housing 23 extends from the inlet flange 30 of the turbine inlet housing 23 in a spiral or worm-like circumferential direction around the turbine rotor 19 and thus the rotor blades 20 of the turbine rotor 19. This inlet channel 25 of the turbine inlet casing 23 has a downstream end 33 adjacent to the inlet flange 30, coupled to it on the flow side, as seen in the direction of flow through the inlet channel 25, and a downstream end 34 as seen in the direction of flow through the inlet channel 25. Starting from the upstream end 33 of the inlet channel 25 towards the downstream end 34 of the same, the flow cross-section of the inlet channel 25 decreases. During operation, the turbine inlet housing 23 is subject to varying deformations along its circumference. Consequently, in radial turbines known from the prior art, the radial gap between the radially outer ends of the rotor blades 20 of the turbine rotor 19 and the insert 26 mounted on the turbine inlet housing 23 also decreases differently in the circumferential direction. In order to prevent the rotor blades 20 from running into the insert 26 in sections of the circumferential extension of the insert 26 of the turbine inlet housing 23 where the radial gap between the insert 26 and the rotor blades 20 decreases more significantly during operation, the invention provides that a wall 35 of the insert 26, which limits the flow channel, is drawn radially outwards in a defined circumferential section 36, thereby increasing the nominal radial gap between the rotor blades 20 and the insert 26 when the turbine rotor 13 is stationary. This is intended to compensate for the greater deformation of the turbine housing, namely the turbine inlet housing 23, which develops during operation in this circumferential section and thus prevent the rotor blades 20 of the turbine rotor 19 from running into the insert 26 in this circumferential section.Outside this circumferential section 36, where there is a lower risk of the turbine blades 20 running into the insert 26, the insert 26 is not drawn radially outwards on its wall 35 which limits the flow channel in order to ensure a high efficiency of the radial turbine. The circumferential section 36 of the insert 26, in which the wall 35 of the insert 26 is drawn radially outwards relative to the other circumferential sections of the same, thereby increasing the nominal radial gap between the rotor blades 20 and the insert 26, has a circumferential extent of 120°±40°, in particular a circumferential extent of 120°±30°, preferably of 120°±20°, and most preferably of 120°±10°. The nominal radial gap between the rotor blades 20 and the insert 26 of the radial turbine 11 is the radial gap when the turbine rotor 13 is stationary and the radial turbine 11 is cooled. During operation with the rotating turbine rotor 13, particularly during the heating and cooling phases of the radial turbine 11, this gap changes non-uniformly in the circumferential direction of the insert 26. The defined contouring of the wall 35 of the insert 26 in the circumferential section 36 ensures that, during operation with the rotating turbine rotor 13, particularly during the heating and cooling phases of the radial turbine 11, the radial gap between the rotor blades 20 and the insert 26 of the radial turbine 11 is uniform in the circumferential direction of the insert 26. This prevents the rotor blades from running into the insert 26 at high efficiency of the radial turbine 11. The invention is based on the finding that, in a circumferential extent of 120°±40°, the turbine inlet housing 23 and the insert 26 mounted on the turbine inlet housing 23 are subject to a different deformation during operation than in other circumferential sections of the same, such that in this circumferential section 36, the running-in of the rotor blades 20 of the turbine rotor 19 into the insert 26 is more likely, so that, according to the invention, in this circumferential section 36, the radially inner wall 35 of the insert 26 is pulled radially outwards. Fig. 4 visualizes the exact positioning or orientation of the circumferential section 36 of the insert 26 where the radially inner wall 35 of the same is drawn radially outwards. Fig. 4 shows that the circumferential section 36 is bounded by two ends 37, 38. A first end 37 preferably coincides with the upstream end 33 or the downstream end 34 of the inlet channel 25 of the turbine inlet housing 23, wherein the upstream end 33 of the inlet channel 25, viewed in the flow direction 32 of the inlet channel 25, abuts the inlet flange 30 of the turbine inlet housing 23. The circumferential section 36 with the radially outwardly extended wall 35 of the insert 26 extends from its first end 37 towards its second end 38, namely in the direction of flow 32 of the inflow channel 25 opposite to the direction of flow 32 of the same. The circumferential section 36 of the insert 26, on which the radially inner wall 35 is drawn radially outwards, therefore runs over a circumferential section of the inflow channel 25, which, viewed in the flow direction 32 of the inflow channel 25, lies aft, as it faces the downstream end 34 of the inflow channel 25. According to Fig. 4, a longitudinal center axis 40 of the inlet flange 30 runs in the projection perpendicular to a longitudinal center axis 41 of the insert piece 26. Fig. 4 further visualizes a connection flange 39 of the turbine inlet housing, to which the turbine outlet housing 24 engages. The radial turbine 11 according to the invention is preferably used in the turbocharger 10 shown in Fig. 1, which comprises a radial compressor 12. The invention relates not only to the radial turbine 11 and the turbocharger 10 comprising the radial turbine 11, but also to the insert 26 itself, with which radial turbines 11 or turbochargers 10 already installed in the field can be retrofitted. By replacing an existing insert with the insert 26 according to the invention, a conventional radial turbine 11 installed in the field can therefore be converted or modified into a radial turbine 11 according to the invention. As previously explained, the wall 35 of the insert 26 is drawn radially outwards in the circumferential section 36. This increases the flow-relevant radius of the radially inner wall 35 in the circumferential section 36. This increase can be constant over the entire circumferential extent 36; however, it is also possible for this increase in the flow-relevant radius to change over the circumferential region 36. It can be provided that the increase in radius and thus the radial outward pulling of the wall 35 from the ends 37, 38 of the circumferential section 36 towards its center initially increases continuously and then remains constant for a central area of ​​the circumferential section 36. Reference symbol list 10 Turbocharger 11 Turbine 12 Compressor 13 Compressor rotor 14 Shaft 15 Rotor blade 16 Compressor exhaust housing 17 Compressor inlet housing 18 Insert 19 Turbine rotor 20 Rotor blade 21 Shaft 22 Bearing housing 23 Turbine inlet housing 24 Turbine exhaust housing 25 Inlet channel 26 Insert 27 Protective cover 28 Protective cover 29 Protective cover 30 Flange 31 Flange 32 Flow direction 33 End 34 End 35 Wall 36 Circumferential section 37 End 38 End 39 Connection flange 40 Longitudinal center axis 41 Longitudinal center axis

Claims

Radial turbine (11) for a turbocharger (10), comprising a turbine housing and a turbine rotor (19), wherein the turbine housing has a turbine inlet housing (23), a turbine outlet housing (24) and an insert (26) mounted on the turbine inlet housing (23), wherein the insert (26) adjoins radially outside the rotor blades (20) of the turbine rotor (19) and sectionally delimits a flow channel of the radial turbine (11) in the region of the rotor blades (20), characterized in that a wall (35) of the insert (26) delimiting the flow channel is drawn radially outwards at a defined circumferential section (36) having a circumferential extent of 120°±40°, with sectionally increasing a nominal radial gap between the rotor blades (20) and the insert (26) when the turbine rotor is stationary. Radial turbine according to claim 1, characterized in that the circumferential section (36), in which the wall (35) of the insert (26) is drawn radially outwards with section-by-section enlargement of the nominal radial gap between the rotor blades (20) and the insert (26), has a circumferential extent of 120°±30°. Radial turbine according to claim 2, characterized in that the circumferential section (36), in which the wall (35) of the insert (26) is drawn radially outwards with section-by-section enlargement of the nominal radial gap between the rotor blades (20) and the insert (26), has a circumferential extent of 120°±20° or 120°±10°. Radial turbine according to one of claims 1 to 3, characterized in that the turbine inlet housing (23) has an inlet flange (30) and a worm-like housing orhas a spirally circumferentially rotating inflow channel (25), wherein the inflow channel (25) has, viewed in the direction of flow through it, an upstream end (33) adjacent to the inflow flange (30) and a downstream end (34) viewed in the direction of flow through it, and wherein the circumferential section (36), in which the wall (35) of the insert (26) is drawn radially outwards with an increase in the nominal radial gap between the rotor blades (20) and the insert (26), is bounded at a first end (37) by the upstream end (33) of the inflow channel (25) and extends from this first end (37) in the direction opposite to the direction of flow through the inflow channel (25) towards a second end (38). Radial turbine according to one of claims 1 to 3, characterized in that the turbine inlet housing (23) has an inlet flange (30) and an inlet channel (25) circumferentially arranged in a helical housing, wherein the inlet channel (25) has, viewed in the direction of flow, an upstream end (33) adjacent to the inlet flange (30) and a downstream end (34) viewed in the direction of flow, and wherein the circumferential section (36), in which the wall (35) of the insert (26) is drawn radially outwards, increasing the nominal radial gap between the rotor blades (20) and the insert (26), is bounded at a first end (37) by the downstream end (34) of the inlet channel (25) and extends from this first end (37) in the direction of flow of the inlet channel (25) opposite to the The flow direction of the inflow channel (25) extends towards a second end (38). Radial turbine according to claim 4 or 5, characterized in that a longitudinal central axis (40) of the inlet flange (30) runs perpendicular to a longitudinal central axis (41) of the insert (26) in the projection. Turbocharger (10) with a compressor (12) and a radial turbine (11), wherein the compressor (12) comprises a compressor housing (16, 17) and a compressor rotor (13) and the radial turbine (11) comprises a turbine housing and a turbine rotor (19), wherein the compressor rotor (13) and the turbine rotor (19) are coupled via shafts (14, 21) mounted in a bearing housing (22), characterized in that the radial turbine (11) is designed according to one of claims 1 to 6. Turbocharger according to claim 7, characterized in that the compressor (12) is designed as a radial compressor. Insert (26) of a turbine inlet housing (23) of a radial turbine (11), wherein the insert (26) radially outwards defines a flow channel section by section, characterized in that a wall (35) of the insert (26) defining the flow channel is drawn radially outwards at a defined circumferential section (36) which has a circumferential extent of 120°±40°. Insert according to claim 9, characterized in that the circumferential section (36) in which the wall (35) of the insert (26) is drawn radially outwards has a circumferential extent of 120°±30° or of 120°±20° or of 120°±10°.

Images