EP2937521A1

EP2937521A1 - Turbine with variable geometry and bypass channel for an exhaust gas turbocharger

Info

Publication number: EP2937521A1
Application number: EP14165847.6A
Authority: EP
Inventors: Kanagaraj Thangavelu; Deepak Hassan Mallappa
Original assignee: Bosch Mahle Turbo Systems GmbH and Co KG
Current assignee: BMTS Technology GmbH and Co KG
Priority date: 2014-04-24
Filing date: 2014-04-24
Publication date: 2015-10-28

Abstract

The invention relates to a radial turbine (1) for an exhaust gas turbocharger, in particular of an internal combustion engine, having a turbine housing (2), having a housing interior space (5) enclosed by the turbine housing (2), having a turbine wheel (6) which is rotatably mounted in the turbine housing (2), which turbine wheel (6) separates the housing interior space (5) into a high-pressure region (7) and a low-pressure region (8), having a bypass line (9) which is provided in the turbine housing (2) and fluidically connects the high-pressure region (7) with the low-pressure region (8), having a variable turbine geometry (11), which comprises a plurality of guide blades (12) connected upstream of the turbine wheel (6), which are adjustable between a first position, in which a flow cross-section between the guide blades (12) for exhaust gas to flow through is maximal and a second position, in which this flow cross-section is minimal, wherein the guide blades (12) are formed in such a manner, using a face plate (16) as closure element (15) with a passage opening (17), that at least one guide blade (12) opens the bypass line (9) in the first position, closing it off in the second position.

Description

The invention relates to a turbine for an exhaust gas turbocharger and to an exhaust gas turbocharger having such a turbine. The invention furthermore relates to a guide blade for such a turbine. Finally, the invention relates to an internal combustion engine having such an exhaust gas turbocharger.
For regulating the turbine output of an exhaust gas turbocharger of an internal combustion engine, a so-called waste gate is often employed. This can be used to regulate the charge pressure in the case of turbochargers for internal combustion engines. An alternative to this concept are adjustable guide blades, which allow a variation of the inflow of exhaust gas to the turbine wheel of the turbine part of the exhaust gas turbocharger by means of adjustable guide blades. Such adjustable guide blades are generally also called variable turbine geometry ("VTG"). Said adjustability allows an optimal adaptation of the flow of exhaust gas onto the turbine wheel as a function of the exhaust gas quantity currently entering the turbine. Adjusting the guide blades into a first position with maximum flow cross section for the case of a large exhaust gas quantity ensures that the exhaust gas molecules do not strike the turbine wheel with too high a velocity. However, when the exhaust gas quantity entering the turbine decreases for example because the internal combustion engine which is connected upstream of the exhaust gas turbocharger happens to be operated with low rotational speed, adjusting the guide blades into a second position with minimum flow cross-section results in an acceleration of the exhaust gas molecules. As a result, fewer gas molecules strike the turbine wheel however with increased velocity, resulting in the turbine wheel being accelerated. As a consequence, more fresh air can be delivered by the compressor of the exhaust gas turbocharger which is drive-connected to the turbine, as a result of which in turn the charge pressure generated by the compressor in the internal combustion engine rises. This permits a rapid increase of the rotational speed of the internal combustion engine, in particular at a low starting rotational speed and at full load.
However, it proves to be problematic with such variable turbine geometries under certain operating conditions of the exhaust gas turbocharger and of the internal combustion engine connected upstream of the turbocharger that the exhaust gas flow strikes the turbine wheel with too high a velocity despite the guide blade being adjusted into the opened position so that the rotational speed of the turbine wheel under certain conditions increases excessively. This can result in too high a charge pressure being generated by the compressor.
It is therefore an object of the present invention to create an improved embodiment for a turbine, in particular for an exhaust gas turbocharger, in which the problem described above no longer occurs.
This object is solved through the subject of the independent patent claims. Preferred embodiments are subject of the dependent claims.
Accordingly, the basic idea of the invention is to provide a bypass line in the turbine housing of a turbine equipped with variable turbine geometry, via which at least a part of the exhaust gas flow entering the turbine housing can be conducted past the turbine wheel when required. Said bypass line in this case is closed off through the guide blades of the variable turbine geometry or, if required, opened for exhaust gas to flow through. For this purpose, a plurality of guide blades of said variable turbine geometry which are connected upstream of the turbine wheel are adjustable in the known manner between a first position, in which a flow cross-section between the guide blades is maximal for the throughflow of exhaust gas and a second position, in which this flow cross-section is minimal. A design of the guide blades in such a manner that at least one guide blade in the first position opens the bypass line and closes it in the second position is substantial to the invention. The guide blade concerned thus follows the operational principle of a waste gate valve. This means the guide blades in their first position make available the already mentioned maximum flow cross-section for the exhaust gas entering the turbine and in addition at least a part of the exhaust gas mass flow that has entered the turbine housing can be conducted past the turbine wheel. Undesirably high acceleration of the turbine wheel because of too high an exhaust gas mass flow, the gas molecules of which moreover have too high a gas velocity, and too high a turbine output which is connected to this is thereby avoided. This results in an improved efficiency of the exhaust gas turbocharger using the turbine introduced here. The turbine according to the invention thus combines within it the advantages of a variable turbine geometry and a waste gate device mentioned at the outset, which in this case is realised in the form of said bypass line.
In a preferred embodiment, the bypass line is designed in such a manner that it is closed off by all guide blades when these are in the first position. For this purpose, the bypass line which is substantial to the invention can be composed of multiple bypass channels which are fluidically connected in parallel with one another. If the number of channels corresponds to the number of guide blades which are present in the turbine, each individual guide blade can be assigned exactly one bypass channel. Thus, each guide blade assumes the function of a waste gate valve for the bypass channel assigned to it.
In a further preferred embodiment, the at least one guide blade is designed in such a manner that it opens the bypass channel only in the first position. In other words, if said guide blade is moved out of the first position this results in a closing of the bypass line or of the bypass channels. In this case, the guide blades follow the operational principle of a conventional variable turbine geometry without additional waste gate device.
In a further preferred embodiment, there exists a position of the guide blades with a flow cross-section that is reduced compared with the first position. This position, which is called third position here, corresponds to the flow cross-section that can be maximally made available by the variable turbine geometry with closed bypass line. However, this flow cross-section is at least slightly smaller than that with opened bypass line, i.e. said third position is an intermediate position between the first position of the guide blades and the second position, which is accompanied by the minimal flow cross-section.
As already mentioned, an embodiment in which the bypass line comprises a number of bypass channels which are connected fluidically in parallel with one another, which corresponds to the number of guide blades, proves to be particularly advantageous. Then, each bypass channel can be individually assigned a guide blade in such a manner that each guide blade opens the bypass channel assigned to it in the first position, closing it in the second position. In this way, a high absolute line cross-section can be achieved in the entire bypass line without this having to be closed off by a single guide blade. Each individual bypass channel rather has a channel cross-section which compared to the line cross-section of the entire bypass line is greatly reduced. In other words, the sum of all channel cross-sections corresponds to the line cross-section of the bypass line. On the individual guide blades, no major design changes will then have to be carried out in order to form these as valve for the bypass line as will still be discussed in more detail in the following.
Modern turbines for exhaust gas turbochargers are typically designed in the manner of a radial turbine with a radial fluid inlet and an axial fluid outlet. For installation space considerations it therefore proves to be advantageous to arrange the bypass channels along the axial direction of the turbine, which is defined by the axis of rotation of the turbine wheel. In a preferred embodiment, the bypass channel is thus arranged at least in sections, preferentially completely, parallel to an axis of rotation about which the respective guide blade is rotationally adjustable between the first and the second position. This permits integrating the respective bypass channel into a conventional turbine with variable turbine geometry without major design changes having to be performed on said turbine.
An embodiment, in which the guide blade comprises a guide blade leaf which is attached in a rotationally fixed manner to a bearing pin extending along an axial direction, proves to be particularly easy to manufacture from a production point of view. By means of said guide blade leaf, the flow cross-section can be adjusted in the known manner. For closing off or opening the respective bypass channel, a closure element is provided on the bearing pin or the guide blade leaf, which is arranged in the respective bypass channel. The closure element in turn is provided with a passage opening in such a manner that said passage opening in the first position of the guide blade is arranged in the bypass channel so that the closure element opens the bypass channel for exhaust gas to flow through. Compared with this, said passage opening is arranged outside the bypass channel when the guide blade is moved away from the first position to the second position. Thus, the bypass channel is closed off by the closure element.
Particularly practically, the bearing pins of the individual guide blades can each be rotatably mounted on a blade bearing ring which is attached in a fixed location on the turbine housing. In this way, the adjusting mechanism for adjusting the guide blades between the first and the second position can be realised through the rotational movement of the guide blade which is required anyhow in the known manner for adjusting the flow cross-section. Adjusting the guide blades between the first and the second position in this scenario takes place through rotational adjusting of the bearing pin and of the guide blade leaf attached thereon about an axis of rotation defined through the centre longitudinal axis of the bearing pin. Consequently, no separate adjusting mechanism for the guide blades for opening and closing off the bypass channels is required. This results in cost advantages in the production of the turbine according to the invention.
In an advantageous further development, the closure element is formed as a face plate, which is provided at the axial face end on the bearing pin or on the guide blade leaf. Conventional guide blades can be complemented in a simple design manner by such a face plate which itself can be produced in a simple manner.
In a particularly preferred embodiment, said face plate can be formed cylindrically and arranged concentrically to the bearing pin. In this embodiment, the passage opening penetrates the cylindrical face plate along the common axial direction of the face plate and of the bearing pin.
It proves to be advantageous, furthermore, to arrange the bypass channels in parallel with and adjacent to the bearing pin. If the cylindrical face plate is provided with a larger diameter than the bearing pin, the face plate with suitable dimensioning and arrangement relative to the bypass channel and bearing pin projects into the bypass channel. If the passage opening, with respect to a top view of the face plate, is now provided eccentrically on said face plate in a suitable location, a rotation of the bearing pin and of the face plate fastened thereto brings about that the passage opening through a rotational movement of the guide blade for releasing the bypass channel can be moved into said bypass channel and for closing off, back out of said bypass channel again.
However, an embodiment in which the passage opening is formed as a recess provided on the circumferential side of the cylindrical face plate proves to be particularly simple with respect to design.
For the purpose of a reliable adjustable mounting of the closure element or of the face plate of the guide blades over a multiplicity of adjusting cycles it is proposed to attach in the turbine housing a common fastening ring which is arranged concentrically to the turbine wheel. Said fastening ring can comprise on a first face end facing the guide blades for each closure element or for each face plate a recess which is formed complementarily to the closure element or to the face plate, in which the closure element or the face plate can be at least partially received.
In another preferred embodiment, the bypass channels of the bypass line in the turbine housing can each have a cylindrical geometrical shape. In terms of production, the bypass channels can thus be introduced into the turbine housing in a simple manner in the form of bores.
The invention furthermore relates to a guide blade for the turbine explained above.
The invention furthermore relates to an exhaust gas turbocharger having a turbine with one or multiple of the features mentioned above.
Finally, the invention also relates to an internal combustion engine having such an exhaust gas turbocharger.
Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description with the help of the drawings.
It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference numbers relate to same of similar or functionally same components.
It shows, in each case schematically

Fig. 1: an example of a turbine according to the invention with a variable turbine geometry in a longitudinal section, wherein the guide blades of which are located in a first position, in which they open bypass channels which are provided in the turbine housing,
Fig. 2: a top view of the substantial component of the variable turbine geometry of the turbine of Figure 1,
Fig. 3: the turbine of Figure 1 with the guide blades in a second position, in which they close off the bypass channels,
Fig. 4: a top view of the substantial components of the variable turbine geometry of the turbine of Figure 3,
Fig. 5a/b: a guide blade of the variable turbine geometry of the Figures 1 to 4 in a separate representation.

Figure 1 illustrates an example of a turbine 1 according to the invention for an exhaust gas turbocharger, which in the example of the Figures is embodied as a so-called radial turbine, in a longitudinal section. The turbine 1 has a turbine housing 2 with an inlet opening, which is not evident in the longitudinal section of Figure 1, and an outlet opening 4. The turbine housing 2 surrounds a housing interior space 5, through which exhaust gas expelled from an internal combustion engine flows. Within the turbine housing 2, in the housing interior space 5, a turbine wheel 3 with a shaft 6 is arranged, through which an axis of rotation D of the turbine wheel 3 is defined. The axis of rotation D extends along an axial direction A of the turbine 1, which separates the housing interior space into a high-pressure region 7 formed as a volute and which is in fluid connection with the inlet opening and a low-pressure region 8 which is in fluid connection with the outlet opening 4. In the turbine housing 2, a bypass line 9 is furthermore provided, which comprises multiple bypass channels 10, of which in the longitudinal section of Figure 1 only two such channels 10 are shown.
Furthermore, the turbine 1 comprises a variable turbine geometry 11, the substantial components of which are shown in Figure 2 in a separate and schematic representation. The variable turbine geometry 11 comprises a plurality of guide blades 12. Connected upstream of the turbine wheel 3, which can be adjustably mounted on a conventional guide blade bearing ring 19 familiar to the relevant person skilled in the art.
Such a guide blade 12 is exemplarily shown in a separate representation in Figure 5, wherein Figure 5a shows a top view of the guide blade 12 and Figure 5b and a longitudinal section. As is evident from Figure 5, the guide blade 12 has a guide blade leaf 13, which is attached in a rotationally fixed manner to a bearing pin 14 which extends along an axial direction A. By means of said guide blade leaf 13, by rotating the guide blade 12 about its centre longitudinal axis M of the bearing pin 14, the flow cross-section can be adjusted in the known manner.
The bypass line 9 shown in Figure 1 is now designed in such a manner that following the operational principle of a waste gate valve it can be optionally opened or closed off by all guide blades 12 of the variable turbine geometry 11. For this purpose, each bypass channel 10 is assigned to a certain guide blade 12, i.e. the number of guide blades 12 corresponds to that of the bypass channels 10. It is evident, in addition, that the bypass channels 10 each have a cylindrical geometry in the manner of a bore and extend along the axial direction A of the turbine housing 2 in the same.
For closing off the bypass channel 10, each guide blade 12 has a closure element 15 in the form of a cylindrical face plate 16 which is shown in Figure 5, which is arranged concentrically to the bearing pin 14 and is attached to the bearing pin 14 on the end face. In a version, the face plate 16 may also be attached to the guide blade leaves 13.
Each face plate 16 is provided with a passage opening 17, which with respect to the top view of the guide blade 12 shown in Figure 5a is eccentrically arranged on the same in the axial direction A. In the exemplary scenario of the figures, the passage opening 17 is formed as a recess provided on the circumferential side 18 of the face plate 16 (see Fig. 5a). The passage opening 17 penetrates the cylindrical face plate 16 along the axial direction A. Figure 1 shows the guide blades 12 in a first position, in which they open the bypass channels 10 for exhaust gas to flow through. In the first position, the face plate 16 projects into the bypass channel 10 in such a manner that the passage opening 17 is arranged in the bypass channel 10. Consequently, the bypass channel 10 is opened for exhaust gas to flow through. In the first position, the flow cross-section between two adjacent guide blades 12 is maximal. If the guide blades 12 are moved away out of the first position through rotation about their centre longitudinal axis M, the movement of the face plate 16 implies a movement of the passage opening 17 provided thereon out of the bypass channel 10, so that the latter is now closed off by the face plate 16 in a fluid-tight manner.
This situation is shown by the Figures 3 and 4, which correspond to the Figures 1 and 2, i.e. Figure 3 shows the turbine 1 in a longitudinal section, Figure 4 the variable turbine geometry 11 in a top view. As already explained, the adjustment of the guide blade leaves 13, which is accompanied by the rotating of the guide blades 12 in the process, brings about a reduction of the flow cross-section between two adjacent guide blades 12 in the conventional manner. Even with the third position of the guide blades 12 shown in the Figures 3 and 4, which corresponds to an intermediate position of the guide blades 12 between the first and the second position, in which the bypass channels 10 are just no longer opened, the flow cross-section between two adjacent guide blades 12 is reduced with respect to the first position.
As illustrated in figure 3, a fastening ring 20 arranged concentrically to the turbine wheel 6 can be provided in the turbine housing 2. On its face end 21 facing the guide blades 12, the fastening ring 20 can have a recess 22 for each closure element 15, in particular for each face plate 16. As can be seen from figure 3, each recess 22 is formed complementarily to the closure element 15 or to the face plate 16, in which the closure element 10 or the face plate 16 is at least partially received.

Claims

A turbine (1) for an exhaust gas turbocharger, in particular of an internal combustion engine,
- having a turbine housing (2) comprising an inlet and an outlet opening (4),

- having a housing interior (5), which is at least partially enclosed by the turbine housing (2) and through which exhaust gas can flow,

- having a turbine wheel (6) which is rotatably mounted in the turbine housing (2), which separates the housing interior space (5) into a high-pressure region (7) which is in fluid connection with the inlet opening and a low-pressure region (8) which is in fluid connection with the outlet opening (4),

- having a bypass line (9) which is provided in the turbine housing (2) and fluidically connects the high-pressure region (7) with the low-pressure region (8),

- having a variable turbine geometry (11), which comprises a plurality of guide blades (12) connected upstream of the turbine wheel (6), which are adjustable between a first position, in which a flow cross-section between the guide blades (12) for the through-flow of exhaust gas is maximal and a second position, in which this flow cross-section is minimal,

- wherein the guide blades (12) are designed in such a manner that at least one guide blade (12) opens the bypass line (9) in the first position, closing it off in the second position.
The turbine according to claim 1,
characterized in that
the bypass line (9) is designed in such a manner that it is closed off by all guide blades (12) when these are in the first position.
The turbine according to claim 1 or 2,
characterized in that
the at least one guide blade (12), preferentially all guide blades (12), is designed in such a manner that it opens the bypass line (9) only in the first position.
The turbine according to any one of the claims 1 to 3,
characterized in that
- the guide blades (12) are adjustable into a third position with reduced maximum flow cross-section with simultaneously closed bypass line (9),

- the third position is an intermediate position between the first and the second position.
The turbine according to any one of the preceding claims,
characterized in that
- the bypass line (9) comprises a number of bypass channels (10) which are fluidically connected in parallel with one another, which corresponds to the number of guide blades (12),

- each bypass channel (10) is assigned a certain guide blade (12) in such a manner that each guide blade (12) opens the bypass channel (10) assigned to it in the first position, closing it off in the second position.
The turbine according to any one of the preceding claims,
characterized in that
- the guide blade (12) comprises a guide blade leaf (13), which is attached in a rotationally fixed manner to a bearing pin (14) extending along an axial direction (A),

- on the bearing pin (14) or the guide blade leaves (13) a closure element (15) which is arranged in the respective bypass channel (10), which comprises a passage opening (17), is provided,

- the passage opening (17) in the first position is arranged in the bypass channel (10) so that the closure element (15) opens the bypass channel (10) for a fluid to flow through and in the second position is arranged outside the bypass channel (10) so that the closure element (15) closes off the bypass channel (10).
The turbine according to claim 6,
characterized in that
the respective bearing pin (14) of each guide blade (12) is rotatably mounted on a guide blade ring (19) which is attached in a fixed location on the turbine housing (2), wherein the adjusting of the guide blades (12) between the first and the second position takes place by rotating the bearing pin (14) and the guide blade leaf (13) attached thereon about an axis of rotation defined by the centre longitudinal axis (M) of the bearing pin (14).
The turbine according to claim 6 or 7,
characterized in that
the closure element (15) is designed as a face plate (16), which is axially provided on the face end of the bearing pin (14) or on the guide blade leaf (13).
The turbine according to claim 8,
characterized in that
- the face plate (16) is designed cylindrically and arranged concentrically to the bearing pin (14),

- the passage opening (17) extends along the axial direction (A) of the cylindrical face plate (16).
The turbine according to claim 8 or 9,
characterized in that
the passage opening (17) with respect to a top view of the face plate (16) in axial direction (A) is eccentrically arranged on the same.
The turbine according to any one of the claims 8 to 10,
characterized in that
the passage opening (17) is formed as a recess provided on the circumferential side (18) of the cylindrical face plate (16).
The turbine according to any one of the claims 8 to 11,
characterized in that
in the turbine housing (2) a fastening ring (20) which is arranged concentrically to the turbine wheel (6) is provided, which on a face end (21) facing the guide blades (12) for each closure element (15), in particular for each face plate (16), has a recess (22) which is formed complementarily to the closure element (15) or to the face plate (16), in which the closure element (10) or the face plate (16) is at least partially received.
The turbine according to any one of the claims 5 to 12,
characterized in that
the bypass channels (10) in the turbine housing (2) each have a cylindrical geometrical shape.
A guide blade (12) for a turbine (1) according to any one of the preceding claims,
- having a guide blade leaf (13), which is attached in a rotationally fixed manner to a bearing pin (14) extending along an axial direction (a),

- having a closure element (15) arranged in the respective bypass channel (10) and attached to the bearing pin (14) or to the guide blade leaf (13) for closing off a bypass channel (10) provided in the turbine housing (2) of the turbine (1),

- wherein the closure element (15) has a passage opening (17), which can be introduced into the bypass channel (10) for opening the latter for fluid to flow through.
The guide blade according to claim 14,
characterized in that
the closure element (15) is designed as a face plate (16), which is attached to the bearing pin (14) or to the guide blade leaf (13).
The guide blade according to claim 14 or 15,
characterized in that
- the face plate (16) is formed cylindrically and with respect to the axial direction (a) is arranged concentrically to the bearing pin (13),

- the passage opening (17) extends along the axial direction (a) of the cylindrical face plate (16) and with respect to a top view of the face plate (16) in the axial direction (a) is eccentrically arranged on the same.
An exhaust gas turbocharger having a turbine (1) according to any one of the claims 1 to 13.
An internal combustion engine having an exhaust gas turbocharger according to claim 17.