EP1320670A1

EP1320670A1 - Exhaust gas turbocharger, supercharged internal combustion engine and corresponding method

Info

Publication number: EP1320670A1
Application number: EP01978360A
Authority: EP
Inventors: Werner Bender; Helmut Daudel; Helmut Finger; Peter Fledersbacher; Siegfried Sumser; Freidrich Wirbeleit
Original assignee: DaimlerChrysler AG; 3K Warner Turbosystems GmbH
Current assignee: 3K Warner Turbosystems GmbH; Mercedes Benz Group AG
Priority date: 2000-09-29
Filing date: 2001-09-12
Publication date: 2003-06-25
Also published as: JP2004510094A; WO2002027164A1; US20030230085A1; DE10048237A1

Abstract

The invention relates to an internal combustion engine, which is provided with an exhaust gas recirculation system (23) and which has an exhaust gas turbocharger (2) having a variable turbine geometry (8). In order to improve the behavior of the exhaust gas, the exhaust gas turbine (3) is provided with two inflow channels (10, 11), which are separated from one another in a pressure-tight manner, whereby an inflow channel (10) communicates with an exhaust gas line (17), from which a recirculation line (24) of the exhaust gas recirculation system (23) branches.

Description

Exhaust gas turbocharger, supercharged internal combustion engine and method therefor

14. The invention relates to an exhaust gas turbocharger, a supercharged internal combustion engine and a method therefor according to the preamble of claims 1, 7 and 14 respectively.

A supercharged internal combustion engine is known from the publication DE 197 34 494 Cl, the exhaust gas turbocharger of which has an exhaust gas turbine with a variable turbine geometry. By adjusting the variable turbine geometry, the effective flow inlet cross-section in the turbine to the turbine wheel can be changed, whereby the exhaust gas back pressure in the line between the cylinder outlet of the internal combustion engine and the inlet of the turbine is influenced in a targeted manner, thereby adjusting the power consumption of the turbine and, accordingly, the compressor output of the compressor can. To improve the exhaust gas behavior of the internal combustion engine, in particular for NO _x reduction, an exhaust gas recirculation device is provided for returning exhaust gas from the exhaust system into the intake tract. The amount of the recirculated exhaust gas mass flow is set depending on the state variables and operating parameters of the internal combustion engine. If single-flow turbines with variable turbine geometry are used in such supercharged internal combustion engines with exhaust gas recirculation, the pressure drop to the fresh air side required for returning the desired amount of exhaust gas is achieved by accumulating the entire exhaust gas mass flow. However, as the mass flow returned increases, the charge change in the cylinders is negatively influenced and fuel consumption increases.

The invention is based on the problem of reducing pollutant emissions and fuel consumption in supercharged internal combustion engines with exhaust gas recirculation.

This problem is solved according to the invention with the features of claims 1, 7 and 14, respectively. The subclaims indicate preferred further developments.

The exhaust gas turbine of the novel exhaust gas turbocharger is designed with two passages and has two inflow ducts, each with a flow inlet cross section to the turbine wheel, the two inflow ducts being formed separately and being shielded from one another in a pressure-tight manner, in particular also being pressure-tightly shielded from the environment. In addition, each inflow channel has its own inflow connection for the separate supply of exhaust gas.

This design of the exhaust gas turbocharger makes it possible to provide two independent exhaust gas lines between the cylinder outlets of the internal combustion engine and the exhaust gas turbine and to supply each inflow channel with exhaust gas separately. With such an exhaust gas turbocharger, a new type of internal combustion engine can be are formed such that each exhaust line only receives the exhaust gas of a part of the cylinders of the engine and exactly one of the two exhaust lines is connected to the intake tract via a return line of the exhaust gas recirculation device. Only the part of the engine exhaust gas of this exhaust gas line is accumulated in a high amount in accordance with the required exhaust gas recirculation quantity, as a result of which significantly fewer charge exchange disadvantages are to be expected during the exhaust gas recirculation mode of operation and a correspondingly lower fuel consumption and nevertheless the exhaust gas behavior can be positively influenced. Advantageously, the exhaust gas line from which the return line of the exhaust gas recirculation branches off is supplied with the exhaust gas from a certain number of cylinders of the internal combustion engine, in particular a smaller number of cylinders and possibly only one cylinder than the parallel exhaust gas line, which is not involved in the exhaust gas recirculation.

Due to the two separate and pressure-tightly shielded inflow ducts in the exhaust gas turbine, the exhaust gas back pressure in that exhaust line or that inflow duct of the turbine, which or which does not communicate with the exhaust gas recirculation device, can expediently be manipulated via the variable turbine geometry arranged in the flow inlet cross section of this inflow duct. By adjusting the variable turbine geometry, the turbine output and thus also the work to be given off by the compressor or the amount of air conveyed can be influenced in such a way that a pressure drop that enables the exhaust gas recirculation occurs between the exhaust gas line involved in the exhaust gas recirculation and the intake tract. In particular, it is possible to to drive the internal combustion engine to move the variable turbine geometry to the second inflow channel of the turbine, which is not involved in the exhaust gas recirculation, in the direction of its open position, in which the turbine geometry forms only a small flow resistance in the flow inlet cross section, so that the exhaust gas back pressure in this inflow channel is reduced and less compression work is given off and accordingly, a lower boost pressure is generated, which corresponds to the optimal air ratio. Regardless of the exhaust gas back pressure in the exhaust gas line that communicates with the inflow duct not involved in the exhaust gas recirculation, a higher exhaust gas back pressure for returning exhaust gas into the intake tract, which exceeds the charge pressure on the intake side, can be located in the parallel exhaust gas line be generated.

While the line for the exhaust gas recirculation is backed up with one line supplied to the turbine, the desired turbine speed is coordinated via the channel, which corresponds to the variable turbine geometry.

The increased exhaust gas back pressure in the first exhaust gas line communicating with the exhaust gas recirculation can be supported by arranging a variable or unchangeable flow obstacle in the form of a guide vane or a similar design in the flow inlet cross section which is assigned to the inflow channel assigned to the first exhaust gas line. It may be expedient here to additionally or alternatively also provide a variable turbine geometry in this flow inlet cross section. A combination turbine with a semi-axial and a radial flow inlet cross section is selected as the preferred turbine type, the variable turbine geometry being expediently arranged in the radial flow inlet cross section and the exhaust gas recirculation being assigned to the semi-axial inflow channel or flow inlet cross section. Such combination turbines with a semi-axial and a radial flow inlet cross section only have to be modified compared to combination turbines known from the prior art in such a way that the inflow channels assigned to the two flow inlet cross sections are mutually pressure-tight to prevent undesired pressure compensation between these inflow channels. This is achieved, for example, by connecting a flow ring, which is arranged between the semi-axial and radial flow inlet cross section, in a pressure-tight manner to a partition between the inflow channels.

In a preferred development of the internal combustion engine, a bypass line connecting the two exhaust gas lines outside the exhaust gas turbine is provided, which is equipped with an adjustable bypass valve. Depending on the position of the bypass valve, pressure equalization between the two exhaust gas lines can be permitted, in order to create the same pressure conditions in both turbine inflow channels, particularly in engine operation without exhaust gas recirculation. The bypass valve can advantageously also be switched to a position in which exhaust gas is discharged from one of the two exhaust gas lines or from both exhaust gas lines bypassing the exhaust gas turbine from the exhaust gas line. Further advantages and expedient embodiments can be found in the further claims, the description of the figures and the drawings. Show it:

1 is a schematic representation of a supercharged internal combustion engine with a double-flow combination turbine with semi-axial and radial flow inlet cross section,

2 shows a section through a combination turbine with two inflow channels which are formed separately and are pressure-tight against one another,

3 shows a section through a combination turbine in a further embodiment,

4 shows a section through a double-flow radial turbine,

Fig. 5 is a graph showing the course of the exhaust gas mass flow through a turbine as a function of the pressure gradient across the turbine, shown for each of the two inflow channels of the combination turbine.

In the following figures, the same components are provided with the same reference symbols.

The internal combustion engine 1 shown in FIG. 1 - an Otto engine or a diesel engine - comprises an exhaust gas turbocharger 2 with a turbine 3 in the exhaust line 4 and with a compressor 5 in the intake tract β, the movement of the turbine wheel via a shaft 7 on the compressor wheel of the Compressor 5 is transmitted. The turbine 3 of the exhaust gas turbocharger 2 is equipped with a variable Bine geometry 8 equipped, via which the effective flow inlet cross-section to the turbine wheel 9 can be adjusted depending on the state of the internal combustion engine. The turbine 3 is designed as a dual-flow combination turbine with two floods or inflow channels 10 and 11, of which a first inflow channel 10 has a semi-axial flow inlet cross section 12 to the turbine wheel 9 and the second inflow channel 11 has a radial flow inlet cross section 13 to the turbine wheel 9. The two inflow channels 10 and 11 are separated by a partition 14 fixed to the housing and are shielded from one another in a pressure-tight manner.

The variable turbine geometry 8 is expediently located in the radial flow inlet cross section 13 of the inflow duct 11 and is designed in particular as a guide grille with adjustable guide vanes or as a guide grid that can be displaced axially into the radial flow inlet cross section 13, a variable adjustable flow inlet cross section to the turbine wheel 9 being released depending on the position of the guide grid becomes.

Each flood or inflow channel 10 or 11 is provided with an inflow connection 15 or 16. Exhaust gas can be supplied separately to the associated inflow channel 10 or 11 via each inflow connection 15 or 16. The exhaust gas is supplied via two independently configured exhaust pipes 17 and 18, which are part of the exhaust line 4. Each exhaust pipe 17 or 18 is assigned to a defined number of cylinder outlets of the internal combustion engine. In the exemplary embodiment, the internal combustion engine is V-shaped and has two cylinder banks 19 and 20, each with the same Number of cylinders. The first exhaust line 17 leads from the cylinder bank 19 assigned to it to the first inflow duct 10, the second exhaust line 18 accordingly leads from the second cylinder bank 20 to the second inflow duct 11. Between the two exhaust lines 17 and 18 there is a connecting bypass line 21 with an upstream of the turbine 3 adjustable blow-off or Blow valve 22 arranged. The bypass valve 22- can be placed in a blocking position, in which the bypass line 21 is shut off and pressure exchange between the exhaust gas lines 17 and 18 is prevented, in a through position in which the bypass line is open and pressure exchange is possible, and in a blow-off position are displaced, in which exhaust gas is discharged from one of the two exhaust gas lines or from both exhaust gas lines bypassing the turbine from the exhaust gas line.

Furthermore, an exhaust gas recirculation device 23 is provided, which comprises a return line 24 between the first exhaust line 17 and the intake tract 6 directly upstream of the cylinder inlet of the internal combustion engine 1, as well as a check valve 25 or check valve or flap valve, that between a blocking position blocking the return line 24 and a releasing opening position is adjustable or adjusts itself. An exhaust gas cooler 26 is also advantageously arranged in the return line 24.

All the control elements of the various adjustable components, in particular the variable turbine geometry 8, the blow-off valve 22 and the check valve 25, are moved into their desired position via control signals which can be generated in a regulating and control device 27. poses.

During operation of the internal combustion engine, the turbine power is transferred to the compressor 5, which draws in ambient air at the pressure pi and compresses it to an increased pressure p ₂ . A charge air cooler 28, through which the compressed air flows, is arranged downstream of the compressor 5 in the intake tract 6. After leaving the charge air cooler 28, the air is compressed to the charge pressure p _2s , with which it is introduced into the cylinder inlet of the internal combustion engine. At the cylinder outlet, the exhaust gas back pressure p ₃ Zylinder prevails in the first exhaust line 17, which is assigned to the first cylinder bank 19; Exhaust gas back pressure p _{32 is present} in second exhaust line 18, which is assigned to second cylinder bank 20. In the turbine 3, the exhaust gas is expanded to the low pressure ₄ and then initially subjected to a catalytic cleaning and finally blown off into the environment.

In the exhaust gas recirculation mode in the fired drive mode of operation, the check valve 25 of the exhaust gas recirculation device 23 is set in the open position so that exhaust gas can flow from the first exhaust line 17 into the intake tract 6. In order to ensure a pressure gradient that enables exhaust gas recirculation with an exhaust gas back pressure p _3i in exhaust gas line 17 that exceeds charging pressure p ₂ s, variable turbine geometry 8 is set in the radial flow inlet cross section 13 of second flow channel 11 into a position in which a pressure gradient that enables exhaust gas recirculation between first exhaust pipe 17 and intake tract 6. Such a pressure drop arises taking into account the required fuel-air ratio in particular in the case of a position of the variable turbine geometry 8 which is offset in the direction of its open position.

Such a pressure drop can be supported in that the first flow inlet cross section 12 in the first inflow duct 10 is designed to be relatively small and assumes a value that may advantageously be slightly larger than the second flow inlet cross section 13 in the stowed position of the variable turbine geometry, but is smaller than this cross section in the open position of the variable turbine geometry. Due to the relatively small first flow inlet cross section 12, a relatively high exhaust gas back pressure p ₃ ι can be achieved in the first exhaust line 17. With active exhaust gas recirculation, in particular the exhaust gas back pressure p ₃ ι in the first exhaust gas line 17 is higher than the exhaust gas back pressure p ₃₂ in the second exhaust gas line 18, which has no connection to the exhaust gas recirculation device 23.

In engine braking operation, the variable turbine geometry is transferred to its stowed position, in which the radial flow inlet cross section 13 is reduced to a minimum value, as a result of which the exhaust gas back pressure p ₃₂ in the second exhaust gas line 18 increases to a high value, which is in particular greater than the exhaust gas back pressure p _3i in of the first exhaust pipe 17 communicating with the exhaust gas recirculation device 23. This makes it possible to achieve very high engine braking powers by greatly increasing the exhaust gas back pressure p ₃₂ without exceeding the critical speed limit of the exhaust gas turbocharger by actuating the valves 22 and 25 in an advantageous manner , 2, an exhaust gas turbocharger 2 with an exhaust gas turbine 3 with variable turbine geometry 8 is shown. The turbine 3 comprises a first inflow duct 10 with a semi-axial flow entry cross section 12 and a second inflow duct 11 with a radial flow entry cross section 13. Exhaust gas from the inflow ducts 10 and 11 can be fed to the turbine wheel 9 via the flow entry cross sections 12 and 13. A fixed grid 29 is located in the semi-axial flow inlet cross section 12, whereas a die 33 is arranged in the radial flow inlet cross section 13 in addition to a guide grid 30. The two inflow channels 10 and 11 are separated by a partition 14 fixed to the housing. Arranged in the region of the flow inlet cross sections 12 and 13 is a flow ring 31 which divides the two flow inlet cross sections and has a streamlined contour, the radial outside of which faces the radially inward end region of the partition wall 14. For a pressure-tight shielding between the inflow channels 10 and 11, an annular sealing element 32 is arranged between the end face of the partition wall 14 and the radially outer side of the flow ring 31.

The axially displaceable die 33 in the radial flow inlet cross section 13 is fastened to an axial slide 34, which surrounds the turbine wheel 9 in a ring. The rigid guide grid, which dips into the movable die, is attached to the flow ring 31 in the example shown.

The first inflow channel 10, which in the semi-axial Flow inlet cross section 12 opens out, has a considerably smaller volume than the second inflow channel 11 with a radial flow inlet cross section 13.

The turbine 3 of the exhaust gas turbocharger 2 according to FIG. 3 also has a first inflow duct 10 with a semi-axial flow inlet cross section 12 and a second inflow duct 11 with a radial flow inlet cross section 13, which are divided by a partition 14, the two flow inlet cross sections 12 and 13 being directly from the flow ring 31 are limited and a sealing element 32 is arranged between the flow ring 31 and the partition 14. The grating element in the semi-axial flow inlet cross section 12 is designed as a fixed grille 29, while an adjustable guide grille 30 with adjustable guide blades is arranged in the radial flow entry cross section 13. In the exemplary embodiment according to FIG. 3, the volumes of inflow channels 10 and 11 are approximately the same size.

The sectional view according to FIG. 4 shows a radial turbine with two radial inflow channels 10 and 11. The inflow ducts 10 and 11 of the turbine 3, which is also referred to as a two-segment turbine, take the form of partial spirals and open out on radially opposite sides via their flow inlet cross sections 12 and 13, respectively, into the turbine space accommodating the turbine wheel 9. It can be expedient to provide an angle of the mouth cross sections of the inflow channels to the turbine wheel 9 that is different from 180 °. The guide vane 30, which surrounds the turbine wheel 9 radially, has adjustable guide vanes.

5 shows a graph with the course of the turbine throughput parameters φ as a function of the pressure gradient p ₃ / p ₄ above the exhaust gas turbine, p ₃ denoting the exhaust gas back pressure upstream of the turbine and p ₄ the relaxed pressure downstream of the turbine. On the one hand, the throughput parameter φi for the first flow channel is shown; Throughput parameter φi is shown as a line due to the fixed geometry in the flow inlet cross section assigned to the first inflow channel. The throughput parameter φ ₂ that can be represented in the second inflow channel is characterized by a hatched area due to the variably adjustable turbine geometry with a variable flow inlet cross-section, the lower limit φ ₂ , u of which corresponds to the closed position of the variable turbine geometry and the upper limit of φ ₂ , o to the open position of the turbine geometry. A dashed line in the adjustment area of the variable turbine geometry exemplifies a current guide vane position in which, due to the comparatively small flow inlet cross-section in the first flow duct with fixed grille and the resulting high level of accumulation in this inflow duct, a high exhaust gas back pressure p ₃ ι occurs in the first inflow duct, which one Exhaust gas recirculation favors. In the second inflow duct with variable turbine geometry, on the other hand, there is a lower exhaust gas back pressure p ₃₂ , which means that the turbine can be operated in more favorable efficiency ranges.

Claims

claims

1. Internal combustion engine with an exhaust gas turbocharger and an exhaust gas recirculation device, the exhaust gas turbocharger (2) having a variable turbine geometry (8) equipped exhaust gas turbine (3) in the exhaust line (4) and a compressor (5) in the intake tract (6) of the internal combustion engine (1) and the exhaust gas recirculation device (23) comprises a return line (24) between the exhaust line (4) and the intake tract (6) and an adjustable shut-off valve (25), with a regulating and control device (27), in which, depending on the state of the internal combustion engine (1) Control signals for setting the variable turbine geometry (8) and the check valve (25) can be generated, characterized in that the exhaust gas turbine (3) has two channels with two separate inflow channels (10, 11) each with a flow inlet cross section (12, 13) to the turbine wheel (9) is formed, the two inflow ducts (10, 11) being shielded from one another in a pressure-tight manner that at least one flow inlet cross Section (12, 13) of an inflow duct (10, 11) to the turbine wheel (9) can be variably adjusted via the variable turbine geometry (8) that two separate exhaust gas lines in the exhaust line (4) (17, 18) are provided, with each of which a part of the cylinder outlets of the internal combustion engine (1) is connected to an inflow channel (10, 11) such that the return line (24) of the exhaust gas recirculation device (23) is exactly one of the two exhaust lines

(17) connects to the intake tract (6).

2. Internal combustion engine according to claim 1, so that the first exhaust gas line (17) communicating with the return line (24) is associated with a smaller number of cylinder outlets than the second exhaust line (18) is associated with the return line (24).

3. Internal combustion engine according to claim 1 of FIG. 2, so that the first inflow channel (10) in the exhaust gas turbine (3), which communicates with the return line (24) of the exhaust gas recirculation device, is designed to be smaller than the second flow channel (11).

4. Internal combustion engine according to one of claims 1 to 3, characterized in that the flow inlet cross section (12) assigned to the first inflow channel (10) is small compared to the flow inlet cross section (13) assigned to the second inflow channel (11) and can optionally be reduced to zero.

5. Internal combustion engine according to one of claims 1 to 4, so that the variable turbine geometry (8) is arranged in the flow inlet cross section (13) of the second flow channel (11) that does not communicate with the return line (24).

6. Internal combustion engine according to one of claims 1 to 5, d a d u r c h g e k e n n z e i c h n e t that a bridging line (21) connecting the two exhaust pipes (17, 18) is provided with an adjustable bypass valve (22).

7. Exhaust gas turbocharger for an internal combustion engine, in particular for an internal combustion engine according to one of claims 1 to 6, with an exhaust gas turbine (3) and a compressor (5) which is connected via a shaft (7) to the exhaust gas turbine (3), the Exhaust gas turbine (3) with two inflow channels (10, 11) each with a flow inlet cross-section (12, 13) to the turbine wheel (9) and in at least one of the flow inlet cross-sections (12, 13) a variable turbine geometry (8) is provided for variable cross-sectional adjustment , characterized in that the two inflow channels (10, 11) are formed separately and are shielded from one another in a pressure-tight manner and each have an inflow connection (15, 16) for the separate supply of exhaust gas.

8. Exhaust gas turbocharger according to claim 7, characterized in that the exhaust gas turbine (3) is designed as a combination turbine and the first inflow channel (10) has a semi-axial flow inlet cross section (12) to the turbine wheel (9) and the second inflow channel (11) has a radial flow inlet cross section (13) having.

9. Exhaust gas turbocharger according to claim 8, so that the variable turbine geometry (8) is arranged in the radial flow inlet cross section (13).

10. Exhaust gas turbocharger according to claim 8 or 9, so that the two inlet channels (10, 11) are separated by a partition (14) in the housing of the charger (2).

11. Exhaust gas turbocharger according to one of claims 8 to 10, characterized in that a flow ring (31) is provided between the flow inlet cross-sections (12, 13) of the two inflow channels (10, 11), wherein between the flow ring (31) and partition (14) Sealing element (32) is provided.

12. Exhaust gas turbocharger according to one of claims 7 to 11, characterized in that the variable turbine geometry (8) is designed as a guide grille (30) with adjustable guide vanes.

13. Exhaust gas turbocharger according to one of claims 7 to 12, that the variable turbine geometry (8) is designed as a guide vane (30) which is adjustable axially into the flow inlet cross section.

14. A method for operating an internal combustion engine according to one of claims 1 to 6, characterized in that in the fired drive mode of operation, the exhaust gas from the exhaust pipe (17), which is connected to the first inflow channel (10), is returned to the intake tract (6) becomes that the exhaust gas recirculation is prevented during engine braking and the variable turbine geometry (8) in the second flow channel (11) is transferred to a congestion position increasing the exhaust gas back pressure.

15. The method according to claim 14, so that the exhaust pipes (17 and 18) are connected by opening the blow-off valve (22) and the braking power and turbine speed are regulated by blowing in the blow-off valve (22) in engine braking operation.