DE102013215574A1 - Charged internal combustion engine with exhaust aftertreatment and method for operating such an internal combustion engine - Google Patents

Abstract

The invention relates to a supercharged internal combustion engine (1) having an intake line (2) for supplying charge air and an exhaust line (4) for discharging the exhaust gas and having at least two exhaust gas turbochargers (6, 7) connected in series. 4) arranged turbine (6a, 7a) and in the intake passage (2) arranged compressor (6b, 7b) and of which a first exhaust gas turbocharger (6) as a low-pressure stage (6) and a second exhaust gas turbocharger (7) as a high-pressure stage ( 7), wherein - the second turbine (7a) of the second exhaust gas turbocharger (7) upstream of the first turbine (6a) of the first exhaust gas turbocharger (6) and the second compressor (7b) of the second exhaust gas turbocharger (7) downstream of the first compressor (6b) of the first exhaust gas turbocharger (6) is arranged, - a first bypass line (14) is provided upstream of the first turbine (6a) forming a node (8) of the exhaust pipe (4) a a second bypass line (12) is provided, which branches off from the exhaust line (4) upstream of the second turbine (7a) and in which a shut-off element (13) is arranged, and - downstream of the turbines (6a, 7a) in the Exhaust pipe (4) at least one exhaust aftertreatment system (15) is provided, wherein a valve (9) at the node (8) in the exhaust pipe (4) is arranged.

Description

• – die zweite Turbine des zweiten Abgasturboladers stromaufwärts der ersten Turbine des ersten Abgasturboladers angeordnet ist und der zweite Verdichter des zweiten Abgasturboladers stromabwärts des ersten Verdichters des ersten Abgasturboladers angeordnet ist,
• – eine erste Bypassleitung vorgesehen ist, die stromaufwärts der ersten Turbine unter Ausbildung eines Knotenpunktes von der Abgasleitung abzweigt,
• – eine zweite Bypassleitung vorgesehen ist, die stromaufwärts der zweiten Turbine von der Abgasleitung abzweigt und in der ein Absperrelement angeordnet ist, und
• – stromabwärts der Turbinen in der Abgasleitung mindestens ein Abgasnachbehandlungssystem vorgesehen ist.

The invention relates to a supercharged internal combustion engine with an intake pipe for supplying charge air and an exhaust pipe for discharging the exhaust gas and at least two exhaust gas turbochargers connected in series, each comprising a turbine disposed in the exhaust pipe and a compressor arranged in the intake manifold and of which a first Exhaust gas turbocharger is used as a low pressure stage and a second exhaust gas turbocharger is used as a high-pressure stage, wherein

• The second turbine of the second exhaust gas turbocharger is arranged upstream of the first turbine of the first exhaust gas turbocharger and the second compressor of the second exhaust gas turbocharger is arranged downstream of the first compressor of the first exhaust gas turbocharger
• A first bypass line is provided, which branches off from the exhaust line upstream of the first turbine, forming a junction,
• - A second bypass line is provided, which branches off from the exhaust pipe upstream of the second turbine and in which a shut-off element is arranged, and
• - At least one exhaust aftertreatment system is provided downstream of the turbines in the exhaust pipe.

Furthermore, the invention relates to a method for operating a supercharged internal combustion engine of the type mentioned above.

An internal combustion engine of the type mentioned is used as a motor vehicle drive. In the context of the present invention, the term internal combustion engine comprises gasoline engines, diesel engines, but also hybrid internal combustion engines, which use a hybrid combustion process, and hybrid drives, which in addition to the internal combustion engine comprise an electric motor which can be electrically connected to the internal combustion engine, which receives power from the internal combustion engine or as switchable auxiliary drive additionally delivers power.

The charge is used primarily to increase the performance of the internal combustion engine. The air required for the combustion process is compressed, which allows each cylinder per working cycle, a larger air mass can be supplied. As a result, the fuel mass and thus the medium pressure can be increased.

The charge is a suitable means to increase the capacity of an internal combustion engine with unchanged displacement, or to reduce the displacement at the same power. In any case, the charging leads to an increase in space performance and a lower power mass. At the same vehicle boundary conditions, the load collective can thus be shifted to higher loads in which the specific fuel consumption is lower. The latter is also referred to as downsizing.

Charging thus supports the constant effort in the development of internal combustion engines to minimize fuel consumption due to the limited resources of fossil fuels, in particular due to the limited reserves of mineral oil as a raw material for the recovery of fuels for the operation of internal combustion engines. H. to improve the efficiency of the internal combustion engine.

As a rule, an exhaust gas turbocharger is used for the supercharging, in which a compressor and a turbine are arranged on the same shaft, wherein the hot exhaust gas flow is supplied to the turbine and relaxes with energy release in this turbine, whereby the shaft is rotated. The energy emitted by the exhaust gas flow to the turbine and finally to the shaft is used to drive the compressor, which is also arranged on the shaft. The compressor conveys and compresses the charge air supplied to it, whereby a charging of the cylinder is achieved. Optionally, a charge air cooling is additionally provided, with which the compressed charge air is cooled before entering the cylinder.

The advantage of the exhaust gas turbocharger, for example in comparison to a mechanical supercharger, is that there is no mechanical connection to the power transmission between the supercharger and the internal combustion engine. While a mechanical supercharger obtains the energy required for its drive completely from the internal combustion engine and thus reduces the power provided and thus adversely affects the efficiency, the exhaust gas turbocharger uses the exhaust gas energy of the hot exhaust gases.

The interpretation of the turbocharger turbocharger is difficult, with basically a noticeable increase in performance in all speed ranges is sought. In supercharged internal combustion engines with an exhaust gas turbocharger falls below a certain speed, a strong torque drop is observed. This effect is undesirable and therefore also counts among the most serious disadvantages of turbocharging.

This torque drop becomes understandable if it is taken into account that the boost pressure ratio depends on the turbine pressure ratio. For example, if the engine speed is reduced, this leads to a smaller exhaust gas mass flow and thus to a smaller turbine pressure ratio. As a result, at lower speeds towards the boost pressure ratio also decreases, which is synonymous with a torque drop.

The torque characteristic of a supercharged internal combustion engine is attempted to improve by different measures according to the prior art, for example, by a small design of the turbine cross-section and simultaneous Abgasabblasung, but this leads to disadvantages at high speeds. If the exhaust gas mass flow exceeds a critical value, part of the exhaust gas flow is conducted past the turbine as part of an exhaust gas blow-by means of a bypass line.

Basically, a small design of the turbine cross-section is possible together with a charge air blower, this variant is rarely used due to the energetic disadvantages of Ladeluftabblasung, and the existing compressor can get to their delivery limit and thus the desired performance can not be displayed.

The exhaust gas turbocharger can also be designed for high speeds with a large turbine cross section. In this case, the suction system is then designed in such a way that a dynamic charging takes place by wave processes at low speeds. Disadvantages are the high construction costs and the sluggish behavior with changes in speed.

A turbine with variable turbine geometry allows an adjustment of the turbine geometry or the effective turbine cross-section at the respective operating point of the internal combustion engine, so that a control of the turbine geometry in terms of low and high speeds as well as low and high loads can be done.

The torque characteristic of a supercharged internal combustion engine may be further improved by a plurality of turbochargers connected in parallel or in series, optionally in combination with a mechanical supercharger.

The internal combustion engine, which is the subject of the present invention, has at least two turbochargers arranged in series. By switching in series of two exhaust gas turbochargers, one of which is an exhaust gas turbocharger as a high pressure stage and an exhaust gas turbocharger as a low pressure stage, the compressor map can be widened in an advantageous manner, both towards smaller compressor streams as well as towards larger compressor streams.

In particular, in the case of the exhaust gas turbocharger serving as a high-pressure stage, it is possible to shift the surge limit to smaller compressor flows, whereby high charge pressure ratios can be achieved even with small compressor flows, which significantly improves the torque characteristic in the lower part load range. This is achieved by designing the high-pressure turbine for small exhaust gas mass flows and providing a bypass line, with which increasing exhaust gas mass flow increasingly exhaust gas is passed to the high-pressure turbine. For this purpose, the bypass line branches off from the exhaust gas line upstream of the high-pressure turbine and flows back into the exhaust gas line downstream of the turbine, wherein a shut-off element is arranged in the bypass line in order to control the exhaust gas flow passed by the high-pressure turbine.

However, two turbochargers connected in series offer even more advantages. The increase in performance through charging can be further increased. Furthermore, the response of such a supercharged internal combustion engine, especially in the partial load range, significantly improved over a comparable internal combustion engine with single-stage supercharging. The reason for this is that the smaller high-pressure stage is less sluggish than a larger exhaust-gas turbocharger used in the context of a single-stage supercharger because the rotor or impeller of a smaller exhaust-gas turbocharger accelerates and decelerates faster.

This also has advantages in terms of particle emissions. Since the necessary increase in the air mass supplied to the cylinders of the increased amount of fuel due to the inertia of the wheels takes place only at a delay when accelerating, the charge air is fed to the engine almost instantaneously in a smaller high-pressure turbocharger, and thus operating conditions with increased particle emission are almost avoided.

Turbocharging in combination with exhaust aftertreatment proves to be problematic. An internal combustion engine according to the preamble of claim 1, for example, in the European patent application EP 1 396 619 A1 described. The EP 1 396 619 A1 has the simultaneous use of an exhaust turbocharging and exhaust aftertreatment to the object, with the closest possible arrangement of the exhaust aftertreatment system is sought at the outlet of the internal combustion engine. Several concepts are shown. In an embodiment according to the EP 1 396 619 A1 the exhaust gas flow is directed by means of suitable switching devices and bypass lines in such a way that it is guided past both turbines. This offers in terms of a catalyst arranged in the exhaust pipe downstream of the turbine, in particular after a cold start or in the warm-up phase of the internal combustion engine, advantages, since the hot exhaust gases are fed directly to the catalyst and are not first passed under heat through the viewable as a temperature sink turbine. In this way, the catalyst reaches its light-off temperature faster after a cold start or in the warm-up phase. Another embodiment provides for the arrangement of a second catalytic converter in the bypass line bypassing the two turbines.

A disadvantage of the in the EP 1 396 619 A1 The concept described is that in the warm-up phase of the internal combustion engine, the entire exhaust gas is supplied for heating the catalysts and no exhaust gas is passed through the turbines, so that no charge takes place during the warm-up phase for lack of boost pressure.

The indicated conflict between exhaust turbocharging and exhaust aftertreatment can not be resolved according to the prior art.

Against this background, it is an object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, with which the disadvantages known in the prior art can be overcome and with which, in particular after a cold start high charging pressures can be provided and a fast Heating the exhaust aftertreatment systems can be realized.

Another object of the present invention is to provide a method of operating a supercharged internal combustion engine of the type mentioned above.

• – die zweite Turbine des zweiten Abgasturboladers stromaufwärts der ersten Turbine des ersten Abgasturboladers angeordnet ist und der zweite Verdichter des zweiten Abgasturboladers stromabwärts des ersten Verdichters des ersten Abgasturboladers angeordnet ist,
• – eine erste Bypassleitung vorgesehen ist, die stromaufwärts der ersten Turbine unter Ausbildung eines Knotenpunktes von der Abgasleitung abzweigt,
• – eine zweite Bypassleitung vorgesehen ist, die stromaufwärts der zweiten Turbine von der Abgasleitung abzweigt und in der ein Absperrelement angeordnet ist, und stromabwärts der Turbinen in der Abgasleitung mindestens ein Abgasnachbehandlungssystem vorgesehen ist, und die dadurch gekennzeichnet ist, dass
• – ein Ventil am Knotenpunkt in der Abgasleitung angeordnet ist.

The first sub-task is solved by a supercharged internal combustion engine with an intake for supplying charge air and an exhaust pipe for discharging the exhaust gas and at least two exhaust gas turbochargers connected in series, each comprising a turbine disposed in the exhaust pipe and a compressor arranged in the intake manifold and of where a first exhaust gas turbocharger is used as a low-pressure stage and a second exhaust gas turbocharger serves as a high-pressure stage, wherein

• The second turbine of the second exhaust gas turbocharger is arranged upstream of the first turbine of the first exhaust gas turbocharger and the second compressor of the second exhaust gas turbocharger is arranged downstream of the first compressor of the first exhaust gas turbocharger
• A first bypass line is provided, which branches off from the exhaust line upstream of the first turbine, forming a junction,
• A second bypass line is provided, which branches off the exhaust line upstream of the second turbine and in which a shut-off element is arranged, and downstream of the turbines in the exhaust line at least one exhaust aftertreatment system is provided, and which is characterized in that
• - A valve is arranged at the node in the exhaust pipe.

The internal combustion engine according to the invention is equipped with two turbines arranged in series, arranged in an exhaust line, and two compressors connected in series and arranged in an intake line.

Advantageously, therefore, embodiments in which the first compressor is designed to be larger than the second compressor, because in this embodiment of the internal combustion engine, the first compressor in the two-stage compression forms the low pressure stage, whereas the second compressor compresses the already precompressed air and thus represents the high-pressure stage ,

For the same reason, embodiments are advantageous in which the first turbine is designed to be larger than the second turbine. Because the second turbine serves as a high-pressure turbine, while relaxed in the first turbine, an exhaust stream, which already has a lower pressure and a lower density as a result of passing through the high-pressure stage.

According to the invention, the turbine of the high-pressure stage has no bypass line, whereas the turbine of the low-pressure stage has a bypass line, through which exhaust gas can be conducted past the turbine.

During the warm-up phase, the exhaust gas flow, preferably the entire exhaust gas flow, through the second turbine, i. H. passed through the turbine of the high-pressure stage, and downstream of the second turbine via the first bypass line, which branches off upstream of the first turbine to form a node from the exhaust pipe, passed the first turbine and back into the exhaust pipe.

If the entire exhaust gas flow in the warm-up phase is passed through the smaller second turbine, this produces a sufficiently high boost pressure. At the same time, by bypassing the first turbine, the larger turbine to be regarded as a temperature sink is eliminated and the hot exhaust gas is fed directly to the at least one exhaust aftertreatment system, which is why this system reaches its light-off temperature faster after a cold start or in the warm-up phase.

At the node at which the first bypass line branches off from the exhaust line, a valve is arranged, which blocks the exhaust line to the first turbine and releases the first bypass line in the warm-up phase, so that the entire exhaust gas flow is guided past the larger first turbine. This is a significant advantage compared to conventional embodiments in which the valve is arranged in the bypass line itself and, with the valve open, further exhaust gas can flow into the turbine of the low-pressure stage. Although the turbine of the low-pressure stage forms a certain flow resistance even then. Nonetheless, part of the exhaust flow passes through the larger first turbine. However, this partial flow is a not inconsiderable percentage of the total exhaust gas flow in the operating modes considered here, which is then not directly available to the exhaust aftertreatment system after a cold start for heating.

With the internal combustion engine according to the invention, the first object underlying the invention is achieved, namely provided a supercharged internal combustion engine according to the preamble of claim 1, with the high charge pressures can be provided after a cold start and at the same time a rapid heating of the exhaust aftertreatment systems can be realized.

The at least one exhaust aftertreatment system may be an oxidation catalyst, a three-way catalyst, a storage catalyst, a selective catalyst, and / or a particulate filter.

Further advantageous embodiments of the internal combustion engine according to the invention are discussed in connection with the subclaims.

Advantageous embodiments of the supercharged internal combustion engine, in which the valve at the junction is a 3-2-way valve.

Embodiments of the supercharged internal combustion engine in which the valve at the junction is a pivotable flap are advantageous.

In this connection, embodiments of the supercharged internal combustion engine in which the flap is pivotable against the exhaust gas flow starting from an obstructed first bypass line when the first bypass line is released are advantageous. Then, the flap, if it is defective, pivoted from the exhaust gas flow into the position in which the first bypass line is blocked, and both turbines are flowed through by the exhaust gas.

Advantageous embodiments of the supercharged internal combustion engine, in which the valve is electrically, hydraulically, pneumatically, mechanically or magnetically controlled, preferably by means of motor control.

Embodiments of the supercharged internal combustion engine in which the valve is infinitely variable or controllable in stages, ie. H. is switchable.

Embodiments of the supercharged internal combustion engine in which the first bypass line downstream of the first turbine opens into the exhaust gas line are advantageous.

Embodiments of the supercharged internal combustion engine in which the second bypass line opens into the exhaust gas line upstream of the first turbine and downstream of the second turbine are advantageous.

The fact that the bypass lines open again into the exhaust pipe, has the advantage that then the entire exhaust gas can be supplied to the provided in the exhaust pipe exhaust aftertreatment system.

Advantageous embodiments of the supercharged internal combustion engine, in which an exhaust gas recirculation is provided, which comprises a line which branches off upstream of the two turbines from the exhaust pipe and opens into the intake, preferably downstream of the compressor.

To meet future limits for nitrogen oxide emissions, an exhaust gas recirculation is increasingly used, ie the return of exhaust gases from the exhaust pipe into the intake, in which the nitrogen oxide emissions can be significantly reduced with increasing exhaust gas recirculation rate. The exhaust gas recirculation rate x _{EGR is} determined as follows: x _AGR = m _EGR / (m _EGR + m _{fresh air} ), wherein m _{AGR refers to} the mass of recirculated exhaust gas and m _{fresh air,} the supplied - optionally guided by a compressor and compressed - fresh air or combustion air.

Exhaust gas recirculation is also suitable for reducing emissions of unburned hydrocarbons in the partial load range.

In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates are required, which can be on the order of x _EGR ≈ 60% to 70%.

Advantageous embodiments of the supercharged internal combustion engine, in which the first compressor is designed to be larger than the second compressor.

Advantageous embodiments of the supercharged internal combustion engine, in which the first turbine is designed to be larger than the second turbine.

Embodiments of the supercharged internal combustion engine in which the second turbine of the second exhaust gas turbocharger has a variable turbine geometry are advantageous.

A variable turbine geometry increases the flexibility of charging. It allows a stepless adjustment of the turbine geometry to the respective operating point of the internal combustion engine or to the current exhaust gas mass flow. Unlike a fixed-geometry turbine, there is no need to compromise on turbine design to achieve more or less satisfactory charge in all speed and load ranges.

In particular, the combination of turbine with variable turbine geometry and a bypass line bypassing this turbine allows the design of the high-pressure turbine to very small exhaust gas mass flows and thus to the lower part load range. Consequently, high turbine pressure ratios can be achieved even at low speeds or even at very low exhaust gas mass flows.

Embodiments of the supercharged internal combustion engine in which a third bypass line is provided, which branches off from the intake line upstream of the first compressor and in which a shut-off element is arranged, are advantageous. This bypass line can serve the Ladeluftabblasung and can open again upstream of the first compressor in the intake, whereby the fresh air compressed in the first compressor is not blown off, but only returned. For controlling the blown-off or recycled fresh air quantity, a shut-off element is provided in the bypass line.

However, this third bypass line can also serve for the intake of fresh air and in those cases where hardly or no exhaust gas flows through the first large turbine and therefore makes the second, smaller turbine compressor work. Then, the first compressor is only a flow resistance for the fresh air sucked in by the second compressor. A bypass line then permits the bypassing of the second compressor and thus a dethrottling of the intake line.

Embodiments of the supercharged internal combustion engine in which a charge air cooler is arranged in the intake line downstream of the compressor are advantageous. The intercooler lowers the air temperature and thus increases the density of the charge air, whereby the radiator to a better filling of the combustion chamber with air d. H. contributes to a larger air mass.

In supercharged internal combustion engines having at least two cylinders, in which each cylinder has at least one outlet opening for discharging the exhaust gases from the cylinder and connected to each outlet opening an exhaust pipe, embodiments are advantageous, which are characterized in that the exhaust pipes of at least two cylinders within the Combine cylinder head to at least one total exhaust gas line.

The turbines can then very close to the outlet of the internal combustion engine, d. H. be arranged close to the outlet openings of the cylinder. This has the particular advantage that the exhaust enthalpy can be optimally utilized and a fast response of the turbines can be ensured.

The integration of the exhaust manifold in the cylinder head further leads to a compact design of the cylinder head and thus the internal combustion engine according to the invention and allows a dense packaging of the entire drive unit. In addition, in this way it is possible to participate in a liquid cooling system, which may be provided in the cylinder head, so that the manifolds do not have to be manufactured from thermally highly stressable and thus cost-intensive materials.

In supercharged internal combustion engines with at least one cylinder head, which is connectable to a cylinder block at a mounting end and is equipped with at least one integrated coolant jacket, embodiments are characterized in that the at least one integrated coolant jacket has a lower coolant jacket, which is between the exhaust pipes and the mounting end face of the cylinder head is arranged, and an upper coolant jacket, which is arranged on the opposite side of the lower coolant jacket of the exhaust pipes comprises.

In this context, embodiments of the supercharged internal combustion engine are advantageous in which at least one connection between the lower coolant jacket and the upper coolant jacket, which serves for the passage of coolant, is provided at a distance to the exhaust lines in an outer wall of the cylinder head from which the at least one exhaust gas line exits wherein the at least one connection is arranged adjacent to the region in which the exhaust gas lines merge to the total exhaust gas line.

Coolant can flow out of the lower coolant jacket into the upper coolant jacket via the at least one connection in the outer wall of the cylinder head, and vice versa. This is arranged in the cylinder head at least one compound on the side facing away from the at least two cylinders of the integrated exhaust manifold. The at least one connection is thus so to speak outside the integrated exhaust manifold.

In the present case, the connection is a breakthrough or flow channel which connects the lower coolant jacket to the upper coolant jacket and enables and realizes an exchange of coolant between the two coolant jackets.

On the one hand, cooling takes place in principle also in the area of the outer wall of the cylinder head, which according to the state of the art is consciously dispensed with in order to realize a compact design. On the other hand, the conventional longitudinal flow of the coolant, d. H. the coolant flow in the direction of the longitudinal axis of the cylinder head is supplemented by a coolant transverse flow which runs transversely to the longitudinal flow and preferably approximately in the direction of the cylinder longitudinal axes. The coolant flow passed through the at least one connection contributes significantly to the heat dissipation. In particular, a suitable dimensioning of the cross section of the at least one connection can specifically influence the flow velocity of the coolant in the connection and thus the heat dissipation in the region of this at least one connection.

Particularly advantageous embodiments of the cylinder head, in which the lower and the upper coolant jacket are not connected to each other over the entire area of the outer wall, but also the at least one connection extends only over a portion of the outer wall in particular. As a result, the flow velocity in the at least one connection can be increased, which increases the heat transfer by convection. This also offers advantages in terms of the mechanical strength of the cylinder head.

The cooling of the cylinder head can additionally and advantageously be improved by generating a pressure gradient between the upper and lower coolant jacket, which in turn increases the speed in the at least one connection, which leads to increased heat transfer due to convection.

According to the invention, the at least one connection is arranged adjacent to the region in which the exhaust gas lines merge to form the overall exhaust gas line.

In the area in which the exhaust pipes open into a common exhaust gas line and the hot exhaust gas of the cylinder of the internal combustion engine is collected, the cylinder head is thermally particularly high load.

Embodiments of the supercharged internal combustion engine in which a bypass line is provided, which branches off from the intake line upstream of the second compressor and opens again into the intake line downstream of this second compressor, wherein a shut-off element is arranged in this bypass line. This bypass line allows the bypass of the high pressure compressor. This allows the tuning of the guided by the high pressure compressor fresh air mass flow to the guided through the high-pressure turbine exhaust gas mass flow and thus to the available turbine power.

Advantageous embodiments of the supercharged internal combustion engine, in which the first turbine d. H. the turbine of the low-pressure stage has a variable turbine geometry. The above for the turbine of the high-pressure stage has also valid for the low-pressure turbine, which is why reference is made to these statements. A variable turbine geometry increases the flexibility of charging. It allows by adjusting the blades a stepless adjustment of the turbine geometry to the current exhaust gas mass flow.

However, embodiments of the internal combustion engine in which the first turbine has a fixed, unchangeable turbine geometry are also advantageous. This embodiment has particular cost advantages. On the one hand eliminates the complex and costly adjustment mechanism in this turbine design. On the other hand, in principle no control of the turbine is necessary.

However, embodiments of the internal combustion engine in which the first compressor has a fixed, unchangeable compressor geometry are also advantageous. Solid geometry compressors have cost advantages for the same reasons as fixed geometry turbines, due to their simpler construction.

However, embodiments of the internal combustion engine in which the first compressor has a variable compressor geometry (VVG) are also advantageous. Advantages of the variable compressor geometry of the first compressor, especially in the operating conditions in which hardly any exhaust gas flows through the first, larger turbine and therefore little power from the first turbine to Compression of the fresh air is provided. In these cases, the first compressor only represents a flow resistance for the fresh air sucked in by the second compressor. A variable compressor geometry then allows the intake line to be de-throttled by increasing the flow cross-section of the first compressor.

Embodiments of the internal combustion engine in which the line for exhaust gas recirculation flows downstream of the charge air cooler into the intake line are advantageous. In this way, the exhaust gas flow is not passed through the intercooler and consequently can not pollute this radiator by deposits of pollutants contained in the exhaust stream, in particular soot particles and oil.

Embodiments of the internal combustion engine in which an additional cooler is provided in the line for exhaust gas recirculation are advantageous. This additional cooler lowers the temperature in the hot exhaust gas flow and thus increases the density of the exhaust gases. The temperature of the fresh cylinder charge, which occurs during the mixing of the fresh air with the recirculated exhaust gases, is consequently further reduced, whereby the additional cooler contributes to a better filling of the combustion chamber with fresh mixture.

Embodiments of the internal combustion engine in which a shut-off element is provided in the line for exhaust gas recirculation are advantageous. This shut-off element is used to control the exhaust gas recirculation rate.

The second sub-task on which the invention is based is achieved by a method which is characterized in that in the warm-up phase the first bypass line is released and the exhaust gas flow via the exhaust line to the first turbine is prevented.

The comments made in connection with the internal combustion engine according to the invention also apply to the inventive method.

In the following the invention is based on an embodiment according to 1 described in more detail. Hereby shows:

1 schematically a first embodiment of the supercharged internal combustion engine.

1 shows a first embodiment of the supercharged internal combustion engine 1 using the example of a six-cylinder V-engine. The cylinders 3 the internal combustion engine 1 are arranged on two cylinder banks and thus form two groups of cylinders, each having an exhaust pipe for discharging the hot combustion gases, resulting in an overall exhaust gas line 4 merge, eliminating all exhaust pipes 4 communicate with each other and in all exhaust pipes the same exhaust pressure prevails. Furthermore, the internal combustion engine has 1 via a suction line 2 to supply the cylinders 3 with charge air or fresh mixture.

The internal combustion engine 1 is connected with two in series, in the exhaust pipe 4 arranged turbines 6a . 7a and two in series, in the suction line 2 arranged compressors 6b . 7b equipped, each with a turbine 6a . 7a and a compressor 6b . 7b to an exhaust gas turbocharger 6 . 7 are summarized. Thus, that of the internal combustion engine 1 supplied charge air are compressed in two stages, with a first exhaust gas turbocharger 6 as a low pressure stage 6 serves and a second exhaust gas turbocharger 7 as a high-pressure stage 7 ,

That's why the first compressor 6b designed larger than the second compressor 7b , because in this embodiment of the internal combustion engine 1 the first compressor 6b in the context of the two-stage compression, the low-pressure stage 6 forms, whereas the second compressor 7b compresses the already pre-compressed air and thus the high-pressure stage 7 represents.

For the same reason, the first turbine 6a is designed larger than the second turbine 7a , Because the second turbine 7a serves as a high-pressure turbine 7a while in the first turbine 6a an exhaust stream, which already as a result of passing through the high-pressure stage 7 has a lower pressure and a lower density.

Downstream of the compressors 6b . 7b is a charge air cooler 5 in the intake pipe 2 arranged. The intercooler 5 lowers the air temperature and thus increases the density of the charge air, resulting in a better filling of the cylinder 3 contributes with air.

The second turbine 7a the second exhaust gas turbocharger 7 has a second bypass line 12 on, the upstream of the second turbine 7a from the exhaust pipe 4 branches off and downstream of this second turbine 7a back into the exhaust pipe 4 opens, wherein in the bypass line 12 a shut-off element 13 is arranged.

At the in 1 illustrated embodiment, the first turbine 6a via a fixed, unchangeable turbine geometry. For the purpose of Abgasabblasung is a first bypass line 14 provided upstream of the first turbine 6a forming a node 8th from the exhaust pipe 4 branches off and downstream of this first turbine 6a back into the exhaust pipe 4 opens. At the junction 8th is a valve 9 for controlling the bypass line 14 or the amount of exhaust gas exhausted in the exhaust pipe 4 arranged.

Downstream of the turbines 6a . 7a is in the exhaust pipe 4 an exhaust aftertreatment system 15 intended.

The first compressor 6b can with a third bypass line 10 equipped (indicated by dashed lines), the downstream of the first compressor 6b from the intake pipe 2 branches. This bypass line 10 Serves the charge air blower and can be upstream of the first compressor 6b back into the intake pipe 2 open, causing the first compressor 6b compressed charge air is not blown off, but only returned. To control the blown off or recycled charge air quantity is a shut-off 11 in the bypass line 10 intended.

LIST OF REFERENCE NUMBERS

1

charged internal combustion engine

2

suction

3

cylinder

4

Exhaust pipe, total exhaust pipe

5

Intercooler

6

first exhaust gas turbocharger, low-pressure stage

6a

first turbine

6b

first compressor

7

second turbocharger, high-pressure stage

7a

second turbine

7b

second compressor

8th

junction

9

Valve, 2-3 way valve

10

third bypass line

11

shut-off

12

second bypass line

13

shut-off

14

first bypass line

15

aftertreatment system

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1396619 A1 [0020, 0020, 0020, 0021]

Claims (15)

Charged internal combustion engine ( 1 ) with a suction line ( 2 ) for the supply of charge air and an exhaust pipe ( 4 ) for the removal of the exhaust gas and with at least two exhaust gas turbochargers connected in series ( 6 . 7 ), each one in the exhaust pipe ( 4 ) arranged turbine ( 6a . 7a ) and one in the intake line ( 2 ) arranged compressors ( 6b . 7b ) and of which a first exhaust gas turbocharger ( 6 ) as a low-pressure stage ( 6 ) and a second exhaust gas turbocharger ( 7 ) as a high-pressure stage ( 7 ), wherein - the second turbine ( 7a ) of the second exhaust gas turbocharger ( 7 ) upstream of the first turbine ( 6a ) of the first exhaust gas turbocharger ( 6 ) and the second compressor ( 7b ) of the second exhaust gas turbocharger ( 7 ) downstream of the first compressor ( 6b ) of the first exhaust gas turbocharger ( 6 ), - a first bypass line ( 14 ) provided upstream of the first turbine ( 6a ) forming a node ( 8th ) from the exhaust pipe ( 4 ) branches off, - a second bypass line ( 12 ), which upstream of the second turbine ( 7a ) from the exhaust pipe ( 4 ) and in which a shut-off element ( 13 ), and - downstream of the turbines ( 6a . 7a ) in the exhaust pipe ( 4 ) at least one exhaust aftertreatment system ( 15 ), characterized in that - a valve ( 9 ) at the junction ( 8th ) in the exhaust pipe ( 4 ) is arranged. Charged internal combustion engine ( 1 ) according to claim 1, characterized in that the valve ( 9 ) at the junction ( 8th ) is a 3-2 way valve. Charged internal combustion engine ( 1 ) according to claim 1, characterized in that the valve ( 9 ) at the junction ( 8th ) is a pivotable flap. Charged internal combustion engine ( 1 ) according to claim 3, characterized in that the flap starting from a blocked first bypass line ( 14 ) when releasing the first bypass line ( 14 ) is pivotable against the exhaust gas flow. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the first bypass line ( 14 ) downstream of the first turbine ( 6a ) back into the exhaust pipe ( 4 ) opens. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the second bypass line ( 12 ) upstream of the first turbine ( 6a ) and downstream of the second turbine ( 7a ) back into the exhaust pipe ( 4 ) opens. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the first compressor ( 6b ) is designed to be larger than the second compressor ( 7b ). Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the first turbine ( 6a ) is designed to be larger than the second turbine ( 7a ). Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the second turbine ( 7a ) of the second exhaust gas turbocharger ( 7 ) has a variable turbine geometry. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that a third bypass line ( 10 ) provided upstream of the first compressor ( 6b ) from the suction line ( 2 ) and in which a shut-off element ( 11 ) is arranged. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that downstream of the compressor ( 6b . 7b ) a charge air cooler ( 5 ) in the intake line ( 2 ) is arranged. Charged internal combustion engine ( 1 ) according to one of the preceding claims with at least two cylinders ( 3 ), each cylinder ( 3 ) at least one outlet opening for discharging the exhaust gases from the cylinder ( 3 ) and to each outlet opening an exhaust pipe ( 4 ), characterized in that the exhaust pipes ( 4 ) of at least two cylinders ( 3 ) within the cylinder head to at least one total exhaust line ( 4 ) merge. Charged internal combustion engine ( 1 ) according to one of the preceding claims, having at least one cylinder head, which is connectable to a cylinder block at a mounting end face and is equipped with at least one integrated coolant jacket, characterized in that the at least one integrated coolant jacket has a lower coolant jacket which is located between the exhaust pipes ( 4 ) and the mounting end face of the cylinder head, and an upper coolant jacket, which on the opposite side of the lower coolant jacket exhaust pipes ( 4 ) is arranged. Charged internal combustion engine ( 1 ) according to claim 13, characterized in that spaced from the exhaust pipes ( 4 ) in an outer wall of the cylinder head, from which the at least one exhaust gas line ( 4 ), at least one connection between the lower one Coolant jacket and the upper coolant jacket is provided, which serves for the passage of coolant, wherein the at least one compound is disposed adjacent to the region in which the exhaust pipes ( 4 ) to the total exhaust line ( 4 ) merge. Method for operating a supercharged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that in the warm-up phase, the first bypass line ( 14 ) and the exhaust gas flow via exhaust pipe ( 4 ) to the first turbine ( 6a ) is prevented.

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