Internal combustion engine with a fresh air system, an exhaust system and at least one exhaust gas turbocharger

Abstract

Internal combustion engine (1, 2, 3, 4) with a fresh air system (5), with an exhaust system (8), and with an exhaust gas turbocharger (11, 12), wherein the exhaust gas turbocharger comprises a turbine (13, 16) and a compressor (15, 18), wherein the turbine (13) is arranged in the exhaust system (8) and the compressor (15, 18) is arranged in the fresh air system (5), wherein the pressure pulsations acting on the turbine (13, 16) in the exhaust gas stream can be varied in strength and / or number by means of an actuating device (31 to 37), characterized in that at least two exhaust gas turbochargers (11, 12) are provided, wherein the turbines (13, 16) are fed by separate exhaust gas streams (9, 10), wherein upstream of the turbines (13, 16) the exhaust gas streams (9, 10) are connected via a connecting line (48) are connectable or separable, wherein the connecting line (48) has the actuating means (37), wherein by opening the connecting line (48) by means of the actuating means (37) the number of the turbine (13,16) effective exhaust pulses can be increased.

Description

[0001] The invention relates to an internal combustion engine with the features of the preambles of claims 1, 2 and 3. Furthermore, the invention relates to a method with the features of the preamble of claim 5 for controlling and / or regulating such an internal combustion engine.

[0002] A fresh gas system supplies the internal combustion engine with fresh gas, and the resulting exhaust gas is discharged via an exhaust system. An exhaust gas turbocharger consists of a compressor and a turbine, with the turbine located in the exhaust system and the compressor in the intake system of the internal combustion engine. The exhaust gas turbocharger uses the turbine to utilize the pressure in the exhaust gas stream. This is known as ram air turbocharging. In internal combustion engines that predominantly use ram air turbocharging to drive the turbine, the exhaust gases first flow into a larger volume, for example, a suitable reservoir upstream of the turbine. The flow velocity to the turbine is therefore nearly constant, resulting in good efficiency. However, increased back pressure in the exhaust system can be detrimental to the engine.

[0003] The exhaust gas flow velocity is not constant, especially near the cylinders; pressure waves are generated in the exhaust gas flow when the exhaust valves open. The kinetic energy of the exhaust gas flow can be used to drive the turbine. This is known as pulse charging. To utilize pulse charging, the volume in the exhaust pipe upstream of the turbine is kept as small as possible, meaning the narrowest possible pipes are used. In this way, some of the kinetic energy of the pressure waves can be used to drive the turbine. At maximum power output and high engine speeds, pulse charging can negatively impact efficiency and place a greater load on the turbine than in a continuous exhaust gas flow. A disadvantage is the constantly changing inflow velocity of the exhaust gas to the turbine.The turbine blade angles are designed for a specific speed range, so deviations can lead to shock losses and a decrease in efficiency. Therefore, in practice, a design compromise is usually sought regarding the geometry of the exhaust system, especially the exhaust manifold and its volume.

[0004] A generic internal combustion engine is known from DE 10 2006 054 043 A1. The internal combustion engine comprises a fresh air system, an exhaust system, and an exhaust gas turbocharger. An intercooler is arranged in the fresh air system. The exhaust gas turbocharger has a compressor located upstream of the intercooler in the fresh air system and a turbine located in the exhaust system. A first line, namely a high-pressure EGR line for high-pressure exhaust gas recirculation, is provided. This first line branches off from the exhaust system upstream of the turbine of the exhaust gas turbocharger. The first line includes a high-pressure EGR valve. The first line opens into the fresh air system downstream of the intercooler. Furthermore, a second line, namely a low-pressure EGR line for low-pressure exhaust gas recirculation, is provided. This second line branches off from the exhaust system downstream of the turbine of the exhaust gas turbocharger.The second line features a low-pressure EGR valve. This second line connects to the fresh air system upstream of the turbocharger compressor. An exhaust flap is located downstream of the branch point of the low-pressure EGR line. At least one differential pressure sensor is located in the low-pressure EGR line, which determines the pressure difference between a location upstream and a location downstream of the low-pressure EGR valve. The exhaust flap is thus located downstream of the turbine and downstream of the branch point of the high-pressure EGR line in the exhaust system. In the fresh air system, viewed in the direction of flow, the compressor, the charge air cooler, a control flap, and a variable intake manifold are located. The recirculated exhaust gas mass flow is controlled by the exhaust flap and the two EGR valves.The internal combustion engine can be operated either without exhaust gas recirculation, with either high-pressure or low-pressure exhaust gas recirculation, or with both high-pressure and low-pressure recirculation simultaneously. The recirculated low-pressure exhaust gas flow is fed into the fresh air intake system between the air mass meter and the compressor via the exhaust flap and the low-pressure EGR valve located upstream of the compressor. Initially, only the low-pressure EGR valve is used, as long as a sufficient pressure differential exists to drive the low-pressure EGR flow. If this is no longer the case, the exhaust flap is also opened to increase the pressure differential across the low-pressure EGR valve. The recirculated exhaust gas via the low-pressure EGR line is virtually pulsation-free. The exhaust flap is actuated in the closing direction to regulate the volume flow through the low-pressure EGR line.In this configuration, the high-pressure EGR valve is located at the end of the high-pressure EGR line, near the fresh gas system's inlet point. The volume of the high-pressure EGR line thus acts as dead volume, reducing surge charging.

[0005] From EP 2 647 807 A1, an internal combustion engine with an exhaust gas turbocharger and a control unit is known. The exhaust gas turbocharger has a turbine with variable turbine geometry. The turbine has adjustable guide vanes, whereby the rotational speed of the turbine can be adjusted to regulate the boost pressure by adjusting the guide vanes. The variable guide vanes are pivoted by means of an actuating mechanism, the actuating mechanism being arranged in a connecting chamber between the turbine housing and a central housing, the central housing enclosing a connecting shaft between the compressor and the turbine. The use of such exhaust gas turbochargers is known for both gasoline and diesel engines. When the exhaust gas mass flow increases, this leads to turbulence downstream of the guide vanes. For example, such turbulence can be described by the model of a Rankine vortex.These vortices exhibit pressure pulsations, the frequency of which is proportional to the exhaust gas flow rate. If these pressure pulsations are amplified by a geometry-related resonance in the turbine housing and exhaust pipes, this can lead to unwanted noise. The control unit regulates the flow rate through the turbine by adjusting it as soon as the flow rate falls within a resonance range of the pressure pulsation. The flow rate is adjusted by changing either the opening degree of a throttle valve, the opening degree of an EGR valve, and / or the position of the guide vanes.

[0006] From DE 10 2014 208 293 A1, a turbocharged, spark-ignition internal combustion engine with at least two cylinders is known, in which - each cylinder has at least one exhaust port to which an exhaust pipe is connected for the removal of exhaust gases via an exhaust system, - each cylinder has at least one inlet opening to which an intake line for supplying charge air via the intake system is connected, - at least two cylinders are configured in such a way that they form at least two groups, each with at least one cylinder, wherein the at least one cylinder of a first group is a cylinder that is in operation even when the internal combustion engine is partially shut down, and the at least one cylinder of a second group is designed as a load-dependent switchable cylinder, - at least one exhaust gas recirculation system is provided, and - at least one exhaust gas turbocharger is provided, comprising a turbine arranged in the exhaust gas discharge system and a compressor arranged in the intake system.

[0007] In this context, an internal combustion engine can be effective in which a second flow of the turbine is blocked by means of a shut-off element when cylinders are deactivated, so that the pressure impulses of the cylinders still in operation cannot propagate into this second flow and dissipate or weaken, whereby the exhaust gas volume located in the second flow between the at least one deactivated cylinder and the impeller would eliminate any damping effect.

[0008] From DE 198 26 355 A1, a device for controlling an exhaust gas turbocharger turbine for internal combustion engines is known, comprising a valve assembly. The valve assembly is arranged in an exhaust system in the region of at least two exhaust gas streams and has two valve elements. The first valve element closes an opening between one exhaust gas stream and the other. The second valve element closes an opening between one exhaust gas stream and a connecting pipe. In a first position, in which the exhaust gas streams are separated by the first valve element, pulse charging of the exhaust gas turbocharger turbine is generated. In a second position, in which the first valve element opens the opening between the two exhaust gas streams, continuous charging of the exhaust gas turbocharger turbine is generated.In a third position, in which the first valve element is open, the second valve element releases an opening between one exhaust gas stream and a connecting pipe.

[0009] The invention is therefore based on the objective of designing and further developing the aforementioned internal combustion engine in such a way that the efficiency of the internal combustion engine can be increased.

[0010] This problem underlying the invention is now solved by an internal combustion engine with the features of claim 1, an internal combustion engine with the features of claim 2, and an internal combustion engine with the features of claim 3. The pressure pulsations acting on the turbine in the exhaust gas stream can be varied in strength and / or number by means of an actuating device. The pressure pulsations acting on the turbine in the exhaust gas stream can be varied in amplitude and / or number by means of the actuating device. The actuating device can be used, in particular, to increase the turbine power in a lower or medium speed range by means of pulse charging. Here, the strength, and thus the amplitude and / or the number, of the pressure pulsations acting on the turbine is preferably greater than in a higher speed range.At high engine speeds, particularly in the range of maximum power, the effect of pulse charging is reduced by the actuator, thereby improving efficiency and reducing stress on the turbine, as a continuous exhaust gas flow is supplied to the turbine. Pulse charging acting on the turbine can be regulated and / or controlled by the actuator. Multiple actuators may be present. The actuator is typically designed as an exhaust flap. The exhaust flap is continuously variable. The exhaust flap can also be referred to as a resonance flap. Alternatively, the actuator could be designed as a valve, for example, an electromagnetically actuated valve.

[0011] According to the embodiment of claims 2 and 3, a resonance volume arranged or formed upstream of the turbine can be connected to or shut off from the exhaust system by means of the actuating device. Opening the actuating device allows the resonance volume to be activated, while closing the actuating device decouples the resonance volume from the turbine. This allows the pressure pulsations acting on the turbine to be either attenuated by activating the resonance volume for buffering, or transmitted directly to the turbine by shutting off the resonance volume using the actuating device.

[0012] There are various ways to arrange and / or design one or more such actuators. According to the embodiment of claim 3, the resonance volume is formed by at least a portion of a high-pressure EGR section, wherein the high-pressure EGR section branches off from the exhaust system at a draw-off point and opens into the fresh air system at an inlet point. In this embodiment, the actuator is arranged in an exhaust gas recirculation section—referred to as the EGR section—such that the EGR section can be selectively activated as a resonance volume by opening the actuator or decoupled from the turbine by closing the actuator. The EGR section is designed as a high-pressure EGR section.

[0013] For this purpose, the actuating device according to claim 3 is arranged close to the extraction point in order to keep the total volume between the exhaust valves and the turbine as small as possible when the actuating device is closed, thus enabling optimal use of pulse charging. The actuating device is arranged closer to the extraction point than to the inlet point, with a high-pressure EGR valve located downstream of the actuating device in the high-pressure EGR path. The volume between the extraction point on the exhaust side and an EGR cooler is used as a resonance volume. The branch is located upstream of the turbine. Using the resonance volume, it is possible to partially or completely buffer the pressure surges of the exhaust processes and to make the turbine supply partially or completely shock-free, i.e., continuous.

[0014] For operating points where pulse charging is desired, the resonance flap is closed. This blocks the high-pressure EGR path, preventing high-pressure EGR operation. In a preferred embodiment, a low-pressure EGR path (LP-EGR path) is also provided, branching off downstream of the turbine. EGR operation can be implemented via this low-pressure EGR path when the resonance flap, or exhaust flap, used to control the resonance volume is closed. For other operating points, where the turbine is partially or additionally subjected to pulse-free operation, the controlled resonance flap opens access to the high-pressure EGR path (HP-EGR path) sufficiently to utilize at least part of it as an effective resonance volume, thus achieving the desired degree of pulse-free operation at the turbine.

[0015] The EGR mass flow is controlled by a high-pressure EGR valve (HPEG), which is preferably located downstream of the resonance flap and preferably downstream of an EGR cooler in the HPEG system. The HPEG system extracts the exhaust gas upstream of the turbine and introduces it into the fresh air system either upstream or downstream of the compressor on the intake side. Preferably, the introduction of such a high-pressure EGR system occurs downstream of the compressor. Within the HPEG system, in the direction of flow (i.e., from the exhaust side), are the resonance flap, the EGR cooler, and the HPEG valve.

[0016] In the embodiment of claim 2, the actuator is used to connect and disconnect a dead volume from the exhaust system. The dead volume is connected to the exhaust system at a connection point between the cylinders and the turbine. Preferably, the dead volume has only one connection point to the exhaust system and is not subject to the exhaust gas flow, but can be connected to the exhaust gas flow via the actuator. This allows the controllable resonance volume to be separate from the EGR system. This has the advantage that EGR operation is possible even when the actuator is closed. Furthermore, in another embodiment, this switchable or controllable dead volume can be present without high-pressure and / or low-pressure EGR.

[0017] The invention can be used for a variety of engine designs with different numbers of cylinders and cylinder arrangements. For example, the internal combustion engine can have six cylinders, with half of the cylinders each expelling exhaust gas into a separate exhaust stream. The six cylinders can further have two fresh air streams, with each fresh air stream and each exhaust stream belonging to a cylinder group sharing a common exhaust gas turbocharger. Downstream of the two compressors, the fresh air supply can enter a common line, into which the high-pressure exhaust gas recirculation (HPFRC) sections also open. From this common line, the fresh air supplies then branch off to the two cylinder groups and finally to the individual cylinders.

[0018] The embodiment according to claim 1 relates to an internal combustion engine with more than one exhaust gas turbocharger, in particular with two, three, or four exhaust gas turbochargers. The turbines of the exhaust gas turbochargers are supplied with air in groups, for example, by bank. Thus, the number of exhaust pulses per operating cycle can be increased or decreased by means of a switchable connecting line between the two exhaust gas banks. Increasing the number of exhaust pulses, and therefore increasing the number of pressure pulsations, can lead to improved responsiveness at low engine speeds.For example, if an internal combustion engine has six cylinders, with three cylinders each exhausting into a separate exhaust stream and each of these two exhaust streams assigned to a turbine, then a connecting pipe is provided between these two exhaust streams, branching off between the cylinders and their respective turbines. This connecting pipe can be opened and / or closed by means of an exhaust flap. This exhaust flap can be referred to as a switching flap. When the connecting pipe is open, six cylinders, instead of three, exhaust to one turbine, resulting in a doubling from three to six pressure pulses. The number of pressure pulses is thus doubled.

[0019] The connecting pipe, however, represents an additional volume. In a preferred embodiment, the volume of the connecting pipe is small in order to avoid compensating for the effect of the increased number of exhaust pulses with the additional resonance volume of the connecting pipe. Therefore, the connecting pipe is preferably kept short. However, the geometric design of the connecting pipe is limited by the design of the engine and, in particular, the exhaust manifold. In embodiments where the connecting pipe can contribute significantly as a resonance volume, the connecting pipe is preferably openable and closed near the branch points by means of appropriate actuating devices. For this purpose, two switching flaps can be provided at the ends of the connecting pipe in one embodiment, by means of which the connecting pipe can be opened and closed.Opening the connecting pipe results in more exhaust pulses reaching the turbines, but also reduces the pulse charging effect due to the buffering action of the open connecting pipe.

[0020] The invention is further solved by a method with the features of claim 5. The method serves to control and / or regulate the internal combustion engine with a fresh air system, an exhaust system, and an exhaust gas turbocharger, wherein the exhaust gas turbocharger comprises a turbine and a compressor, the turbine being arranged in the exhaust system and the compressor in the fresh air system. It is particularly advantageous that the pressure pulsations acting on the turbine in the exhaust gas stream can be varied in strength and / or number by means of an actuating device.

[0021] In a first, lower speed range, the effect of pulse charging is increased by means of the actuator, and in a second, higher speed range, the effect of pulse charging is reduced by means of the actuator. This avoids pulse losses at high speeds and improves responsiveness at lower speeds.

[0022] In the second, higher speed range, a resonance volume located or formed upstream of the turbine can be connected to the exhaust system via the actuator. In the first, lower speed range, the resonance volume can be fluidly isolated from the exhaust system using the actuator. This has the advantage that pressure pulsations in the higher speed range are buffered by opening the resonance volume, while in the lower speed range, the pressure pulsations in the exhaust stream are not attenuated by the resonance volume but are instead directed straight to the turbine to improve responsiveness.

[0023] According to claim 5, at least two exhaust gas turbochargers are provided, wherein the turbines of the exhaust gas turbochargers are fed by separate exhaust gas streams, and upstream of the turbines the exhaust gas streams can be selectively connected or disconnected via a connecting line by means of the actuator. Opening the actuator, and thus opening the connecting line, increases the number of exhaust gas pulses acting on the turbine. Closing the actuator, and thus closing the connecting line, decreases the number of exhaust gas pulses acting on the turbine. This reduces pulse losses and improves the response and / or efficiency.

[0024] The disadvantages mentioned at the beginning are therefore avoided and corresponding advantages are achieved.

[0025] There are now numerous possibilities for elaborating and further developing the invention. For this purpose, reference may first be made to the claims subordinate to claims 1, 2, and 3. A preferred embodiment of the invention will be explained in more detail below with reference to the drawing and the accompanying description.

[0026] The drawing shows: Fig. 1 in a highly schematic representation an internal combustion engine with a high-pressure EGR system, wherein the high-pressure EGR system is at least partially used as a resonance volume, Fig. 2 in a schematic representation a second internal combustion engine with a high-pressure EGR system, wherein an additional dead volume, which can be switched on by means of an actuator, is present, Fig. 3 in a schematic representation a third internal combustion engine without a high-pressure EGR system, wherein also as in Fig. 2. a switchable dead volume is present, and Fig. 4 in a highly schematic representation a fourth internal combustion engine with two exhaust gas turbochargers and with two exhaust gas streams leading to the respective turbines, wherein the two exhaust gas streams can be connected to each other via an actuating device, namely a switching flap and a corresponding connecting line.

[0027] In the Fig. Figures 1 to 4 show different internal combustion engines. These engines can be either gasoline or diesel. Each engine has a fresh air intake 5, at least one cylinder 6 or 7, and an exhaust system 8. The fresh air intake 5 supplies the at least one cylinder 6 or 7 with fresh air, and the exhaust gas is discharged from the cylinders 6 and 7 via the exhaust system 8. The number and arrangement of the cylinders can vary. In the illustrated configuration, there are six cylinders, with three cylinders 6 and three cylinders 7 grouped together in banks. The internal combustion engine can be configured as a 6-cylinder boxer engine. Each cylinder 6 has an exhaust system 9, and each cylinder 7 has an exhaust system 10. The two exhaust systems 9 and 10 together form the exhaust system 8.The design according to the invention can also be transferred to other engine types that differ from a 6-cylinder boxer engine in the number and arrangement of cylinders.

[0028] The internal combustion engines 1 to 4 preferably have two exhaust gas turbochargers 11, 12. Exhaust gas turbocharger 11 has a turbine 13 arranged in the exhaust gas stream 9, a shaft 14 and a compressor 15. The turbine 13 drives the compressor 15 in the fresh air system 5 via the shaft 14. Exhaust gas turbocharger 12 has a turbine 16, a shaft 17 and a compressor 18.

[0029] The fresh air system 5 initially comprises two separate fresh air ducts 19 and 20, with fresh air duct 19 supplying compressor 15 and fresh air duct 20 supplying compressor 18. Downstream of compressors 15 and 18, the fresh air system 5 comprises a fresh air duct 21, in which the fresh air from both fresh air ducts 19 and 20 is combined in this common fresh air duct 21 downstream of compressors 15 and 18. From the common fresh air duct 21, the fresh air system 5 then branches off to the cylinder banks and finally to the individual cylinders 6 and 7.

[0030] The internal combustion engines 1, 2 (cf. Fig. 1, Fig. 2) feature a high-pressure EGR section 22, 23. The high-pressure EGR section 22 branches off from the exhaust stream 9 at a sampling point 24. The high-pressure EGR section 23 branches off from the exhaust stream 10 at a sampling point 25. The two sampling points 24, 25 are each located between cylinders 6 and 7, respectively, and their respective turbines 13 and 16. At least a portion of the exhaust gas flow can now be reintroduced into the fresh air system 5 via the high-pressure EGR section 22, 23. The high-pressure EGR section 22 and the high-pressure EGR section 23 open into the fresh air stream 21 at an inlet point 26. The inlet point 26 is located downstream of the two compressors 15, 18. Alternatively, the inlet point 26 can also be arranged or designed upstream of the compressors 15, 18.

[0031] A high-pressure EGR valve 27, 28 is preferably arranged in each of the high-pressure EGR sections 22, 23. An EGR cooler 29, 30 is preferably arranged in each of the high-pressure EGR sections 22, 23. The two EGR coolers 29, 30 can either be structurally separate or formed by a single unit. Preferably, the high-pressure EGR valve 27, 28 is arranged downstream of the EGR cooler 29, 30, i.e., closer to the inlet point 26 than the EGR cooler 29, 30.

[0032] The aforementioned disadvantages are now avoided by the fact that the pressure pulsations acting on the turbines 13, 16 in the exhaust gas stream can be varied in strength and / or number by means of an actuating device 31 to 37. The pulse charging can be regulated and / or controlled by means of the actuating devices 31 to 37. The actuating devices 31 to 37 are preferably designed as actuating flaps, in particular as exhaust flaps. In an alternative embodiment, it is conceivable that the actuating devices 31 to 37 are designed, for example, as a valve. In the case of the internal combustion engines 1 to 4, the actuating devices 31 to 36 serve to at least partially open or close a resonance volume upstream of the turbines 13, 16 in order to partially or completely buffer pressure surges during the exhaust process from the cylinders 6, 7 and thus to make the supply to the turbines 13, 16 partially or completely shock-free.The actuators 31, 32 are arranged in the high-pressure EGR section 22, 23. They are located near the extraction points 24, 25. The high-pressure EGR sections 22, 23, or the corresponding pipe volume, serve as the resonance volume. In the direction of flow, the actuators 31, 32 are arranged upstream of the EGR cooler 29, 30. Preferably, the actuators 31, 32 are arranged at a considerable distance from the EGR cooler 29, 30. In particular, the distance between the actuators 31, 32 and the extraction point 24, 25 is smaller than the distance to the EGR cooler 29, 30. For operating points where pulse charging is desired, the actuators 31, 32 are closed, thus closing the resonance volume of the high-pressure EGR section 22, 23. Thus, the effect of pulse charging can be used, particularly in low or medium engine speed ranges, to increase torque. The turbine power is increased by pulse charging.At high engine speeds, the resonance volume of the high-pressure EGR path 22, 23 is opened, thus reducing the pressure pulsations.

[0033] When the actuators 31, 32 are closed, exhaust gas recirculation preferably occurs via a low-pressure EGR system 38, 39, wherein the low-pressure EGR system 38, 39 branches off from the exhaust gas stream 9, 10 downstream of the turbines 13, 16. The low-pressure EGR systems 38, 39 open into the fresh air system upstream of the compressors 15, 18, specifically into the corresponding fresh air streams 19, 20. The low-pressure EGR systems 38, 39 each preferably have a low-pressure EGR valve 40, 41 and an EGR cooler 42, 43. The two EGR coolers 42, 43 can be formed by a single unit together with the EGR coolers 29, 30 or be separate components. The EGR valves 42, 43 are located downstream of the EGR coolers 40, 41. If the high-pressure EGR path 22, 23 is now closed off by means of the actuators 31, 32, exhaust gas recirculation can take place via the low-pressure EGR path 38, 39.For the other operating points, where a partially or completely shock-free supply to the turbocharger turbine 13, 16 is desired, the controlled resonance flap, namely the corresponding actuator 31, 32, opens the access to the high-pressure EGR path 22, 23 sufficiently to provide enough effective resonance volume to achieve the desired degree of shock-free supply to the turbine. The actual control of the high-pressure EGR mass flow is performed by the high-pressure EGR valves 27, 28. The [unclear text] Fig. The low-pressure EGR sections 38, 39 shown in 1 to 4 are not mandatory, but optional.

[0034] Within the high-pressure EGR section 22, 23, in the direction of flow, i.e., coming from the exhaust side, are the resonance flap, namely the actuators 31, 32, the EGR coolers 29, 30, and the high-pressure EGR valves 27, 28. The volume between the extraction point 24, 25 on the exhaust side and the respective EGR cooler 29, 30 serves as the resonance volume. By additionally installing the resonance flap or the actuators 31, 32 of the corresponding control system, the efficiency of the turbines 13, 16 can be increased and their stress reduced.

[0035] In the Fig. 2 and Fig. Figure 3 shows embodiments of the invention, wherein the resonance volume is not, or not only, a corresponding high-pressure EGR section 22, 23, but a dead volume 44, 45. The dead volume 44, 45 can be connected to the exhaust system 8, namely the corresponding exhaust stream 9, 10, at a connection point 46, 47 between the turbine and the cylinders 6, 7 via an actuating device 33, 34. The actuating devices 33, 34 can also be designed as resonance flaps. The dead volume 44, 45 is not part of one of the EGR sections. The dead volume 44, 45 can be formed by an additional component, for example, by a corresponding housing. Because the dead volume 44, 45 forms a resonance volume on the one hand and is not part of the high-pressure EGR sections 22, 23 on the other, high-pressure EGR operation can advantageously also take place when the corresponding actuators 33, 34 and 35, 36 are closed. In the Fig. In the embodiment shown in Figure 2, two high-pressure EGR sections 22, 23 are depicted, wherein these high-pressure EGR sections 22, 23 preferably have corresponding actuating means 31, 32 in order to selectively activate or deactivate the resonance volume of the high-pressure EGR sections 22, 23. It is conceivable that in an alternative embodiment (not shown) dead volumes 44, 45 and high-pressure EGR sections 22, 23 are present, but only the dead volumes 44, 45 can be deactivated and activated. In the embodiment shown in Fig. In the configuration shown in section 3, there is no high-pressure EGR line.

[0036] The in Fig.Figure 4 of the embodiment of the internal combustion engine according to the invention now features a connecting line 48, within which a corresponding actuating device 37, namely a switching flap (not further specified), is provided. The connecting line 48 connects the two exhaust streams 9, 10 upstream of the turbines 13, 16. If the turbines 13, 16 are supplied bank by bank, the number of exhaust pulses per operating cycle can be increased by means of the switchable connecting line 48 between the two cylinder banks, namely the corresponding cylinders 6, 7. This results in improved responsiveness and improved efficiency, as the actuating device 37 is opened, thus allowing six exhaust pulses, instead of just three, to act on the respective turbine 13, 16.The number of pressure pulsations in the exhaust gas flow on the turbine 13, 16 is increased per unit of time at a fixed rotational speed, namely doubled.

[0037] In embodiments where the connecting line 48 can significantly contribute as a resonance volume, the connecting line 48 is preferably openable and closed near the branch points (not further specified) by means of corresponding actuating means 31, 32. The actuating means 31, 32 can be provided either in addition to the actuating means 37 or, in a preferred embodiment, as an alternative to the actuating means 37. The actuating means 37 can be replaced by the two actuating means 31, 32, so that the actuating means 31, 32 serve as switching flaps and can open and close the resonance volume of the connecting line.

[0038] The number of pressure pulsations can be increased in one configuration at lower speeds. Since adding the extra volume of the connecting line could create an additional resonance volume – depending on the design of the connecting line – opening can, for example, occur at higher speeds in other configurations. REFERENCE MARK LIST 1 internal combustion engine 2 Internal combustion engine 3 Internal combustion engine 4 Internal combustion engine 5 Fresh air system 6 cylinders 7 cylinders 8 Exhaust system 9 Exhaust system 10 Exhaust system 11 exhaust gas turbochargers 12 exhaust gas turbochargers 13 Turbine 14 wave 15 compressors 16 Turbine 17th wave 18 compressors 19 Fresh air duct 20 Fresh air duct 21 Fresh air duct 22 High-pressure EGR section 23 High-pressure EGR section 24 sampling point 25 sampling point 26 Induction point 27 High-pressure EGR valve 28 High-pressure EGR valve 29 EGR coolers 30 EGR coolers 31 Actuators 32 actuators 33 Actuators 34 Actuators 35 actuators 36 actuators 37 actuators 38 Low-pressure EGR section 39 Low-pressure EGR line 40 EGR valve 41 EGR valve 42 EGR coolers 43 EGR cooler 44 dead volume 45 dead volume 46 liaison point 47 liaison point 48 Connecting line

Claims

[1] Internal combustion engine (1, 2, 3, 4) with a fresh air system (5), with an exhaust system (8), and with an exhaust gas turbocharger (11, 12), wherein the exhaust gas turbocharger comprises a turbine (13, 16) and a compressor (15, 18), wherein the turbine (13) is arranged in the exhaust system (8) and the compressor (15, 18) is arranged in the fresh air system (5), wherein the pressure pulsations acting on the turbine (13, 16) in the exhaust gas stream can be varied in strength and / or number by means of an actuating device (31 to 37), characterized by, that at least two exhaust gas turbochargers (11, 12) are provided, wherein the turbines (13, 16) are fed by separate exhaust gas streams (9, 10), wherein upstream of the turbines (13, 16) the exhaust gas streams (9, 10) can be connected or disconnected via a connecting line (48), wherein the connecting line (48) has the actuating means (37), wherein by opening the connecting line (48) by means of the actuating means (37) the number of exhaust pulses acting on the turbine (13, 16) can be increased. [2] Internal combustion engine (1, 2, 3, 4) with a fresh air system (5), with an exhaust system (8), and with an exhaust gas turbocharger (11, 12), wherein the exhaust gas turbocharger comprises a turbine (13, 16) and a compressor (15, 18), wherein the turbine (13) is arranged in the exhaust system (8) and the compressor (15, 18) is arranged in the fresh air system (5), wherein the pressure pulsations acting on the turbine (13, 16) in the exhaust gas stream can be varied in strength and / or number by means of an actuating device (31 to 37), characterized by , that by means of the actuating means (31 to 36) a resonance volume arranged or formed upstream of the turbine (13, 16) can be connected to or shut off from the exhaust system (8), wherein a dead volume (44, 45) is provided as the resonance volume. [3] Internal combustion engine (1, 2, 3, 4) with a fresh air system (5), with an exhaust system (8), and with an exhaust gas turbocharger (11, 12), wherein the exhaust gas turbocharger comprises a turbine (13, 16) and a compressor (15, 18), wherein the turbine (13) is arranged in the exhaust system (8) and the compressor (15, 18) is arranged in the fresh air system (5), wherein the pressure pulsations acting on the turbine (13, 16) in the exhaust gas stream can be varied in strength and / or number by means of an actuating device (31 to 37), characterized by, that by means of the actuating means (31 to 36) a resonance volume arranged or formed upstream of the turbine (13, 16) can be connected to or shut off from the exhaust system (8), the resonance volume being formed by at least a part of a high-pressure EGR path (22, 23), wherein the high-pressure EGR path (22, 23) branches off from the exhaust system (8) at a withdrawal point (24) and opens into the fresh air system (5) at an inlet point (26), wherein the actuating means (31 to 36) is arranged closer to the withdrawal point (24, 25) than to the inlet point (26), wherein a high-pressure EGR valve (27, 28) is arranged downstream of the actuating means (31, 32) in the high-pressure EGR path (22, 23), wherein between the actuating means (31, 32) and The high-pressure EGR valve (27, 28) is connected to an EGR cooler (29, 30) in the high-pressure EGR path (22, 23). [4] Internal combustion engine (1, 2, 3, 4) according to any one of the preceding claims, characterized by, that downstream of the turbine (13, 16) a low-pressure EGR section (38, 39) branches off from the exhaust system (8) and leads into the fresh air system (5). [5] Method for controlling and / or regulating an internal combustion engine (1, 2, 3, 4) with a fresh air system (5), with an exhaust system (8), and with an exhaust gas turbocharger (11, 12), wherein the exhaust gas turbocharger comprises a turbine (13, 16) and a compressor (15, 18), wherein the turbine (13) is arranged in the exhaust system (8) and the compressor (15, 18) is arranged in the fresh air system (5), wherein the strength and / or number of pressure pulsations acting on the turbine (13, 16) in the exhaust gas stream are changed by means of an actuating device (31 to 37), characterized by, that at least two exhaust gas turbochargers (11, 12) are provided, wherein the turbines (13, 16) of the exhaust gas turbochargers (11, 12) are fed by separate exhaust gas streams (9, 10), wherein upstream of the turbines (13, 16) the exhaust gas streams (9, 10) are selectively connected or separated via a connecting line (48) by means of the actuating device (37), wherein by opening the actuating device (37) and thus by opening the connecting line (48) the number of exhaust shocks acting on the turbine (13, 16) is increased and by closing the actuating device (37) and thus by closing the connecting line (48) the number of exhaust shocks acting on the turbine (13, 16) is decreased. [6] Method according to claim 5, characterized by, that in a first, lower speed range the effect of pulse charging is increased by means of the actuating device (31 to 37) and in a second, higher speed range the effect of pulse charging is reduced by means of the actuating device (31 to 37). [7] Method according to claim 5 or 6, characterized by , that in the second, higher speed range a resonance volume arranged or formed upstream of the turbine (13, 16) is connected to the exhaust system (8) by means of the actuating means (31 to 36) and in the first, lower speed range the resonance volume is fluidly separated from the exhaust system (8) by means of the actuating means (31 to 36).

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