Method for operating a device for exhaust gas turbocharging of an internal combustion engine and device

Abstract

Method for operating a device (1) for exhaust gas turbocharging of an internal combustion engine (2), comprising at least one exhaust gas turbine assembly (3) with at least one exhaust gas turbine (13) driven by an exhaust gas mass flow of the internal combustion engine (2) and with at least one charging compressor (23) driven by the exhaust gas turbine (13) for providing a fresh air mass flow for turbocharging the internal combustion engine (2), wherein the mechanical power provided by the exhaust gas turbine (13) is split to operate, in addition to the charging compressor (23), a cooling device (4) for cooling the exhaust gas mass flow of the internal combustion engine (2), and wherein the cooling device (4) provides a cooling air mass flow by means of at least one cooling compressor unit (14) driven by the mechanical power of the exhaust gas turbine (13) and supplies the cooling air mass flow to a heat exchanger assembly (24).wherein the cooling air mass flow directed to the heat exchanger device (24) is adjustable by means of at least one controllable valve device (34) so ​​that the temperature of the exhaust gas mass flow can be selectively reduced at least by drawing off the drive power for the cooling compressor unit (14), characterized in that the heat exchanger device (24) is arranged in a thermally conductive manner on the exhaust gas turbine (13) or in a thermally conductive manner on an exhaust gas system, so that the cooling air mass flow flowing through the heat exchanger device (24) cools the exhaust gas turbine (13) or the exhaust gas system at least section by section.

Description

[0001] The present invention relates to a method for operating a device for exhaust gas turbocharging of an internal combustion engine. The device comprises at least one exhaust gas turbine assembly with at least one exhaust gas turbine driven by an exhaust gas mass flow from the internal combustion engine and at least one charging compressor driven by the exhaust gas turbine for providing a fresh air mass flow for turbocharging the internal combustion engine.

[0002] As part of ongoing optimization efforts to reduce gaseous pollutant emissions, rapidly reaching the catalyst's light-off temperature is a key development goal for future exhaust aftertreatment systems. According to current technology, reducing heat losses from all components of the exhaust system upstream of the first catalyst represents a well-established and largely optimized solution. Furthermore, in turbocharged engines, bypassing the exhaust turbine using wastegate valves reduces heat losses during the warm-up phase. However, the wastegate valve is typically installed for turbocharger boost pressure control and thus serves a dual purpose in such cases.

[0003] Due to the significant difference in enthalpy between the intake air mass flow and the exhaust gas mass flow, a portion of the exhaust gas mass flow must be diverted around the turbine at high engine speeds and loads. This is typically achieved using adjustable wastegate valves integrated into the exhaust gas turbocharger and is known as boost pressure control. The undesirable side effect of this is that the exhaust gas mass flow leaving the internal combustion engine (ICE) no longer transfers its enthalpy to the turbine, but instead passes directly to the first catalytic converter. Furthermore, for the reasons mentioned above, in state-of-the-art exhaust systems, the catalytic converters are positioned very close to the engine or optimized for minimal heat loss to ensure the earliest possible light-off.

[0004] The result is a very high thermal load on the catalyst and thus accelerated chemical aging, which reduces its conversion capacity over the vehicle's lifetime or, if the maximum permissible temperatures are exceeded, even leads to its destruction. To counteract this, the catalyst is designed to be volumetrically large enough to still possess sufficient conversion capacity at the end of the vehicle's life. In addition, state-of-the-art measures must be taken to limit the maximum exhaust gas temperature under high loads. These so-called component protection measures generally lead to an increase in CO2 emissions.

[0005] The requirement for the catalyst to be operational as early as possible and the boost pressure control required in turbo engines therefore create a direct conflict of objectives with the lowest possible CO2 emissions during high-load operation or with the volumetric design of the catalyst.

[0006] DE 10 2005 062 186 B4 discloses a device for exhaust gas cooling in which an air-gap-insulated exhaust manifold is designed as a heat exchanger. For cooling, the air gap of the exhaust manifold can be supplied with compressor air from the exhaust gas turbocharger. The cooling air flowing through the exhaust manifold can be controlled by a valve. After passing through the exhaust manifold, the cooling air can be supplied either to the process air or to the exhaust gas. A wastegate valve is provided on the exhaust gas turbine.

[0007] From DE 10 2006 011 889 A1, a device for exhaust gas cooling is known, incorporating an air-gap-insulated exhaust manifold as a heat exchanger. The cooling airflow through the double-walled exhaust manifold can be generated by a single exhaust gas turbocharger or a smaller auxiliary turbocharger specifically designed for this purpose. A valve assembly is provided in the cooling air duct for regulating the cooling airflow.

[0008] DE 10 2014 018 318 A1 also discloses a device for exhaust gas cooling with an air-gap-insulated exhaust manifold as a heat exchanger. The cooling airflow through the double-walled exhaust manifold is generated by an electrically driven compressor and controlled by a valve assembly.

[0009] From DE 10 2016 116 995 A1, DE 10 2019 008 665 A1, DE 10 2017 200 966 A1, and JP 2005 220 778 A, a device for exhaust gas cooling with an air-gap-insulated exhaust manifold as a heat exchanger is known. The cooling airflow through the double-walled exhaust manifold is generated by the compressor of an exhaust gas turbocharger and controlled by a valve assembly.

[0010] WO 2014 205 168 A1 describes a device for exhaust gas cooling in which an air / exhaust gas heat exchanger is provided on an exhaust pipe. The cooling airflow through the heat exchanger is generated by a Roots compressor. The cooling airflow through the exhaust manifold is controlled by a valve assembly.

[0011] Generic processes are known from DE 10 2009 049 394 A1, DE 10 2012 107 322 A1, and DE 10 2013 205 740 A1. A generic process is also known from DE 10 2023 109 913 B3, which constitutes a subsequently published prior art.

[0012] In contrast, the object of the present invention is to provide an improved method for exhaust gas turbocharging of an internal combustion engine. In particular, the problems and conflicting objectives discussed above are to be solved in a structurally simple and reliable manner.

[0013] This problem is solved by a method having the features of claim 1 and by a device according to the invention as described in claim 12. Preferred embodiments of the invention are the subject of the dependent claims. Further advantages and features of the present invention will become apparent from the general description and the description of the exemplary embodiment.

[0014] The method according to the invention serves to operate a device for the exhaust gas turbocharging of an internal combustion engine. The device comprises at least one exhaust gas turbine assembly with at least one exhaust gas turbine driven by an exhaust gas mass flow from the internal combustion engine. The device comprises at least one charging compressor driven by the exhaust gas turbine for providing a fresh air mass flow (from compressed fresh air) for turbocharging the internal combustion engine. The mechanical power provided by the exhaust gas turbine (at a shaft or turbocharger shaft) is split to operate, in addition to the charging compressor, a cooling device for cooling the exhaust gas mass flow of the internal combustion engine. The cooling device provides a cooling air mass flow (from compressed cooling air) by means of at least one cooling compressor unit driven by the mechanical power of the exhaust gas turbine.The cooling device directs the cooling air mass flow to a (convective) heat exchanger. The cooling air mass flow to the heat exchanger can be adjusted by means of at least one controllable valve to selectively cool the exhaust gas mass flow (to a defined temperature level). In particular, the temperature (or exhaust gas enthalpy) of the exhaust gas mass flow can be selectively reduced, at least by drawing power from the cooling compressor unit (so-called T4 reduction). The heat exchanger is thermally connected to the exhaust gas turbine or to an exhaust gas system, so that the cooling air mass flow through the heat exchanger cools the exhaust gas turbine or the exhaust gas system, at least in sections.

[0015] Preferably, the cooling air mass flow is supplied to a heat exchanger located at least partially upstream of the exhaust gas turbine and / or at least partially on the exhaust gas turbine and / or at least partially downstream of the exhaust gas turbine. The terms "upstream" and "downstream" refer specifically to the direction of flow of the exhaust gas mass flow. Specifically, the exhaust gas mass flow flows from the internal combustion engine to the exhaust gas turbine and then to an exhaust system. Specifically, the heat exchanger serves to transfer heat from the exhaust gas mass flow and / or the exhaust gas turbine and / or an exhaust system to the cooling air mass flow. Specifically, the cooling air mass flow is heated in the heat exchanger. Specifically, the exhaust gas mass flow and / or the exhaust gas turbine and / or the exhaust system are cooled by the heat exchanger.

[0016] It is possible and advantageous for the exhaust gas mass flow from the internal combustion engine to pass at least partially through the heat exchanger before reaching the exhaust turbine, so that the temperature of the exhaust gas mass flow can be selectively reduced both by drawing power from the cooling compressor unit and by convection cooling of the heat exchanger. Preferably, the cooling air mass flow is supplied to the heat exchanger at least partially before reaching the exhaust turbine. In particular, the heat exchanger is arranged at least partially between the internal combustion engine and the exhaust turbine.

[0017] In particular, the heat exchanger is located between the internal combustion engine and the exhaust gas turbine (or downstream of the internal combustion engine and upstream of the exhaust gas turbine). The cooling system directs the cooling air mass flow to a (convective) heat exchanger before it reaches the exhaust gas turbine. The cooling air mass flow directed to the heat exchanger can be adjusted by means of at least one controllable valve to selectively cool the exhaust gas mass flow (to a defined temperature level). Specifically, the temperature (or exhaust gas enthalpy) of the exhaust gas mass flow can be selectively reduced both by drawing power from the cooling compressor unit (so-called T4 reduction) and by convection cooling of the heat exchanger (so-called T3 and T4 reduction). This provides a combined T3 and T4 reduction.

[0018] This design offers many advantages. A significant advantage is that enthalpy can be selectively extracted from the exhaust gas mass flow by the exhaust turbine, thus achieving the desired reduction in exhaust gas temperature at high loads (T4 reduction). The extracted enthalpy is converted into mechanical energy in the exhaust turbine and then used by the cooling compressor unit to generate the cooling air mass flow. This cooling air mass flow is used, in particular, to achieve convection cooling of the exhaust gas components upstream of the first catalyst (combined T3 and T4 reduction). This allows the problems and conflicting objectives discussed above to be resolved reliably and with minimal design complexity.

[0019] It is possible and advantageous for the exhaust gas mass flow from the internal combustion engine to first pass at least partially through the exhaust gas turbine and only then reach the heat exchanger. In particular, the cooling air mass flow to the heat exchanger is supplied at least partially downstream of the exhaust gas turbine. It is also possible for the exhaust gas mass flow to pass the heat exchanger only downstream of (or behind) the exhaust gas turbine. In particular, the heat exchanger is arranged downstream of (or behind) the exhaust gas turbine. In particular, the exhaust gas turbine is then arranged between the heat exchanger and the internal combustion engine.

[0020] In one embodiment, the exhaust gas mass flow is fed to the heat exchanger between the exhaust gas turbine and an exhaust system and / or within the exhaust system. In particular, the heat exchanger is arranged downstream of (or downstream of) the exhaust gas turbine.

[0021] According to the invention, the heat exchanger is arranged in a thermally conductive manner on the exhaust gas turbine, so that the cooling air mass flowing through the heat exchanger cools the exhaust gas turbine at least section by section (directly). In particular, the heat exchanger is connected to a turbine housing or the like.

[0022] According to the invention, the heat exchanger device is arranged in a thermally conductive manner on an exhaust gas system, such that the mass flow of cooling air passing through the heat exchanger device cools the exhaust gas system at least partially (directly). For example, the heat exchanger device is connected to a converter and / or inlet hopper or the like.

[0023] In particular, the temperature of the exhaust gas mass flow is reduced by drawing drive power for the cooling compressor unit in and / or after the exhaust gas turbine. Specifically, the temperature of the exhaust gas mass flow is reduced by convection cooling of the heat exchanger unit upstream, in, and / or downstream of the exhaust gas turbine. Specifically, the exhaust gas enthalpy of the exhaust gas mass flow is reduced by a combination of convection cooling of the heat exchanger unit (especially upstream of the exhaust gas turbine) and drawing drive power for the cooling compressor unit (in or downstream of the exhaust gas turbine). Specifically, the ratio of the drive power drawn for the cooling compressor unit (the T4 reduction) to the convection cooling of the heat exchanger unit (the T3 and T4 reductions) is adjusted by means of the valve assembly.

[0024] This design also offers many advantages. A significant advantage is the reduction of boost pressure by means of the cooling device. In particular, the invention provides a simple and variable cooling device that enables exhaust aftertreatment and boost pressure reduction, drawing its energy from the excess exhaust enthalpy and thus resolving the previously discussed conflicting objectives particularly advantageously. In this way, the boost pressure can be reduced without, for example, the need for a wastegate valve. Consequently, no hot exhaust gas flows occur that could damage the catalytic converter. A combination of the previously described approach with a wastegate valve is also advantageous.

[0025] It is preferred and advantageous that the cooling air mass flow is adjusted by means of the valve assembly so that an enthalpy imbalance between the exhaust gas turbine and the supercharger is at least partially compensated. In particular, the exhaust gas enthalpy of the exhaust gas mass flow is reduced by means of the cooling device to such an extent that it is no greater than the exhaust gas enthalpy required for the required operation of the supercharger. It is also taken into account that a portion of the exhaust gas enthalpy contained in the exhaust gas mass flow is required for the drive power of the cooling compressor unit. In other words, any excess exhaust gas enthalpy present for the desired boost pressure is preferably converted into cooling power by means of the cooling device.

[0026] In a particularly preferred and advantageous embodiment, the boost pressure (provided by the exhaust gas turbine) is at least partially regulated by the cooling device and preferably controlled to a setpoint. In particular, the exhaust gas enthalpy of the exhaust gas mass flow is reduced to such an extent that it corresponds to the exhaust gas enthalpy required for the setpoint boost pressure. If the exhaust gas enthalpy of the exhaust gas mass flow is already sufficiently low (e.g., due to certain operating conditions of the internal combustion engine), the reduction of the exhaust gas enthalpy of the exhaust gas mass flow can be deliberately omitted. Specifically, the cooling capacity is reduced if insufficient exhaust gas enthalpy is available for the desired boost pressure.

[0027] Preferably, the boost pressure is regulated at least by reducing the exhaust gas enthalpy contained in the exhaust gas mass flow by extracting the drive power required for the cooling compressor unit and / or by selectively cooling the exhaust gas mass flow by means of the cooling air mass flow (to a target value).

[0028] It is preferred that a boost pressure control (implemented within the scope of the present invention by means of the cooling device) operates without bypassing the exhaust gas mass flow at the exhaust turbine. In particular, the boost pressure control does not require a wastegate valve. A wastegate valve is understood to include, in particular, a wastegate flap or other devices for bypassing the exhaust gas mass flow. Specifically, the boost pressure can be controlled solely by the cooling device, at least in certain operating conditions or even in all operating conditions of the internal combustion engine. In particular, the boost pressure can be reduced and preferably controlled to a setpoint by means of the cooling device without the use of a wastegate valve. Specifically, the boost pressure control is achieved solely by means of the cooling device.

[0029] It is also possible that the boost pressure control is achieved using at least one wastegate valve in addition to the cooling system. For example, the boost pressure can be controlled by the wastegate valve in defined load conditions, either additionally or solely. In such configurations, however, it is preferred that at least a targeted reduction of the boost pressure is achieved using the cooling system.

[0030] In particular, bypassing the exhaust gas mass flow around the exhaust turbine and, for example, a wastegate valve, is used (only) to heat a catalytic converter to operating temperature and / or to provide a backup boost pressure control in the event of a cooling system failure. Specifically, this bypass does not serve as boost pressure control during normal operation.

[0031] It is preferred and advantageous that the valve assembly comprises at least one controllable (adjustable) throttle valve for influencing the cooling air mass flow. In particular, the throttle valve is arranged between the cooling compressor unit and the heat exchanger assembly. The valve assembly is specifically designed and configured to regulate the cooling air mass flow and / or adjust its flow velocity. The valve assembly is also specifically designed and configured to generate a defined back pressure at the outlet of the cooling compressor unit. Furthermore, the valve assembly is designed to operate the cooling compressor unit at the most favorable operating point.

[0032] It is also preferred and advantageous that the valve assembly includes at least one controllable (adjustable) recirculation valve. In particular, the recirculation valve allows the cooling air mass flow from an outlet side of the cooling compressor unit to be routed back to an inlet side of the cooling compressor unit via a bypass. This results in a recirculation of the cooling air mass flow. Preferably, the recirculation is activated at least when the power drawn from the charging compressor is at least approximately equal to the exhaust gas turbine power generated. In particular, the recirculation is activated in a transient case and / or at speeds below a certain threshold. The recirculation valve also includes an integrated throttle.

[0033] In an advantageous embodiment, the valve assembly comprises at least one controllable (adjustable) combined cold air switching valve. In particular, the cold air switching valve combines the functions of a throttle valve and a recirculation valve. Specifically, the cold air switching valve is designed as a directional control valve with an integrated throttle. For example, a 3 / 2-way valve is provided. In particular, the integrated throttle enables a continuous transition between the switching positions of the directional control valve.

[0034] In an advantageous and preferred embodiment, the cooling compressor unit can only be driven by the exhaust gas turbine together with the charging compressor. Preferably, the cooling compressor unit is arranged (non-rotatably) on a common shaft (for example, a turbocharger shaft) with the charging compressor and / or the exhaust gas turbine. In particular, the cooling compressor unit comprises at least one cooling compressor. Specifically, the cooling compressor and the charging compressor are separate compressors. Such a concept with separate compressors has the advantage that the cooling air and the process air are completely separated and only thermally coupled. The compressors are, in particular, completely separated and only mechanically coupled to the exhaust gas turbine via the shaft.

[0035] Preferably, the cooling air mass flow is routed independently of the process air flow for the internal combustion engine and, in particular, the fresh air mass flow for the internal combustion engine. Specifically, the internal combustion engine and the cooling system are mechanically coupled only via the exhaust turbine, functionally only via the charge control system, and thermally only via the heat exchanger. In particular, the cooling air mass flow is fluidically separated from the process air for the internal combustion engine (and especially from the fresh air mass flow for the internal combustion engine). Specifically, separate flow channels are provided for each.

[0036] In an advantageous embodiment, the cooling compressor unit and the charging compressor are provided by a common combined compressor. In particular, the combined compressor can be driven by the exhaust gas turbine. Specifically, the combined compressor is arranged on a common shaft with the exhaust gas turbine. Specifically, downstream of the combined compressor, the air mass flow exiting the combined compressor is split into the cooling air mass flow and the fresh air mass flow. The cooling air mass flow is then supplied to the heat exchanger assembly, controlled, in particular, by the valve assembly as described above. In this embodiment, the valve assembly can include the throttle valve and / or the recirculation valve and / or the cold air switching valve.

[0037] In particular, the cooling air mass flow is released into the atmosphere after passing through the heat exchanger. Specifically, the cooling air mass flow is discharged from the vehicle after passing through the heat exchanger. Specifically, the cooling air mass flow does not serve as combustion air for the internal combustion engine.

[0038] The device according to the invention is designed for exhaust gas turbocharging of an internal combustion engine. The device is suitable and configured to be operated according to the method presented here. In particular, the device comprises the features necessary for carrying out the method. Specifically, the features are configured as described within the framework of the method according to the invention and its embodiments. The device can comprise at least one internal combustion engine.

[0039] The heat exchanger assembly comprises, in particular, at least one (complex) heat exchanger. The heat exchanger assembly provides, in particular, a flow of cooling air mass flow around exhaust gas-carrying components. The heat exchanger assembly includes, in particular, an increase in surface area and, for example, fins or ribs or the like.

[0040] It is possible that at least one charge air cooler for the fresh air mass flow is arranged between the supercharger and the internal combustion engine. In particular, the catalyst assembly is arranged in the exhaust gas mass flow downstream of the exhaust turbine. In particular, the catalyst assembly comprises at least one catalyst. The fresh air is in particular ambient air. The cooling air is in particular ambient air. The fresh air and / or the cooling air are in particular drawn in via at least one common air filter or via separate air filters.

[0041] In particular, the cooling air mass flow is adjusted so that the exhaust gas mass flow of the internal combustion engine is cooled to a temperature level corresponding to the exhaust gas enthalpy of the exhaust gas mass flow at a reduced boost pressure. Specifically, the mechanical power provided by the exhaust turbine from the exhaust gas enthalpy is divided, on the one hand, into the power required by the supercharger for the fresh air mass flow to operate the turbocharged internal combustion engine (charge exchange work during turbocharging) and, on the other hand, into the power required to operate the (convective) cooling system. The cooling system may also draw power from other sources, such as electrical power to operate its electrical or electronic components. Specifically, the cooling capacity of the cooling system includes the drive power of the cooling compressor unit and / or the cooling capacity of the cooling air mass flow.

[0042] Further advantages and features of the present invention will become apparent from the exemplary embodiments, which are explained below with reference to the accompanying figures.

[0043] The figures show: Fig. 1 a highly schematic diagram to illustrate a state-of-the-art device for exhaust gas turbocharging of an internal combustion engine; Fig. 2 a highly schematic diagram to illustrate a device for exhaust gas turbocharging of an internal combustion engine; Fig. 2a a diagram illustrating a device operated according to the method according to the invention; Fig. 2b a diagram illustrating another device operated according to the method according to the invention; Fig. 3. A highly schematic diagram to illustrate a device; and Fig. 4 A highly schematic diagram to illustrate another device.

[0044] The Fig. Figure 1 shows, for the introduction, a prior art device 1 for exhaust gas turbocharging of an internal combustion engine 2. An exhaust gas turbine assembly 3 comprises an exhaust gas turbine 13 driven by an exhaust gas mass flow from the internal combustion engine 2. This turbine is connected to a charging compressor 23 via a shaft 33. A wastegate valve 5 is also associated with the exhaust gas turbine assembly 3.

[0045] A fresh air mass flow at pressure (p0) and temperature (T0) enters the compressor (V) of the exhaust gas turbocharger from the intake system (ANS). The compressor then charges the air mass flow to pressure and temperature levels (p2; T2). Subsequently, the air is cooled in the charge air cooler (LLK) to pressure and temperature levels (p21; T21), and the cooled mass flow is fed to the internal combustion engine (ICE). Here, the fuel is added, and the actual combustion process takes place. The exhaust gas mass flow at pressure and temperature levels (p3; T3) is fed to the turbine (T) of the exhaust gas turbocharger, where it performs work required to drive the compressor (V). As a result, the exhaust gas mass flow has cooled to pressure and temperature levels (p4; T4) and is fed to the exhaust system (ESA) with its exhaust aftertreatment components. As soon as the described enthalpy imbalance occurs between the turbine (T) and the compressor (V), i.e.If the turbine (T) can convert more exhaust gas enthalpy into mechanical work than the compressor (V) can absorb, the wastegate valve (WG) opens and a portion of the exhaust gas mass flow bypasses the turbine (T). The wastegate thus regulates or limits the boost pressure. Of course, various designs exist according to the current state of the art. Examples include variable turbine geometry (VTG) and multiple turbocharging units connected in parallel or series, which will not be discussed in detail here, as the basic principle of boost pressure control is essentially the same.

[0046] The Fig. Figure 2 shows a device for exhaust gas turbocharging of an internal combustion engine 2, which in this embodiment is not covered by the subject matter of the claims. The mechanical power provided at the shaft 33 is split to operate not only the charging compressor 23 but also a cooling device 4 for cooling the exhaust gas mass flow of the internal combustion engine 2. The cooling device 4 comprises a cooling compressor unit 14, which is arranged here on the shaft 33 and is driven by the mechanical power of the exhaust gas turbine 13.

[0047] The cooling compressor unit 14 generates a cooling air mass flow and directs it via a valve assembly 34 to a heat exchanger unit 24. The valve assembly 34 is equipped with a throttle valve 44 and a recirculation valve 54. The recirculation valve 54 opens and closes a bypass 64.

[0048] The cooling air mass flow is adjusted by means of the valve assembly 34 so that the exhaust gas mass flow is cooled in a targeted manner. For this purpose, the temperature of the exhaust gas mass flow is reduced both by drawing drive power for the cooling compressor unit 14 and by the convection cooling of the heat exchanger assembly 24.

[0049] In an advantageous embodiment, the valve device 34 reduces the boost pressure when a boost pressure limit is exceeded by selectively cooling the exhaust gas mass flow with the cooling air mass flow and requiring part of the exhaust gas enthalpy for the cooling compressor unit 14.

[0050] The exhaust gas turbocharger features a conventional compressor (V1) and is supplemented by a second compressor (V2) mounted on the same shaft. The regular path of the air and exhaust gas mass flow remains largely unchanged. The added compressor (V2) draws in a cooling air mass flow independent of the process air supply of the combustion engine. The air mass flow from V2 is fed to a controllable throttle, the cooling air control valve (CAC), regulated, and then fed to the exhaust gas heat exchanger (EGH).

[0051] One objective here is the convective cooling of the exhaust gas components, ultimately lowering the exhaust gas temperature from one level (p31; T31) to another (p32; T32). The exhaust gas heat exchanger (EGH) can be a complex system, similar to those used in exhaust gas recirculation lines. However, convective cooling can also be achieved simply by directing airflow around exhaust components with the largest possible surface area (e.g., in pipe exhaust manifolds). In an advantageous configuration, the surfaces of the exhaust gas components in the area of ​​the EGH are optimized for maximum convective heat transfer (e.g., fins to increase surface area). After passing through the exhaust gas components (or the EGH), the cooling air mass flow is released into the atmosphere and discharged from the vehicle. The advantage of this design is that the cooling air mass flow is completely independent of the process air mass flow of the internal combustion engine (ICE).The VKM and the cooling system are practically only mechanically coupled via the ATL shaft and thus via the boost pressure control, and thermally via the AGWT.

[0052] The KLRV (cooling air regulation valve) is required to regulate the cooling air mass flow and to build up a certain stagnation pressure on the outlet side in order to operate the compressor (V2) at a more favorable operating point. This may be necessary because the compressors (V1) and (V2) are mechanically coupled by the common shaft and therefore always rotate at the same speed. Due to installation space restrictions and the need for minimal inertia (transient behavior), the design of the compressor (V2) may also be limited, and the KLRV must set a specific pressure ratio for an optimal compressor operating point. Furthermore, the flow velocity can be adjusted with it. In an advantageous configuration, the KLRV can also be used for boost pressure control. In this case, the wastegate (WG) on the turbine could be omitted.The full turbine power is always converted into mechanical energy, making a wastegate unnecessary with a suitable turbine design. Boost pressure control is achieved via the KLRV (cooling regulator valve). Once the target boost pressure is reached by the compressor (V1), the compressor (V2) and the KLRV convert the "excess" mechanical turbine power into compressor power (V2) and ultimately into "cooling energy".

[0053] Another useful additional device is the bypass valve (ULV). For operating points where the compressor output (V1) equals the turbine output (T), for example, during transient periods or at low speeds, it is essential to prevent compressor (V2) from cannibalizing compressor (V1). To this end, the compressed air from V2 is routed through a bypass channel controlled by the ULV and fed back into the compressor inlet V2. This essentially constitutes recirculation, similar to that in a wind tunnel. This principle of compressor-side recirculation has been state-of-the-art in turbocharged engines for decades and is implemented using the bypass valve, albeit for a completely different operating point (maintaining turbocharger speed during abrupt throttle closure in overrun mode). It is therefore a well-known, relatively simple component.

[0054] Theoretically, in the configuration shown here, the wastegate for boost pressure control is no longer required and could therefore be omitted. However, bypassing the exhaust turbine is still advisable to bring the catalytic converter up to operating temperature quickly. Furthermore, the wastegate provides a failsafe solution should the described boost pressure control via the KLRV (catalytic converter recirculation valve) fail. It is therefore recommended not to omit the wastegate.

[0055] The Fig. Figure 2a shows a variant of device 1 from the Fig. 2, in which the cooling air mass flow is supplied to a heat exchanger 24 located downstream of the exhaust gas turbine 13. After passing through the heat exchanger 24, the cooling air mass flow is then discharged to the atmosphere through an outlet (not shown). The exhaust gas mass flow coming from the internal combustion engine 2 first passes through the exhaust gas turbine 13 and only reaches the heat exchanger 24 downstream of the exhaust gas turbine 13. The exhaust gas mass flow can be supplied to the heat exchanger 24 between the exhaust gas turbine 13 and an exhaust system (ESG), or alternatively or additionally within the ESG. Accordingly, the heat exchanger 24 can be located at least partially within the ESG.

[0056] The Fig. Figure 2b shows a variant of device 1 from the Fig. 2 or 2a, in which the cooling air mass flow is supplied to a heat exchanger 24 arranged on the exhaust gas turbine 13. For example, the heat exchanger 24 is (thermally) coupled to a turbine housing of the exhaust gas turbine 13. The heat exchanger 24 can serve to cool the exhaust gas mass flow upstream and / or downstream of the exhaust gas turbine 13 by means of the cooling air mass flow. In other words, the exhaust gas mass flow can enter the heat exchanger 24 upstream and / or downstream of the exhaust gas turbine 13. Additionally or alternatively, the heat exchanger 24 can serve to cool the exhaust gas turbine 13 directly by means of the cooling air mass flow. Additionally or alternatively, the heat exchanger 24 can also be (thermally) coupled to the exhaust gas system.

[0057] In principle, combinations of the ones in the Fig. 2, Fig. 2a and Fig. The arrangements of the heat exchanger device 24 shown in 2b are possible and advantageous. The following arrangements with reference to the Fig. 3 and Fig. The heat exchanger devices 24 described in section 4 can be positioned in the device 1 as required with reference to the Fig. 2a and Fig. 2b is described.

[0058] The Fig. Figure 3 shows an embodiment of the device 1, which in this embodiment is not covered by the claims. Here, the valve assembly 34 comprises a cold air switching valve 74, which provides the function of the throttle valve 44 and the recirculation valve 54.

[0059] Here, the two throttle valves KLRV and ULV are replaced by the combined cold air switching valve (KLUV). This valve operates on the principle of a 3 / 2 control valve, but instead of simple on / off control, it uses an integrated throttle, resulting in a continuous transition. The challenge lies in the more complex control, as independent operation is no longer possible. The advantage is the simpler mechanical design. The rest of the design remains unchanged.

[0060] The Fig. Figure 4 shows a variant of the device 1, which in this embodiment is not covered by the claims. In this variant, the charging compressor 23 and the cooling compressor unit 14 are provided by a common combination compressor 43.

[0061] In the variant shown here, the second compressor V2 is omitted. Both the process air mass flow for the combustion engine and the cooling air mass flow are supplied by the common compressor (V1). Downstream, the cooling air mass flow is split by a branch into the process air mass flow for the combustion engine and the cooling air mass flow. The cooling air mass flow is regulated by the KLRV (cooling air regulation valve). The advantage of this arrangement lies in its even simpler design.

[0062] The challenge here is that compressor V1 must supply both mass flows. Therefore, this compressor should be significantly larger. This is feasible under static full load, but may result in significant disadvantages in transient behavior.

[0063] An advantage of the invention presented here is that more enthalpy can be extracted from the exhaust gas mass flow through the turbine, thus easily achieving the desired reduction in exhaust gas temperature at high loads (T4 reduction). The extracted enthalpy is converted into mechanical energy in the turbine and then used by means of an additional blower to generate a cooling air mass flow. This cooling air mass flow is used to achieve convection cooling of the exhaust gas components upstream of the first catalyst (combined T3 and T4 reduction). Reference symbol list: 1 Device 2 Internal combustion engine 3 Exhaust gas turbine unit 4 Cooling unit 5 Wastegate valve 13 Exhaust gas turbine 14 Cooling compressor unit 23 charging compressors 24 Heat exchanger unit 33 wave 34 Valve assembly 43 Combi compressors 44 Throttle valve 54 Recirculation valve 64 Bypass 74 Cold air changeover valve

Claims

[1] Method for operating a device (1) for exhaust gas turbocharging of an internal combustion engine (2), comprising at least one exhaust gas turbine assembly (3) with at least one exhaust gas turbine (13) driven by an exhaust gas mass flow of the internal combustion engine (2) and with at least one charging compressor (23) driven by the exhaust gas turbine (13) for providing a fresh air mass flow for turbocharging the internal combustion engine (2), wherein the mechanical power provided by the exhaust gas turbine (13) is split to operate, in addition to the charging compressor (23), a cooling device (4) for cooling the exhaust gas mass flow of the internal combustion engine (2), and wherein the cooling device (4) provides a cooling air mass flow by means of at least one cooling compressor unit (14) driven by the mechanical power of the exhaust gas turbine (13) and supplies the cooling air mass flow to a heat exchanger assembly (24),wherein the cooling air mass flow directed to the heat exchanger device (24) is adjustable by means of at least one controllable valve device (34) so ​​that the temperature of the exhaust gas mass flow can be selectively reduced at least by drawing off the drive power for the cooling compressor unit (14), characterized by , that the heat exchanger device (24) is arranged in a heat-conducting manner on the exhaust gas turbine (13) or in a heat-conducting manner on an exhaust gas system, such that the cooling air mass flow flowing through the heat exchanger device (24) cools the exhaust gas turbine (13) or the exhaust gas system at least section by section. [2] Method according to the preceding claim, wherein the exhaust gas mass flow coming from the internal combustion engine (2) partially passes through the heat exchanger device (24) before reaching the exhaust gas turbine (13), so that the temperature of the exhaust gas mass flow can be selectively reduced both by drawing the drive power for the cooling compressor unit (14) and by the convection cooling of the heat exchanger device (24). [3] Method according to one of the preceding claims, wherein the exhaust gas mass flow coming from the internal combustion engine (2) first passes partially through the exhaust gas turbine (13) and only then reaches the heat exchanger device (24). [4] Method according to one of the preceding claims, wherein the valve device (34) can be controlled taking into account a boost pressure limit of the internal combustion engine (2) in order to reduce the boost pressure available from the exhaust gas turbine (13) at least when the boost pressure limit is exceeded by selectively cooling the exhaust gas mass flow by means of the cooling air mass flow. [5] Method according to one of the preceding claims, wherein the cooling air mass flow is adjusted by means of the valve device (34) so ​​that an enthalpy imbalance between exhaust gas turbine (13) and charging compressor (23) is at least partially compensated. [6] Method according to one of the preceding claims, wherein the boost pressure is at least partially controlled by means of the cooling device (4). [7] Method according to one of the preceding claims, wherein the boost pressure is controlled at least by reducing the exhaust gas enthalpy contained in the exhaust gas mass flow by extracting the drive power required for the cooling compressor unit (14) and / or by selectively cooling the exhaust gas mass flow by means of the cooling air mass flow. [8] Method according to one of the preceding claims, wherein a boost pressure control does not require bypassing the exhaust gas mass flow at the exhaust gas turbine (13) and in particular without a wastegate valve (5) and / or wherein bypassing the exhaust gas mass flow at the exhaust gas turbine (13) and in particular a wastegate valve (5) is used to heat a catalyst device to an operating temperature and / or to enable boost pressure control as a substitute in the event of a malfunction of the cooling device (4). [9] Method according to one of the preceding claims, wherein the valve assembly (34) comprises at least one controllable throttle valve (44) for influencing the cooling air mass flow and wherein the valve assembly (34) comprises at least one controllable recirculation valve (54) and wherein, by means of the recirculation valve (54), the cooling air mass flow can be directed from an outlet side of the cooling compressor unit (14) via a bypass (64) back to an inlet side of the cooling compressor unit (14) so ​​that recirculation takes place, wherein the recirculation is activated at least when the power taken off the charging compressor (23) is at least approximately equal to the generated exhaust gas turbine power. [10] Method according to one of the preceding claims, wherein the cooling compressor unit (14) can only be driven by the exhaust gas turbine (13) together with the charging compressor (23) and wherein the cooling compressor unit (14) is preferably arranged on a common shaft (33) with the charging compressor (23) and / or the exhaust gas turbine (13). [11] Method according to one of the preceding claims, wherein an air flow of the cooling air mass flow is independent of an air flow of process air, in particular of the fresh air mass flow, for the internal combustion engine (2). [12] Device (1) for exhaust gas turbocharging of an internal combustion engine (2), suitable and designed to be operated according to the method according to one of the preceding claims.

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