Internal combustion engine with twin-flow axial turbine and grouped cylinders

Abstract

Internal combustion engine with at least one cylinder head with at least two cylinders, in which - each cylinder has at least one exhaust port for removing exhaust gases from the cylinder via an exhaust system, and an exhaust pipe is connected to each exhaust port, - at least two cylinders are configured in such a way that they form two groups, each with at least one cylinder, - combine the exhaust pipes of the cylinders of each cylinder group into a single exhaust pipe by forming an exhaust manifold, and - at least one exhaust gas turbocharger is provided, each exhaust gas turbocharger comprising a turbine (1) arranged in the exhaust gas discharge system and a compressor arranged in the intake system, and - the two exhaust gas lines with a twin-flow turbine (1) of an exhaust gas turbocharger, which comprises at least one impeller (3) mounted in a turbine housing (2) on a rotatable shaft (4) and equipped with impeller blades (3a), are connected in such a way that each exhaust gas line is connected to one of the two streams (5, 6) of the axial turbine (1), wherein the two streams (5, 6) - in continuation of the exhaust gas lines - are separated from each other up to the at least one impeller (3) by means of at least one housing wall (2a, 2b) and thus also the exhaust gas discharge systems of the cylinder groups, characterized in that - the double-flow turbine (1) is a double-flow axial turbine (1), wherein the two flows (5, 6) are arranged side by side and spirally enclose the runner (3) at least along an arc-shaped section, and - the turbine housing (2) is modular in design and comprises a housing ring (2c) which can be slid onto the shaft (4) and which is arranged upstream of the at least one impeller (3) and has at least one housing wall (2b) for the purpose of separating the two streams (5, 6).

Description

[0001] The invention relates to an internal combustion engine with at least one cylinder head with at least two cylinders, in which - each cylinder has at least one exhaust port for removing exhaust gases from the cylinder via an exhaust system, and an exhaust pipe is connected to each exhaust port, - at least two cylinders are configured in such a way that they form two groups, each with at least one cylinder, - combine the exhaust pipes of the cylinders of each cylinder group into a single exhaust pipe by forming an exhaust manifold, and - at least one exhaust gas turbocharger is provided, each exhaust gas turbocharger comprising a turbine arranged in the exhaust gas discharge system and a compressor arranged in the intake system, and - the two total exhaust gas lines with a twin-flow turbine of an exhaust gas turbocharger, which includes at least one impeller mounted on a rotatable shaft in a turbine housing and equipped with rotor blades, are connected in such a way that each total exhaust gas line is connected to one of the two streams of the axial turbine, wherein the two streams - in continuation of the total exhaust gas lines - are separated from each other by means of at least one housing wall up to the at least one impeller and thus also the exhaust gas discharge systems of the cylinder groups.

[0002] An internal combustion engine of the aforementioned type is used as a motor vehicle drive and is described, for example, in DE 20 2013 103 700 U1. Within the scope of the present invention, the term internal combustion engine includes gasoline engines, diesel engines, but also hybrid internal combustion engines that utilize a hybrid combustion process, as well as hybrid drives that, in addition to the internal combustion engine, comprise an electric motor that can be connected to the internal combustion engine for drive purposes and which receives power from the internal combustion engine or provides additional power as a switchable auxiliary drive.

[0003] Internal combustion engines consist of a cylinder block and at least one cylinder head, which are connected to form at least two cylinders. The cylinder head typically houses the valve train. To control the gas exchange, an internal combustion engine requires control elements—usually in the form of valves—and actuating devices to actuate these control elements. The valve actuation mechanism required for the movement of the valves, including the valves themselves, is called the valve train. During the gas exchange, the combustion gases are expelled through the exhaust ports of the at least two cylinders, and the cylinders are filled with fresh air-fuel mixture or charge air through the intake ports.

[0004] According to the prior art, the exhaust pipes connecting to the exhaust ports are at least partially integrated into the cylinder head and are combined into a single exhaust pipe or, alternatively, into two or more exhaust pipes in groups. The merging of exhaust pipes into a single exhaust pipe is generally, and within the scope of the present invention, referred to as an exhaust manifold.

[0005] The way in which the exhaust pipes of the cylinders are joined in each individual case, i.e. the specific design of the exhaust pipe system, depends essentially on which operating ranges the operating behavior of the internal combustion engine is to be optimized.

[0006] In turbocharged internal combustion engines where at least one turbine of an exhaust gas turbocharger is provided in the exhaust gas removal system and which are intended to exhibit satisfactory operating behavior in the lower speed range or with smaller quantities of exhaust gas, a so-called pulse charging is sought, i.e. preferred.

[0007] The aim is to utilize the dynamic wave processes occurring in the exhaust system – particularly during the charge exchange – for the purpose of charging and improving the operating behavior of the internal combustion engine.

[0008] The evacuation of combustion gases from a cylinder of an internal combustion engine during the charge exchange process relies essentially on two different mechanisms. At the beginning of the charge exchange, when an exhaust valve opens near bottom dead center, the combustion gases flow at high velocity through the exhaust port into the exhaust system due to the high pressure level prevailing in the cylinder towards the end of combustion and the associated high pressure differential between the combustion chamber and the exhaust pipe. This pressure-driven flow process is accompanied by a high pressure peak, also known as the pre-exhaust surge, which propagates along the exhaust pipe at the speed of sound. The pressure decreases, or rather, drops, to a greater or lesser extent with increasing distance due to friction.

[0009] As the charge exchange progresses, the pressures in the cylinder and in the exhaust pipe equalize, so that the combustion gases are no longer primarily evacuated by pressure, but are expelled as a result of the piston's stroke.

[0010] At low engine speeds, the exhaust pulse can be advantageously used for pulse charging, whereby short, high pressure pulses are used to generate energy in the turbine. In this way, high boost pressure ratios, i.e., high boost pressures on the intake side, can be generated by exhaust gas turbocharging even at low engine speeds or with small exhaust gas volumes.

[0011] Pulse charging proves particularly advantageous for accelerating the turbine wheel, i.e., increasing the turbine speed, which can drop noticeably during idle operation of the internal combustion engine or under low load and often needs to be increased again as quickly as possible by means of exhaust gas flow when the load increases. The inertia of the wheel and the friction in the shaft bearings generally delay the acceleration of the wheel to higher speeds and thus an immediate increase in boost pressure.

[0012] In order to utilize the dynamic wave processes occurring in the exhaust system, particularly the pre-exhaust pulses, for pulse charging to improve the operating characteristics of the internal combustion engine, the pressure peaks or pre-exhaust pulses in the exhaust system must be maintained. It is particularly advantageous if the pressure pulses in the exhaust pipes reinforce each other, or at least do not weaken or cancel each other out.

[0013] It is therefore advantageous to group the cylinders or to combine the exhaust pipes in such a way that the high pressures, especially the pre-exhaust pulses of the individual cylinders, are maintained in the exhaust system and mutual influence can be largely avoided.

[0014] An internal combustion engine in which the cylinders are grouped is also the subject of the present invention. According to the invention, at least two cylinders are configured such that they form two groups, each with at least one cylinder. The exhaust pipes of the cylinders in each cylinder group converge to form a single exhaust pipe via an exhaust manifold. The cylinders are grouped in such a way that the dynamic wave processes in the exhaust pipes of the cylinders within a group have as little adverse effect on each other as possible.

[0015] In a cylinder head with four cylinders arranged in a row, it is advantageous to group two cylinders with a firing interval of 360° crankshaft angle into a cylinder group. For example, if ignition in the cylinders is initiated according to the firing order 1-2-4-3 or 1-3-4-2, it is advantageous to group the outer cylinders into a first group and the inner cylinders into a second group.

[0016] In connection with the grouping of cylinders for the purpose of implementing pulse charging, two further aspects must be considered that are highly relevant to the separation of the exhaust systems of the cylinder groups. Firstly, exhaust manifolds are increasingly being integrated into the cylinder head to benefit from liquid cooling provided in the cylinder head and to avoid the need to manufacture the manifolds from thermally resistant materials, which are expensive. Secondly, there is a general effort to position the turbine in the exhaust system as close as possible to the exhaust port of the internal combustion engine, i.e., close to the exhaust ports of the cylinders. This has several reasons and advantages, particularly because it shortens the exhaust pipes between the cylinders and the turbine.Not only is the path of the hot exhaust gases to the turbine shortened, but the volume of both the individual exhaust manifolds and the entire exhaust system upstream of the turbine also decreases. The thermal inertia of the exhaust system is likewise reduced. In this way, the exhaust gas enthalpy of the hot exhaust gases, which is largely determined by the exhaust pressure and temperature, can be optimally utilized, ensuring a rapid turbine response. Shortening the pipe lengths and the associated reduction in exhaust gas volume upstream of the impeller further improves the turbine's response.

[0017] While the significantly shorter distances from the cylinder exhaust ports to the turbine are achieved according to the concept described above, this can also have disadvantages. Due to the turbine's proximity to the engine, the exhaust systems of the cylinder groups may not remain sufficiently separated from each other.

[0018] EP 2 146 072 A1 describes a turbocharged multi-cylinder internal combustion engine in which the cylinders are grouped into two cylinder banks and a twin-scroll axial turbine is provided in the exhaust system. The exhaust pipes of the cylinders of each cylinder bank converge within the cylinder head, forming an integrated exhaust manifold, to form a single exhaust pipe. To improve the torque characteristics, one exhaust pipe is connected to one of the streams of the twin-scroll axial turbine.

[0019] The DE 26 18 194 A1 also features a twin-flow turbine.

[0020] US 4,648,790 A describes a single-flow axial turbine.

[0021] Against this background, the object of the present invention is to provide an internal combustion engine according to the preamble of claim 1 which is optimized with regard to the separation of the exhaust gas removal systems.

[0022] This task is solved by an internal combustion engine with at least one cylinder head with at least two cylinders, in which - each cylinder has at least one exhaust port for removing exhaust gases from the cylinder via an exhaust system, and an exhaust pipe is connected to each exhaust port, - at least two cylinders are configured in such a way that they form two groups, each with at least one cylinder, - combine the exhaust pipes of the cylinders of each cylinder group into a single exhaust pipe by forming an exhaust manifold, and - at least one exhaust gas turbocharger is provided, each exhaust gas turbocharger comprising a turbine arranged in the exhaust gas discharge system and a compressor arranged in the intake system, and - the two exhaust gas lines with a twin-flow turbine of an exhaust gas turbocharger, which includes at least one impeller mounted on a rotatable shaft in a turbine housing and equipped with rotor blades, are connected in such a way that each exhaust gas line is connected to one of the two streams of the axial turbine, wherein the two streams - in continuation of the exhaust gas lines - are separated from each other by means of at least one housing wall up to the at least one impeller and thus also the exhaust gas discharge systems of the cylinder groups, and which is characterized by the fact that - the double-flow turbine is a double-flow axial turbine, wherein the two flows are arranged side by side and spirally enclose the runner at least along an arc-shaped section, and - the turbine housing is modular in design and includes a housing ring that can be slid onto the shaft, which is arranged upstream of the at least one impeller and has at least one housing wall to separate the two streams.

[0023] In the internal combustion engine according to the invention, the exhaust gas discharge systems of the cylinder groups are kept separate from each other not only up to the turbine housing, but also up to the point where they enter the at least one impeller, and thus also within the housing. The connection between the exhaust gas discharge systems of the two cylinder groups is therefore located further away from the exhaust ports of the cylinders, thereby increasing the exhaust gas path between a cylinder of one group and a cylinder of the other group. This counteracts the risk of mutual, and in particular detrimental, interference during the charge exchange. The pressure peaks or pre-exhaust pulses are maintained at least until they enter the at least one impeller. The maintenance of these pressure pulses, in turn, supports pulse charging.

[0024] The disadvantages that can arise from a turbine arrangement close to the engine and / or an integration of the exhaust manifolds into the cylinder head are advantageously compensated for according to the invention. This applies even if the internal combustion engine according to the invention does not necessarily have to be, or is not, a turbocharged internal combustion engine.

[0025] According to the invention, the turbine housing has a modular design and comprises a housing ring that can be slid onto the shaft, is arranged upstream of the at least one impeller, and has at least one housing wall to separate the two streams. In some cases, the housing structure is too complex to be manufactured in one piece by casting or machining. In such cases, a modular design is recommended, which may also be necessary for assembly reasons.

[0026] A monolithic housing is characterized by its low weight and compact design. Simplified assembly due to the reduced number of components is an advantage of the associated turbine. Furthermore, the housing is gas-tight because of the absence of joints. Preferably, the monolithic housing is manufactured as a cast component, for example, from aluminum, steel, gray cast iron, thermally resistant nickel-containing materials, or similar materials.

[0027] While a multi-part housing wall has a gap of varying size between each pair of adjacent sections, allowing for some interaction between the neighboring fluxes, a single-piece housing wall eliminates this gap. This supports the housing wall's primary function: to largely separate the adjacent fluxes and prevent any interaction between them.

[0028] However, designs of the internal combustion engine in which the housing wall separating the two flues is modular in construction can still be advantageous.

[0029] This solves the problem underlying the invention, namely providing an internal combustion engine according to the preamble of claim 1 which is optimized with regard to the separation of the exhaust gas removal systems.

[0030] The turbine used in the internal combustion engine according to the invention is an axial turbine, i.e., the flow towards the rotor blades is essentially axial. Essentially axial, within the scope of the present invention, means that the velocity component in the axial direction is greater than the radial velocity component.

[0031] Therefore, the axial turbine can also be designed in a mixed-flow configuration, as long as the velocity component in the axial direction is greater than the velocity component in the radial direction. The velocity vector of the flow in the region of the at least one impeller preferably runs parallel to the shaft of the axial turbine, so that the flow is exactly axial.

[0032] The use of an axial turbine eliminates the radial supply of exhaust gas via spiral or screw casing, which is absolutely necessary in radial turbines, i.e., inherently unavoidable, which in principle reduces pressure loss in the exhaust gas due to deflection and can or could increase the exhaust gas enthalpy at the turbine inlet.

[0033] According to the invention, the axial turbine is the turbine of an exhaust gas turbocharger. An exhaust gas turbocharger comprises a turbine arranged in the exhaust gas discharge system and a compressor arranged in the intake system.

[0034] Turbocharging primarily serves to increase the power output of the internal combustion engine. The air required for the combustion process is compressed, allowing a larger mass of air to be supplied to each cylinder per combustion cycle. This increases the fuel mass and thus the mean effective pressure.

[0035] Turbocharging is a suitable means of increasing the power output of an internal combustion engine without changing its displacement, or of reducing the displacement while maintaining the same power output. In either case, turbocharging leads to increased power output per unit volume and a more favorable power-to-weight ratio. Reducing the displacement allows the load spectrum to be shifted towards higher loads, where specific fuel consumption is lower. Turbocharging, in combination with suitable transmission designs, can also achieve a so-called downspeeding, which likewise results in lower specific fuel consumption. Turbocharging thus supports the ongoing effort in internal combustion engine development to minimize fuel consumption, i.e., to improve the efficiency of the engine.

[0036] Compared to a mechanical supercharger, the advantage of an exhaust gas turbocharger is that there is no mechanical connection for power transmission between the supercharger and the internal combustion engine, nor is one required. While a mechanical supercharger draws the energy required for its operation directly from the internal combustion engine, the exhaust gas turbocharger utilizes the energy of the hot exhaust gases.

[0037] Preferably, an intercooler is provided to cool the compressed intake air before it enters the cylinders. This further increases the density of the supplied intake air. The cooling also contributes to increased compression and improved cylinder filling. It can be advantageous to equip the intercooler with a bypass line to allow the intercooler to be bypassed when necessary, for example, after a cold start.

[0038] The torque characteristics of a turbocharged internal combustion engine can be improved by providing several turbochargers, exhaust gas turbochargers and / or mechanical turbochargers, arranged in parallel and / or in series in the exhaust gas discharge system.

[0039] Further advantageous embodiments of the internal combustion engine according to the invention are discussed in connection with the dependent claims.

[0040] Advantageous embodiments of the internal combustion engine are those in which the housing ring and the at least one impeller have essentially the same diameter. This ensures that no undercuts are required when the exhaust gas is fed radially into the housing.

[0041] Advantageous are embodiments of the internal combustion engine in which at least one housing wall is a fixed wall rigidly connected to the turbine housing. This housing wall design ensures that the heat introduced into the housing wall by the hot exhaust gas is dissipated advantageously and sufficiently into and via the housing.

[0042] Advantageous are embodiments of the internal combustion engine in which - each impeller section formed by two adjacent impeller blades is provided with a partition wall that divides the respective impeller section into two impeller blade channels, each partition wall forming a continuation of the at least one housing wall separating the two channels, so that the associated two impeller blade channels form continuations of the two channels.

[0043] The distance from the exhaust openings of the cylinders to the at least one impeller of the turbine, via which the exhaust gas discharge systems are separated in the internal combustion engine according to the invention, may prove to be too short in individual cases.

[0044] According to the embodiment in question, the exhaust gas discharge systems of the cylinder groups are not only separated from each other up to the point of entry into the at least one impeller, but also within the impeller itself or in the associated impeller blades. For this purpose, the impeller sections formed by the impeller blades are each divided into two impeller channels by means of a partition, which is why the exhaust gas flows of the cylinder groups cannot communicate with each other within the turbine impeller, or at least not yet, as they flow through it.

[0045] The proposed impeller design, which incorporates partitions into the impeller sections, results in a longer path length from the cylinder exhaust ports to the junction of the cylinder groups' exhaust systems into a common exhaust system. This ensures the maintenance of pressure pulses in the exhaust system at least up to the junction point.

[0046] At a specific rotational speed or angular velocity of the impeller, different circumferential speeds exist within the impeller. The partition effectively prevents mixing due to radial velocity components.

[0047] Since the partition walls connect to at least one housing wall as a continuation of the housing wall, the inventive design of the impeller also has the advantageous effect of preventing backflow of exhaust gas introduced from one stream into the impeller into the other stream.

[0048] Advantageous embodiments of the internal combustion engine are those in which the two rotor blade channels of each impeller section are radially spaced at different distances from the axis of rotation of at least one impeller. The two rotor blade channels of an impeller section enclose or encase the impeller shaft like a shell over different diameters, i.e., at different distances from the axis of rotation. In this respect, an inner rotor blade channel near the shaft and an outer rotor blade channel are formed.

[0049] In this context, embodiments of the internal combustion engine are also advantageous in which each partition wall is formed in one piece with the two impeller blades of the associated impeller section, so that each impeller forms a monolithic component.

[0050] In this case, the impeller is manufactured as a single, monolithic component, creating a permanent bond between the partition and the impeller blade. This reduces the number of components, thereby lowering manufacturing and assembly costs. Furthermore, the monolithic impeller is lighter than a modular impeller because no fasteners are required to form the connection.

[0051] In this context, embodiments of the internal combustion engine in which the at least one impeller is modularly constructed, with each partition wall being connected to the impeller blades of the corresponding impeller section, can also be advantageous.

[0052] This design of an impeller allows for the retrofitting of an existing impeller of a single-flow turbine, i.e., the conversion of an existing impeller into an impeller according to the invention. Furthermore, the blades and the partition can be made of different materials. A modular design allows for easy variation of the impeller construction, for example, an impeller for a turbine with more than two flows. Thus, the concept according to the invention can also be applied, for example, to four-flow turbines, in which each impeller section formed by two adjacent blades is provided with three partitions that divide the respective impeller section into four blade channels, extending the four flows. The above applies in principle to multi-flow turbines, i.e., turbines with n flows (n ≥ 2), even with a monolithic impeller design.

[0053] Furthermore, embodiments of the internal combustion engine are advantageous in which the exhaust gas discharge systems of the cylinder groups are at least partially separated from each other downstream of the at least one impeller. This further extends the distance from the exhaust ports of the cylinders to the connection point of the exhaust gas discharge systems of the cylinder groups.

[0054] In this context, embodiments of the internal combustion engine are also advantageous in which the rotor blade channels arranged adjacent to the rotatable shaft open into a first collecting pipe and the rotor blade channels located radially further away from the axis of rotation open into a second collecting pipe.

[0055] In this context, advantageous are embodiments of the internal combustion engine in which at least one segmented exhaust aftertreatment system is provided, which has two channel-shaped segments separated from each other, wherein the rotor blade channels arranged adjacent to the rotatable shaft are connected to a first segment and the rotor blade channels located radially further away from the axis of rotation are connected to a second segment.

[0056] The channel-shaped segments of the exhaust aftertreatment system, which are preferably gas-tight, ensure that the exhaust gas flows of the individual cylinder groups of the internal combustion engine are separated from each other even during exhaust aftertreatment.

[0057] The exhaust gases discharged from the cylinders are fed via manifolds, the main exhaust pipe, impeller or turbine blade channel, and, if applicable, via a collector pipe, to the individual channel-shaped segments, so that the exhaust flows of the cylinder groups are separated from each other upstream and during aftertreatment. The pressure pulse or pre-exhaust pulse of one cylinder therefore cannot propagate from the exhaust aftertreatment system towards another cylinder and adversely affect the charge exchange of that cylinder, or reduce or weaken the pressure pulses in the exhaust system of the other cylinder group.

[0058] Advantageous are embodiments of the internal combustion engine in which at least one exhaust aftertreatment system is provided in the exhaust system; for example, an oxidation catalyst, a three-way catalyst, a storage catalyst, a selective catalyst and / or a particulate filter.

[0059] Advantageous are embodiments of the internal combustion engine in which the at least one housing wall - separating two adjacent flues - has a free tongue-like end on the impeller side, which reaches as close as possible to the at least one impeller.

[0060] This embodiment aims to minimize the interaction between the exhaust systems, i.e., to increase the degree of separation between the flues and the exhaust discharge systems. The rationale behind this measure is that a gap of some size must remain between the housing wall and the impeller to allow the impeller to rotate freely without rubbing against the housing wall. In this particular design, this gap should be as narrow as possible.

[0061] Advantageous are embodiments of the internal combustion engine in which the two exhaust gas discharge systems of the two cylinder groups can be connected to each other by releasing at least one transfer channel.

[0062] Pulse charging doesn't only have advantages. The charge exchange is generally worsened due to the pressure pulses in the exhaust system. The cylinders in a group can interfere with each other during the charge exchange, i.e., impair each other's performance. The pressure waves emanating from one cylinder travel not only through that cylinder's exhaust pipe, but also along the exhaust pipes of the other cylinders in the group, potentially all the way to the exhaust port at the end of each pipe. Exhaust gas already expelled into one exhaust pipe during the charge exchange can thus re-enter the cylinder due to the pressure wave originating from another cylinder. This proves particularly disadvantageous if there is overpressure at the exhaust port of a cylinder towards the end of the charge exchange.The pressure wave from another cylinder propagates along the exhaust pipe towards the exhaust port, counteracting the evacuation of the combustion gases from that cylinder. During this phase of the charge exchange, the combustion gases are primarily expelled due to the piston's stroke. In some cases, exhaust gas from one cylinder can even enter another before its exhaust port closes. This impaired charge exchange leads to disadvantages, particularly under increasing load and engine speed. The exhaust gas remaining in the cylinder, i.e., the residual gas component, significantly influences the knocking behavior of a spark-ignition internal combustion engine, with the risk of knocking increasing with a higher proportion of residual exhaust gas.

[0063] Furthermore, it should be considered that a turbine operates most efficiently without intermittent or alternating partial pressure. To optimally operate a turbine located downstream of the cylinders in the exhaust system at high engine speeds, the turbine should be subjected to an exhaust pressure that is as constant as possible over time. Therefore, a pressure that changes only slightly upstream of the turbine wheel is preferred to achieve so-called ram air charging.

[0064] A sufficiently large exhaust gas volume upstream of the turbine impeller can smooth out pressure pulsations in the exhaust pipes. Therefore, with regard to turbocharging, it is advantageous to combine the exhaust pipes of all cylinders to maximize the exhaust gas volume of the exhaust system upstream of a turbine and to minimize pressure fluctuations.

[0065] Therefore, it is advantageous to provide the possibility of connecting the two exhaust gas removal systems of the two cylinder groups by opening at least one transfer channel.

[0066] Several concepts can be distinguished, for example, one in which the two exhaust manifolds of the two cylinder banks can be connected or separated. The exhaust system is then configured according to the current objective, enabling the internal combustion engine to be charged by separating the exhaust manifolds (pulse charging) or by connecting them (continuous charging). A disadvantage of the concept described above is that connecting the manifolds creates a connection close to the cylinder exhaust ports, thus exacerbating the residual gas problem and the associated knocking issue described above.

[0067] Alternatively, the streams of the twin-scroll turbine are connected or separated within the turbine housing. The streams are then either separated or connected, with the internal combustion engine being operated and charged by means of pulse charging or stagnation charging.

[0068] Advantageous are embodiments of the internal combustion engine in which the exhaust pipes of the cylinders of each cylinder group merge within the cylinder head to form a total exhaust pipe by means of two exhaust manifolds.

[0069] The twin-flow axial turbine integrated into the exhaust system can then be positioned very close to the exhaust port of the internal combustion engine, i.e., close to the cylinder exhaust ports. This offers the aforementioned advantages: optimal utilization of the exhaust gas enthalpy and a rapid turbine response.

[0070] Furthermore, integrating the exhaust manifolds into the cylinder head results in a compact design for the at least one cylinder head and thus for the internal combustion engine according to the invention, and allows for tight packaging of the entire drive unit. In addition, this method allows the system to utilize any liquid cooling provided in the cylinder head, so that the manifolds do not need to be made of thermally highly resistant and therefore expensive materials.

[0071] The shortening of the pipe lengths and the associated reduction in the exhaust gas volume upstream of the turbine impeller supports pulse charging in the lower speed range.

[0072] Advantageous embodiments of the internal combustion engine are those in which impeller blade sections located adjacent to the rotating shaft and those located radially further from the axis of rotation have different profiles. This embodiment takes into account the fact that at a specific rotational speed or angular velocity of the impeller, different circumferential speeds are present or generated in the impeller, so that the gas dynamics of the exhaust gas flow differ in impeller blade sections located at different distances from the rotating shaft. The different conditions may require different profiles, whereby the term "profiling" encompasses, according to the invention, a multitude of parameters that influence the flow; for example, the local blade thickness, the local change in thickness, i.e.,The local thickness gradient, as well as the curvature of the blade in both radial and axial directions, and similar parameters are recorded. In particular, all parameters and influencing factors relevant to airfoil theory are captured.

[0073] The invention is described below using an exemplary embodiment and in accordance with Fig. 1 described in more detail. This shows: Fig. 1 in a half section and partially cut the twin-flow axial turbine of a first embodiment of the internal combustion engine.

[0074] Fig. Figure 1 shows in a half section and partially cut the twin-flow axial turbine 1 of a first embodiment of the internal combustion engine.

[0075] The axial turbine 1 has a turbine housing 2 in which an impeller 3 is mounted on a rotatable shaft 4. A bearing housing 13 serves to receive the shaft 4. The two fluxes 5, 6 are arranged side by side and spirally encircle the impeller 3 at least along an arc-shaped section.

[0076] The two streams 5, 6 are separated from each other up to the impeller 3 by means of housing walls 2a, 2b. That is, the housing wall 2a, 2b, which separates the two streams 5, 6, is, like the turbine housing 2 itself, of modular construction. A first housing wall 2a is fixed and formed integrally with the turbine housing 2. A housing ring 2c, which is pushed onto the shaft 4 and is located upstream of the impeller 3, has a second housing wall 2b to separate the two streams 5, 6. This second housing wall extends the first housing wall 2a and has a free, tongue-like end on the impeller side, which reaches as close as possible to the impeller 3. The housing ring 2c and the impeller 3 have essentially the same diameter.

[0077] The airflow towards the impeller blades 3a of the impeller 3 is essentially axial, i.e., from right to left. The impeller blades 3a, which are wing-like and connected to the shaft 4, guide the exhaust gas from the cylinders through the impeller 3. The outflow from the impeller 3 is also axial.

[0078] Each impeller section 7 of the impeller 3, formed by two adjacent blades 3a, is provided with a partition 10 that divides the respective impeller section 7 into two blade channels 8, 9: a first blade channel 8 located adjacent to the shaft 4 and a blade channel 9 located radially further from the axis of rotation 4. The partition 10 forms – even when the impeller 3 is rotating – a continuation of the housing wall 2b of the ring 2c, which separates the two streams 5, 6. In this way, the two blade channels 8, 9 form the continuations of the two streams 5, 6, and the exhaust gas flows 11, 12 of the cylinder groups are kept separate from each other even as they flow through the impeller 3.

[0079] The insertion of partitions 10 into the impeller sections 7 increases the distances from the exhaust openings of the cylinders to the connection point of the exhaust gas removal systems of the cylinder groups.

[0080] At the in Fig. In the embodiment shown in Figure 1, the guide vane sections 8' located adjacent to the rotatable shaft 4 and the guide vane sections 9' located radially further from the axis of rotation 4 also have different profiles. Reference sign 1 twin-flow axial turbine 2 turbine housings 2a Housing wall 2b Housing wall 2c housing ring 3 wheel 3a Running blade 4. Axis of rotation, shaft 5 first flood 6 second flood 7 Wheel section 8 first impeller channel 8' adjacent to the shaft blade section 9 second impeller channel 9' further from the axis of rotation, the blade section 10 Partition wall 11 Exhaust gas flow of the first cylinder group 12 Exhaust gas flow of the second cylinder group 13 bearing housings

Claims

[1] Internal combustion engine with at least one cylinder head with at least two cylinders, in which - each cylinder has at least one exhaust port for removing exhaust gases from the cylinder via an exhaust system, and an exhaust pipe is connected to each exhaust port, - at least two cylinders are configured in such a way that they form two groups, each with at least one cylinder, - combine the exhaust pipes of the cylinders of each cylinder group into a single exhaust pipe by forming an exhaust manifold, and - at least one exhaust gas turbocharger is provided, each exhaust gas turbocharger comprising a turbine (1) arranged in the exhaust gas discharge system and a compressor arranged in the intake system, and - the two exhaust gas lines with a twin-flow turbine (1) of an exhaust gas turbocharger, which comprises at least one impeller (3) mounted in a turbine housing (2) on a rotatable shaft (4) and equipped with impeller blades (3a), are connected in such a way that each exhaust gas line is connected to one of the two streams (5, 6) of the axial turbine (1), wherein the two streams (5, 6) - in continuation of the exhaust gas lines - are separated from each other up to the at least one impeller (3) by means of at least one housing wall (2a, 2b) and thus also the exhaust gas discharge systems of the cylinder groups, characterized by , that - the double-flow turbine (1) is a double-flow axial turbine (1), wherein the two flows (5, 6) are arranged side by side and spirally enclose the runner (3) at least along an arc-shaped section, and - the turbine housing (2) is modular in design and comprises a housing ring (2c) which can be slid onto the shaft (4) and which is arranged upstream of the at least one impeller (3) and has at least one housing wall (2b) for the purpose of separating the two streams (5, 6). [2] Internal combustion engine according to claim 1, characterized by , that the housing ring (2c) and the at least one impeller (3) have substantially the same diameter. [3] Internal combustion engine according to any one of the preceding claims, characterized by , that at least one casing wall (2a, 2b) is an immovable wall firmly connected to the turbine casing (2). [4] Internal combustion engine according to any one of the preceding claims, characterized by , that - each impeller section (7) of an impeller (3) formed by two adjacent impeller blades (3a) is provided with a partition (10) which divides the respective impeller section (7) into two impeller blade channels (8, 9), wherein each partition (10) forms a continuation of the at least one housing wall (2a, 2b) separating the two flutes (5, 6) from each other, so that the associated two impeller blade channels (8, 9) form continuations of the two flutes (5, 6). [5] Internal combustion engine according to claim 4, characterized by , that the two impeller channels (8, 9) of each impeller section (7) are spaced radially apart from the axis of rotation (4) of the at least one impeller (3). [6] Internal combustion engine according to claim 4 or 5, characterized by , that each partition wall (10) is formed in one piece with the two running blades (3a) of the associated running wheel section (7), so that the at least one running wheel (3) forms a monolithic component. [7] Internal combustion engine according to claim 4 or 5, characterized by , that the at least one running wheel (3) is modular in design, wherein each partition (10) is connected to the running blades (3a) of the associated running wheel section (7). [8] Internal combustion engine according to any one of claims 4 to 7, characterized by , that the exhaust gas discharge systems of the cylinder groups are also separated from each other at least sectionally downstream of the at least one impeller (3). [9] Internal combustion engine according to any one of claims 4 to 8, characterized by , that the impeller blade channels (8) arranged adjacent to the rotatable shaft (4) open into a first collecting pipe and the impeller blade channels (9) located radially further away from the axis of rotation (4) open into a second collecting pipe. [10] Internal combustion engine according to claim 8 or 9, characterized by, that at least one segmented exhaust aftertreatment system is provided, which has two channel-shaped segments separated from each other, wherein the impeller blade channels (8) arranged adjacent to the rotatable shaft (4) are connected to a first segment and the impeller blade channels (9) located radially further away from the axis of rotation (4) are connected to a second segment. [11] Internal combustion engine according to any one of the preceding claims, characterized by , that the at least one - two adjacent floods (5, 6) - housing wall (2a, 2b) has a free tongue-like end on the impeller side, which reaches as close as possible to the at least one impeller (3). [12] Internal combustion engine according to any one of the preceding claims, characterized by that the two exhaust gas removal systems of the two cylinder groups can be connected to each other by releasing at least one transfer channel. [13] Internal combustion engine according to any one of the preceding claims, characterized by, that the exhaust pipes of the cylinders of each cylinder group within the cylinder head merge to form a total exhaust pipe by forming two exhaust manifolds. [14] Internal combustion engine according to any one of the preceding claims, characterized by , that the blade sections (8') located adjacent to the rotatable shaft (4) and the blade sections (9') located radially further from the axis of rotation (4) have different profiles.

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