DE102015205910A1 - Two-stage rechargeable internal combustion engine with turbocharger and method for operating such an internal combustion engine - Google Patents

Abstract

Supercharged internal combustion engine with - an intake system (1) for supplying charge air, - an exhaust gas removal system for discharging exhaust gas, - at least one exhaust gas turbocharger (2) having a turbine arranged in the Abgasabführsystem turbine (4) and in the intake system (1) arranged radial compressor (3 ), the radial compressor (3) being equipped with at least one impeller (3c) mounted on a rotatable shaft (3b), and - an electrically driven axial compressor (5) with at least one impeller mounted on a rotatable shaft (5b) (5c) and which is arranged upstream of the radial compressor (3) in the intake system (1) and whose outlet region (5a) is coaxial with the shaft (5b) of the axial compressor (5), the radial compressor (3) having an inlet region (3a). has, which is coaxial with the shaft (3b) of the radial compressor (3) and coaxial with the outlet region (5a) of the axial compressor (5) extends and is formed, wherein - the at least one impeller (3c) of the centrifugal compressor (3) and the at least one impeller (5c) of the axial compressor (5) spaced from each other in a common compressor housing (6) on a common shaft (3b, 5b, 7) are arranged, between the at least one impeller (3c) of the radial compressor (3) and the at least one impeller (5c) of the axial compressor (5) a housing-fixed guide (8) is arranged.

Description

• – einem Ansaugsystem zum Zuführen von Ladeluft,
• – einem Abgasabführsystem zum Abführen von Abgas,
• – mindestens einem Abgasturbolader, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Radialverdichter umfasst, wobei der Radialverdichter mit mindestens einem auf einer drehbaren Welle gelagerten Laufrad ausgestattet ist, und
• – einem elektrisch antreibbaren Axialverdichter, der mit mindestens einem auf einer drehbaren Welle gelagerten Laufrad ausgestattet ist und der stromaufwärts des Radialverdichters im Ansaugsystem angeordnet ist und dessen Austrittsbereich koaxial zur Welle des Axialverdichters verläuft, wobei der Radialverdichter einen Eintrittsbereich aufweist, der koaxial zur Welle des Radialverdichters und koaxial zum Austrittsbereich des Axialverdichters verläuft und ausgebildet ist.

The invention relates to a supercharged internal combustion engine with

• An intake system for supplying charge air,
• An exhaust gas removal system for removing exhaust gas,
• - At least one exhaust gas turbocharger, which comprises a arranged in Abgasabführsystem turbine and a suction arranged in the radial compressor, wherein the centrifugal compressor is equipped with at least one mounted on a rotatable shaft impeller, and
• - An electrically driven axial compressor which is equipped with at least one mounted on a rotatable shaft impeller and which is arranged upstream of the centrifugal compressor in the intake system and whose outlet region is coaxial with the shaft of the axial compressor, wherein the centrifugal compressor has an inlet region which is coaxial with the shaft of the centrifugal compressor and is coaxial with the exit region of the axial compressor and is formed.

Furthermore, the invention relates to a method for operating such an internal combustion engine.

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

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

The charge is a suitable means to increase the capacity of an internal combustion engine with unchanged displacement or to reduce the displacement at the same power. In any case, the charging leads to an increase in space performance and a lower power mass. If the displacement is reduced, then the load spectrum can be shifted to higher loads, where the specific fuel consumption is lower. By charging in combination with a suitable transmission design and a so-called downspeeding can be realized, in which also a lower specific fuel consumption can be achieved.

Charging thus supports the constant effort in the development of internal combustion engines to minimize fuel consumption, d. H. to improve the efficiency of the internal combustion engine.

Frequently, an exhaust gas turbocharger is used for charging, in which a compressor and a turbine are arranged on the same shaft. The hot exhaust stream is supplied to the turbine and relaxes with energy release in the turbine, causing the shaft to rotate. The energy emitted by the exhaust gas flow to the turbine and finally to the shaft is used to drive the compressor, which is also arranged on the shaft. The compressor conveys and compresses the charge air supplied to it, whereby a charging of the cylinder is achieved. Advantageously, a charge air cooler is provided downstream of the compressor in the intake system, with which the compressed charge air is cooled before entering the at least one cylinder. The radiator lowers the temperature and thus increases the density of the charge air, so that the cooler to a better filling of the cylinder, d. H. contributes to a larger air mass. There is a compaction by cooling.

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

The advantage of an exhaust gas turbocharger in comparison to a mechanical supercharger is that an exhaust gas turbocharger uses the exhaust gas energy of the hot exhaust gases, while a mechanical supercharger obtains the energy required for its drive directly or indirectly from the internal combustion engine. In general, a mechanical connection, such as a traction drive, for power transmission between the supercharger and the internal combustion engine is required.

The advantage of a mechanical supercharger over an exhaust gas turbocharger is that the mechanical supercharger can generally generate and provide the requested boost pressure independently of the current operating state of the internal combustion engine, in particular also at low speeds of the crankshaft. This applies in particular to a mechanical loader which can be driven by means of an electric machine.

Difficulties are the interpretation of the turbocharger, which is basically a noticeable increase in performance in all speed ranges sought. When charged with an exhaust gas turbocharger internal combustion engines falls below a certain speed, a strong torque drop is observed. This effect is undesirable and is one of the disadvantages of turbocharging.

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

The torque characteristic of a charged by turbocharging internal combustion engine is trying to improve the prior art by various measures.

For example, by a small design of the turbine cross-section and simultaneous Abgasabblasung. Such a turbine is also referred to as a waste gate turbine. If the exhaust gas mass flow exceeds a critical size, part of the exhaust gas flow is conducted past the turbine by means of a bypass line as part of the so-called exhaust gas blow-off. However, this approach has the disadvantage that the charging behavior at high speeds is insufficient.

The torque characteristic of a supercharged internal combustion engine may be further characterized by a plurality of turbochargers arranged in parallel, i. H. be improved by a plurality of parallel turbines of smaller turbine cross-section, with turbines are switched successively with increasing exhaust gas quantity.

The torque characteristic can also be advantageously influenced by means of a plurality of exhaust-gas turbochargers connected in series. By switching in series of two exhaust gas turbochargers, one of which is an exhaust gas turbocharger as a high pressure stage and an exhaust gas turbocharger as a low pressure stage, the compressor map can be widened in an advantageous manner, both towards smaller compressor streams as well as towards larger compressor streams.

In particular, in the case of the exhaust gas turbocharger serving as a high-pressure stage, the pumping limit can be shifted toward smaller compressor flows, whereby high boost pressure ratios can be achieved even with small compressor flows, which significantly improves the torque characteristic in the lower rpm range. This is achieved by designing the high-pressure turbine for small exhaust gas mass flows and providing a bypass line, with which increasing exhaust gas mass flow increasingly exhaust gas is passed to the high-pressure turbine. For this purpose, the bypass line branches off the exhaust-gas removal system upstream of the high-pressure turbine and returns to the exhaust-gas removal system upstream of the low-pressure turbine. In the bypass line, a shut-off element is arranged to control the exhaust gas flow passed past the high-pressure turbine.

However, the use of multiple turbochargers also has disadvantages, as will be explained below with reference to the two-stage charging.

In the design of the turbocharger turbocharger is trying hard, the turbine or turbines as close to the outlet of the engine, d. H. near the exhaust ports of the cylinder, to be arranged in order to be able to use the exhaust enthalpy of the hot exhaust gases, which is largely determined by the exhaust pressure and the exhaust gas temperature, optimally and to ensure a fast response of the turbocharger. Not only the way of the hot exhaust gases to the turbine is shortened by a close-coupled arrangement, also the volume of Abgasabführsystems upstream of the turbine decreases. The thermal inertia of the Abgasabführsystems also decreases by reducing the mass and the length of the portion of Abgasabführsystems to the turbine.

For the reasons mentioned above, the turbines are usually arranged on the exhaust side of the cylinder head. The exhaust manifold is often integrated in the cylinder head according to the prior art. The integration of the exhaust manifold also allows a dense packaging of the drive unit. In addition, it is possible to participate in a liquid cooling system, which may be provided in the cylinder head, so that the manifold does not have to be manufactured from materials capable of bearing high thermal loads, which are cost-intensive.

In a two-stage charging prepares the close-coupled arrangement of the turbine of the low-pressure stage naturally greater problems. It should also be borne in mind that the turbine of an exhaust-gas turbocharger is generally designed in radial design, ie the flow of the rotor blades is essentially radial. In the context of the present invention, essentially radial means that the velocity component is in the radial direction Direction is greater than the axial velocity component.

Consequently, after flowing through the high-pressure turbine, the exhaust gas must first be diverted or deflected via the exhaust-gas removal system in order to be able to be fed to the low-pressure stage downstream of the high-pressure turbine of the radial turbine. This not only increases the distance, but also the volume and the thermal inertia between the two turbines considerably.

In order to use the exhaust energy as efficiently as possible, the exhaust gas should be deflected as little as possible. Any change in direction of the exhaust gas flow, for example as a result of a curvature of the Abgasabführsystems, has a pressure drop in the exhaust gas flow and thus enthalpy loss.

Occasionally, the low-pressure turbine of an exhaust gas turbocharger is also designed as an axial turbine, ie, the flow of the impeller blades takes place substantially axially. In the context of the present invention, essentially axial means that the velocity component in the axial direction is greater than the radial velocity component. According to the state of the art, however, the inlet region for supplying the exhaust gas is also often designed as an all-round spiral or screw housing in axial turbines. The EP 1 710 415 A1 describes such an axial turbine.

The said for the turbines applies in an analogous manner to the compressors of the exhaust gas turbocharger, the compressors are also arranged on the outlet side due to the outlet side arrangement of the turbines and compressed in the compressors charge air downstream of the compressor must first be passed to the inlet side of the cylinder head to to be fed to the cylinders. Unlike the turbines, compressors are defined by their outflow. A radial compressor is thus a compressor whose outflow from the blades takes place substantially radially. By contrast, the outflow from the impeller blades of an axial compressor takes place substantially axially.

In order to avoid a pressure loss on the inlet side or to minimize the pressure loss, the charge air should be deflected as little as possible. The intake system should be as short as possible and should have as few changes of direction upstream of the compressors, downstream of the compressors and between the compressors.

For the reasons mentioned above, it may be advantageous to combine the radial compressor of an exhaust gas turbocharger with an axial compressor, wherein the axial compressor is arranged upstream of the centrifugal compressor in the intake system. The internal combustion engine according to the invention realizes this charging concept. According to the invention, the axial compressor is an electrically drivable compressor.

In the present case, the axial compressor has an outlet region, which runs coaxially with the shaft of the axial compressor, so that the outflow of the charge air from the axial compressor via the outlet region takes place essentially axially. The radial compressor also has an inlet region which is coaxial to the shaft of the centrifugal compressor and coaxial with the outlet region of the axial compressor and is designed so that the flow of the charge air to the centrifugal compressor takes place substantially axially.

The charge air does not have to be deflected after flowing through the axial compressor to be fed to the centrifugal compressor. Unnecessary pressure losses in the charge air flow due to flow deflection are avoided and the precompressed charge air can be further compressed in the centrifugal compressor. The efficiency and the charge pressure ratio of the two-stage compression are increased.

The use of an axial compressor instead of another exhaust gas turbocharger also allows a denser packaging, in particular a reduction of the distance, the volume and the mass of the intake between the two compressors.

An internal combustion engine of the aforementioned type describes, for example, the German patent application DE 100 50 161 A1 , Since the energy provided by the on-board battery of a vehicle is limited, the electric drive of the axial compressor can only be regarded and used as an auxiliary drive or as an additional drive.

In light of the above, it is an object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, the charging performance of which is further improved and the charging thereof has a smaller space requirement and enables denser packaging.

A further sub-task of the present invention is to show a method for operating such an internal combustion engine.

• – einem Ansaugsystem zum Zuführen von Ladeluft,
• – einem Abgasabführsystem zum Abführen von Abgas,
• – mindestens einem Abgasturbolader, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Radialverdichter umfasst, wobei der Radialverdichter mit mindestens einem auf einer drehbaren Welle gelagerten Laufrad ausgestattet ist, und
• – einem elektrisch antreibbaren Axialverdichter, der mit mindestens einem auf einer drehbaren Welle gelagerten Laufrad ausgestattet ist und der stromaufwärts des Radialverdichters im Ansaugsystem angeordnet ist und dessen Austrittsbereich koaxial zur Welle des Axialverdichters verläuft, wobei der Radialverdichter einen Eintrittsbereich aufweist, der koaxial zur Welle des Radialverdichters und koaxial zum Austrittsbereich des Axialverdichters verläuft und ausgebildet ist,

die dadurch gekennzeichnet ist, dass

• – das mindestens eine Laufrad des Radialverdichters und das mindestens eine Laufrad des Axialverdichters beabstandet zueinander in einem gemeinsamen Verdichtergehäuse auf einer gemeinsamen Welle angeordnet sind, wobei zwischen dem mindestens einen Laufrad des Radialverdichters und dem mindestens einen Laufrad des Axialverdichters eine gehäusefeste Leiteinrichtung angeordnet ist.

The first subtask is solved by a supercharged internal combustion engine

• An intake system for supplying charge air,
• An exhaust gas removal system for removing exhaust gas,
• - At least one exhaust gas turbocharger, which comprises a arranged in Abgasabführsystem turbine and a suction arranged in the radial compressor, wherein the centrifugal compressor is equipped with at least one mounted on a rotatable shaft impeller, and
• - An electrically driven axial compressor which is equipped with at least one mounted on a rotatable shaft impeller and which is arranged upstream of the centrifugal compressor in the intake system and whose outlet region is coaxial with the shaft of the axial compressor, wherein the centrifugal compressor has an inlet region which is coaxial with the shaft of the centrifugal compressor and is coaxial with the exit region of the axial compressor and is formed,

which is characterized in that

• - The at least one impeller of the centrifugal compressor and the at least one impeller of the axial compressor spaced from each other in a common compressor housing are arranged on a common shaft, wherein between the at least one impeller of the centrifugal compressor and the at least one impeller of the axial compressor, a housing-fixed guide is arranged.

In the internal combustion engine according to the invention, the shaft of the centrifugal compressor is at the same time the shaft of the axial compressor, d. H. the axial compressor and the centrifugal compressor share a common shaft, on which also the at least one impeller of the turbine is arranged. Consequently, the at least one impeller of the centrifugal compressor, the at least one impeller of the axial compressor and the at least one impeller of the turbine in the same direction and at the same speed to run and that without exception. A coupling for mechanical decoupling of the impellers of the centrifugal compressor, the axial compressor and / or the turbine is not necessary and not provided.

The elimination of a coupling makes the charging according to the invention very compact and results in a relatively small space requirement of the charge. In addition, the design is simplified by using a single rigid shaft and the elimination of bearings.

Since the axial compressor and the centrifugal compressor share a common shaft, on which also the at least one impeller of the turbine is arranged, the two compressors also share the turbine, which drives both compressors.

Although the axial compressor is electrically driven. However, this electric drive is to be regarded as an auxiliary drive and is used in case of need only in addition to the turbine. The electric drive is used in particular to accelerate the shaft and the wheels with increased load requirement and thus improves the response of the charge. Since the energy provided by the on-board battery of a vehicle is limited, the electric drive is not used continuously.

According to the invention, a housing-fixed guide is arranged between the at least one impeller of the radial compressor and the at least one impeller of the axial compressor. Using this guide means, the flow of the charge air after flowing through the axial compressor and before entering the centrifugal compressor can be influenced, whereby the charging behavior is further improved. The efficiency and the charge pressure ratio of the two-stage compression are increased.

The internal combustion engine according to the invention has an improved charging behavior and a charge, which has a small space requirement and allows a denser packaging. As a result, the first object underlying the invention is achieved.

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

Advantageous embodiments of the supercharged internal combustion engine, in which

Embodiments of the supercharged internal combustion engine in which the turbine of the at least one exhaust-gas turbocharger is a radial turbine are advantageous. This embodiment also allows a tight packaging of the exhaust gas turbocharger and thus the overall charge.

For reasons of packaging and embodiments of the supercharged internal combustion engine are advantageous in which only one exhaust gas turbocharger is provided.

Advantageous embodiments of the supercharged internal combustion engine, in which the radial compressor is designed smaller than the axial compressor.

In the case of the two compressors arranged in series and arranged in the intake system, it may be advantageous to make the axial compressor larger than the downstream radial compressor, since in a two-stage compression the radial compressor forms the high-pressure stage and the charge air compressed, which was already pre-compressed in the then used as a low pressure stage axial compressor.

Nevertheless, the axial compressor does not necessarily have to be made larger than the centrifugal compressor. In particular, the axial compressor can also be the same size or be designed to be smaller in order to accomplish the compression of the charge air at small charge air quantities in a satisfactory manner and ensure. For larger amounts of charge air, the axial compressor could then be bypassed by means of a bypass line and the centrifugal compressor make the compression of the charge air in the context of a single-stage compression.

Therefore, embodiments of the supercharged internal combustion engine in which the radial compressor is designed to be larger than the axial compressor or the same size are also advantageous.

Advantageous embodiments of the supercharged internal combustion engine can be for the reasons mentioned above, in which a first bypass line is provided, which has a shut-off and the upstream of the axial compressor branches off from the intake system and opens between the axial compressor and the centrifugal compressor back into the intake system.

If the axial compressor designed smaller than the compressor of at least one exhaust gas turbocharger, the axial compressor takes over the compression of the charge air at low charge air quantities or low speeds to improve the torque characteristics in the lower speed range. For larger amounts of charge air, the axial compressor could then be bypassed by means of the first bypass line and the centrifugal compressor ensures the compression of the charge air at higher speeds in the context of a single-stage charge.

If the axial compressor is designed to be larger than the compressor of the at least one exhaust gas turbocharger, the axial compressor takes over the precompression of the charge air with larger charge air quantities or higher speeds and the centrifugal compressor serves as a high-pressure stage in a two-stage charge, in which the precompressed charge air is further compressed. For smaller amounts of charge air, the axial compressor could then be bypassed by means of the first bypass line and the centrifugal compressor ensures the compression of the charge air at lower speeds in the context of a single-stage charge. In most cases, however, the axial compressor will not provide too much flow resistance with small amounts of charge air, so a first bypass line will not be required under all circumstances.

Embodiments of the supercharged internal combustion engine may also be advantageous in which a second bypass line is provided, which has a shut-off element and which branches off from the intake system between the axial compressor and the centrifugal compressor and opens again into the intake system downstream of the radial compressor. The second bypass line serves to bypass the centrifugal compressor.

If the axial compressor designed smaller than the compressor of at least one exhaust gas turbocharger, the axial compressor takes over the compression of the charge air at low charge air quantities or low speeds to improve the torque characteristics in the lower speed range. For small amounts of charge air, the centrifugal compressor could then be bypassed by means of a second bypass line. In most cases, however, the radial compressor will not be too great a flow resistance with small charge air quantities, which is why a second bypass line will not be absolutely necessary.

Advantageous embodiments of the supercharged internal combustion engine, in which for the purpose of Abgasabblasung a third bypass line is provided, which branches off upstream of the turbine from Abgasabführsystem and downstream of the turbine opens again into the Abgasabführsystem, wherein a shut-off in the third bypass line is provided to control the Abgasabblasung.

The provision of a third bypass line allows the design of the turbine to medium exhaust gas mass flows and thus to the middle part load range. With regard to the bypass of the turbine by means of bypass line has already been carried out. Reference is made to the corresponding statements.

Advantageous embodiments of the supercharged internal combustion engine, in which the axial compressor has an inlet region which is coaxial with the common shaft and is formed so that the flow of the charge air to the axial compressor takes place substantially axially. This embodiment facilitates the arrangement of the at least one impeller of the axial compressor in the compressor housing and the formation of the electric drive.

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

A variable turbine geometry increases the flexibility of charging. She allows one stepless adjustment of the turbine geometry to the respective operating point of the internal combustion engine, in particular to the current exhaust gas mass flow. Unlike a fixed-geometry turbine, the turbine does not need to be designed for discrete exhaust levels, which is why the turbine provides a satisfactory boost in a wide range of speeds and loads, namely the desired charge pressure on the intake side.

Embodiments of the supercharged internal combustion engine in which the guide is adjustable are advantageous. The diffuser implements a variable compressor geometry in the centrifugal compressor.

Basically, the guide allows the optimization of the flow to the radial compressor and thus increasing the compressor pressure ratio or boost pressure ratio. The velocity vector of the flow in the region of the at least one impeller of the radial compressor preferably also has a tangential component to the shaft, d. H. a twist, whereby the efficiency is increased. A variable compressor geometry is particularly advantageous if the turbine of the at least one exhaust-gas turbocharger has a variable turbine geometry and a variable compressor geometry can then be continuously tuned to the turbine geometry. In particular, if only a small exhaust gas mass flow is passed through the turbine, a variable compressor geometry proves to be advantageous, since by adjusting the blades, the pumping limit of the compressor in the compressor map to small compressor streams can be moved and so working of the compressor is avoided beyond the surge line ,

If the axial compressor takes over the compression of the charge air at small charge air quantities or low engine speeds, the radial compressor represents only a flow resistance on the way to the cylinders. A variable compressor geometry makes it possible to reduce this flow resistance by opening the geometry.

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

Advantageous embodiments of the supercharged internal combustion engine, in which for the electric drive of the axial compressor, an electric motor is provided which comprises a stator and a rotor.

Thus, an electric motor, i. H. an electric drive, are formed with a rotatably connected to the impeller of the axial compressor rotor and a stator fixed to the housing, which surrounds the rotor circumferentially. In this case, the rotor made of a magnetic material is preferably annular and is seated on the radially outer edge of the compressor impeller. When the stator, preferably a coil, is energized, an electromagnetic force rotating the rotor is generated.

Advantageous in this context, therefore, embodiments of the supercharged internal combustion engine, in which the stator is at least arranged in the common compressor housing and mounted fixed to the housing, and embodiments of the supercharged internal combustion engine, wherein the stator comprises a bestrombare coil for establishing a magnetic field.

Embodiments of the supercharged internal combustion engine in which the rotor is non-rotatably connected to the at least one impeller of the axial compressor, as well as embodiments of the supercharged internal combustion engine in which the rotor comprises at least one permanent magnet for establishing a magnetic field, are also advantageous.

Embodiments of the internal combustion engine in which the rotor is arranged on radially outer edges of the at least one impeller of the axial compressor are also advantageous in this connection.

Embodiments of the supercharged internal combustion engine in which the shut-off element in the first, second, and / or third bypass line is a valve or a throttle valve are advantageous.

In this case, embodiments in which the shut-off element is electrically, hydraulically, pneumatically, mechanically or magnetically controllable, preferably by means of motor control, are advantageous.

The second sub-problem underlying the invention, namely to show a method for operating an internal combustion engine of the type described above, is achieved by a method which is characterized in that the axial compressor is additionally electrically driven to increase the speed n _{compressor of} the common shaft ,

What has already been said for the internal combustion engine according to the invention also applies to the A method according to the invention, which is why at this point in general reference is made to the statements made above with regard to the supercharged internal combustion engine. The various internal combustion engines sometimes require different process variants.

The electric drive of the axial compressor can be used if necessary to improve the response. In this way, it is possible in particular to optimize the transient operating behavior or the charging behavior.

Advantageous are process variants in which the axial compressor is additionally electrically driven in order to increase a boost pressure downstream of the compressor.

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

1 schematically the charging of a first embodiment of the internal combustion engine, partially cut.

1 schematically shows the charging of a first embodiment of the supercharged internal combustion engine, partially cut.

For supplying the charge air to the cylinders, the internal combustion engine has an intake system 1 , For the purpose of charging the cylinder is an exhaust gas turbocharger 2 provided, which is arranged in the Abgasabführsystem turbine 4 and one in the intake system 1 arranged compressor 3 includes. The compressor 3 is a centrifugal compressor 3 and with one on a rotatable shaft 3b mounted impeller 3c fitted.

To improve the torque characteristic is upstream of the centrifugal compressor 3 the exhaust gas turbocharger 2 an electrically drivable axial compressor 5 in the intake system 1 arranged, likewise with a on a rotatable shaft 5b mounted impeller 5c Is provided.

The axial compressor 5 has an entrance area 5d and an exit area 5a , each coaxial with the shaft 5b of the axial compressor 5 run. Both the flow of charge air to the axial compressor 5 as well as the outflow of the charge air from the axial compressor 5 therefore takes place substantially axially. The centrifugal compressor 3 has an entrance area 3a on, both coaxial with the shaft 3b of the centrifugal compressor 3 as well as coaxial with the exit area 5a of the axial compressor 5 runs and is formed. The flow of charge air to the compressor 3 the exhaust gas turbocharger 2 also takes place substantially axially.

Between the wheel 3c of the centrifugal compressor 3 and the impeller 5c of the axial compressor 5 spaced apart in a common compressor housing 6 on a common wave 3b . 5b . 7 are arranged, is a housing-fixed guide 8th intended.

The axial compressor 5 is electrically driven, wherein the electric drive, ie the electric motor 9 , if necessary, switched on, that can be switched on.

The electric motor 9 is presently using a rotationally fixed with the compressor wheel 5c connected rotor 9b and a stator fixed to the housing 9a who is the rotor 9b encompasses circumferentially, trained.

The one made of a permanent magnet 9b' manufactured rotor 9b is annular and sits on the radially outer edges of the compressor rotor blades. When energizing the stator 9a , a coil 9a' , one becomes the rotor 9b generates rotating electromagnetic force.

LIST OF REFERENCE NUMBERS

1

 intake system

2

 turbocharger

3

 Compressor of turbocharger, centrifugal compressor

3a

 Entry area of the centrifugal compressor

3b

 Shaft of centrifugal compressor

3c

 Impeller of the centrifugal compressor

4

 Turbine of the exhaust gas turbocharger

5

 axial compressor

5a

 Outlet area of the axial compressor

5b

 Shaft of the axial compressor

5c

 Impeller of the axial compressor

5d

 Entry area of the axial compressor

6

 common compressor housing

7

 common wave

8th

 guide

9

 electric motor

9a

 stator

9a'

 energizing coil

9b

 rotor

9b'

 permanent magnet

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• EP 1710415 A1 [0024]
• DE 10050161 A1 [0031]

Claims (19)

Charged internal combustion engine with - an intake system ( 1 ) for supplying charge air, - an exhaust gas removal system for discharging exhaust gas, - at least one exhaust gas turbocharger ( 2 ), which is arranged in the Abgasabführsystem turbine ( 4 ) and one in the intake system ( 1 ) arranged radial compressor ( 3 ), wherein the radial compressor ( 3 ) with at least one on a rotatable shaft ( 3b ) mounted impeller ( 3c ), and - an electrically driven axial compressor ( 5 ) with at least one on a rotatable shaft ( 5b ) mounted impeller ( 5c ) and the upstream of the radial compressor ( 3 ) in the intake system ( 1 ) is arranged and its exit area ( 5a ) coaxial with the shaft ( 5b ) of the axial compressor ( 5 ), wherein the radial compressor ( 3 ) an entrance area ( 3a ) coaxial with the shaft ( 3b ) of the radial compressor ( 3 ) and coaxial with the exit area ( 5a ) of the axial compressor ( 5 ) and is formed, characterized in that - the at least one impeller ( 3c ) of the radial compressor ( 3 ) and the at least one impeller ( 5c ) of the axial compressor ( 5 ) spaced apart in a common compressor housing ( 6 ) on a common wave ( 3b . 5b . 7 ) are arranged, wherein between the at least one impeller ( 3c ) of the radial compressor ( 3 ) and the at least one impeller ( 5c ) of the axial compressor ( 5 ) a housing-fixed guide ( 8th ) is arranged. Supercharged internal combustion engine according to claim 1, characterized in that the turbine ( 4 ) of the at least one exhaust gas turbocharger ( 2 ) is a radial turbine. Supercharged internal combustion engine according to claim 1 or 2, characterized in that the radial compressor ( 3 ) is designed smaller than the axial compressor ( 5 ). Supercharged internal combustion engine according to claim 1 or 2, characterized in that the radial compressor ( 3 ) is designed to be larger than the axial compressor ( 5 ). Supercharged internal combustion engine according to one of the preceding claims, characterized in that a first bypass line is provided, which has a shut-off element and the upstream of the axial compressor ( 5 ) from the intake system ( 1 ) branches off and between the axial compressor ( 5 ) and the centrifugal compressor ( 3 ) back into the intake system ( 1 ) opens. Supercharged internal combustion engine according to one of the preceding claims, characterized in that a second bypass line is provided, which has a shut-off element and between the axial compressor ( 5 ) and the centrifugal compressor ( 3 ) from the intake system ( 1 ) branches off and downstream of the centrifugal compressor ( 3 ) back into the intake system ( 1 ) opens. Supercharged internal combustion engine according to one of the preceding claims, characterized in that for the purpose of Abgasabblasung a third bypass line is provided, the upstream of the turbine ( 4 ) branches off the exhaust system and downstream of the turbine ( 4 ) opens again into the exhaust gas removal system, wherein a shut-off element is provided in the third bypass line for controlling the Abgasabblasung. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the axial compressor ( 5 ) an entrance area ( 5d ) coaxial with the common shaft ( 3b . 5b . 7 ) and is formed so that the flow of the charge air to the axial compressor ( 5 ) is effected substantially axially. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the turbine ( 4 ) of the at least one exhaust gas turbocharger ( 2 ) has a variable turbine geometry. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the guide device ( 8th ) is adjustable. Supercharged internal combustion engine according to one of the preceding claims, characterized in that downstream of the compressor ( 3 . 5 ) an intercooler in the intake system ( 1 ) is arranged. Supercharged internal combustion engine according to one of the preceding claims, characterized in that for the electric drive of the axial compressor ( 5 ) an electric motor ( 9 ) is provided, which is a stator ( 9a ) and a rotor ( 9b ). Supercharged internal combustion engine according to claim 12, characterized in that the stator ( 9a ) at least in the common compressor housing ( 6 ) is arranged and mounted fixed to the housing. Supercharged internal combustion engine according to claim 12 or 13, characterized in that the stator ( 9a ) an energizable coil ( 9a' ) to build up a magnetic field. Supercharged internal combustion engine according to one of claims 12 to 14, characterized in that the rotor ( 9b ) rotatably with the at least one impeller ( 5c ) of the axial compressor ( 5 ) connected is. Supercharged internal combustion engine according to one of claims 12 to 15, characterized in that the rotor ( 9b ) at least one permanent magnet ( 9b' ) to build up a magnetic field. Supercharged internal combustion engine according to claim 15 or 16, characterized in that the rotor ( 9b ) on radially outer edges of the at least one impeller ( 5c ) of the axial compressor ( 5 ) is arranged. Method for operating a supercharged internal combustion engine according to one of the preceding claims, characterized in that the axial compressor ( 5 ) is additionally electrically driven to the speed n _{compressor of} the common shaft ( 7 ) increase. Method according to claim 18, characterized in that the axial compressor ( 5 ) is additionally electrically driven to a boost pressure downstream of the compressor ( 3 . 5 ) increase.

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