DE202014103104U1 - Charged internal combustion engine with turbocharger - Google Patents

Abstract

Supercharged internal combustion engine with - an intake system (1) for supplying charge air, - an exhaust gas discharge system for removing exhaust gas, and - at least one exhaust gas turbocharger (2), which has a turbine (4) arranged in the exhaust gas discharge system and a compressor (1) arranged in the intake system (1) 3), the compressor (3) being equipped with at least one impeller (3d) mounted in a compressor housing (3e) on a rotatable shaft (3c), characterized in that - an electrically driven second compressor (5) upstream of the compressor (3) of the at least one exhaust gas turbocharger (2) is arranged in the intake system (1), the second compressor (5) comprising at least one impeller (5d) mounted in a compressor housing (5e) on a rotatable shaft (5c) and an axial compressor ( 5b), the outlet area (5a) of which runs coaxially to the shaft (5c) of the second compressor (5), so that the charge air flows out of the second compressor (5) via the outlet area (5a) takes place essentially axially, and - the compressor (3) of the at least one exhaust gas turbocharger (2) has an inlet area (3a) which is coaxial to the shaft (3c) of the compressor (3) and coaxial to the outlet area (5a) of the second Compressor (5) runs and is designed so that the flow of the charge air to the compressor (3) of the at least one exhaust gas turbocharger (2) takes place essentially axially.

Description

The invention relates to a supercharged internal combustion engine with
An intake system for supplying charge air,
An exhaust gas discharge system for discharging exhaust gas, and
- At least one exhaust gas turbocharger comprising a turbine arranged in the Abgasabführsystem and a compressor disposed in the intake compressor, wherein the compressor is equipped with at least one mounted in a compressor housing on a rotatable shaft impeller.

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, which use a hybrid combustion process, and hybrid drives, which in addition to the internal combustion engine comprise an electric motor which can be electrically connected to the internal combustion engine, which receives power from the internal combustion engine or as switchable auxiliary drive additionally delivers power.

In recent years, there has been a trend toward small, supercharged engines, with supercharging primarily a method of increasing performance by compressing the air needed for the engine combustion process. The economic importance of these engines for the automotive industry continues to increase.

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 an exhaust gas turbocharger compared to a mechanical supercharger is that there is no mechanical connection to the power transmission between the supercharger and the internal combustion engine or is required. 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 charge is - as already mentioned - the increase in performance. 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.

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.

Another fundamental goal is to reduce pollutant emissions. In the solution of this task, the charging can also be effective. With targeted design of the charge namely benefits in efficiency and in the exhaust emissions can be achieved.

The interpretation of the turbocharger turbocharger is difficult, with basically a noticeable increase in performance in all speed ranges is sought. In the prior art, however, a strong torque drop is observed when falling below a certain speed.

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

In practice, the relationships described above often lead to a small exhaust gas turbocharger, ie an exhaust gas turbocharger with a small turbine cross section is used, whereby the turbine pressure ratio can be increased. However, this degrades the charge at high speeds and shifts the torque drop only towards low speeds. In addition, this approach, ie the reduction of the turbine cross section, limits, since the desired charging and performance increase should be possible without restriction and to the desired extent, even at high speeds.

The torque characteristic of a supercharged internal combustion engine is tried to improve in the prior art by various measures.

For example, by a small design of the turbine cross-section and simultaneous Abgasabblasung, the Abgasabblasung can be controlled by means of boost pressure or by means of exhaust pressure. 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 - as already mentioned above - the disadvantage that the charging behavior at higher 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 engine map can be widened in an advantageous manner, both towards smaller compressor streams and 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 towards smaller compressor flows, which means that 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 in 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.

Naturally, in a two-stage supercharger, the engine-mounted arrangement of the turbine of the low-pressure stage causes greater problems. It should also be taken into account that the turbine of an exhaust gas turbocharger is usually designed in a radial design, ie. H. the flow of the blades takes place substantially radially. In the context of the present invention, essentially radial means that the velocity component in the radial direction is greater than the axial velocity component. The velocity vector of the flow cuts the shaft of the turbocharger at a right angle, if the flow is exactly radial.

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. However, everything should be avoided which reduces the pressure in the exhaust gas and reduces the exhaust gas energy still available at the turbine.

In order to be able to flow radially to the rotor blades, the inlet region for supplying the exhaust gas according to the prior art is designed as a spiral or worm casing running all around, so that the inflow of the exhaust gas to the turbine takes place substantially radially. Such a radial turbine is used for example in the EP 1 710 415 A1 described.

The supply of the exhaust gas to the low pressure turbine by means of spiral or worm housing requires the multiple deflection of the exhaust gas or the exhaust gas flow with large changes in direction. As already stated, however, any change in direction causes a pressure drop in the exhaust gas flow, which is why less energy can be withdrawn from the exhaust gas at the low-pressure turbine.

Occasionally, the low pressure turbine of an exhaust gas turbocharger is also designed as an axial turbine, d. H. 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. The velocity vector of the flow in the region of the impeller preferably runs parallel to the shaft of the exhaust gas turbocharger, if the flow is exactly axial.

In the case of axial turbines, however, the inlet region for supplying the exhaust gas is often designed as a spiral or worm casing running all around, so that the flow of the exhaust gas at least in the inlet region runs or is guided obliquely or radially to the shaft, for which purpose a deflection the exhaust gas between the turbines is required or is. Losses in the available at the turbine runner exhaust enthalpy must be taken into account. 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.

In this respect, a multiple deflection of the charge air flow with large changes in direction in order to transfer the charge air to the inlet side of the cylinder head and feed to the compressors is to be regarded as disadvantageous. This is a pressure maintenance, especially in the compressed charge air, detrimental.

The use of a plurality of exhaust gas turbochargers has, in particular due to the complex exhaust pipe system, also disadvantages in terms of a tight packaging of the drive unit in the engine compartment.

Against this background, it is the object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, with which the disadvantages known from the prior art are overcome, the charging behavior is improved and their charging has a smaller space requirement.

• – einem Ansaugsystem zum Zuführen von Ladeluft,
• – einem Abgasabführsystem zum Abführen von Abgas, und
• – mindestens einem Abgasturbolader, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst, wobei der Verdichter mit mindestens einem in einem Verdichtergehäuse auf einer drehbaren Welle gelagerten Laufrad ausgestattet ist,

die dadurch gekennzeichnet ist, dass

• – ein elektrisch antreibbarer zweiter Verdichter stromaufwärts des Verdichter des mindestens einen Abgasturboladers im Ansaugsystem angeordnet ist, wobei der zweite Verdichter mindestens ein in einem Verdichtergehäuse auf einer drehbaren Welle gelagertes Laufrad umfasst und ein Axialverdichter ist, dessen Austrittsbereich koaxial zur Welle des zweiten Verdichters verläuft, so dass die Abströmung der Ladeluft aus dem zweiten Verdichter via Austrittsbereich im Wesentlichen axial erfolgt, und
• – der Verdichter des mindestens einen Abgasturboladers einen Eintrittsbereich aufweist, der koaxial zur Welle des Verdichters und koaxial zum Austrittsbereich des zweiten Verdichters verläuft und ausgebildet ist, so dass die Anströmung der Ladeluft zu dem Verdichter des mindestens einen Abgasturboladers im Wesentlichen axial erfolgt.

This problem is solved by a supercharged internal combustion engine

• An intake system for supplying charge air,
• An exhaust gas discharge system for discharging exhaust gas, and
• At least one exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system, the compressor being equipped with at least one impeller mounted on a rotatable shaft in a compressor housing,

which is characterized in that

• - An electrically drivable second compressor is arranged upstream of the compressor of the at least one exhaust gas turbocharger in the intake system, wherein the second compressor at least comprises an impeller mounted in a compressor housing on a rotatable shaft and is an axial compressor, the outlet region is coaxial with the shaft of the second compressor, so that the outflow of the charge air from the second compressor via the outlet region is substantially axially, and
• - The compressor of the at least one exhaust gas turbocharger has an inlet region which is coaxial with the shaft of the compressor and coaxial with the outlet region of the second compressor and is formed so that the flow of the charge air to the compressor of the at least one exhaust gas turbocharger takes place substantially axially.

The inventive supercharged by exhaust gas turbocharger internal combustion engine is equipped with an additional compressor in Axialbauweise, which is arranged upstream of the compressor of the at least one exhaust gas turbocharger in the intake system.

This second compressor also has an outlet region, which runs coaxially to the shaft of the compressor, so that the outflow of the charge air from this additional compressor takes place substantially axially. The charge air must therefore not be deflected after flowing through the second compressor to be supplied to the compressor of the at least one exhaust gas turbocharger. Since a deflection or change in direction of the charge air flow does not occur, 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 compressor of the exhaust gas turbocharger. The efficiency and the charge pressure ratio of the two-stage compression can be increased.

The use of an axial compressor instead of a further exhaust gas turbocharger together with the outlet region designed according to the invention permits dense packaging, in particular a reduction of the distance, the volume and the mass of the intake system between the two compressors.

The above-described effects and technical effects are further assisted and made possible by the fact that the compressor of the at least one exhaust gas turbocharger has an inlet region, which is coaxial with the shaft of the compressor and coaxial with the outlet region of the second compressor and is formed, so that the flow of the charge air to the compressor of the at least one exhaust gas turbocharger takes place substantially axially.

According to the invention, the second compressor is an electrically drivable compressor, so that there is no mechanical connection to the power transmission between the compressor and the internal combustion engine or is required, which is why the second compressor has a small space requirement and allows a dense packaging of the charge or the internal combustion engine. In addition, the second compressor can be designed as a switchable compressor, which is switched on only in case of need for precompression of the charge air, especially if the available exhaust gas energy is not sufficiently high for a satisfactory charge.

Thus, the object underlying the invention is achieved, namely provided a supercharged internal combustion engine, with which the disadvantages known from the prior art are overcome, the charging behavior is improved and their charging has a smaller space requirement.

Advantageous embodiments of the internal combustion engine, in which the electrically driven second compressor is designed as a switchable compressor.

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

Embodiments of the internal combustion engine in which the compressor of the at least one exhaust-gas turbocharger is a radial compressor are advantageous. This embodiment allows a tight packaging of the exhaust gas turbocharger and thus the overall charge. The compressor housing can be designed as a spiral or worm housing, wherein the deflection of the charge air flow in the compressor of the exhaust gas turbocharger can be used advantageously to the compressed charge air on the shortest route from the outlet side, on which the turbine of the exhaust gas turbocharger is arranged on the inlet side respectively.

Embodiments of the 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, embodiments of the internal combustion engine are advantageous in which only one exhaust gas turbocharger is provided.

Advantageous embodiments of the internal combustion engine, in which the compressor of the at least one exhaust gas turbocharger is designed to be smaller than the second compressor.

In two connected in series, arranged in the intake compressor, it may be advantageous to make the second compressor larger than the downstream compressor of the exhaust gas turbocharger, since in a two-stage compression of the compressor of the supercharger forms the high-pressure stage and compresses the charge air already in the was then precompressed as a low pressure stage second compressor.

Nevertheless, the second compressor does not necessarily have to be made larger than the compressor of the at least one exhaust gas turbocharger. In particular, the second compressor may also be the same size or be made 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 second compressor could then be bypassed by means of a bypass line and the compressor of the at least one exhaust gas turbocharger make the compression of the charge air in the context of a single-stage compression.

Therefore, embodiments of the internal combustion engine in which the compressor of the at least one exhaust gas turbocharger is designed to be larger than the second compressor or the same size are also advantageous.

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

Such a drive is for example in the German patent application DE 100 40 122 A1 described and discussed. Thus, an electric motor, ie an electric drive, can be formed, which comprises a rotor rotatably connected to the compressor impeller and a fixed stator fixed to the housing, which radially surrounds the rotor. 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.

The compressor impeller may also be divided into two areas, namely a Vorsahrläuferrad, which forms the rotor, and a Hauptläufrad comprising the shaft hub and the blades of the compressor rotor. The Vorsattläuferrad is arranged upstream of the main rotor.

Embodiments of the 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. It allows a 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 have to be designed for specific amounts of exhaust gas, 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.

Also advantageous are embodiments of the internal combustion engine in which a bypass line is provided, in which a shut-off element is arranged and branches off upstream of the turbine of the at least one exhaust gas turbocharger from Abgasabführsystem and downstream of this turbine opens again into the Abgasabführsystem.

The provision of a bypass line allows the design of the turbine or the high-pressure turbine to small or medium exhaust gas mass flows and thus to the lower or middle part load range.

Embodiments of the internal combustion engine in which a first bypass line is provided, which has a shut-off element and which branches off from the intake system upstream of the second compressor and opens again into the intake system between the compressors, are advantageous.

If the second compressor designed smaller than the compressor of at least one exhaust gas turbocharger, the second 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 charge air quantities of the second compressor could then be bypassed by means of the first bypass line and the compressor of the at least one exhaust gas turbocharger provides for the compression of the charge air at higher speeds in the context of a single-stage charge.

If the second compressor designed to be larger than the compressor of at least one exhaust gas turbocharger, the second compressor takes over the pre-compression of the charge air at larger charge air quantities or higher speeds and the compressor of the at least one exhaust gas turbocharger serves Frame of a two-stage supercharging as a high pressure stage, in which the pre-compressed charge air is further compressed. For smaller amounts of charge air, the second compressor could then be bypassed by means of the first bypass line and the compressor of the at least one exhaust gas turbocharger provides for the compression of the charge air at lower speeds in the context of a single-stage charge. In most cases, however, the second 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 internal combustion engine in which the compressor of the at least one exhaust-gas turbocharger has a variable compressor geometry are advantageous.

If the second compressor designed smaller than the compressor of at least one exhaust gas turbocharger, the second compressor takes over the compression of the charge air at small charge air quantities or low speeds. The compressor of the at least one exhaust gas turbocharger then represents only a flow resistance on the way to the cylinders for the already compressed charge air. A variable compressor geometry makes it possible to reduce this flow resistance by opening the geometry.

A variable compressor geometry is particularly advantageous if the turbine of the exhaust gas turbocharger has a variable turbine geometry and a variable compressor geometry can then be tuned continuously 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 ,

Embodiments of the internal combustion engine in which a second bypass line is provided which has a shut-off element and branches off the intake system upstream of the compressor of the at least one exhaust-gas turbocharger and opens into the intake system downstream of the compressor of the at least one exhaust-gas turbocharger are advantageous.

Like the previous embodiment concerning the variable compressor geometry, the second bypass line makes it possible to eliminate the compressor of the at least one exhaust gas turbocharger as a flow resistance. If the second compressor designed smaller than the compressor of at least one exhaust gas turbocharger, the second compressor takes over the compression of the charge air at small charge air quantities or low speeds. The compressor of the at least one exhaust gas turbocharger can then be bypassed via the second bypass line.

Advantageous embodiments of the 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 flows downstream of the turbine back into the Abgasabführsystem, wherein for controlling the Abgasabblasung a shut-off in the third bypass line is provided. 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.

Embodiments of the internal combustion engine in which downstream of the at least one impeller of the second compressor a guide device is arranged in the outlet region of the second compressor are advantageous. The velocity vector of the flow in the region of the at least one impeller of the compressor of the exhaust gas turbocharger preferably also has a radial component to the shaft, whereby the efficiency is increased.

Therefore, embodiments of the internal combustion engine in which upstream of the at least one impeller of the compressor of the exhaust gas turbocharger a guide device is provided in the inlet region are also advantageous.

In this connection, embodiments of the internal combustion engine in which the guide device is mounted in the outlet region of the second compressor are advantageous.

Also advantageous in this context are embodiments of the internal combustion engine, in which the guide receives the shaft of the second compressor for storage.

Advantageous embodiments of the internal combustion engine, in which upstream of the at least one impeller of the second compressor, a holder for the purpose of supporting the shaft of the second compressor is arranged.

Embodiments of the internal combustion engine in which a charge air cooler is arranged in the intake system downstream of the compressor are advantageous. The intercooler lowers the air temperature and thus increases the density of the charge air, which also makes the radiator a better filling of the air Combustion chamber with air, that contributes to a larger air mass.

Embodiments of the internal combustion engine in which a section of the intake system provided between the outlet region of the second compressor and the inlet region of the compressor of the at least one exhaust gas turbocharger is tapered are advantageous. This is advantageous in terms of embodiments in which a two-stage compression of the charge air takes place, d. H. the density of the charge air is already increased upstream of the compressor of the exhaust gas turbocharger.

Embodiments of the 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.

Embodiments of the supercharged internal combustion engine in which exhaust gas recirculation is provided are advantageous.

Advantageous in this connection are embodiments of the supercharged internal combustion engine in which exhaust gas recirculation is provided which comprises a line which branches off from the exhaust gas removal system upstream of the turbine and opens into the intake system, preferably downstream of the compressor.

To comply with future limits for nitrogen oxide emissions, an exhaust gas recirculation is increasingly used, ie the return of exhaust gases from the exhaust side to the inlet side, in which the nitrogen oxide emissions can be significantly reduced with increasing exhaust gas recirculation rate. In this case, the exhaust gas recirculation rate x _{AGR is} determined by x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR designates} the mass of recirculated exhaust gas and m _{fresh air} the supplied fresh air or combustion air, possibly guided and compressed by a compressor. Exhaust gas recirculation is also suitable for reducing emissions of unburned hydrocarbons in the partial load range. In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates are required.

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

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

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

Also advantageous are embodiments of the supercharged internal combustion engine, in which an exhaust gas recirculation is provided, which comprises a line which branches off from the Abgasabführsystem downstream of the turbine and opens into the intake system, preferably upstream of the compressor.

In contrast to the high-pressure EGR already mentioned, which removes exhaust gas from the exhaust gas removal system upstream of the turbine and introduces the compressor into the intake system downstream of the compressor, in a low-pressure EGR exhaust gas is returned to the inlet side, which has already passed through the turbine. For this purpose, the low-pressure EGR comprises a return line, which branches off downstream of the turbine from the Abgasabführsystem and opens upstream of the compressor in the intake system.

The exhaust gas, which is returned to the inlet side by means of low-pressure EGR and is preferably cooled, is mixed with fresh air upstream of the compressor. The mixture of fresh air and recirculated exhaust gas produced in this way forms the charge air, which is supplied to the compressors and compressed.

It is harmless that, as part of the low-pressure EGR exhaust gas is passed through the compressor, since usually exhaust gas is used, which downstream of the turbines of an exhaust aftertreatment, in particular in the particulate filter was subjected. Deposits in the compressor, which change the geometry of the compressor, in particular the flow cross-sections, and thus worsen the efficiency of the compressor, are therefore not to be feared.

For operating an internal combustion engine of the type described above, the electrically drivable second compressor is preferably designed as a switchable compressor, which is switched on as soon as the engine speed n _{mot of} the internal combustion engine falls below a predefinable speed n _{threshold, 1} and / or a higher torque is requested. The various internal combustion engines sometimes require different approaches.

Here, the second compressor is the compression of the charge air at small charge air quantities or low speeds, d. H. to improve the torque characteristic in the lower speed range. For larger charge air quantities or higher speeds of the second compressor could then be bypassed by means of the first bypass line and the compressor of the at least one exhaust gas turbocharger provides for the compression of the charge air at higher speeds in the context of a single-stage charge.

In internal combustion engines in which a first bypass line is provided which has a shut-off and the upstream of the second compressor branches off the intake system and opens between the compressors back into the intake system, it is advantageous to open the first bypass line, as soon as the speed n _mot of Internal combustion engine exceeds a predetermined speed n _{threshold, 2} .

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 turbine 4 is a radial turbine 4a and the compressor 3 is a centrifugal compressor 3b in its case 3e an impeller 3d on a rotatable shaft 3c is stored.

To assist the supercharging when needed and to improve the torque characteristic is upstream of the compressor 3 the exhaust gas turbocharger 2 an electrically drivable second compressor 5 in the intake system 1 arranged in the compressor housing 5e an impeller 5d on a rotatable shaft 5c is stored. This second compressor 5 is an axial compressor 5b , its entrance area 5g or exit area 5a coaxial with the shaft 5c of the second compressor 5 runs and is formed so that both the flow of charge air to the second compressor 5 as well as the outflow of the charge air from the second compressor 5 essentially axially.

Downstream of the impeller 5d of the second compressor 5 is a guide 5f in the exit area 5a of the second compressor 5 arranged. The guide 5f also takes the wave 5c of the second compressor 5 for storage, with one upstream of the impeller 5d arranged bracket 5h the bearing of the shaft 5c of the second compressor 5 added.

The compressor 3 the exhaust gas turbocharger 2 has an entrance area 3a on, coaxial with the shaft 3c of the compressor 3 and coaxial with the exit area 5a of the second compressor 5 runs and is formed so that the flow of charge air to the compressor 3 the exhaust gas turbocharger 2 is done essentially axially and the section 6 of the intake system 1 between the compressors 3 . 5 is relatively short and small volume and has no direction changes.

The second compressor 5 is electrically driven and switched on if necessary, wherein the electric drive, ie the electric motor, using a rotationally fixed to the compressor wheel 5d connected rotor 8b and a stator fixed to the housing 8a who is the rotor 8b radially surrounds, is formed.

The rotor made of a magnetic material 8b is annular and sits on the radially outer edges of the compressor rotor blades. When energizing the stator 8a , a coil, becomes a rotor 8b generates rotating electromagnetic force.

The compressor 3 the exhaust gas turbocharger 2 is designed larger than the second compressor 5 , which is switched on only when needed. In the present case, the second compressor takes over 5 the compression of the charge air at low speeds, ie in the lower speed range. At higher speeds, the compressor provides 3 the exhaust gas turbocharger 2 for the compression of the charge air as part of a single-stage charge, the second compressor 5 by means of bypass line 7 that is upstream of the second compressor 5 from the intake system 1 branches off and between the compressors 3 . 5 back into the intake system 1 flows, can be bypassed. Input of this first bypass line 7 is one as a shut-off element 7a Serving flap 7b intended.

LIST OF REFERENCE NUMBERS

1

 intake system

2

 turbocharger

3

 Compressor of the exhaust gas turbocharger

3a

 Entry area of the compressor of the exhaust gas turbocharger

3b

 centrifugal compressors

3c

 Shaft of the compressor of the exhaust gas turbocharger

3d

 Impeller of the compressor of the exhaust gas turbocharger

3e

 Compressor housing of the exhaust gas turbocharger

4

 Turbine of the exhaust gas turbocharger

4a

 radial turbine

5

 second compressor

5a

 Outlet area of the second compressor

5b

 axial compressor

5c

 Shaft of the second compressor

5d

 Impeller of the second compressor

5e

 Compressor housing of the second compressor

5f

 guide

5g

 Entry area of the second compressor

5h

 bracket

6

 Section of the intake system, intermediate piece

7

 first bypass line

7a

 shut-off

7b

 flap

8a

 stator

8b

 rotor

AGR

 Exhaust gas recirculation

m _AGR

 Mass of recirculated exhaust gas

_{Fresh air}

 Mass of supplied fresh air or charge air

x _AGR

 Exhaust gas recirculation rate

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, 0027]
• DE 10040122 A1 [0050]

Claims (16)

Charged internal combustion engine with - an intake system ( 1 ) for supplying charge air, - an exhaust gas removal system for discharging exhaust gas, and - at least one exhaust gas turbocharger ( 2 ), which is arranged in the Abgasabführsystem turbine ( 4 ) and one in the intake system ( 1 ) arranged compressors ( 3 ), wherein the compressor ( 3 ) with at least one in a compressor housing ( 3e ) on a rotatable shaft ( 3c ) mounted impeller ( 3d ), characterized in that - an electrically drivable second compressor ( 5 ) upstream of the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) in the intake system ( 1 ), wherein the second compressor ( 5 ) at least one in a compressor housing ( 5e ) on a rotatable shaft ( 5c ) stored impeller ( 5d ) and an axial compressor ( 5b ) whose exit area ( 5a ) coaxial with the shaft ( 5c ) of the second compressor ( 5 ), so that the outflow of the charge air from the second compressor ( 5 ) via exit area ( 5a ) takes place substantially axially, and - the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) an entrance area ( 3a ) coaxial with the shaft ( 3c ) of the compressor ( 3 ) and coaxial with the exit area ( 5a ) of the second compressor ( 5 ) and is formed so that the flow of charge air to the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) is effected substantially axially. Supercharged internal combustion engine according to claim 1, characterized in that the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) a radial compressor ( 3b ). Supercharged internal combustion engine according to claim 1 or 2, characterized in that the turbine ( 4 ) of the at least one exhaust gas turbocharger ( 2 ) a radial turbine ( 4a ). Supercharged internal combustion engine according to one of the preceding claims, characterized in that the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) is designed to be larger than the second compressor ( 5 ). Supercharged internal combustion engine according to one of the preceding claims, characterized in that the second compressor ( 5 ) an entrance area ( 5g ) coaxial with the shaft ( 5c ) of the second compressor ( 5 ) and is formed so that the flow of the charge air to the second 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 a first bypass line ( 7 ) is provided which a shut-off ( 7a ) and the upstream of the second compressor ( 5 ) from the intake system ( 1 ) branches off and between the compressors ( 3 . 5 ) back into the intake system ( 1 ) opens. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) has a variable compressor geometry. 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 the upstream of the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) from the intake system ( 1 ) branches off and downstream of the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) 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 downstream of the at least one impeller ( 5d ) of the second compressor ( 5 ) a guiding device ( 5f ) in the exit area ( 5a ) of the second compressor ( 5 ) is arranged. Supercharged internal combustion engine according to claim 11, characterized in that the guide device ( 5f ) in the exit area ( 5a ) of the second compressor ( 5 ) is stored. Supercharged internal combustion engine according to claim 11 or 12, characterized in that the guide device ( 5f ) the wave ( 5c ) of the second compressor ( 5 ) for storage. Supercharged internal combustion engine according to one of the preceding claims, characterized in that upstream of the at least one Impeller ( 5d ) of the second compressor ( 5 ) a holder ( 5h ) for the purpose of supporting the shaft ( 5c ) of the second compressor ( 5 ) is arranged. 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 a between the exit region ( 5a ) of the second compressor ( 5 ) and the entrance area ( 3a ) of the compressor ( 3 ) of the at least one exhaust gas turbocharger ( 2 ) section ( 6 ) of the intake system ( 1 ) rejuvenated.

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