DE102016218883A1 - Internal combustion engine with exhaust gas recirculation and air cooling and method for operating such an internal combustion engine - Google Patents

Abstract

The invention relates to an internal combustion engine (1) having - at least one cylinder, - an intake system (3) for supplying the at least one cylinder with charge air, - an exhaust gas removal system (2) for discharging the exhaust gases, - an exhaust gas recirculation system (4, 4 '), which comprises a return line (4a) which branches off from the exhaust gas removal system (2) to form a second node (3a) and forms a shut-off element in the return line (4a) (4b), and - at least one air cooler (5, 5 ') arranged upstream of the second node (3a) in the intake system (3). It is intended to provide an internal combustion engine (1) of the above type with which the disadvantages known from the prior art are overcome and with which, in particular, the problem due to the formation of condensate is counteracted. This is achieved by an internal combustion engine (1) of the type mentioned, which is characterized in that the intake system (3) downstream of the at least one air cooler (5, 5 ') has a depression (3b), wherein the return line (4a) under training of the second node (3a) opens into this depression (3b).

Description

• – mindestens einem Zylinder,
• – einem Ansaugsystem zur Versorgung des mindestens einen Zylinders mit Ladeluft,
• – einem Abgasabführsystem zur Abführung der Abgase,
• – einer Abgasrückführung, die eine Rückführleitung umfasst, welche unter Ausbildung eines ersten Knotenpunktes von dem Abgasabführsystem abzweigt und unter Ausbildung eines zweiten Knotenpunktes in das Ansaugsystem mündet, wobei in der Rückführleitung ein Absperrelement angeordnet ist, und
• – mindestens einem Luftkühler, der stromaufwärts des zweiten Knotenpunktes im Ansaugsystem angeordnet ist.

The invention relates to an internal combustion engine with

• At least one cylinder,
• An intake system for supplying the at least one cylinder with charge air,
• An exhaust gas removal system for removing the exhaust gases,
• An exhaust gas recirculation, which comprises a return line, which branches off to form a first node of the Abgasabführsystem and opens to form a second node in the intake system, wherein in the return line, a shut-off is arranged, and
• - At least one air cooler, which is arranged upstream of the second node in the intake system.

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.

In the development of internal combustion engines, efforts are constantly being made to minimize fuel consumption. In addition, the aim is to reduce pollutant emissions in order to be able to comply with future limit values for pollutant emissions.

Internal combustion engines are increasingly equipped with a charge, the charge is primarily a method of increasing performance, in which the charge air required for the engine combustion process is compressed, whereby each cylinder per cycle a larger charge 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 cubic capacity is reduced, the load spectrum can be shifted to higher loads at the same vehicle boundary conditions, where the specific fuel consumption is lower. The charging of an internal combustion engine thus supports the efforts to minimize fuel consumption, d. H. to improve the efficiency of the internal combustion engine.

By means of a suitable transmission design, a so-called downspeeding can additionally be realized, as a result of which a lower specific fuel consumption is likewise achieved. Downspeeding exploits the fact that the specific fuel consumption at low speeds is regularly lower, especially at higher loads.

The emissions of carbon dioxide, which correlate directly with fuel consumption, decrease anyway with decreasing fuel consumption. With a targeted design of the charge but also advantages in the other exhaust emissions can be achieved. Thus, by means of suitable charging, for example in the diesel engine, the nitrogen oxide emissions can be reduced without sacrificing efficiency. At the same time, the hydrocarbon emissions can be favorably influenced.

However, further measures are needed to meet future emission limits. Among other things, the development work focuses on reducing nitrogen oxide emissions, which are of particular relevance to diesel engines. Since the formation of nitrogen oxides requires not only an excess of air but also high temperatures, one concept for reducing nitrogen oxide emissions is to use combustion processes with lower combustion temperatures.

Here, the exhaust gas recirculation (EGR), ie the return of combustion gases from the exhaust side to the inlet side, expedient in which with increasing exhaust gas recirculation rate, the nitrogen oxide emissions can be significantly reduced. In this case, the exhaust gas recirculation rate x _{AGR is} determined as x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR designates} the mass of recirculated exhaust gas and m _{fresh air} the fresh air supplied. The oxygen provided via exhaust gas recirculation may need to be considered.

In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates may be required, which may be on the order of x _AGR ≈ 60% to 70% and more. Such high recirculation rates require cooling of the recirculating exhaust gas, with which the temperature of the exhaust gas is lowered and the density of the exhaust gas is increased, so that a larger Exhaust mass can be returned. Consequently, exhaust gas recirculation is regularly equipped with a radiator.

The internal combustion engine, which is the subject of the present invention, has an exhaust gas recirculation, the return line of which branches off from the Abgasabführsystem to form a first node and opens into the intake system to form a second node. In the return line a shut-off is arranged, which acts as an EGR valve and with activated exhaust gas recirculation of the setting of the return rate, d. H. the setting of the recirculated exhaust gas quantity is used. The use of a composite valve arranged at the second node allows the design of the recirculated exhaust gas quantity and at the same time the throttling of the intake fresh air quantity.

Problems may arise in introducing the recirculated exhaust gas into the intake system as the temperature of the recirculated hot exhaust gas decreases and condensate forms.

On the one hand, condensate can form when the recirculated hot exhaust gas in the intake system coincides with cool fresh air and is mixed. The exhaust gas cools, whereas the temperature of the fresh air is raised. The temperature of the mixture of fresh air and recirculated exhaust gas, d. H. the temperature of the combustion air is below the exhaust gas temperature of the recirculated exhaust gas. As part of the cooling of the exhaust gas previously contained gaseous in the exhaust gas or in the combustion air, especially water, condense out when the taut temperature of a component of the gaseous combustion air flow is exceeded. It comes to a condensation in the free combustion air flow, often impurities in the combustion air form the starting point for the formation of condensate droplets.

On the other hand, condensate can form when the recirculated hot exhaust gas or the combustion air strikes the inner wall of the intake system, since the wall temperature is generally below the taut temperature of the relevant gaseous components.

Condensate and condensate droplets are undesirable and lead to increased noise emission in the intake system, possibly damaging the blades of a compressor arranged in the intake compressor of a supercharger or an exhaust gas turbocharger. The latter is associated with a reduction in the efficiency of the compressor and thus the charge.

Critical to note is the condensate formation described above, especially when the exhaust gas is introduced upstream of a compressor impeller in the intake system, as for example in an charged by turbocharging internal combustion engine, which is equipped with a low-pressure EGR, wherein the recirculated exhaust gas downstream of the Turbine of an exhaust gas turbocharger removed from the Abgasabführsystem and is introduced upstream of the compressor of the exhaust gas turbocharger in the intake system.

The exhaust gas recirculated to the intake side by means of low pressure EGR is mixed with fresh air upstream of the compressor of the exhaust gas turbocharger. The mixture of fresh air and recirculated exhaust gas produced in this way forms the charge air which is supplied to the compressor and compressed, the compressed charge air is cooled regularly downstream of the compressor by means of intercooler to lower the temperature of the charge air before entering the cylinder and the Increase cylinder filling.

Even if condensate formation upstream of the compressor is prevented or minimized, for example, by limiting the amount of exhaust gas recirculated by low pressure EGR, problems may arise downstream of the compressor due to the cooling of the compressed charge air in the charge air cooler. In the context of charge air cooling, liquids which have previously been gaseous in the charge air, in particular water, can condense out if the dew temperature of a component of the gaseous charge air flow is undershot. Depending on the arrangement of the intercooler, precipitated condensate may collect in the intercooler and / or downstream of the charge air cooler in the intake system, which is then introduced unpredictably and in large quantities abruptly, for example, at a lateral acceleration due to cornering, a slope or a shock in the cylinder. The latter is also referred to as a water hammer, which can not only lead to a serious failure of the operation of the internal combustion engine, but also to irreversible damage to the engine and must be prevented.

Against the background of the above, it is an object of the present invention to provide an internal combustion engine according to the preamble of claim 1, with which the known from the prior art disadvantages are overcome and with the particular problem of condensation is counteracted.

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

• – mindestens einem Zylinder,
• – einem Ansaugsystem zur Versorgung des mindestens einen Zylinders mit Ladeluft,
• – einem Abgasabführsystem zur Abführung der Abgase,
• – einer Abgasrückführung, die eine Rückführleitung umfasst, welche unter Ausbildung eines ersten Knotenpunktes von dem Abgasabführsystem abzweigt und unter Ausbildung eines zweiten Knotenpunktes in das Ansaugsystem mündet, wobei in der Rückführleitung ein Absperrelement angeordnet ist, und
• – mindestens einem Luftkühler, der stromaufwärts des zweiten Knotenpunktes im Ansaugsystem angeordnet ist,

und die dadurch gekennzeichnet ist, dass

• – das Ansaugsystem stromabwärts des mindestens einen Luftkühlers eine Senke aufweist, wobei die Rückführleitung unter Ausbildung des zweiten Knotenpunkt in diese Senke mündet.

The first subtask is solved by an internal combustion engine

• At least one cylinder,
• An intake system for supplying the at least one cylinder with charge air,
• An exhaust gas removal system for removing the exhaust gases,
• An exhaust gas recirculation, which comprises a return line, which branches off to form a first node of the Abgasabführsystem and opens to form a second node in the intake system, wherein in the return line, a shut-off is arranged, and
• At least one air cooler, which is arranged upstream of the second node in the intake system,

and which is characterized in that

• - The intake downstream of the at least one air cooler has a depression, wherein the return line opens to form the second node in this sink.

The internal combustion engine, which is the subject of the present invention, has at least one exhaust gas recirculation and is not mandatory, but is preferably a supercharged internal combustion engine.

In the internal combustion engine according to the invention, an air cooler is arranged in the intake system upstream of the second node and thus upstream of the junction of the return line. This objective or constructional feature of the internal combustion engine according to the invention has several advantageous effects, to which a brief statement is made below.

With activated exhaust gas recirculation, the recirculated exhaust gases are not passed through said air cooler, but introduced downstream of the air cooler in the intake system, whereby a condensate formation by introduction of recirculated exhaust gas is at least counteracted.

In addition, the return line with deactivated exhaust gas recirculation, d. H. with the shut-off element closed, to collect condensate that has separated out. For this purpose, the second node, d. H. the confluence of the exhaust gas recirculation into the intake system in a sink, so that in the air cooler and basically upstream of the second node condensate excreted can first get into this depression and from the sink into the return line. The closed shut-off serves as a barrier and prevents condensate from the return line unintentionally enters the Abgasabführsystem.

In addition, the return line of the exhaust gas recirculation with the EGR valve open, d. H. opened shut-off for discharging or disposing of the condensate, in particular the previously collected condensate serve. Two scenarios are basically possible or effective.

With activated exhaust gas recirculation condensate previously collected contrary to the flow direction of the recirculated exhaust gas can get into the Abgasabführsystem, this condensate either enters the Abgasabführsystem in liquid form and there at least partially evaporated due to the high temperatures or the condensate is due to the hot return line already in gaseous form and enters the hot exhaust system as steam. The return line then serves as a drainage.

When activating the exhaust gas recirculation condensate previously collected but can also be entrained by the exhaust gas flow in the return line and get into the intake system. The condensate is also present here either liquid or gaseous and is introduced via the intake system into the cylinder. The hot return line also serves to collect, evaporate and remove the condensate.

The internal combustion engine according to the invention has a sink in the exhaust system, d. H. a siphon in which condensate can be separated and collected. A sink in the sense of the present invention is any sink in the intake system which, due to its geodetic height, is suitable for collecting condensate.

For this purpose, the drain should have at least one region which is geodetically lower in the installation position of the internal combustion engine than the regions which approach this lower region downstream and upstream.

The internal combustion engine according to the invention solves the first object underlying the invention, namely to provide an internal combustion engine according to the preamble of claim 1, with which the disadvantages known from the prior art are overcome and with the particular problem due to condensation is counteracted.

Embodiments of the internal combustion engine may be advantageous in which a cooler is provided in the return line of the exhaust gas recirculation.

Advantageous embodiments of the internal combustion engine, in which a charge is provided. It is referred to in the In connection with the charging already mentioned advantages and made remarks.

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

Embodiments of the internal combustion engine in which the depression in the installation position of the internal combustion engine forms the geodetically lowest point in the intake system between the at least one air cooler and the at least one cylinder are advantageous.

Embodiments of the internal combustion engine may also be advantageous in which the depression in the installation position of the internal combustion engine locally forms a geodetically deeper point in the intake system. Ie. between the at least one air cooler and the at least one cylinder, there is at least one geodetically deeper than the sink location in the intake system.

Embodiments of the internal combustion engine in which at least one compressor drivable by means of an auxiliary drive is arranged in the intake system are advantageous, wherein the compressor is preferably arranged upstream of the at least one air cooler.

The advantage of a drivable by auxiliary drive compressor, d. H. Laders, compared to an exhaust gas turbocharger is that the loader can always generate and provide the required boost pressure, regardless of the operating condition of the internal combustion engine. This is especially true for a loader that is electrically driven by electric motor and therefore independent of the speed of the crankshaft.

In fact, according to the state of the art, it is difficult to increase the power by means of turbocharging in all engine speed ranges. It is observed a greater torque drop 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 or the turbine output. If the engine speed is reduced, this leads to a smaller exhaust gas mass flow and thus to a smaller turbine pressure ratio or a smaller turbine power. Consequently, the boost pressure ratio also decreases toward lower speeds. This is synonymous with a torque drop.

Nevertheless, embodiments of the internal combustion engine can be advantageous in which at least one exhaust gas turbocharger is provided which comprises a turbine arranged in the exhaust gas removal system and a compressor arranged in the intake system, wherein the compressor is preferably arranged upstream of the at least one air cooler. In an exhaust gas turbocharger, a compressor and a turbine are arranged on the same shaft. The hot exhaust gas flow is supplied to the turbine and relaxes with release of energy in the turbine, causing the shaft to rotate. The output from the exhaust stream to the shaft energy is used to drive the also arranged on the shaft compressor. 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 certain amount of compression by cooling.

The advantage of an exhaust gas turbocharger in comparison to a - drivable by auxiliary drive - loader is that an exhaust gas turbocharger uses the exhaust gas energy of the hot exhaust gases, while a loader requires the energy required for its drive directly or indirectly from the internal combustion engine and thus, at least as long as the drive power does not come from an energy recovery, adversely affects the efficiency, d. H. decreases.

If it is not an electric machine, d. H. is electrically driven supercharger is regularly a mechanical or kinematic connection for power transmission between the charger and the internal combustion engine is required, which also adversely affects or determines the packaging in the engine compartment.

In order to counteract a torque drop at low speeds, particularly embodiments of the internal combustion engine are advantageous in which at least two exhaust gas turbochargers are provided. If the engine speed is reduced, this leads to a smaller exhaust gas mass flow and thus to a lower boost pressure ratio.

By using a plurality of exhaust gas turbochargers, for example a plurality of exhaust gas turbochargers connected in series or in parallel, the torque characteristic of a supercharged internal combustion engine can be appreciably improved.

To improve the torque characteristic, a further compressor may be provided in addition to the at least one exhaust gas turbocharger, both by means of an auxiliary drive drivable loader and a compressor of another exhaust gas turbocharger.

If a compressor is arranged in the intake system, embodiments of the supercharged internal combustion engine may be advantageous in which the return line opens downstream of the compressor to form the second node in the intake system, wherein the compressor is preferably arranged upstream of the at least one air cooler.

In a so-called high pressure EGR, the exhaust gas is introduced downstream of the compressor into the intake system. In order to provide or to ensure the pressure gradient between the exhaust-gas removal system and the intake system required for a return, the exhaust gas is preferably taken from the exhaust-gas removal system upstream of the associated turbine during an exhaust-gas turbocharging. The high-pressure EGR has the advantage that the exhaust gas does not pass through the compressor and therefore no exhaust aftertreatment, for example in a particle filter, has to be subjected before the recirculation. 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 not to be feared. Condensation takes place, if at all, downstream of the compressor, which heats the charge air supplied to it as part of the compression.

In an internal combustion engine with an exhaust gas turbocharger, embodiments are therefore advantageous for the abovementioned reasons, in which the return line branches off from the exhaust gas removal system upstream of the turbine, forming the first node.

Also for the reasons mentioned above, embodiments of the supercharged internal combustion engine are advantageous in use of an exhaust gas turbocharger in which the return line of the exhaust gas recirculation branches off from the Abgasabführsystem forming the first node upstream of the turbine and opens to form the second node downstream of the compressor in the intake system, preferably between the second node and the compressor, a charge air cooler is arranged in the intake system.

When operating an internal combustion engine with turbocharging and simultaneous use of a high-pressure EGR, a conflict may arise when the recirculated exhaust gas is taken from the Abgasabführsystem upstream of the turbine and is no longer available for driving the turbine.

With an increase in the exhaust gas recirculation rate, the exhaust gas flow introduced into the turbine simultaneously decreases. The reduced exhaust gas mass flow through the turbine causes a smaller turbine pressure ratio, whereby the charge pressure ratio also decreases, which is equivalent to a smaller compressor mass flow. In addition to the decreasing boost pressure, additional problems with the operation of the compressor with regard to the surge limit can occur. Disadvantages can also arise in the pollutant emissions, for example, with regard to the formation of soot in diesel engines during acceleration.

For this reason, concepts are required which ensure sufficiently high boost pressures with simultaneously high exhaust gas recirculation rates. One solution is the so-called low-pressure EGR, with which exhaust gas is fed back into the intake system, which has already flowed through the turbine. For this purpose, the low-pressure EGR comprises a return line, which branches off from the exhaust-gas removal system downstream of the turbine. The return line preferably opens into the intake system upstream of the compressor in order to be able to realize the pressure gradient required between the exhaust-gas removal system and the intake system for a return.

Therefore, embodiments of the internal combustion engine can be advantageous in which a further exhaust gas recirculation is provided, which comprises a return line, which branches off from the Abgasabführsystem downstream of the turbine and opens upstream of the compressor in the intake system.

In order to generate the required pressure gradient, in a low-pressure EGR, a shut-off element may be provided downstream of the diversion of the return line in the exhaust system to accumulate the exhaust gas and increase the exhaust pressure and / or provide a shut-off element upstream of the return line in the intake system inlet side to lower the pressure upstream of the compressor. Both measures are energetically disadvantageous. In particular, the inlet-side throttling of the charge air upstream of the compressor must be regarded as counterproductive in view of the charging of the internal combustion engine.

The exhaust gas recirculated by means of low-pressure EGR is mixed with fresh air upstream of the compressor. The mixture of fresh air and recirculated exhaust gas thus produced forms the charge air which is supplied to the compressor and compressed, the compressed charge air downstream of the compressor in the air cooler or intercooler is cooled.

Providing a low-pressure EGR as further exhaust gas recirculation in an internal combustion engine according to the invention is particularly advantageous, since a low-pressure EGR can be seen particularly critically with regard to the formation of condensate, ie requires a measure with which the problem is counteracted due to condensation.

Since exhaust gas is passed through the compressor in a low-pressure EGR, the exhaust gas downstream of the turbine is preferably subjected to exhaust gas aftertreatment.

Therefore, embodiments of the internal combustion engine in which at least one exhaust aftertreatment system is provided in the exhaust gas removal system between the turbine and the branch of the return line from the exhaust gas removal system are advantageous.

Embodiments of the internal combustion engine in which a particle filter is provided as exhaust gas aftertreatment system for after-treatment of the exhaust gas are advantageous.

To minimize the emission of soot, a regenerative particle filter is used in the present case, which filters out and stores the soot particles from the exhaust gas, wherein these soot particles are intermittently burned as part of the regeneration of the filter. The temperatures required for the regeneration of the particulate filter are at about 550 ° C with no catalytic support. Therefore, additional measures are regularly used to ensure regeneration of the filter under all operating conditions.

The regeneration of the filter introduces heat into the exhaust gas and increases the exhaust gas temperature and thus the exhaust gas enthalpy. At the outlet of the filter is thus an energy-rich exhaust gas available, which can be used on the inlet side in the compressor.

Embodiments of the internal combustion engine may also be advantageous in which an oxidation catalytic converter is provided as exhaust gas aftertreatment system for the after-treatment of the exhaust gas.

Embodiments of the internal combustion engine in which the turbine of a proposed exhaust-gas turbocharger has a variable turbine geometry which permits a further adaptation to the operation of the internal combustion engine by adjusting the turbine geometry or the effective turbine cross-section are advantageous. In this case, adjustable guide vanes for influencing the flow direction are arranged in the inlet region of the turbine. Unlike the vanes of the rotating impeller, the vanes do not rotate with the shaft of the turbine.

If the turbine has a fixed invariable geometry, the vanes are not only stationary, but also completely immovable in the entry area, i. H. fixed rigidly, if any guide is provided. With a variable geometry, however, the vanes are indeed arranged stationary, but not completely immobile, but rotatable about its axis, so that the flow of the blades can be influenced.

By adjusting the turbine geometry, it is possible to influence the exhaust gas pressure upstream of the turbine, thereby influencing the pressure gradient between the exhaust gas removal system and the intake system and thus the return rate of a high-pressure EGR.

Advantageous embodiments of the internal combustion engine, in which a bypass line is provided for bypassing the air cooler, which bridges the radiator. It may be useful to bridge the radiator, for example, to avoid that the air is additionally deprived of heat.

Embodiments of the internal combustion engine in which liquid cooling is provided to form an engine cooling are advantageous.

Embodiments of the internal combustion engine in which the at least one cylinder head of the internal combustion engine is equipped to form a liquid cooling system with at least one coolant jacket integrated in the cylinder head are advantageous.

A liquid cooling proves to be particularly advantageous in turbocharged engines, since the thermal load of turbocharged engines compared to conventional internal combustion engines is significantly higher. The cylinder head has an integrated exhaust manifold, this is thermally higher load than a conventional cylinder head, which is equipped with an external manifold. There are increased demands on the cooling.

The second sub-task on which the invention is based, namely to disclose a method for operating an internal combustion engine of the type described above, is achieved by a method which is characterized in that the exhaust gas recirculation is deactivated by closing the shut-off element and condensate discharged in the intake system upstream of the second node is collected in the return line with closed shut-off.

What has already been said for the internal combustion engine according to the invention also applies to the inventive method. Different embodiments of the internal combustion engine according to the invention require correspondingly different process variants, for which reference is made to the corresponding explanations.

Process variants are advantageous in which condensate collected in the return line is disposed of by opening the shut-off element.

Advantageous in this context are process variants in which condensate collected in the return line is introduced into the intake system when the shut-off element is opened with the exhaust gas to be recirculated and disposed of with it.

Also advantageous in this context are process variants in which condensate collected in the return line is introduced into the exhaust gas removal system when the shut-off element is opened and thus disposed of.

Advantageous are process variants in which the shut-off element of the exhaust gas recirculation is closed in the warm-up phase or after a cold start of the internal combustion engine.

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

1 schematically a first embodiment of the internal combustion engine.

1 schematically shows a first embodiment of the internal combustion engine 1 , The internal combustion engine 1 has an intake system 3 to supply the cylinders of the cylinder head 1a with charge air and an exhaust gas removal system 2 for removing the exhaust gases from the cylinders.

The internal combustion engine 1 is for charging with an exhaust gas turbocharger 6 equipped, the one in the exhaust system 2 arranged turbine 6b and one in the intake system 3 arranged compressor 6a includes.

Furthermore, an exhaust gas recirculation 4 . 4' provided with a return line 4a , the upstream of the turbine 6b forming a first node 2a from the exhaust system 2 branches off and downstream of the compressor 6a forming a second node 3a into the intake system 3 empties. In the return line 4a is a shut-off element 4b arranged, the setting of the recirculated exhaust gas amount, ie the return rate, and thus the activation or deactivation of the exhaust gas recirculation 4 . 4' serves.

Between the compressor 6a the exhaust gas turbocharger 6 and the second node 3a is an air cooler 5 in the intake system 3 arranged, with which in the compressor 6a compressed charge air is cooled.

Downstream of this intercooler 5 ' is a sink 3b . 3b' in the intake system 3 provided, in which the return line 4a under formation of the second node 3a opens. The valley 3b . 3b' is at the in 1 illustrated embodiment, a local sink 3b' ie a geodetically lower location 3b' in the intake system 3 so it's between the intercooler 5 ' and the cylinder head 1a Positions in the intake system 3 geodesically deeper than the sink 3b . 3b' are located.

The return line 4a so can with deactivated exhaust gas recirculation 4 . 4' ie with closed shut-off element 4b , used to collect condensate.

With activated exhaust gas recirculation 4 . 4' can the return line 4a then be used for discharging the previously collected condensate, wherein the collected condensate either against the flow direction of the recirculated exhaust gas into the Abgasabführsystem 2 passes or from the exhaust gas flow in the return line 4a entrained and into the intake system 3 is introduced. The high temperatures in the return line 4a or in the exhaust gas removal system 2 ensure at least partial evaporation of the condensate. The latter is to be regarded as extremely beneficial.

LIST OF REFERENCE NUMBERS

1

 Internal combustion engine

1a

 cylinder head

2

 Abgasabführsystem

2a

 first node

3

 intake system

3a

 second node

3b

 Sink in the intake system

3b'

 locally geodetic lower location in the intake system

4

 Exhaust gas recirculation

4'

 High-pressure exhaust gas recirculation

4a

 Return line

4b

 Shut-off element, EGR valve

5

 air cooler

5 '

 Intercooler

6

 turbocharger

6a

 Compressor of the exhaust gas turbocharger

6b

 Turbine of the exhaust gas turbocharger

AGR

 Exhaust gas recirculation

m _AGR

 Mass of recirculated exhaust gas

_{Fresh air}

 Mass of supplied fresh air or combustion air

x _AGR

 Exhaust gas recirculation rate

Claims (16)

Internal combustion engine ( 1 ) with - at least one cylinder, - an intake system ( 3 ) for supplying the at least one cylinder with charge air, - an exhaust gas discharge system ( 2 ) for the removal of the exhaust gases, - an exhaust gas recirculation ( 4 . 4' ), which is a return line ( 4a ), which forms a first node ( 2a ) of the exhaust gas removal system ( 2 ) branches off and forming a second node ( 3a ) into the intake system ( 3 ), wherein in the return line ( 4a ) a shut-off element ( 4b ), and - at least one air cooler ( 5 . 5 ' ) upstream of the second node ( 3a ) in the intake system ( 3 ), characterized in that - the intake system ( 3 ) downstream of the at least one air cooler ( 5 . 5 ' ) a sink ( 3b ), wherein the return line ( 4a ) forming the second node ( 3a ) in this sink ( 3b ) opens. Internal combustion engine ( 1 ) according to claim 1, characterized in that the sink ( 3b ) in the installation position of the internal combustion engine ( 1 ) one between the at least one air cooler ( 5 ) and the at least one cylinder geodetically lowest point in the intake system ( 3 ). Internal combustion engine ( 1 ) according to claim 1, characterized in that the sink ( 3b ) in the installation position of the internal combustion engine ( 1 ) locally a geodetically deeper location ( 3b' ) in the intake system ( 3 ). Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that at least one drivable by means of auxiliary drive compressor in the intake system ( 3 ) is arranged. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that at least one exhaust gas turbocharger ( 6 ) is provided, the one in Abgasabführsystem ( 2 ) arranged turbine ( 6b ) and one in the intake system ( 3 ) arranged compressors ( 6a ). Internal combustion engine ( 1 ) according to claim 4 or 5, characterized in that the return line ( 4a ) downstream of the compressor ( 6a ) forming the second node ( 3a ) into the intake system ( 3 ) opens. Internal combustion engine ( 1 ) according to claim 5 or 6, characterized in that the return line ( 4a ) upstream of the turbine ( 6b ) forming the first node ( 2a ) from the exhaust gas removal system ( 2 ) branches off. Internal combustion engine ( 1 ) according to one of claims 5 to 7, characterized in that the return line ( 4a ) of exhaust gas recirculation ( 4' ) forming the first node ( 2a ) upstream of the turbine ( 6b ) from the exhaust gas removal system ( 2 ) branches off and forming the second node ( 3a ) downstream of the compressor ( 6a ) into the intake system ( 3 ), wherein between the second node ( 3a ) and the compressor ( 6a ) a charge air cooler ( 5 ' ) in the intake system ( 3 ) is arranged. Internal combustion engine ( 1 ) according to claim 8, characterized in that a further exhaust gas recirculation is provided which comprises a return line, which downstream of the turbine from the exhaust system ( 2 ) branches off and upstream of the compressor in the intake system ( 3 ) opens. Internal combustion engine ( 1 ) according to claim 9, characterized in that between the turbine and the branch of the return line from Abgasabführsystem ( 2 ) at least one exhaust aftertreatment system in the exhaust gas removal system ( 2 ) is provided. Internal combustion engine ( 1 ) according to claim 10, characterized in that for the treatment of the exhaust gas, a particulate filter is provided as exhaust aftertreatment system. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that a bypass line for bypassing the air cooler ( 5 . 5 ' ) is provided. Method for operating an internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the exhaust gas recirculation ( 4 . 4' ) by closing the shut-off element ( 4b ) and in the intake system ( 3 ) upstream of the second node ( 3a ) separated condensate in the return line ( 4a ) with closed shut-off element ( 4b ) is collected. Method according to claim 13, characterized in that in the return line ( 4a ) collected condensate by opening the shut-off ( 4b ) is disposed of. Method according to claim 14, characterized in that in the return line ( 4a ) collected condensate when opening the shut-off ( 4b ) with recirculating exhaust gas into the intake system ( 3 ) is introduced and disposed of. Method according to claim 14 or 15, characterized in that in the return line ( 4a ) collected condensate when opening the shut-off ( 4b ) into the exhaust gas removal system ( 2 ) is introduced and disposed of.

Images