DE102010011026A1 - Internal combustion engine for use in vehicle i.e. car, has heat exchanger arranged at exhaust gas line in direction of flow of exhaust gas, where compressed fresh air is led through heat exchanger before introduction into turbine - Google Patents

Abstract

The engine (1) has a compressor (5) arranged in an air intake part (6). The compressor compresses fresh air, which is introduced into an exhaust gas line (4) in a direction of flow of exhaust gas after a discharge passage (7) in a cylinder head (8) and before a turbine (3). A heat exchanger (9) is arranged at the exhaust gas line in the direction of flow of the exhaust gas after the discharge passage and before the turbine, where the compressed fresh air is led through the heat exchanger before introduction into the turbine.

Description

The invention relates to an internal combustion engine with a turbocharger having the features of the preamble of patent claim 1.

It is known from the prior art that conventional supercharging systems for internal combustion engines use turbochargers for the partial utilization of the exhaust gas enthalpy or mechanically driven compressors.

For the general state of the art, for example, the German Offenlegungsschrift DE 32 25 867 A1 pointed. For this purpose, an internal combustion engine with a turbocharger is known, wherein a bypass line is provided between the intake line connected to the supercharger downstream of the throttle valve and the outlet line opening into the turbine, in which a valve is arranged which only shuts off the bypass line when the exhaust gas pressure in the exhaust line exceeds the boost pressure in the intake pipe by a certain amount and a connection adversely affects the performance of the internal combustion engine. Below this pressure range, the valve is open and the connection between the inlet line and the outlet line is released. As a result, the operating state of the internal combustion engine in which the boost pressure is higher than the exhaust gas pressure, fresh gas from the inlet line into the outlet line and an automatic secondary air supply occur. In contrast, when the exhaust pressure is higher than the boost pressure, exhaust gas flows from the exhaust passage into the intake passage, so that automatic exhaust gas recirculation takes place.

Next is from the German patent application DE 198 47 477 A1 an internal combustion engine with a turbocharger whose turbine in the exhaust line and the compressor are arranged in the intake manifold. In this known embodiment, the fresh air compressed by the compressor in the flow direction of the exhaust gas can be introduced downstream of the exhaust duct in a cylinder head and upstream of the turbine into the exhaust gas line. By this measure, it is possible, in particular at a fuel-air ratio near λ = 1 or higher (lean air-fuel ratio) to blow secondary air into the exhaust system to achieve a secondary oxidation, whereby the exhaust emissions of the internal combustion engine can be significantly reduced.

Furthermore, in turbocharging the turbine causes a high exhaust back pressure and thus considerable charge exchange losses. This leads to high levels of residual gas and thus in Otto internal combustion engines, to avoid knocking combustion, to an unfavorable late ignition. Accordingly, supercharged internal combustion engines achieve poor efficiency, especially at high loads. The exhaust gas mass flow is only partially used because the o. G. Bypass valve opens and the exhaust gas is passed partially unused to the exhaust gas turbine. At stoichiometric combustion (λ <1) and high engine load, the fuel is not completely burned and thus the efficiency of the entire system decreases again.

During mechanical charging, the exhaust gas enthalpy is not used at all; the compressor is driven by the crankshaft. Thus, the efficiency of mechanical charging is also very low.

The object of the present invention is to improve the efficiency of an internal combustion engine with a turbocharger.

This object is solved by the features in the characterizing part of patent claim 1.

Advantageous developments of the invention are described in the subclaims 2 to 5.

By separating the individual cylinder groups according to claim 2, the charge exchange and thus the efficiency of the internal combustion engine is substantially improved.

The embodiment according to claim 3 causes a very fast reaching the conversion temperature of the emission control system, such as a three-way catalyst and at high mass flows is a cooling effect for the emission control system against excessive temperatures, which lead to destruction of the emission control system achieved.

With the embodiment according to claim 4, in particular the instationary behavior of the internal combustion engine with a turbocharger can be improved.

With the embodiment according to claim 5, it is possible to maintain a single "scroll" for the fresh air compressed and heated in two heat exchangers.

In the following the invention with reference to a particularly preferred embodiment is explained in more detail in a single figure.

1 shows very schematically an inventive embodiment of an internal combustion engine with a turbocharger.

1 shows very schematically an embodiment of the invention for an internal combustion engine 1 with a turbocharger 2 consisting of a turbine 3 and one in a suction line 6 the internal combustion engine 1 arranged compressor 5 , Next points the turbocharger 2 an electric machine 11 on that with the compressor 5 and the turbine 3 is operatively connected and can work as a generator or as a prime mover, ie that the compressor 5 and / or the turbine 3 from the electric machine 11 is affordable.

The of the compressor 5 compressed fresh air is in the intake manifold 6 promoted, wherein the flow direction of the fresh air is represented symbolically by arrows. The intake manifold 6 splits after the compressor 5 in three subducts 6a . 6b . 6c on.

The first partial intake line 6a is used to supply six cylinders symbolically represented by circles 10 with fresh air, which is a combustion in the cylinders 10 is supplied. The example six cylinders 10 are in a cylinder head 8th , representative of the internal combustion engine 1 arranged. On the fresh air supply side facing away from the cylinder 10 the exhaust gases flow out of the cylinders 10 in the cylinder head 8th arranged outlet channels 7 that extends to the exhaust system 4 extend. Furthermore, the exhaust gases flow to the outlet channels 7 in the exhaust system 4 , which is designed in the present embodiment in two columns, that is, there are each 3 cylinders 10 to a first cylinder group 10a and a second cylinder group 10b summarized. A flow direction of the exhaust gases is also symbolically represented by arrows. Thereafter, the exhaust gases flow through the exhaust line 4 each in a heat exchanger 9 and further in the direction of ambient air. It may be provided to reach the ambient air, not shown exhaust gas purification systems.

The second partial intake line 6b is used for a so-called secondary air injection. For this purpose, the compressed fresh air flows through a secondary air valve 12 and further into the exhaust system 4 , for every cylinder 10 in the flow direction of the exhaust gas to the outlet channel 7 , The crossing points of fresh air in the exhaust system 4 are symbolically represented by small dots. In another embodiment, the crossing points may also be in the area of the outlet channels 7 be arranged. The crossing points are in this embodiment in the area between the outlet channels 7 and the heat exchangers 9 , The compressed fresh air is added to the exhaust gas in order to achieve a post combustion oxidation (λ <1, excess fuel) of the hydrocarbons and thus to reduce the raw emissions of the internal combustion engine.

The third partial intake line 6c is after the compressor 5 through the heat exchangers 9 and then into the turbine 3 guided.

According to the invention here is the exhaust line 4 in the flow direction of the exhaust gas to the outlet channel 7 and in front of the turbine 3 the heat exchanger 9 arranged and the compressed fresh air is before placing in the turbine 3 through the heat exchanger 9 directed. Thus, the energy for the turbocharger 2 only by those in the heat exchangers 9 heated fresh air provided. The advantage of the system according to the invention is thus in the significantly reduced exhaust backpressure and this advantageous feature would according to the prior art by the post-expansion of the exhaust gases in the turbine 3 be abandoned.

Particularly preferred are the cylinders 10 as in the present embodiment exhaust side to at least two cylinder groups 10a . 10b summarized, each with a cylinder group 10a . 10b a separate heat exchanger 9 assigned.

In a further, particularly preferred embodiment variant is in the heat exchanger 9 integrated an emission control system or the heat exchanger 9 is designed as an exhaust gas purification system, for example as a three-way catalyst.

In this particularly preferred embodiment, at least the compressor 5 from an electric machine 11 drivable, the electric machine 11 is operable both as a generator and as a motor.

To further improve the system can also a twin-scroll turbocharger as a turbocharger 2 be provided.

The inventively proposed system thus includes a compressor 5 , at least one exhaust gas heat exchanger 9 and a turbine 3 as well as an electric machine 11 , which is operable as an electric motor or generator. In normal operation of the internal combustion engine 1 gets the from the compressor 5 compressed air through the exhaust gas heat exchanger 9 directed and heated. Subsequently, the fresh air through the turbine 3 relaxed. The released work can be used to either the fresh air for the internal combustion engine 1 to compact or with the help of the electric machine 11 produce electrical power that can be used for example with a hybrid system for a vehicle drive.

In substoichiometric combustion, a portion of the compressed fresh air in the exhaust system 4 are passed to post-oxidation and increase the exhaust gas temperature in order to use the exhaust enthalpy as completely as possible.

The heat exchanger 9 can preferably be carried out as a catalyst and during engine warm-up, the compressor 5 be turned off, whereby the catalyst is thermally insulated and reaches its operating temperature faster. As in the present embodiment, a plurality of heat exchangers may also be used to form individual cylinder groups 10a . 10b to be separated in the interest of undisturbed charge exchange to improve the efficiency of the internal combustion engine 1 , In the case of a four-cylinder internal combustion engine 1 can, for example, cylinder groups 10a . 10b each formed with two cylinders.

With the electric machine 11 The system can be powered and started up in transient operation. Once the desired boost pressure is reached, the electric machine 11 As a generator, take the surplus energy and provide the electrical energy to the entire vehicle.

Summary of the advantages according to the invention:

The system described causes a significantly lower exhaust gas back pressure than a conventional exhaust gas turbocharger and thus lower gas exchange losses. The lower exhaust back pressure reduces in the Otto internal combustion engine 1 the tendency for knocking combustion and advantageously allows earlier firing angles, thereby increasing combustion efficiency. The preferably designed as a catalyst heat exchanger 9 can be closer to the cylinder head 8th be arranged as in a conventional exhaust turbocharger, in which the catalyst after the turbocharger 2 is installed. Thus, the catalyst can start faster, ie reach its operating temperature and the catalyst heating phase associated with disadvantages in the efficiency can be reduced. At high exhaust gas flow rate, the catalyst is cooled by the compressed fresh air and the entire exhaust system is thermally less burdened. This makes complex compensators and sealing systems for the exhaust system 4 advantageously superfluous.

By the exhaust system supplied secondary air at substoichiometric combustion, z. B. at full load, the exhaust enthalpy is fully utilized by post-oxidation of unburned hydrocarbons (HC) and thus raising the exhaust gas temperature as fully as possible. A bypass valve (wastegate) is not required in an advantageous manner, ie the wastegate can be omitted, since the surplus power of the turbine 3 through the electric machine 11 is removed.

By dividing it into several separate heat exchangers 9 can the cylinder groups 10a . 10b be separated on the exhaust side, which is always possible only with great effort in the conventional turbocharger. By this measure can also several turbochargers 2 or use a twin-scroll turbocharger.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

turbocharger

3

turbine

4

exhaust gas line

5

compressor

6

intake line

6a

first partial intake line

6b

second partial suction line

6c

third partial suction line

7

exhaust port

8th

cylinder head

9

heat exchangers

10

cylinder

10a

cylinder group

10b

cylinder group

11

electric machine

12

Secondary air valve

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

• DE 3225867 A1 [0003]
• DE 19847477 A1 [0004]

Claims (5)

Internal combustion engine ( 1 ) with a turbocharger ( 2 ), consisting of a turbine ( 3 ) and one in a suction line ( 6 ) of the internal combustion engine ( 1 ) arranged compressors ( 5 ), wherein from the compressor ( 5 ) compressed fresh air in the flow direction of an exhaust gas to an outlet channel ( 7 ) in a cylinder head ( 8th ) of the internal combustion engine ( 1 ) and in front of the turbine ( 3 ) in the exhaust line ( 4 ) can be introduced, characterized in that the exhaust line ( 4 ) in the flow direction of the exhaust gas to the outlet channel ( 7 ) and in front of the turbine ( 3 ) a heat exchanger ( 9 ) and wherein the compressed fresh air before introduction into the turbine ( 3 ) through the heat exchanger ( 9 ) is conductive. Internal combustion engine according to claim 1, wherein the internal combustion engine ( 1 ) several cylinders ( 10 ), characterized in that the cylinders ( 10 ) on the exhaust side to at least two cylinder groups ( 10a . 10b ) and per cylinder group ( 10a . 10b ) a heat exchanger ( 9 ) assigned. Internal combustion engine according to one of the claims 1 or 2, characterized in that in the heat exchanger ( 9 ) an emission control system is integrated. Internal combustion engine according to one of the claims 1 to 3, characterized in that at least the compressor ( 5 ) of an electric machine ( 11 ) is drivable. Internal combustion engine according to one of the claims 2 to 4 , characterized in that the turbocharger ( 2 ) is a twin-scroll turbocharger.

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