WO2012048784A1

WO2012048784A1 - Exhaust gas recirculation with condensate discharge

Info

Publication number: WO2012048784A1
Application number: PCT/EP2011/004690
Authority: WO
Inventors: Arnd Bressel; Heinz-Dieter Hesse
Original assignee: Daimler Ag
Priority date: 2010-10-14
Filing date: 2011-09-20
Publication date: 2012-04-19
Also published as: DE102010048466A1

Abstract

The invention relates to a an EGR device (EGR = exhaust gas recirculation) (35) of an internal combustion engine (1), in particular of a motor vehicle, having at least one EGR cooler (22) arranged in an EGR path (18), wherein the EGR device (35) is designed as a low-pressure EGR device (10) and wherein the EGR path (18) is arranged between a branch point (17) from an exhaust gas path (12) and an injection point (19) of recirculated exhaust gas into a fresh air path (3). It is essential to the invention that at least one condensate discharge device (25) for discharging condensate from the EGR path is arranged in the EGR path (18) downstream of at least one EGR cooler (22) and upstream of the injection point (19) in the exhaust gas flow direction (23). By means of this arrangement advantageously the majority of the condensate can be removed from the recirculated exhaust gas.

Description

Exhaust gas recirculation with condensate discharge

The present invention relates to an EGR (EGR exhaust gas recirculation) device of an internal combustion engine, in particular of a motor vehicle, and an exhaust system equipped with such an EGR device.

When exhaust gases are recirculated from an exhaust path of internal combustion engines into the fresh air path, in particular when the exhaust gas is removed downstream of the oxidation catalytic converter, an aggressive pathway can form in an EGR path when the dew point for the condensate is reached. Education is undershot. The dew point depends on the respective exhaust gas composition. Since condensation can not always be prevented, corrosion is currently avoided in large parts of the EGR path, e.g. expensive and high-alloy chromium nickel steel used.

For example, in the article "The supercharging concept of the Volkswagen's 2, CRC 103kW engine with high and low pressure exhaust gas recirculation to meet the Bin5 emission requirements", Greiner et al., 2008 is such a harmful condensate Education themed. It is described that, therefore, even under unfavorable boundary conditions, such a formation of condensate should be avoided since, for example, erosion damage to a compressor wheel of a charging device can occur due to condensate drops. Through an optimal distribution of high pressure and low pressure EGR can be ensured for each operating point that the dew point of the condensate components of the cooled exhaust gas at the compressor inlet is not exceeded. Thus, with such optimal distribution of high pressure and low pressure EGR, an emission optimized exhaust gas recirculation rate can be set while preventing the formation of condensed droplets.

In WO 2006/087062 A1, the formation in the case of a low-pressure EGR is avoided in that the intercooler is designed as a down-flow cooler, so that any condensate formed at the lowest point of the vertical intercooler accumulate and subsequently derived. In the case of a high-pressure EGR, at least one EGR cooler is preferred, which forms the last EGR cooler in the exhaust gas flow direction as such a downflow cooler so that any condensate formed can collect at the lowest point of the EGR cooler designed as a downflow cooler.

In EP 2 161 430 A1 a charge air cooler with condensate drain is described. The AG R- orrichtung is designed as a low-pressure AG R. In the intercooler accumulating condensate can be collected at the lowest point. The intercooler is equipped with a condensate drain opening, which is fluidly connected to the charge air path via a condensate drain line. In this case, the condensate discharge point is arranged in the charge air flow direction after the intercooler. The condensate discharge opening can be closed by means of a closure element. Thus, any accumulating condensate can be retained by the intercooler when an introduction of the condensate in the charge air path is unfavorable due to the respective operating state. If an introduction of condensate is unproblematic, the closure element can be opened and the condensate introduced into the charge air path. Thus, much of the condensate remains in the EGR path. However, this is not only detrimental to the components arranged in the EGR path, but can also lead to undesirable negative effects in the area of the internal combustion engine. In addition, a temporary concentration of the condensate in the EGR path and / or in the EGR path can increase the negative effects.

The present invention addresses the problem of providing for an EGR device of the generic type and for an exhaust system with such an EGR device an improved or at least one alternative embodiment, which is characterized in particular by an increased service life.

According to the invention, this problem is solved by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea of providing an EGR device of an internal combustion engine, in particular of a motor vehicle, with at least one EGR cooler arranged in an EGR path with at least one condensate discharge device for discharging to provide condensate from the EGR path. The EGR device is designed as a low-pressure EGR, wherein the EGR path between a branch point from the exhaust path and an introduction point of recirculated exhaust gas is arranged in the fresh air path. In this case, the Kondensatabführvorrichtung is arranged in the EGR path in the exhaust gas flow direction after at least one EGR cooler and before the discharge point. By using at least one Kondensatabführvorrichtung it is possible to remove the eventually formed aggressive condensates consistently from the EGR path at least partially, whereby a significant reduction in the corrosion load of the arranged after the Kondensatabführvorrichtung in the EGR path components can be achieved. An EGR path is to be understood as meaning that line region, including the components arranged therein and through which the exhaust gas recirculated flows, by means of which the recirculated exhaust gas is supplied to the fresh air path. As a result, the EGR path is located between a branch point of the exhaust gas from the exhaust path and the point of introduction of recirculated exhaust gas into the fresh air path. The exhaust path is consequently the line region through which exhaust gas flows. The fresh air path is that line region over which fresh air is supplied to the internal combustion engine. In the present case, a high-pressure EGR should be understood to mean an EGR device in which the point of introduction is arranged downstream of a compressor of a charging device. Thus, the recirculated exhaust gas is introduced into a high-pressure region. Accordingly, a low-pressure EGR is understood to mean an EGR device in which the point of introduction of the recirculated exhaust gas is arranged in front of a compressor of a charging device. Thus, in a low pressure EGR, the recirculated exhaust gas is introduced into a low pressure region. It is the combination of low pressure EGR and high pressure EGR possible in an EGR device, as well as the single application of high pressure or low pressure EGR is conceivable.

Preferably, the highest possible amount of condensate is deposited in the EGR path and / or in the at least one EGR cooler. In this case, more than one EGR cooler can be arranged in the EGR path. In the exhaust gas flow direction downstream of each of the EGR coolers, or preferably at least downstream of the last EGR cooler in the exhaust gas flow direction, a condensate removal device can be arranged in each case. In this case, so much condensate can be removed by means of the at least one Kondensatabführvorrichtung that in the recirculated exhaust gas in the outflow direction after the at least one Kondensatabführvorrichtung less than 40 percent by weight of the original, contained in the branch point condensate is still present. Preferred are after the at least one Kondensatabführvorrichtung still present less than 30 weight percent, more preferably less than 20 weight percent and most preferably less than 10 weight percent of the original condensate contained at the branch point. The more condensate is removed from the recirculated exhaust gas, the lower the risk of damage to the components arranged in the EGR path and beyond. In addition, by means of the condensate removal device, the exhaust emission values with respect to the condensate ingredients can thus be improved.

The separated in the respective EGR cooler condensate consists of mainly water and sulfur oxides, which react in conjunction with the water to sulfurous acid or sulfuric acid. Furthermore, nitrogen oxides or nitrogen oxide acids can occur in the condensate, as can combustion residues. The problem with the condensate, especially with sulfur-containing fuel, is the occurrence of sulfuric acid or sulfurous acid. Thus, as a condensate usually highly concentrated sulfuric acid or sulfuric acid is deposited, which can be significantly diluted only after reaching the dew point of the water vapor. Furthermore, in the case of the condensate, a concentration of the sulfuric acid or of the sulfurous acid occurs when it is attempted to evaporate the condensate. As a result, the condensate can be evaporated again only at very high temperatures. Accordingly, either complete prevention of condensate formation or complete removal of the condensate is advantageous, with complete removal of the condensate formed reducing the recirculated exhaust gas to the less aggressive and corrosive and improving exhaust emission levels.

The EGR cooler, which is arranged in the exhaust gas flow direction in front of the Kondensatabführvorrichtung, in a preferred embodiment of the invention may have an inclination relative to the horizontal of more than 5 degrees. Preferably, an inclination of more than 10 degrees, more preferably an inclination of more than 15-20 degrees. Here, the degrees refer to the horizontal in the case of

Motor vehicle to the indication relative to the horizontal when the vehicle is horizontal. In the EGR path in the exhaust gas flow direction may be positioned in front of the point of introduction, a closure element which is designed as a valve, flap, throttle element, throttle or the like.

The Kondensatabführvorrichtung may have a condensate collection area in which the deposited condensate can be collected. This condensate collecting region may be formed integrally with the respective EGR cooler, wherein the EGR collecting region, in this case preferably at the lowest point of the EGR cooler is arranged. In addition, the EGR collection area or the EGR cooler may have a drain opening through which the accumulated condensate may exit from the EGR cooler or from the condensate collection area.

Furthermore, at least one condensate removal device may have a condensate return line which connects the condensate removal device to the exhaust gas path in a fluidic manner. Thus, the condensate can be returned to the exhaust path via the condensate return line. Preferably, a return point, at which the condensate return line opens into the exhaust path, arranged in the exhaust gas flow direction to the branch point. Thus, the condensate can be introduced into the exhaust path so that it does not at least partially back into the EGR path. Thus, a concentration of condensate in the EGR path can be prevented. It can be arranged in the region of the return line both in the exhaust path and in the return line closure elements as described above. The condensate collecting device can be designed in such a way that it is possible to receive at least one further condensate. By including further condensates in the condensate collector condensate separated from the exhaust gas can be diluted, which can drastically reduce the risk potential of the condensate. In the case of, for example, a dilution of the condensate - as described above - the Kondensatabführvorrichtung can be designed such that the condensate can be discharged into the environment. If necessary, a review of the hazard class of the condensate is required. Thus, if necessary, the risk potential of the condensate can be estimated by means of a concentration determination and, depending on the dilution, the condensate can be released to the environment.

In an advantageous embodiment of the invention, the Kondensatabführvorrichtung is equipped with an ion exchanger, with which the condensate is neutralized. Because in The condensate contains mainly sulfuric acid or sulfurous acid, the condensate can be at least partially neutralized by replacing the protons of the condensate by, for example, sodium ions by means of an ion exchanger. As a result, the risk potential of the condensate can be significantly reduced and discharge into the environment is less of a concern.

Furthermore, it is advantageous if the coolant of the at least one EGR cooler has a lower temperature than the coolant of a charge air cooler arranged in the fresh air path in the fresh air flow direction downstream of the introduction point. In this case, condensation in the at least one EGR cooler can be forced and the condensation in the charge air cooler can at least be reduced, preferably avoided. In this case, the exhaust gas fresh air mixture can be further cooled in this case by the intercooler, but partly due to the higher-temperature cooling fluid of the intercooler subsequent condensation of the condensate in the intercooler is at least reduced. The EGR cooler may be cooled with the cooling fluid with which the internal combustion engine is cooled. In this case, the exhaust gas temperature may be less than 100 ° C after leaving the at least one EGR cooler. Preferably, the exhaust gas temperature is less than 95 ° C, more preferably less than 85 ° C. However, it is also possible to cool the EGR cooler with a cooling fluid, with which the air conditioner is operated. In this case, the exhaust gas temperature after leaving the at least one EGR cooler, less than 50 ° C, more preferably less than 42 ° C.

Such an EGR device can be used in an exhaust system of a motor vehicle.

Other important features and advantages of the invention will become apparent from the

Subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention. Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description, wherein the same

Refers to reference to the same or similar or functionally identical components.

It show, each schematically:

1 shows an internal combustion engine with an EGR device according to the invention,

2 shows an EGR cooler with a condensate discharge device.

An internal combustion engine 1 illustrated in FIG. 1 has an exhaust system 2 and a fish air path 3 as well as a low-pressure charging device 4 and a high-pressure charging device 5. In the fresh air path 3, an air filter 6 is arranged and a charge air cooler 7. The fresh air flowing via the fresh air path 3 can be compressed by means of a compressor 8 of the low-pressure charger 4 or by means of a compressor 9 of the high-pressure charger 5.

The exhaust system 2 has a low pressure EGR 10 (exhaust gas recirculation EGR) and a high pressure EGR 11 and an exhaust path 12. In the exhaust path 12 is a

Catalyst 13 is arranged. The exhaust gas flowing in the exhaust path 12 drives a turbine 14 of the low-pressure charger 4, as well as a turbine 15 of the high-pressure charger 5. The high-pressure EGR 1 branches off exhaust gas from a manifold region 16 of the exhaust system 2 and supplies this recirculated exhaust gas to the fresh air path 3 after the charge air cooler 7. Thus, by means of the high pressure EGR 11 recirculated exhaust gas is introduced into a high pressure region of the fresh air path 3. In the case of the low-pressure EGR 10, the exhaust gas is taken off the exhaust gas path 12 at a branching point 17 and introduced into the fresh air path 3 via an EGR path 18 at an introduction point 19. In this case, the branch point 17 is arranged in the exhaust gas path 12 in the exhaust gas flow direction 20 downstream of the catalytic converter 13. The introduction point 19 is arranged in the fresh air flow direction 21 in front of the compressor 8. Thus, by means of the low-pressure EGR 10

recirculated exhaust gas is introduced into a low pressure region of the fresh air path 3.

In the EGR path 18, according to FIG. 1, an EGR cooler 22 is arranged, with which the recirculated exhaust gas can be cooled to the desired setpoint temperature. In the exhaust gas flow direction 23 after the EGR cooler 22 is in the EGR path 8 a

Closing element 24 is arranged, which may be formed for example as a valve, throttle, flap, throttle or the like. In the exhaust gas flow direction 23 At the end of the EGR cooler 22, a Kondensatabführvorrichtung 25 is arranged. The Kondensatabführvorrichtung 25 is fluidly connected via a discharge opening 26 with the EGR cooler 22. The Kondensatabführvorrichtung 25 may have a ion exchanger 27 and / or a Kondensatsammeieinrichtung 28. Furthermore, the Kondensatabführvorrichtung 25 may have a condensate return line 29 which connects the EGR cooler 22 fluidly with the exhaust path 12. Preferably, this is a

Introductory point 30 at which the condensate return line 29 opens into the exhaust path 12, in the exhaust gas flow direction 20 after the branch point 17. Die

Kondensatabführvorrichtung 25, as shown in Fig. 1, in

Exhaust gas flow direction 23 may be connected to the end of the EGR cooler 22, or to the EGR path 18 between the EGR cooler 22 and the introduction point 19 or between the EGR cooler 22 and the closure element 24. Further, the ion exchanger 27 and the Kondensatsammeieinrichtung 28 integrally formed. Additionally or alternatively, the Kondensatabführvorrichtung 25 a

Drain line 31 or have a drain opening 32, with which the condensate can be discharged into the environment. In the case of using a condensate return line 29, the condensate can be recycled into the exhaust path 12.

The illustrated in Fig. 2 EGR cooler 22 is inclined relative to a horizontal 33 at an angle o. Preferably, the angle <x is more than 5 degrees or 10 degrees, more preferably more than 15 degrees, and most preferably more than 20 degrees. The EGR cooler 22 may be formed as a long shell-and-tube heat exchanger, wherein the exhaust gas flow direction 23 and a condensate flow direction 34

can be oriented opposite. Thus, an AGR device 35 may include as essential components the EGR path 18, at least one EGR cooler 22, and at least one closure member 24 that may be configured as an EGR valve. As another essential ingredient, AG R device 35 has the

Kondensatabführvorrichtung 25 on. This Kondensatabführvorrichtung 25 may turn the Kondensatsammeieinrichtung 28, the condensate return line 29, and the ion exchanger 27, the discharge opening 26, the drain opening 32 and the drain line 31 have.

Claims

Daimler AG claims

An EGR (EGR) device (35) of an internal combustion engine (1), in particular of a motor vehicle, having at least one EGR cooler (22) arranged in an EGR path (18), wherein the EGR device (35) is formed as a low-pressure EGR (10) and wherein the EGR path (18) between a

Abzweigungsstelle (17) from an exhaust path (12) and an introduction point (19) of recirculated exhaust gas in a fresh air path (3) is arranged,

characterized in that

in the EGR path (18) in the exhaust gas flow direction (23) after at least one EGR cooler (22) and before the introduction point (9) at least one condensate discharge device (25) arranged to remove condensate from the EGR path (18) is.

2. EGR device according to claim 1,

characterized in that

in the EGR path (18), the recirculated exhaust gas in the exhaust gas flow direction (23) after the at least one condensate discharge device (25) has less than 40% by weight of an original condensate amount contained at the branch point (17).

3. EGR device according to one of the preceding claims,

characterized in that

in the installed position at least one EGR cooler (22) has an inclination (cc) with respect to the horizontal (33) of more than 5 °.

4. EGR device according to one of the preceding claims,

characterized in that

in the EGR path (18) in the exhaust gas flow direction (23) before the introduction point (19) a closure element (24) is arranged.

5. EGR device according to claim 4,

characterized in that

at least one Kondensatabführvorrichtung (25) between the at least one EGR cooler (22) and the closure element (24) is arranged.

6. EGR device according to one of the preceding claims,

characterized in that

the exhaust path (12) and the at least one Kondensatabführvorrichtung (25) via a condensate return line (29) are fluidly connected, via which the condensate is returned to the exhaust path (12).

7. EGR device according to claim 6,

characterized in that

an introduction point (30), at which the condensate return line (29) opens into the exhaust gas path (12), in the exhaust gas flow direction (23) after the branch point (17) is arranged.

8. EGR device according to one of the preceding claims,

characterized in that

the Kondensatabführvorrichtung (25) comprises a Kondensatsammeieinrichtung (28), in which the condensate is collected.

9. EGR device according to claim 8,

characterized in that

the Kondensatsammeieinrichtung (28) is designed for receiving at least one further condensate.

10. EGR device according to one of the preceding claims,

characterized in that

the Kondensatabführvorrichtung (25) is designed such that the condensate is discharged into the environment.

11. EGR device according to one of the preceding claims,

characterized in that - The Kondensatabführvorrichtung (25) has an ion exchanger (27), with which the condensate is neutralized, and / or

- A coolant of the at least one EGR cooler (22) a smaller

Temperature has, as a coolant of a in a fresh air path (3) in fresh air flow direction (21) after the introduction point (19) arranged charge air cooler (7).

12. AG R-orrichtung according to any one of the preceding claims,

characterized in that

at least one EGR cooler (22) has an internal combustion engine Kühllfuid, with at least the EGR cooler (22) and also the internal combustion engine (1) flows through and cooled, wherein when cooled by the

Internal combustion engine Kühllfuid, in the EGR path (18) an exhaust gas temperature in the exhaust gas flow direction (23) after the at least one EGR cooler (22) is less than 100 ° C.

13. AG R device according to one of the preceding claims,

characterized in that

at least one EGR cooler (22) has an air conditioning Kühllfuid with which the at least one EGR cooler (22) and an air conditioner flows through and is cooled.

14. EGR device according to claim 13,

characterized in that

in particular when cooled by the air conditioning Kühllfuid, in the EGR path (18) an exhaust gas temperature in the exhaust gas flow direction (23) after the at least one EGR cooler (22) is less than 50 ° C.

15. exhaust system with an EGR device (35) according to any one of the preceding claims.