EP2627887A1

EP2627887A1 - Exhaust gas recirculation with condensate discharge

Info

Publication number: EP2627887A1
Application number: EP11761509.6A
Authority: EP
Inventors: Thomas Koch; Johannes Ritzinger
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2010-10-14
Filing date: 2011-09-20
Publication date: 2013-08-21
Also published as: US20130219886A1; WO2012048786A1; DE102010048465A1

Abstract

The invention relates to a method for discharging condensate from an EGR path (EGR = exhaust gas recirculation) (16) of an internal combustion engine (1), in particular of a motor vehicle, wherein on the basis of a pressure difference between a condensate collection region (23) disposed in the EGR path (16) and a condensate discharge region (24, 24', 24") at least some collected condensate is discharged from the condensate collection region (23) into the condensate discharge region (24, 24', 24") when the pressure in the condensate collection region (23) is higher than in the condensate discharge region (24, 24', 24").

Description

Exhaust gas recirculation with condensate removal

The present invention relates to a method for removing condensate from an EGR path (EGR exhaust gas recirculation) of an internal combustion engine. Furthermore, the invention relates to an EGR device and an exhaust system with such an EGR device.

In internal combustion engines with exhaust gas recirculation (EGR), a certain proportion of the exhaust gas is returned to the internal combustion engine via an EGR path. Under certain conditions, condensate can precipitate out of the exhaust gas or out of an exhaust gas / fresh air mixture in the EGR path. The condensate can lead to sooting and corrosion of the components in the EGR path. It thus makes sense to remove the condensate as quickly and completely as possible from the EGR path or to suppress the formation of condensate.

In WO 2006/087062 A1, the formation in the case of a low-pressure EGR is avoided in that the charge air cooler is designed as a downflow cooler, so that any condensate that may form can collect at the lowest point of the vertical intercooler and can subsequently be discharged. In the case of a high-pressure EGR, at least one EGR cooler, preferably the last EGR cooler in the exhaust gas flow direction, is designed 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 EGR device is designed as a low-pressure EGR. Any condensate that may accumulate at the lowest point of the intercooler can be collected in the intercooler. The intercooler is equipped with a condensate drain opening, which is fluidly connected to the fresh air path via a condensate drain line. Here, the condensing Sat inlet point 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 charge air cooler when an introduction of the condensate in the fresh 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 fresh air path.

The exhaust system of the internal combustion engine of WO 2009/048408 A1 is equipped with a

High pressure EGR equipped. In this case, one or two first EGR coolers and a second EGR cooler are arranged in the EGR path. By means of a four-way valve, the exhaust gas may be circulated in the EGR path area of the first radiator (s). Due to the longer contact time of the exhaust gas with the / the first EGR cooler / n condensate can be increasingly separated from the circulating exhaust gas. By means of the deposited condensate, the first or the first EGR cooler can be at least partially cleaned of soiling.

In WO 2009 / 072963A1 an internal combustion engine is described with a high-pressure EGR. In the EGR path of the EGR device, two ARG coolers are arranged. In this case, condensate occurring in the second EGR cooler can be introduced via an EGR discharge line in the EGR path in front of the first EGR cooler. In this case, the EGR cooler is formed air-cooled and has a condensate collecting region, which is connected via the Kondensatabführleitung with the EGR path before the first EGR cooler or with the first EGR cooler fludisch conductive. To remove the condensate formed from the EGR path, a pump is arranged in the condensate discharge line, with which the condensate can be transported in the event of a back pressure in the EGR path. However, a promotion of the condensate by means of a pump in the EGR path is structurally complex and are also other components present, they can be damaged due to the aggressive, corrosive atmosphere of the recirculated exhaust gas and impaired in their function.

The present invention addresses the problem of providing an improved or at least one alternative embodiment for a method of removing condensate from its internal combustion engine EGR path, for an EGR device, and an exhaust system having such an EGR device in particular by a simplified, less vulnerable transport of the

Condensates in the respective Kondensatabführbereich distinguished.

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, in a method for

Discharge of condensate from an EGR path of an internal combustion engine, in particular of a motor vehicle, a possibly occurring pressure difference between a arranged in the EGR path condensate collection area and a

Use condensate discharge so that condensate collected by means of the pressure difference in the condensate collecting area is at least partially discharged from the condensate collecting area in the Kondensatabführbereich when in the condensate collecting area, a higher pressure prevails than in the

Kondensatabführbereich. Advantageously, by utilizing the pressure difference between the condensate collecting area and the Kondensatabführbereich the

Condensate by means of this simple process step from the

Be removed condensate collection area. This type of condensate removal from an EGR path can be used on turbocharged gasoline engines as well as supercharged diesel engines. The respective internal combustion engines can be equipped with a high-pressure and / or low-pressure EGR. An EGR path is to be understood as 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 and the part of the fresh air path through which the recirculated exhaust gas flows. As a result, the EGR path is disposed between a branch point of the exhaust gas from the exhaust path and the engine. The exhaust path is consequently the line region through which exhaust gas flows. The fresh air path is the line area over which the

Internal combustion engine is supplied fresh air, wherein at least a portion of the

Line area can also be attributed to the EGR path.

A high-pressure EGR is 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. Under a low-pressure EGR Consequently, one stands for an EGR device in which the introduction point for 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. The separated in a respective heat exchanger condensate consists of mainly water and sulfur oxides, which react in conjunction with the water to sulfurous acid or sulfuric acid or a mixture thereof. Furthermore, nitrogen oxides or nitrogen oxide acids can occur in the condensate, as can combustion residues. The problem with the condensate, especially in the case of sulfur-containing fuel, is the occurrence of sulfuric acid or sulfurous acid or a mixture of the two acids. Thus, as a condensate mainly highly concentrated 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 less aggressive and corrosive and improving exhaust emission levels.

The discharge of the condensate from the condensate collecting region can be controlled / regulated in accordance with a preferred embodiment of the invention by means of a closure element. It can always be when in the

Condensate collecting a higher pressure prevails than in the Kondensatabführbereich the closure element are opened, so that due to the pressure difference, the condensate is discharged from the condensate collection area. In this case, the closure element is preferably opened when the pressure in the condensate collecting region is greater than 20%, particularly preferably greater than 40% or greater than 60%, than the pressure in the condensate discharge region.

Likewise, the closure element is preferably opened for a short time. The opening is carried out so fast that the short-term pressure drop in the EGR path has only a negligible effect with respect to a boost pressure and / or with respect to a lambda control. The closure element can be designed as an electronically controllable valve, as a pressure-controlled valve or the like. The opening of the closure element can be carried out at least in a partial load range such that it simultaneously accumulates the accumulated

Condensate and for Entdrosselung the internal combustion engine is used. Accordingly, if necessary, a diverter valve to avoid pumping the

Compressor loader at load jumps, as it is currently used in gasoline engines to be replaced. Furthermore, such opening of the

Closure element for simultaneous condensate drainage and

Engine throttling in a partial load range provide dynamic advantages, since the charging device starts at a higher speed level.

Another general idea of the invention is an EGR device, in particular an internal combustion engine with a charging device having a turbine and a compressor. As an essential part, the EGR device has at least one condensate discharge device for removing condensate from an EGR path of the AGL device, wherein the condensate discharge device has a condensate collection region arranged in the EGR path and a closure element arranged before or after a discharge opening. However, the EGR device is designed such that due to a pressure difference between the

Condensate collecting area and a condensate discharge area when opening the

Closing element accumulated condensate is discharged from the condensate collection area in the Kondensatabführbereich.

Advantageously, thus in the EGR path separated condensate by means of

Condensate discharge device collected and targeted by opening the

Closure element are removed from the EGR path. Thus, by means of the Kondensatabführvorrichtung the aggressive, corrosive condensate from the recirculated exhaust gas are at least partially removed, so that after the

Kondensatabführvorrichtung arranged components in the EGR path are exposed to a lower corrosive load, resulting in a longer for these components

Durability and lower losses leads. Preference is given to a complete removal of the condensate.

Furthermore, a control regulation device may be provided which controls the opening and closing of the closure element controls. It can the Control device may be formed integrally with the engine controller or constitute a separate unit, optionally with the engine control

communicated. At least one condensate discharge area may be the EGR path before the compressor, an exhaust path after the turbine, the exhaust path after one

Catalytic converter and / or be located outside the EGR device environment. Thus, the condensate can be re-introduced into the fresh air path.

In this case, it is preferable to select the introduction in front of the compressor of the charging device, since there is a low pressure in this fresh air path region. Furthermore, it is also possible to introduce the condensate into the exhaust path. Thus, the condensate can be introduced after the turbine of the charger or after the exhaust gas catalyst in the exhaust path. Preferably, the introduction of the condensate in the exhaust path in the exhaust gas flow direction to the branch point of the EGR path to make, since in this case the introduced into the exhaust path condensate can not get into the EGR path and thus no concentration of the condensate in the

recirculated exhaust gas is possible. For discharging the condensate can

Condensate collection area via a Kondensatabführleitung with the

Kondensatabführbereich be fluidly connected. The Kondensatabführvorrichtung may be arranged in the exhaust gas flow direction in front of a throttle element for limiting the air supply to the internal combustion engine. Furthermore, the

Kondensatabführvorrichtung be arranged in the exhaust gas flow direction after a compressor of the charging device.

The arrangement of the Kondensatabführvorrichtung in the exhaust gas flow direction after a heat exchanger is advantageous. It may be formed integrally with the heat exchanger, the Kondensatabführvorrichtung. The heat exchanger may be an EGR cooler and / or a charge air cooler. Preferably, the Kondensatabführvorrichtung is arranged after the charge air cooler and in front of the throttle element. In this case, simply by controlling the throttle element in the area of the condensate discharge device, a high pressure can be generated, so that by controlling the

Throttle element, a pressure difference between the condensate collection area and the Kondensatabführbereich is generated. In this arrangement the

Kondensatabführvorrichtung with its closure element are also advantageous given the possibilities of Brennkraftmaschinenent throttling in a partial load range.

An inclination of the respective heat exchanger, in particular of the charge air cooler, is preferred, so that the condensate formed in the respective heat exchanger can flow quickly into the condensate discharge device. In the exhaust gas flow direction Before the Kondensatabführvorrichtung can also be arranged a water separator. This water separator can also be arranged in the exhaust gas flow direction after the respective heat exchanger. Preference is given to the use of a

Water separator together with an EGR cooler. By using the

Wasserabscheiders the condensate can be completely separated from the exhaust gas. It is also an integral design of the respective heat exchanger with a water separator conceivable.

An exhaust system equipped with such an EGR device is characterized by a significantly lower load on the components in the EGR path.

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

Subclaims, from the drawings and from the associated Fig. Description 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 exhaust system according to the invention, which has a low-pressure EGR, and with an introduction of the condensate in the exhaust path,

2 shows the internal combustion engine with the exhaust system, which has a low pressure EGR, and with an introduction of the condensate in the EGR path,

3 shows the internal combustion engine with the exhaust system, which has a low-pressure EGR and with a discharge of the condensate into the environment, 4 shows a heat exchanger with downstream in the exhaust gas flow direction condensate discharge device.

An internal combustion engine 1 shown in FIG. 1 is equipped with an exhaust path 2 and a fresh air path 3 and a charging device 4. By means of the exhaust gas flowing in the exhaust path 2, a turbine 5 of the charging device 4 is driven. By means of a compressor 6 of the charging device 4, the fluids flowing in the fresh air path 3 are compressed. Thus, the fresh air path 3 is divided into a low-pressure region 7 and a high-pressure region 8. In the fresh air flow direction 9, the low-pressure region 7 is arranged in front of the compressor 6 and the high-pressure region 8 downstream of the compressor 6. Also in the fresh air flow direction 9 are in the fresh air path 3 after Compressor 6 designed as a charge air cooler heat exchanger 10 and after the formed as intercooler heat exchanger 10, a throttle element 1 1, with the fresh air supply to the engine 1 can be limited arranged. Accordingly, there is a pressure ρ _Ί in the fresh air _path 3 in the low-pressure region 7 and a pressure in the high-pressure region 8 in front of the throttle _element 11 and a pressure p ₂ s _{downstream of the throttle element 11.} In operation of the internal combustion engine 1, the pressure is thus in most cases p ₂ greater than the pressure p ₂ s and also greater than the pressure p

In the exhaust path 2, a catalyst 12 may be arranged. Usually, in a low-pressure EGR 13 shown in FIG. 1 in the exhaust gas flow direction 14 after the catalyst 12 at a branch point 15, partial exhaust gas can be taken off and introduced into the fresh air path 3 via an EGR path 16 at an introduction point 17. In the case of the low-pressure EGR 13, the point of introduction 17 in the direction of fresh air flow 9 lies in front of the compressor 6, so that the recirculated exhaust gas is introduced into the low-pressure region 7 of the fresh air path 3. In addition, as shown in FIG. 1, or in the EGR path 16, an EGR valve 18 can be arranged at the branching point 15, with which the amount of recirculated exhaust gas can be controlled. Furthermore, in the EGR path 16 at least one heat exchanger 19, which is designed as an EGR cooler, may be arranged, with which the recirculated exhaust gas can be cooled.

After the formed as charge air cooler heat exchanger 10 can be arranged in the fresh air path 3 a Kondensatabführvorrichtung 20. The Kondensatabführvorrichtung 20 is equipped with a closure element 21 and has a Kondensatabführleitung 22. The closure element 21 can be used as a throttle element, as a valve or the like. be trained. By means of the closure element 21, the discharge of the condensate from a condensate collecting region 23 in a Kondensatabführbereich 24 can be controlled / regulated. In this case, the condensate collecting region 23 is connected to the condensate discharge region 24 in a fluid-conducting manner via the condensate discharge line 22. In the embodiment shown in FIG. 1, the condensate discharge region 24 is arranged in the exhaust gas path 2 in the exhaust gas flow direction 14 downstream of the catalytic converter 12 and downstream of the EGR valve 18 or downstream of the branching point 15. Thus, the condensate is introduced into the exhaust path 2 so that it can no longer get back into the EGR path 16 and thus no concentration of the condensate takes place in the EGR path 16.

In the embodiment shown in FIG. 2, the condensate formed is introduced via the Kondensatabführleitung 22 in a Kondensatabführbereich 24 '. In this case, the condensate discharge region 24 'lies in the fresh air flow direction 9 in front of the compressor 6.

According to FIG. 3, the condensate can also be released to the environment. As a result, the condensate discharge area 24 "is the environment, in which case the condensate must be discharged against the atmospheric pressure or against the normal pressure p ₀ , consequently, the pressure p ₂ must be greater than the ambient pressure P ₀ so that the pressure Condensate in the Kondensatabführbereich 24 "can be discharged. In this case it should be considered that the condensate should be diluted or neutralized due to its aggressiveness and corrosiveness.

A Kondensatabführvorrichtung 20 shown in Fig. 4 is arranged in the fresh air flow direction 9 after the heat exchanger 10. In this case, the heat exchanger 10 is preferably inclined so that any condensate formed in the heat exchanger 10 can run off in a simplified manner to the condensate discharge device 20. Accordingly, the Kondensatabführvorrichtung 20 is preferably located at the lowest point with respect to the fresh air path 3 and the heat exchanger 10. In this case, in addition to the condensate discharge line 22 and the closure element 21, the condensate discharge device 20 may have a condensate collecting region 23 ', which is designed in the manner of a collecting container, a pipe cavity, a pipe casing or the like. This simplifies the collection of the condensate in the condensate collecting region 23 ', and it is thereby advantageously possible to store the condensate in the condensate collecting region 23', so that Condensate at a favorable pressure difference between the condensate collection area 23 'and the Kondensatabführbereich 24 "can be dissipated.

Thus, an EGR device 25 may comprise as essential components the EGR path 16, at least one heat exchanger 19 designed as an EGR cooler, and at least one closure element 21. In this case, the closure element 21 as

Throttle be formed. As another essential component, the EGR device 25 has the condensate discharge device 20. These

Condensate removal device 25 may in turn have the condensate collection area 23 and the condensate discharge line 22.

Claims

claims

A method for removing condensate from an EGR path (EGR - exhaust gas recirculation) (16) of an internal combustion engine (1), in particular of a motor vehicle, wherein due to a pressure difference between a in the EGR path (16) arranged condensate collecting region (23) and a

Kondensatabführbereich (24,24 ', 24 ") condensate at least partially from the condensate collection area (23) in the Kondensatabführbereich (24,24', 24") is discharged when in the condensate collecting region (23) has a higher pressure than in the Kondensatabführbereich (24, 24 ', 24 ").

Method according to claim 1,

characterized in that

in a full load range and / or in a partial load range of the internal combustion engine (1) by such a short-term opening of a closure element (21), the fluid condensate collecting region (23) from the Kondensatabführbereich (24, 24 ', 24 ") separates the accumulated condensate is, so that the short-term pressure drop is negligible with respect to a boost pressure and / or with respect to a lambda control.

Method according to claim 2,

characterized in that

in a partial load range, the opening of the closure element (21) at the same time for the discharge of the accumulated condensate and for de-throttling the

Internal combustion engine (1) is performed.

EGR device (25), in particular an internal combustion engine (1) with a turbine (5) and a compressor (6) having charging device (4), with at least one condensate removal device (20) for removing condensate from an EGR path (16) of the EGR device (25), wherein the

A condensate discharge device (20) has a condensate collection region (23) arranged in the EGR path (16) and a closure element (21) arranged before or after a discharge opening, wherein the EGR device (25) is designed in such a way that due to a pressure difference between the Condensate collecting region (23) and a Kondensatabführbereich (24, 24 ', 24 ") upon opening of the closure element (21) accumulated condensate of the

Condensate collecting area (23) in the Kondensatabführbereich (24,24 ', 24 ") is discharged.

5. EGR device according to claim 4,

characterized in that

the EGR device (25) has a low pressure EGR (13) and / or a high pressure EGR.

6. EGR device according to one of claims 4 or 5,

characterized in that

a control device is provided which controls the opening and closing of the shutter member (21).

7. EGR device according to one of claims 4 to 6,

characterized in that

at least one Kondensatabführbereich (24,24 ', 24 ") is selected from the following group, the EGR path (16) before the compressor (6), an exhaust path (2) after the turbine (6), the exhaust path (2) after an exhaust gas catalyst (12), an outside of the EGR device (25) lying environment.

8. EGR device according to one of claims 4 to 7,

characterized in that

the condensate collecting region (23) is fluidically connected via a condensate discharge line (22) to the condensate discharge region (24, 24 ', 24 ").

9. EGR device according to one of claims 4 to 8,

characterized in that the Kondensatabführvorrichtung (20) in the exhaust gas flow direction (14) before or after a throttle element (11) for limiting the air supply to the internal combustion engine (1) is arranged.

10. EGR device according to one of claims 4 to 9,

characterized in that

the Kondensatabführvorrichtung (20) in the exhaust gas flow direction (14) after the compressor (6) is arranged.

11. EGR device according to one of claims 4 to 10,

characterized in that

the Kondensatabführvorrichtung (20) in the exhaust gas flow direction (14) after a heat exchanger (10,19) is positioned and / or formed integrally with the heat exchanger (10,19).

12. EGR device according to claim 11,

characterized in that

the heat exchanger (10, 19) is an EGR cooler (19) and / or a charge-air cooler (10).

13. EGR device according to one of claims 4 to 12,

characterized in that

in the exhaust gas flow direction (14) in front of the Kondensatabführvorrichtung (20), a water separator is arranged.

14. Exhaust system, in particular of a motor vehicle, with an EGR device (25) according to one of claims 4 to 13.