DE102011109221B4 - Exhaust gas recirculation system for an internal combustion engine - Google Patents

Abstract

Exhaust gas recirculation system for an internal combustion engine (1), which is equipped with an exhaust gas turbocharger (4) which has an exhaust gas turbine (5) in the exhaust line (3) and a compressor (6) in the intake tract (2), wherein the exhaust gas recirculation system has a return line (15) comprising an exhaust gas cooler (16) between the exhaust line (3) downstream of the exhaust gas turbine (5) and the intake tract (2) upstream of the compressor (6), wherein in the return line (15) a Wasserabscheideeinheit (17) is arranged, of the one Branched condensate line (19), which in the exhaust line (3) opens, characterized in that in the return line (15) downstream of the Wasserabscheideeinheit (17) an adjustable return valve (18) is arranged and that the exhaust gas cooler (16) bridging bypass line ( 22) is arranged, which is associated with an adjustable bypass valve (23), so that hot exhaust gas, bypassing the exhaust gas cooler (16) via the bypass line (22) of the Wasserabscheid eeinheit (17) can be supplied and together with steam via the condensate line (19) in the exhaust line (3) can be derived, wherein in the condensate line (19) a condensate collecting tank (20) is arranged, wherein in the condensate line (19) an adjustable drain valve ( 21), wherein the condensate line (19) opens downstream of an adjustable exhaust valve (12) in the exhaust line (3).

Description

Technical area

The invention relates to an exhaust gas recirculation system for an internal combustion engine according to the preamble of claim 1.

State of the art

From the EP 2 199 585 A1 an internal combustion engine with an exhaust gas turbocharger is known which comprises an exhaust gas turbine in the exhaust system and a compressor in the intake system. The exhaust gas turbine is driven by the pressurized exhaust gases of the internal combustion engine, wherein the rotational movement of the turbine is transmitted to the compressor, which then draws in combustion air and compressed to an increased boost pressure, under which the combustion air is supplied to the cylinders of the internal combustion engine.

To improve the exhaust behavior, the internal combustion engine is equipped with an exhaust gas recirculation system, which is arranged on the low pressure side of the exhaust gas turbocharger and having a return line which branches downstream of the exhaust gas turbine from the exhaust line and opens upstream of the compressor in the intake. In the return line, a cyclone separator is arranged, in which the water content, which is contained in the exhaust gas, is separated, wherein the resulting condensate is introduced back into the exhaust gas line.

From the DE 10 2006 023 589 A1 an exhaust gas recirculation system is known, wherein the recirculated exhaust gas before passing to a compressor passes through a particulate filter and a separator. In the separator, the particles still present in the exhaust gas are separated, so that almost particle-free exhaust gas of the internal combustion engine is supplied with the fresh air as combustion air.

In the DE 10 2008 005 400 A1 a heat exchanger valve device for controlling a fluid flow is described, wherein the valve housing has a heat exchanger output, via which a heat exchanger is supplied from the valve position dependent fluid flow. The valve housing has a second outlet through which, depending on the position of an actuator, a more or less large fluid flow is conducted past the heat exchanger.

The DE 10 2005 023 958 A1 discloses a turbocharger arrangement with exhaust gas recirculation, the arrangement having an exhaust gas cooler and a charge air cooler for cooling recirculated exhaust gas and / or charge air and a compressor for compressing the charge air, and at least one condensate and at least one thermal condensate discharge.

From the WO 01/07774 A1 For example, a diesel engine having an exhaust gas recirculation system is known, comprising a plurality of fuel injector cylinders for each of the cylinders and an intake manifold for distributing intake air to each of the cylinders. The exhaust gas is conducted via an exhaust pipe with a gas turbine into the environment. The gas turbine drives an intake compressor to compress the intake air.

The US 2009 / 0241515A1 FIG. 10 shows an exhaust gas recirculation system disposed between an exhaust system and an intake system including a water separator that separates water from the exhaust gas, wherein the water collected by the water separator is directed back to the exhaust system to a location downstream of the exhaust gas recirculation system.

Disclosure of the invention

The invention has for its object to improve with simple measures the Wasserabscheidegrad in an exhaust gas recirculation system, which is located on the low pressure side.

This object is achieved with the features of claim 1. The dependent claims indicate expedient developments.

The exhaust gas recirculation system according to the invention can be used for internal combustion engines - diesel engines or gasoline engines - which are equipped with an exhaust gas turbocharger comprising an exhaust gas turbine in the exhaust gas line and a compressor in the intake tract. The exhaust gas turbine is driven by the pressurized exhaust gases of the internal combustion engine, wherein the rotational movement of the exhaust gas turbine is transmitted via a shaft to the compressor, which then aspirates combustion air and compressed to an increased boost pressure, under which the combustion air is supplied to the cylinders of the internal combustion engine.

The exhaust gas recirculation system is located on the low pressure side of the exhaust gas turbocharger and comprises a return line, which branches downstream of the exhaust gas turbine from the exhaust line and opens upstream of the compressor in the intake. In the return line, a Wasserabscheideeinheit is arranged, branches from the condensate line, which opens into the exhaust system. Furthermore, in the return line upstream of the Wasserabscheideeinheit an exhaust gas cooler through which the recirculated exhaust gases before the introduction into the intake tract be brought to a lower temperature.

The exhaust gas cooler is bridged by a bypass line, which is assigned to an adjustable bypass valve. This embodiment makes it possible to bridge the exhaust gas cooler in certain operating situations via the bypass line, so that no cooling of the recirculated exhaust gas takes place and instead hot exhaust gas flows through the Wasserabscheideeinheit in which due to the higher temperature level of the exhaust gas, a greater proportion of the condensate transferred to the gaseous state is than is the case with cooled exhaust gas. This makes it possible to bring about specific situations in which the condensate or part of the condensate evaporates in the Wasserabscheideeinheit, the evaporated water is either passed through the condensate line in the exhaust system or discharged into the environment. If the condensate is not removed in liquid form via the condensate line, a complete or at least substantial emptying of the water separation unit is possible in this way. If appropriate, the condensate transferred into the gaseous state can also be conducted together with the exhaust gas into the intake tract.

With the embodiment of the exhaust gas recirculation system according to the invention, it is possible to purge the Wasserabscheideeinheit, optionally also a condensate collection, which is arranged in the condensate line by vaporized condensate and disposed of generally via the exhaust line. About the bypass line of the exhaust gas cooler can be bridged, so that a higher exhaust gas temperature is available for the flushing process and the evaporation rate is increased.

Regardless of the ability to vaporize condensate for purge purposes, the Wasserabscheideeinheit, which is arranged in the return line, the task of reducing the water content in the recirculated exhaust gas stream by deposition. In the Wasserabscheideeinheit takes place a separation of water from the exhaust gas, which is recycled from the exhaust line in the intake. The separated water can be passed through the condensate line in the exhaust system. Conveniently, located in the condensate line, a condensate collection container, in which the precipitated in the Wasserabscheideeinheit condensate is collected. From the condensate collecting the condensate can be passed into the exhaust system, for example, when a defined level in the condensate tank or at regular intervals.

In order to be able to control the discharge of the condensate into the exhaust gas line, an adjustable drain valve is expediently located in the condensate line. In the closed state of the drain valve, the condensate line is closed, so that no condensate can be diverted. A derivative is only possible in the open state of the drain valve.

Appropriately, the condensate line opens downstream of a filter device, which is arranged in the exhaust line, for example, a diesel particulate filter, in the exhaust line. The return line branches advantageously downstream of the filter device, but upstream of the confluence of the condensate line in the exhaust line. This embodiment has the advantage that particles possibly dissolved by the filter device, for example ceramic particles, pass via the return line into the water separation unit in which the particles are deposited, the particles being able to return to the exhaust line via the condensate line and being able to be discharged into the environment , Introduction of the particles into the intake tract and possible damage to the compressor wheel blades by the particles is avoided.

According to another expedient embodiment, the condensate line opens downstream of an adjustable exhaust valve in the exhaust system. The exhaust valve is located in the exhaust system and allows by adjusting in the closed position, an increase in the exhaust backpressure, so that a higher pressure gradient between the exhaust system and the intake system is available, which supports the introduction of exhaust gas in the return line. Together with a return valve, which is arranged in the return line and is advantageously arranged downstream of the Wasserabscheideeinheit, thus several valves for controlling the exhaust gas recirculation and the deposition and the rinsing process are available.

In the exhaust gas recirculation mode, both the bypass valve and the discharge valve in the condensate line are expediently set in the closed position, so that the exhaust gas is guided via the exhaust gas cooler into the return line and the condensate discharge into the exhaust gas line is prevented. In this operating state, the water separation takes place in the Wasserabscheideeinheit, the condensate can then be collected in the condensate collection tank, which is arranged in the condensate line. The return valve in the return line is in the open position to allow the introduction of the exhaust gas into the intake tract. The exhaust valve, which is located in the exhaust line downstream of the branch of the return line, can optionally in the closed position or in a partial closing position be adjusted to increase the exhaust back pressure and thereby improve the return rate.

If exhaust gas recirculation is not carried out via the return line on the low-pressure side, the collected condensate can be discharged. In this phase of operation, the return valve is conveniently closed downstream of the Wasserabscheideeinheit and opened the drain valve in the condensate line, so that condensate can flow from the condensate collection in the exhaust system. The exhaust valve, which is located in the exhaust line downstream of the branch of the return line, can optionally be adjusted to increase the exhaust back pressure in a closing or partial closing position. The bypass valve in the bypass line, which bridges the exhaust gas cooler, can optionally be adjusted to the open position, so that the exhaust gas cooler is at least largely bypassed. Depending on the position of the exhaust valve in the exhaust line and the bypass valve in the bypass line, a rinsing process for rinsing the Wasserabscheideeinheit or the condensate collection container can be influenced. For purging, the return valve downstream of the Wasserabscheideeinheit is also in the closed position, the drain valve in the condensate line is open. By bypassing the exhaust gas cooler, a higher thermal level in the recirculated exhaust gas can be set, whereby the evaporation rate is increased and the flushing process is improved.

Brief description of the drawings

Further advantages and expedient embodiments can be taken from the further claims, the description of the figures and the drawing, in which a supercharged internal combustion engine with a low-pressure exhaust gas recirculation system is shown schematically.

Embodiment (s) of the invention

The internal combustion engine shown in the figure 1 is via an intake system 2 Combustion air supplied, the exhaust gases of the internal combustion engine are via an exhaust line 3 derived. The internal combustion engine is equipped with an exhaust gas turbocharger 4 provided, an exhaust gas turbine 5 in the exhaust system 3 and a compressor 6 in the intake tract 2 having. The exhaust gas turbine 5 is driven by the pressurized exhaust gases of the internal combustion engine. The exhaust gas turbine 5 is about a wave 7 with the compressor 6 coupled and drives this, whereupon the compressor 6 Ambient air sucks and compressed to an increased boost pressure, under which the combustion air is supplied to the cylinders of the internal combustion engine.

The intake combustion air is in the intake system 2 first in an engine air filter 8th cleaned. Downstream of the air filter 8th there is an air mass meter 9 for measuring the airflow. On the air mass meter 9 follows in the intake tract 2 the compressor 6 which has a throttle 10 downstream, over which the air flow can be regulated.

In the exhaust system 3 is located downstream of the exhaust gas turbine 5 a filter device 11 , In particular, a particulate filter, and in the course of an adjustable exhaust valve 12 ,

The internal combustion engine is on the high pressure side of the exhaust gas turbocharger 4 provided with a first exhaust gas recirculation system, which is a return line 13 and an exhaust gas cooler 14 includes. The return line 13 branches upstream of the exhaust gas turbine 5 from the exhaust system 3 and opens downstream of the throttle 10 in the intake tract 2 ,

On the low pressure side of the turbocharger 4 the internal combustion engine is equipped with a further exhaust gas recirculation system, which is a return line 15 which is downstream of the particulate filter 11 from the exhaust system 3 branches and between the air mass meter 9 and the compressor 6 in the intake tract 2 opens. In the return line 15 There is an exhaust gas cooler 16 , a water separation unit 17 and an adjustable return valve 18 for regulating the recirculated exhaust gas mass flow. The water separation unit 17 is via a condensate line 19 in which is a condensate collector 20 and a condensate collector 20 downstream drain valve 21 located, with the intake tract 3 connected; the condensate line 19 opens downstream of the adjustable exhaust valve 12 in the intake tract. Furthermore, the exhaust gas recirculation system is on the low pressure side of the exhaust gas turbocharger 4 with a bypass line 22 with a bypass valve arranged therein 23 Mistake. The bypass line 22 bridges the exhaust gas cooler 16 in the return line 15 , the bypass line 22 Branches downstream of the particulate filter 11 and upstream of the return line 15 from the exhaust system 3 and flows downstream of the exhaust gas cooler 16 in the return line 15 ,

To perform the exhaust gas recirculation on the low pressure side, the return valve 18 open, at the same time can the exhaust valve 12 in the exhaust system 3 closed or partially closed to the exhaust back pressure and thus the pressure gradient between the exhaust line 3 and intake system 2 increase and improve exhaust gas recirculation. The in the return line 15 introduced exhaust gas flows through the Wasserabscheideeinheit 17 in which a water separation takes place. The separated condensate flows over the condensate line 19 in the condensate collector 20 and can be collected there. If necessary or at regular intervals, the drain valve 21 in the condensate line 19 open, allowing the condensate from the condensate collector 20 in the exhaust system 3 downstream of the exhaust valve 12 is initiated.

To the water separation unit 17 and the condensate collector 20 to flush, is expediently the return valve 18 closed, so that the exhaust gas recirculation is prevented in the intake. The exhaust gas flows through the Wasserabscheideeinheit 17 as well as via the condensate line 19 through the condensate collector 20 , in which operation the drain valve 21 is advantageously opened. Due to the high temperature of the exhaust gas remaining water evaporates in the Wasserabscheideeinheit 17 and the condensate collector 20 at least partially. Also in this mode, it is advantageous that the exhaust valve 12 in the exhaust system 3 to increase the exhaust back pressure in the closed position or in a partial closing position.

For rinsing the Wasserabscheideeinheit 17 and the condensate collection tank 20 Although it is basically sufficient that the exhaust gas through the exhaust gas cooler 16 is directed. However, in order to improve the degree of flushing, it is expedient that the exhaust gas, bypassing the exhaust gas cooler 16 over the bypass line 22 is performed in the for this purpose the bypass valve 23 is set in the open position. In this way, the hot exhaust gas from the exhaust system 3 bypassing the exhaust gas cooler 16 directly to Wasserabscheideeinheit 17 as well as to the condensate collector 20 passed, wherein due to the higher temperature of the exhaust gas, an improved scavenging effect is achieved.

Claims (5)

Exhaust gas recirculation system for an internal combustion engine ( 1 ), with an exhaust gas turbocharger ( 4 ), which has an exhaust gas turbine ( 5 ) in the exhaust line ( 3 ) and a compressor ( 6 ) in the intake tract ( 2 ), wherein the exhaust gas recirculation system is a return line ( 15 ) with an exhaust gas cooler ( 16 ) between the exhaust gas line ( 3 ) downstream of the exhaust gas turbine ( 5 ) and the intake tract ( 2 ) upstream of the compressor ( 6 ), wherein in the return line ( 15 ) a water separation unit ( 17 ) is arranged, from which a condensate line ( 19 Branched, which in the exhaust system ( 3 ), characterized in that in the return line ( 15 ) downstream of the water separation unit ( 17 ) an adjustable return valve ( 18 ) and that the exhaust gas cooler ( 16 ) bridging bypass line ( 22 ), which has an adjustable bypass valve ( 23 ), so that hot exhaust gas bypassing the exhaust gas cooler ( 16 ) via the bypass line ( 22 ) of the water separation unit ( 17 ) and together with steam via the condensate line ( 19 ) in the exhaust line ( 3 ) is derivable, wherein in the condensate line ( 19 ) a condensate collector ( 20 ) is arranged, wherein in the condensate line ( 19 ) an adjustable drain valve ( 21 ), wherein the condensate line ( 19 ) downstream of an adjustable exhaust valve ( 12 ) in the exhaust line ( 3 ) opens. Exhaust gas recirculation system according to claim 1, characterized in that the condensate line ( 19 ) downstream of a filter device ( 11 ) in the exhaust line ( 3 ) opens. Exhaust gas recirculation system according to claim 1, characterized in that the return line ( 15 ) upstream of the exhaust valve ( 12 ) from the exhaust line ( 3 ) branches. Internal combustion engine with an exhaust gas recirculation system according to one of claims 1 to 3. Method for operating an exhaust gas recirculation system according to one of claims 1 to 3, wherein exhaust gas via the bypass line ( 22 ) of the water separation unit ( 17 ) and condensate through the condensate line ( 19 ) in the exhaust line ( 3 ) is conducted in operating phases in which no exhaust gas via the return line ( 15 ) in the intake tract ( 2 ).

Images