DE102018205873B3 - Exhaust manifold with air gap insulation - Google Patents

Abstract

An arrangement is provided of at least one exhaust pipe of an internal combustion engine with an exhaust manifold, wherein the exhaust pipe and the exhaust manifold are at least partially thermally insulated from the environment by means of an air splitter, wherein the volume of the air splitter connected to a pipe, circulates through the air of the air splitter can be. A method for regulating the exhaust gas temperature is further provided.

Description

The invention relates to an arrangement of at least one exhaust pipe of an internal combustion engine and an exhaust manifold, which are isolated by an air gap device to the outside, and a method for regulating the exhaust gas temperature.

For removing pollutants from the exhaust gas of internal combustion engines exhaust aftertreatment devices are conventionally arranged in the exhaust tract. Exhaust aftertreatment devices include, for example, oxidation catalysts, lean NOx trap (LNT) and selective catalytic reduction (SCR) catalysts. These catalysts each function effectively in a given temperature window, i. that below and above certain temperatures, the function of the catalysts is limited. In order to comply with the strict regulations according to the EU6.2 and EU7 emission standards, it is necessary to ensure a timely function of the exhaust aftertreatment devices after starting an internal combustion engine, and to maintain them even at low exhaust gas temperatures during low loads of the internal combustion engine. To limit temperature losses of the exhaust gas, e.g. an air gap insulation arranged around the exhaust tract in the region of the exhaust manifold. Air gap insulation means an enclosure of the corresponding piping contained in the air.

In the publication DE 10 2005 062 186 A1 discloses an air gap insulation of an exhaust manifold, which is supplied via a branch from the intake with cooled charge air. In the publication WO 2013/167281 A1 discloses an exhaust manifold cooling device connected to a cooling device. Exhaust heat may also be present at the exhaust manifold for the desired heating of air ( DE 10 2015 110 834 A1 ) or an evaporation agent ( DE 11 2011 102 951 T5 ) be used. Air gap insulations are also known for downstream of an exhaust manifold regions of the exhaust tract ( DE 101 39 424 A1 ).

However, said air gap insulation may result in e.g. Exhaust gas with correspondingly high temperatures reaches the exhaust aftertreatment devices at high loads, since no or too little heat of the exhaust gas can be discharged via the piping of exhaust pipes connecting the internal combustion engine and the exhaust manifold to the surroundings of the exhaust gas tract. Excessively high temperatures of the exhaust gas exceed the functional temperature of the exhaust aftertreatment devices and are also unfavorable for the operation of a turbine of an exhaust gas turbocharger arranged downstream of the exhaust manifold, which leads to energy losses, since the exhaust gas then has to be conducted around the turbine.

It is the object to improve the state of the art for controlling the exhaust gas temperatures.

This object is achieved with an arrangement having the features of claim 1, a motor vehicle having the features of claim 5 and by a method having the features of claim 6. Further advantageous embodiments and embodiments of the invention will become apparent from the dependent claims and claims, the figures and the embodiments. The embodiments of the invention can be combined with each other in an advantageous manner.

A first aspect of the invention relates to an arrangement of an internal combustion engine having at least one exhaust line associated with a cylinder, which merges into an exhaust tract in the region of an exhaust manifold, wherein the exhaust pipe and the exhaust manifold are insulated by an air gap device which at least partially the exhaust pipe and the exhaust manifold and at least one inner shell, which is disposed immediately around the exhaust pipe and the exhaust manifold, and at least one outer shell, which forms the outer boundary of the air-splitting device and includes a volume of the air-splitting device, and wherein the air-splitting device at least one outside the outer Shell extending first pipe, with which the volume has at least a second fluid connection.

The arrangement according to the invention advantageously not only allows thermal insulation of the exhaust manifold, whereby the heat of the exhaust gas in phases of low load for the function of the exhaust aftertreatment devices can be maintained and could not be lost through the walls of the exhaust pipes and the exhaust manifold, but also a discharge of exhaust heat when the temperature of the exhaust gas in unfavorably high levels in phases of high load, which limits the function of a arranged in the exhaust tract turbine of an exhaust gas turbocharger and the exhaust aftertreatment devices.

A first fluidic connection has a control valve that can be opened as required for the flow of air from the volume into the pipeline. The control valve advantageously allows the movement of a volume of gas adapted to the current temperature of the air to flow into the pipeline.

Air from the pipeline can flow back into the volume of the air-splitting device via the second fluid connection. In this way, a flow circuit of the air is ensured in the air-splitting device.

Preferably, the pipeline has at least one check valve. In this way, the flow of the gas is ensured in one direction. In this case, a check valve is preferably arranged in the region of the second fluid connection.

In the pipeline at least one compressor is arranged. The compressor is mainly used for easy compression of the gas. The compressor also has a pump function to direct a flow of the gas in one direction.

At least one cooling device is arranged in the pipeline. By means of the cooling device, the air flowing through is cooled when the temperature of the air in the volume becomes unfavorably high. In this case, the cooling device allows a particularly advantageous rapid cooling in operating phases in which unfavorably hot exhaust gas is passed through the exhaust pipes in rapid change. The first pipeline is bifurcated downstream of the cooling device into a first sub-pipeline and a second sub-pipeline. In this case, the first part of the pipeline at the second fluid connection and the second part of the pipeline lead back into the volume at a third fluid connection.

Preferably, the cooling device is connected to a separate coolant circuit. In this way, removal of heat can be ensured independently of other coolant circuits of a corresponding vehicle.

Alternatively or in addition to the separate circuit, the cooling device is preferably connected to a coolant circuit of the internal combustion engine. The coolant circuit can be used because the temperature differences between the phase-wise hot gas in the air-gap device and the coolant of the coolant circuit of the internal combustion engine is high enough.

A second aspect of the invention relates to a motor vehicle having an arrangement according to the invention.

• - Betreiben der Brennkraftmaschine,
• - Ermitteln der Abgastemperatur,
• - Öffnen des Steuerventils, wenn die Temperatur der Luft in der Luftspalteinrichtung einen bestimmten Schwellenwert erreicht hat,
• - Zirkulieren eines fluiden Kühlmittels in der Kühlvorrichtung, so dass Wärme der Luftspaltluft auf das Kühlmittel übertragen werden kann,
• - Schließen des Steuerventils, wenn die Abgastemperatur wieder unter den besagten Schwellenwert fällt.

A third aspect of the invention relates to a method for controlling an exhaust gas temperature using an arrangement according to the invention, comprising the steps of:

• Operating the internal combustion engine,
• Determining the exhaust gas temperature,
• Opening the control valve when the temperature of the air in the air-splitting device has reached a certain threshold,
• Circulating a fluid coolant in the cooling device so that heat of the air gap air can be transferred to the coolant,
• - closing the control valve when the exhaust gas temperature falls below the said threshold again.

The advantages of the method correspond to the advantages of the arrangement according to the invention.

In an alternative embodiment or in addition to the embodiment of the method described above, the opening and closing of the control valve is regulated in dependence on an operating mode of the internal combustion engine. In this case, the control valve is opened at a high load of the internal combustion engine and closed at a low load. Since high exhaust gas temperatures can not be ruled out even at low loads and short-term phases of a high load possibly do not cause an unfavorable exceeding of the exhaust gas temperatures, the exhaust gas temperatures are advantageously controlled continuously.

Preferably, in the method, the compressor disposed in the pipeline is turned on at the same time as the opening of the control valve.

The provision of electrical energy for the operation of control valves, compressor and cooler advantageously causes only a small additional fuel consumption, since the required amount of energy is marginally low, because the phases of high exhaust gas temperature, especially of high load phases, are comparatively short.

• 1 eine schematische Querschnittsdarstellung einer Ausführungsform der erfindungsgemäßen Anordnung.
• 2 eine Darstellung einer Anordnung von Abgasleitungen.
• 3 ein Flussdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to FIGS. Show it:

• 1 a schematic cross-sectional view of an embodiment of the inventive arrangement.
• 2 a representation of an arrangement of exhaust pipes.
• 3 a flowchart of an embodiment of the method according to the invention.

In 1 is an embodiment of the arrangement according to the invention 1 shown. It puts 1 detailed the in 2 shown section through four exhaust pipes 2 from the corresponding cylinders of an internal combustion engine (not shown) into an exhaust manifold 3 pass. The flues 2 are by means of a flange 4 connected to the internal combustion engine. The exhaust pipes 2 , are in the area upstream of the exhaust manifold 3 shown cut.

An air-splitting device 10 has an inner shell 11 on, directly on the exhaust pipes 2 and the exhaust manifold 3 is applied by means of sliding joints known in the art to a thermally induced expansion of the material of the exhaust pipes 2 and the exhaust manifold 3 at high temperatures. Furthermore, the air-splitting device 10 an outer shell 12 on which the air-splitting device 10 delimited to the outside. Between the inner 11 and outer shell 12 there is an air gap volume 13 , The outer shell 12 is so far from the inner shell 11 spaced, that is a thickness of the air gap volume 13 results, which is sufficient for efficient thermal insulation. The distance between inner 11 and outer shell 12 can be eg 1 cm, 2 cm or 3 cm. The shape of the air-splitting device 10 is according to the juxtaposed exhaust pipes 2 cuboid, with in 1 to see two long and two short sides.

The inner shell 11 and the outer shell 12 may be of the same, similar or different material. The sheaths are made of a material that is stable and temperature resistant, for example, of a metal or a metal alloy, especially of a steel. The covers 11 . 12 can also consist of several superimposed sheets.

The inner one 11 and the outer shell 12 in the illustrated embodiment of 1 different material thicknesses. In this case, the outer shell 12 a thickness of 2 mm, and the inner shell 11 a thickness of 1.2 mm. Alternatively, the inner shell 11 and the outer shell 12 also have the same thicknesses.

In the middle area of the lower long side of the air splitter 10 there is a first fluid connection 14 between the volume 13 and a first pipeline 15 , In the first fluid connection 14 is a control valve 16 arranged. Downstream of the control valve 16 is a compressor 17 in the pipeline 15 arranged. Downstream of the compressor 17 is a cooling device 18 in the first pipeline 15 arranged. The compressor 17 Alternatively, it may also be downstream of the cooling device 18 be arranged.

The cooling device 18 is connected to a coolant circuit, not shown, on the heat of the by the cooling device 18 directed air from the air splitter 10 can be dissipated. The coolant circuit can be a separate, only for the cooling device 18 be provided coolant circuit. However, the coolant circuit may also be the coolant circuit used for the cooling of the internal combustion engine or a coolant circuit of the corresponding motor vehicle used for the cooling of another device.

From the cooler 18 run a first part pipeline 151 and a second sub-pipeline 152 to the volume 13 back. The partial pipeline 151 is via a second fluid compound 21 and the sub-pipeline 152 via a third fluid connection 22 with the volume 13 connected. Alternatively, only the pipeline 15 from the cooler 18 to the volume 13 lead, which are then connected via a corresponding fluid connection.

Through the arrows, the flow direction of the air in the sub-pipes 151 . 152 indexed.

In the field of fluid compounds 21 . 22 is each a check valve 23 arranged. The check valves 23 move with the flow of compressed gas and prevent backflow.

In a method of regulating the exhaust gas temperature by means of the air splitter 10 is determined according to the in 3 illustrated embodiment in a first step S1 the internal combustion engine is operated so that exhaust gas is produced. In a second step S2 the exhaust gas temperature is determined. This can be done by means of a temperature sensor in the exhaust system and alternatively or additionally model-based. As long as the temperature is below a certain threshold, the operation of the internal combustion engine runs with the control valve closed 16 continue.

If the exhaust gas temperature reaches and / or exceeds the said threshold value, the control valve will be reached 16 in a third step S3 open. At the same time the compressor 18 switched on. In a fourth step S4 gets in the cooler 18 a coolant circulates, so that heat of the air in the air splitter 10 can be transferred to the coolant. When the temperature of the exhaust gas falls below the threshold again, in a fifth step S5 the control valve 16 closed again.

Opening and closing the control valve 16 can alternatively or additionally be regulated depending on the operating mode of the internal combustion engine. Since high exhaust gas temperatures occur regularly at a high load of the internal combustion engine, the control valve 16 also be opened immediately when a high load is applied. When a low load is applied, the control valve remains 16 closed or it is closed again after a phase of high load.

LIST OF REFERENCE NUMBERS

1

arrangement

2

exhaust pipe

3

exhaust manifold

4

flange

10

Air splitter

11

inner shell

12

outer shell

13

Air gap volume

14

first fluid compound

15

first pipeline

151

first part pipeline

152

second part pipeline

16

control valve

17

compressor

18

cooler

21

second fluid compound

22

third fluid compound

23

check valve

Claims (8)

Arrangement (1) of an internal combustion engine having at least one exhaust pipe (2) associated with a cylinder, which merges into an exhaust tract in the region of an exhaust manifold (3), the exhaust pipe (2) and the exhaust manifold (3) being directed outwards by an air-splitting device (10) are isolated, which at least partially surrounds the exhaust pipe (2) and the exhaust manifold (3) and at least one inner shell (11), which is arranged immediately around the exhaust pipe (2) and the exhaust manifold (3), and at least one outer shell (12), which forms the outer boundary of the air-splitting device (10) and encloses a volume (13) of the air-splitting device (10), a first fluid connection (14) having a control valve (16), as required, for the flow of air the volume (13) can be opened out, and wherein the air-splitting device (10) has at least one outside the outer shell (12) extending first pipe (15), with which the volume (13) at least one second fluid connection (21), in the pipeline (15) at least one compressor (17) and at least one cooling device (18) is arranged, characterized in that the first pipe (15) downstream of the cooling device (18) in a first sub-pipe (151) and a second sub-pipe (152) are bifurcated, and the first sub-pipe (151) at the second fluid joint (21) and the second sub-pipe (152) at a third fluid joint (22) into the volume (13 ). Arrangement (1) according to Claim 1 in which the pipeline (15) has at least one check valve. Arrangement (1) according to Claim 1 wherein the cooling device (18) is connected to a separate coolant circuit. Arrangement (1) according to Claim 1 or 3 wherein the cooling device (18) is connected to a coolant circuit of the internal combustion engine. Motor vehicle with an arrangement according to one of Claims 1 - 4 , A method of controlling an exhaust gas temperature using an assembly (1) according to any one of Claims 1 - 4 , comprising the steps of: - operating the internal combustion engine, - determining the exhaust gas temperature, - opening the control valve (16) when the temperature of the air in the volume (13) of the air splitter (10) has reached a certain threshold, - circulating a fluid coolant in the cooling device (18), so that heat of the air gap air can be transferred to the coolant, - closing the control valve (16) when the exhaust gas temperature falls below said threshold again. Method according to Claim 6 wherein the opening and closing of the control valve (16) is controlled in response to an operating mode of the internal combustion engine. Method according to Claim 6 or 7 in which the compressor (17) arranged in the pipeline (15) is switched on at the same time as the opening of the control valve (16).

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