DE10357950A1 - Combustion engine exhaust gas system, e.g. for a turbo diesel motor vehicle, has pulsation damping element in the exhaust gas line and or the exhaust gas recirculation line - Google Patents

Abstract

Combustion engine exhaust gas system has at least a pulsation damping element (11) in the exhaust gas line (5) between the combustion engine (1) and the turbine (9) in the flow direction prior to the coupling element (6) and or in the exhaust gas return line (7).

Description

object The present invention is an exhaust system with exhaust gas recirculation and a pulsation damper, in particular an exhaust system of an automobile.

A Variety of automobiles has exhaust systems that include an exhaust gas turbocharger and / or exhaust gas recirculation. An exhaust gas turbocharger uses the thermal energy of the exhaust gas for compression the air or the gas that enters the internal combustion engine of the automobile becomes. In particular, diesel engines have exhaust gas turbochargers and exhaust gas recirculation prevailed. As a rule, at least part of the exhaust gas downstream of the Exhaust gas turbocharger recirculated and with the fresh gas, in particular air, mixed in the gas inlet the internal combustion engine. Such a system is for example known from WO 00/34630 A1.

by virtue of the use of the thermal energy of the exhaust gas through the exhaust gas turbocharger However, the pressure and / or the temperature below which the exhaust gas in the return line is present, much lower than the pressure and / or the temperature the exhaust gas of the internal combustion engine in front of the turbocharger. For certain use cases is however in particular an elevated one Pressure of the exhaust gas in the return necessary and / or advantageous, for example, in the operation of HCCI engines (Homogeneous Charge Compression Ignition), which contributes a very high proportion of exhaust gas the filling the cylinder need. However, the return line before, that is, upstream the exhaust gas turbocharger), it comes due to the pulsatility of the exhaust gas in that, when exhaust gas is recycled, also the recirculated exhaust gas Pulsatil present. This can be short-term Situations arise in which recirculated exhaust gas in the internal combustion engine needed is, but due to the pulsatility of the recirculated exhaust gas flow no exhaust gas flows. This Complicates the control of the exhaust gas recirculation and the engine management considerably and optionally prevents the operation of an internal combustion engine in HCCI mode.

Of these, Based on the object of the present invention, an exhaust system to propose, in which overcome these known from the prior art disadvantages become.

These Task is solved by an exhaust system with the features of claim 1. Advantageous Further developments are the subject of the dependent claims.

The Inventive exhaust system an internal combustion engine is especially for an automobile suitable. The internal combustion engine comprises at least one Gas inlet and at least one gas outlet. The exhaust system according to the invention includes at least one substantially in a flow direction flow-through Exhaust pipe for the discharge the exhaust gases of the internal combustion engine with the at least one Gas outlet is connected to a turbine, at least partially is formed in the exhaust pipe, at least one Pulsationsdämpfungselement for temporal and / or local Equalization of a Exhaust gas flow, at least one return line for the return of the Exhaust gases of the internal combustion engine from the gas outlet to the gas inlet, the return line connectable between the gas outlet and turbine with the exhaust pipe is. This is preferably done via Coupling means such that between 0 and 100%, of the exhaust gas through the return line guided become. The exhaust system according to the invention is characterized in that the at least one Pulsationsdämpfungselement in the exhaust pipe between the internal combustion engine and the turbine in the flow direction is formed before the coupling means and / or in the return line.

The Pulsationsdämpfungselement causes a temporal and / or spatial equalization of Exhaust gas flow. This means, for example, that while staying the same Return conditions, in particular constant mean return volume on exhaust gas, this with temporal homogenization substantially continuously, especially under relatively small pressure fluctuations the gas inlet supplied becomes. A spatial Equalization means in particular, that in the exhaust gas flow is substantially uniformly shaped isobars and / or regions of equal flow velocity form, for example, a laminar, quasi-laminar or plug flow profile ("plug flow").

The formation of the Pulsationsdämpfungselements in the exhaust pipe between the gas outlet and turbine upstream of the coupling means causes in particular in the return line downstream of Pulsationsdämpfüngselements an exhaust gas flow, the pulsatility is significantly lower than upstream of the Pulsationsdämpfungselements when the exhaust gas is at least partially recycled, so that the recirculated exhaust gas can be dosed and regulated in a simple manner. As a coupling means, any active or passive component may be formed, which allows a coupling of the exhaust pipe to the return line, in particular a multi-way valve or a simple derivation of the return line with optionally further control means such as a throttle valve or the like.

The Formation of Pulsationsdämpfungselements in the return line leads in Advantageously, that at the gas inlet of the internal combustion engine one temporally and / or spatially uniform recirculated exhaust gas flow is present. This simplifies the design and control of exhaust gas recirculation in particular in terms of the volume returned and / or the amount returned the exhaust gas compared to a return line without Pulsationsdämpfungselement. Compared to an exhaust gas recirculation, the after the turbine branches, the recirculated exhaust gas has a much higher temperature and / or a higher pressure on, which is especially the cold start of the internal combustion engine is beneficial.

Especially Is it possible and according to the invention, several Pulsation damping elements, in particular one between gas outlet and turbine and one in the return line, train. Equalization can a partial or a substantially complete homogenization in temporal and / or spatial Meaning.

When Pulsationsdämpfungselement each component can be used, which contributes to the required homogenization of the Exhaust gas flow leads. For example Is it possible and according to the invention, the pulsation damping element form in the form of a plurality of blades, each in extend the cross-section of a pipe, which from the exhaust gas flows through becomes. Here, the blades are in the flow direction one behind the other formed offset that a direct flow, ie without hitting at least one shovel is not possible. The blades serve in particular as baffle plates and lead to a deflection at least a part of the exhaust gas and thus to a temporal and / or spatial Homogenization of the exhaust gas flow.

According to one advantageous embodiment of the exhaust system according to the invention comprises the Pulsationsdämpfungselement a honeycomb body.

Let honeycomb body in a particularly advantageous manner as or as part of pulsation damping elements (s) deploy. honeycombs regularly have a variety of cavities, especially channels on, which preferably from an end face of the honeycomb body to other end face of the honeycomb body extend. Such cavities lead, for example for the formation of laminar or quasi-laminar flow profiles in the individual cavities and generally both temporal and spatial Equalization of the flow of Exhaust gas, as the flow through the cavities the flow velocity from parts of the flow lowers and parts of the flow elevated. In particular, it may also be advantageous, the honeycomb body so adapt that a particularly good homogenization of the flow takes place, for example, by the fact that over the cross section of the honeycomb body considered inhomogeneous cell densities are formed. Under the Cell density is understood to mean the number of cavities, in particular channels, per Cross sectional area. The cell density is generally referred to as cpsi (cells per square inch, Cells per square inch). In particular, cavities can also be used over the length of the honeycomb body changing Cross-sectional areas be formed, according to the diffuser or Konfusorprinzip for a slowdown or acceleration of the respective component. Again, it is in advantageously possible, the formation of the individual diffuser or Confusor channels to the usual flow conditions the exhaust gas before the Pulsationsdämpfungselement adapt.

Another advantage of a honeycomb body as Pulsationsdämpfungselementes is in particular that they are available in a wide variety, so that thereby a low-cost Pulsationsdämpfungselement can be provided. In addition, honeycomb bodies are often used for one or more functions in the exhaust system, for example as catalyst support body, particulate filter and / or adsorber structure for at least one component of the exhaust gas. As a catalyst carrier body serving honeycomb body usually have a coating, in particular a ceramic coating such as a washcoat containing catalyst particles, such as noble metal particles, in particular from the platinum group. These catalysts catalyze an implementation of at least portions of the exhaust gas, which reduces the proportion of components in the exhaust gas which are detrimental to man and / or the environment. In a particulate trap, solid components of the exhaust gas, such as soot, which often occurs especially in diesel engines, are filtered out. Such particle filters can be designed as closed or open particle filters. An adsorber structure is understood as meaning a structure which, for example, adsorbs at least one component of the exhaust gas, for example nitrogen oxides (NO _x ), at low operating temperatures and releases them again, for example at higher operating temperatures. Such adsorber structures may consist of honeycomb bodies, which are provided with a corresponding coating.

According to one further advantageous embodiment of the exhaust system according to the invention there is a temporal equalization of the pressure.

By a temporal equalization of the pressure lies despite the pulsatility the exhaust gas always a certain pressure for the return of exhaust gas in the gas inlet the internal combustion engine before, so that virtually at any time a return of the Exhaust gas can take place. This also simplifies the engine control.

According to one further advantageous embodiment of the exhaust system according to the invention is the relationship the full width at half height (FWHM, full width half maximum) of the time course of a pressure pulse after the pulsation damping element to the full width at half height (FWHM) of the time course a pressure pulse before the Pulsationsdämpfungselement greater than one.

A Formation of the pulsation damping element, which achieves this, allows advantageously a good homogenization of the flow.

Especially It is advantageous in this context that the ratio of full width at half height (FWHM, full width half maximum) of the time course of a pressure pulse after the pulsation damping element to the full width at half height (FWHM) of the time course a pressure pulse before the pulsation damping element at least 1.5, preferably at least 2, more preferably at least 3.

ever After embodiment of the Pulsationsdämpungselement it comes in Advantageously, that two consecutive pressure pulses "run into each other", so practically there is a certain amount of pressure for repatriation at any given time.

According to one further advantageous embodiment of the exhaust system according to the invention is a spatial Equalization of Flow rate.

This allows a spatially much easier to control exhaust gas recirculation, leading to particularly uniform results in the internal combustion engine, for example, in HCCI operation leads.

According to one further advantageous embodiment of the exhaust system according to the invention is the relationship full width at half height (FWHM) the frequency distribution the flow rates after the pulsation damping element to the full width at half height (FWHM) of the frequency distribution the flow rates before the pulsation damping element less than one.

The frequency distribution the flow rates or the probability of flow velocities (propagators) are calculated by a corresponding integration of the spatially resolved speeds and optionally a corresponding normalization, for example a standardization to such an extent, that the integral over the total distribution is one.

Especially it is preferred in this context that the ratio of full width at half height (FWHM) of the frequency distribution of flow rates after the pulsation damping element to the full width at half height (FWHM) of the frequency distribution the flow rates before the pulsation damping element less than one-half, preferably less than one third, especially preferably less than a quarter.

A Formation of the pulsation damping element, that fulfills this, allows advantageously a good spatial homogenization of the flow.

According to one Further advantageous embodiment of the honeycomb body is made ceramic material and / or metal formed.

The formation of the honeycomb body of ceramic and / or metallic material offers advantages depending on the application. On the one hand, the formation of the honeycomb body made of ceramic is inexpensive, but the design possibilities of the cavities are regularly limited. In metallic honeycomb bodies, in particular in metallic honeycomb bodies which are formed by winding or twisting one or more metallic layers such as sheet metal layers, it is possible in a simple manner, in particular by manipulation of the metallic layers used, structures for influencing the flow such as microstructures, invaginations and the like, To make holes with dimensions larger than the dimensions of the channels and the like. Such measures can positively influence the equalization of the flow. In particular, such measures can be formed as a function of and adapted to the flow conditions upstream of the pulsation damping element. Under a metallic layer is in this context not only a sheet metal layer of thin high-temperature and corrosion-resistant sheets, in particular having a thickness of less than 80μm, preferably less than 50μm, more preferably less than 30μm to understand, but also metallic layers of a material, which can be flowed through at least partially for a fluid. Such fiber webs as well as powders and / or chips optionally represent corresponding metallic elements sintered on a carrier material. Such are at least partially Fluid-flowable materials can be reinforced and / or combined with sheet metal regions. The term "metallic layer" in the sense of this invention also includes a material that is constructed, for example, partly from metallic material and partly from ceramic material. In particular, so combined layers of composite material can be formed, consisting of metallic and ceramic fibers, of metallic material, in particular reinforced sheet metal ceramic fibers and / or ceramic fibers, which are stored substantially captive in an at least partially permeable metallic shell.

at Formation of the honeycomb body from metallic layers can the individual layers at least partially, at least partially joining techniques be connected to each other, in particular brazed and / or welded, however, it is also possible and according to the invention, the layers not joining techniques connect to each other, so that advantageously achieves increased flexibility of the honeycomb body becomes. The honeycomb body can in a usual Jacket tube are held and with this optionally in sub-areas and / or on a Intermediate element joined by joining technology be, in particular brazed and / or welded. So can a honeycomb body as pulsation damping selement be formed, which is formed of metallic layers, the one another not technical connected to each other, which, however, technical joining at least in some areas and / or over an intermediate element is connected to a jacket tube.

A Combination of all mentioned here activities in a pulsation damping element is possible according to the invention.

At the Structure of the honeycomb body metallic layers often become substantially smooth, for example only having a microstructure, and at least partially structured metallic layers used, for example, a structuring in the form of a corrugation, for example a sinusoidal or triangular corrugation have at least in some areas. So it is possible, for example, a honeycombs from at least one substantially smooth and at least one at least partially structured metallic layer or one at least partially wound metallic layer spirally wound. It is also possible each a plurality of substantially smooth and at least to stack partially structured metallic layers and one or more of these stacks equal or opposite to each other twist. It is possible according to the invention, respectively only one type of metallic layers, such as sheet metal layers, or also several types of metallic layers to build a single honeycomb to use. Also an extruded or layered metallic Powder similar to "Rapid Manufacturing Technology " metallic honeycomb body is used according to the invention.

According to one further advantageous embodiment of the exhaust system according to the invention the turbine is designed as a turbocharger.

One Turbocharger or exhaust gas turbocharger advantageously uses the thermal energy of the exhaust gas for compression of the internal combustion engine flowing Fresh gas.

According to one further advantageous embodiment of the exhaust system according to the invention has the honeycomb body cavities on and the cavities are configured so that the honeycomb body is substantially opaque is.

opaque is called in particular, that such a variety of cavities like for example channels is formed, that substantially only along the channels are looked through by the honeycomb body can, but not at an angle. This can be done by relatively thick Reach cavity walls and / or for example by a large cavity or cell density. It is also possible and according to the invention in the flow direction to vary the cell count, so that, for example, a first Area with a relatively low cell density one area with a significantly increased Cell density follows or vice versa.

According to one further advantageous embodiment of the exhaust system according to the invention is a density of cavities per unit area of the honeycomb more than 100 cpsi (cells per square inch, cells per square inch), and is in particular in a range up to about 600 cpsi.

Such high cell honeycomb body fulfill in particular the criterion of being opaque and also lead to a particularly good Homogenization of the flow.

According to one further advantageous embodiment of the exhaust system according to the invention is the amount of exhaust gas that can flow through the return line, through a return control valve controllable.

By a return control valve can in a particularly simple manner, the amount of exhaust gas, which is recycled, to be controlled. This can be used in particular as a return control valve a substantially infinitely controllable valve can be used, which opened as needed by the engine control or is closed.

According to one further advantageous embodiment of the exhaust system according to the invention is the pulsation damping element in the flow direction in front of the return control valve educated.

hereby is advantageously an already temporally and / or spatially uniform exhaust flow on the return control valve so that a very accurate metering of the proportion of the exhaust gas, which is recycled, can be done. This facilitates in particular the engine control the internal combustion engine, since the amount of recirculated exhaust gas flow reliable and can be precisely dosed.

According to one further advantageous embodiment of the exhaust system according to the invention is the honeycomb body held in an outer housing, which is substantially freely flowed through, wherein the exhaust gas the honeycombs can flow in a first direction and then a Deflection of the exhaust gas takes place in a second direction in which the outer housing is flowed through.

Prefers is the angle between the first direction and the second direction essentially 180 degrees, so that is essentially a reversal the flow direction the exhaust gas takes place. Substantially freely flowable means in particular, that in the area between honeycomb body, which still in a usual Jacket tube may be held, and the outer housing is formed a Rückströmbereich, the does not contain a honeycomb structure and which in particular opposes the flow of exhaust gas as low as possible flow resistance. This can be achieved by a correspondingly formed holder of the honeycomb body be guaranteed or relative to the outer housing.

The Deflection of the exhaust gas flow allows a particularly compact design the honeycomb body, with the particular small building gaps be used advantageously in the engine compartment of a motor vehicle can. So can the honeycomb body or the outer housing of branch off the direction of the exhaust pipe in the connection point of the honeycomb body and form any angle with the exhaust pipe. Also the direction in the exhaust gas in the honeycomb body initiated and the direction in which it is derived from the outer housing, can be any Include angle with each other. Preference is given here, the gas inlet into the honeycomb body and the gas discharge from the outer housing adjacent to each other, particularly preferably near a front side of the honeycomb body execute. The introduced here Angles are preferred to the conditions in the engine compartment Motor vehicle adaptable, in particular to the respective space conditions. So can Also small free volumes in the engine compartment effective and beneficial be used.

By the deflection of the exhaust gas flow from the first to the second direction flows around the exhaust is the outside of the honeycomb body. this leads to to a very even heating of the honeycomb body and thus to relatively low thermal transients and / or gradients. This effect is further supported by the fact that when using a honeycomb in addition to its function as Pulsationsdämpfungselement in addition as Catalyst carrier body the catalyzed conversion takes place exothermically, so that the exhaust gas while flowing through the honeycomb heats up in the first direction. The circulation of the honeycomb body in the second direction through the substantially freely flow-through outer housing leads to a Cooling of the exhaust gas and at the same time to a more uniform temperature of the honeycomb body.

Especially It is advantageous in this context that the honeycomb body a Diameter of 20 to 100 mm, preferably 30 to 80 mm, especially preferably has substantially 40 mm.

Such are relatively small honeycomb body particularly advantageous for the utilization of relatively small spaces in the engine compartment.

According to one further advantageous embodiment of the exhaust system according to the invention is the substantially free-flow volume of the outer housing more than about 20%, preferably more than 40%, of the volume of the honeycomb body. Farther It is also preferred that the volume of the outer housing which can be flowed freely through it clearly larger, preferred essentially twice as large as the volume of the honeycomb body is. In this case, the outer housing advantageously a substantially annular Cross-section whose radius difference is at least 4 mm, and possibly even up to about 15 mm. The training of the outer housing and optionally also the honeycomb body as substantially circular cylindrical components is preferred. Under essentially circular but are also honeycomb bodies to understand, for example, an oval or polygonal cross-section and in a cylindrical outer housing with a circular, elliptical or oval cross-section are included. Under the Radius difference is in such cases to understand a mean radius difference. A radius difference of essentially 7 mm in conjunction with a honeycomb diameter of substantially 40 mm has been found to be advantageous However, other radius differences are possible and according to the invention.

According to one further advantageous embodiment of the exhaust system according to the invention has the honeycomb body has at least two subsets of cavities, wherein the first Subset channels in each case a first input cross section and a first output cross section and the second subset channels in each case a second input cross section and a second output cross section and the relationship from the first input cross section to the first output cross section other than that from the second input section to the second Output section.

By such a preferred embodiment of the honeycomb body can additionally to the pulsation damping properties yet another silencing function be used. By extending a subset of the channels at the same time Narrowing the other subset channels causes a slowdown the exhaust gas flow in a subset and to accelerate the exhaust gas flow in the other subset channels. this leads to with appropriate design of the channel cross-sections to an at least partial destructive interference of the two partial exhaust gas streams when merging the honeycomb body and thus to a sound attenuation.

Advantageous In this case, it is at least a subset of the channels conical expanded and / or conically narrowed. Furthermore, it is advantageous that a first subset of the exhaust gas flows through a first subset of channels and a second subset of the exhaust gas flows through a second subset of channels, wherein the cross sections of at least one of the two subsets channels over the axial length change the honeycomb body, so that the transit time of the exhaust gas in the different subsets channels different is. This difference in transit time can advantageously in a simple manner for the formation of at least partial destructive interference be exploited.

According to one further advantageous embodiment of the exhaust system according to the invention is the honeycomb body as catalyst carrier body, particle filter and / or adsorber for formed at least one component of the exhaust gas.

This advantageously allows a multiple function of the honeycomb body on the one hand as a pulsation damping element and on the other hand in at least one further function. Thus, for example, the pulsation damper can simultaneously serve as a catalyst carrier body, which has a catalytically active coating by which at least a portion of the exhaust gas is catalytically converted. Furthermore, the honeycomb body may alternatively or additionally be designed as an open or closed particle filter for filtering particles in the exhaust gas. Another alternative or additional possibility is the formation of the honeycomb body as an adsorber structure by which at least one component of the exhaust gas is at least temporarily adsorbed and desorbed at other times. This can be done, for example, by forming a corresponding adsorber coating, which adsorbs a component of the exhaust gas, for example nitrogen oxides (NO _x ), in particular at relatively low temperatures and desorbs them again at relatively high temperatures. As a result, this component can be stored until a catalyst, which is formed downstream of the adsorber, has reached its operating temperature, so that then there can be a catalytic conversion of NO _X , so that just in the cold start phase of an automobile, the emission of nitrogen oxides avoided or at least significantly reduced.

According to one further advantageous embodiment of the exhaust system according to the invention is the at least one Pulsationsdämpfungselement in the manifold and / or formed in the collector of the internal combustion engine. The possible close to the motor training of Pulsationsdämpungselements in the manifold and / or in the Collector of the internal combustion engine allows the pulsation-free recycling of Exhaust gas of a relatively high temperature, so that in particular in the Cold start phase of the internal combustion engine, the heating of the internal combustion engine is accelerated in an advantageous manner.

Further advantageous embodiments of the exhaust system according to the invention are described below some embodiments explains without the invention being limited thereto. Show it:

1 schematically a first embodiment of an exhaust system according to the invention;

2 schematically an embodiment of a Pulsationsdämpfungselements;

3 schematically second embodiment of an exhaust system according to the invention;

4 for example, a pressure curve before and after a Pulsationsdämpfungselement;

5 by way of example, a frequency distribution of the speeds before and after a pulsation damping element;

6 schematically a second embodiment of a Pulsationsdämpfungselements in cross section;

7 schematically the second embodiment of a Pulsationsdämpfungselements in longitudinal section;

8th schematically a section of a third embodiment of a Pulsationsdämpfungselements in longitudinal section;

9 schematically a section of the third embodiment of a Pulsationsdämpfungselement in cross section; and

10 a structured metallic layer for the construction of the third embodiment of a Pulsationsdämpfungselement.

1 shows an exhaust system of an internal combustion engine 1 , preferably an internal combustion engine in a motor vehicle. This internal combustion engine 1 has a gas inlet 2 and a gas outlet 3 on. At the gas inlet 2 is a gas supply line 4 connected, over which the internal combustion engine 1 is supplied with gas, wherein the gas consists at least partially of fresh air. The gas outlet 3 is with the exhaust pipe 5 connected, over which the exhaust gases of combustion in the internal combustion engine 1 be derived. The gas outlet 3 can also be a collector into which the exhaust gases of several cylinders flow.

About a coupling agent 6 is a return line 7 with the exhaust pipe 5 connected. The return line 7 is via a return control valve 8th with the gas supply line 4 connected. About the coupling agent 6 , which may be formed as a simple valve, for example a multi-way valve or a simple intersection of lines, it is possible, if appropriate, at least part of the exhaust gas of the internal combustion engine 1 via the return line 7 and the return control valve 8th to the gas inlet 2 the internal combustion engine 1 due. Quantity and duration of the recirculated exhaust gas is here at least on the return control valve 8th and optionally also via the coupling agent 6 or vice versa. Recirculation control valve 8th and coupling agents 6 can also be designed reversed.

Furthermore, the exhaust system according to the invention comprises a turbocharger 9 , which determines the thermal energy of the exhaust gas of the internal combustion engine 1 for the compression of the gas supply line 4 uses flowing fresh air. The exhaust gas, which is the internal combustion engine 1 over the gas outlet 3 is pulsatile, since it is the product of intermittent combustion in the individual cylinders of the internal combustion engine 1 represents. Thus, strong pressure fluctuations occur in the exhaust gas.

The at least partial recirculation of the exhaust gas via the return line 7 serves for example for heating the internal combustion engine 1 or of components in a flow direction 10 in which the exhaust pipe 5 is substantially flowed through, behind the internal combustion engine 1 are, for example, catalyst carrier body, particulate filter and / or adsorber, which require a certain operating temperature. The faster heating of these components reduces in particular the light-off time and thus shortens the phase in which only an insufficient conversion of the exhaust gas takes place. Also important is an exhaust gas recirculation, for example in the field of HCCI (Homogeneous Charge Compression Ignition) technology. This technique is based on a homogeneous ignition in the entire cylinders of the internal combustion engine 1 for very lean air / fuel mixtures, which may be so lean that ignition, for example, by spark plugs is difficult. In order to achieve a sufficiently high temperature for autoignition, in such cases, the return of hot exhaust gas is necessary, which may be present to achieve a high compression under high pressure. Would now an exhaust gas recirculation via a return line 7 take place in the flow direction 10 after the turbocharger 9 from the exhaust pipe 5 Exhaust gas would be recirculated, resulting from the use of the thermal energy of the exhaust gas in the turbocharger 9 already has a significantly reduced temperature and / or a significantly reduced pressure. Hence, the coupling agent is 6 in the flow direction 10 in front of the turbocharger 9 educated. In the coupling agent 6 and thus also at the return control valve 8th However, the exhaust gas is - without the formation of a Pulsationsdämpfungselements - but essentially as pulsatile ago, as is the internal combustion engine 1 through the gas outlet 3 leaves. Thus, however, such exhaust would be difficult regularly for the operation of the internal combustion engine 1 be available.

According to the invention this problem is solved in that at least one Pulsationsdämpfungselement in the exhaust pipe 5 in the flow direction 10 in front of the turbocharger 9 and the coupling agent 6 and / or in the return line 7 is trained. The present embodiment has a first pulsation damping element 11 and a second pulsation damping element 12 on. It should already be noted that these pulsation damping elements 11 . 12 are alternative or cumulative. Thus, according to the invention, it is also possible to use exhaust gas systems which only contain the first pulsation damping element 11 or the second pulsation damping element 12 exhibit.

By the pulsation damping elements 11 . 12 a homogenization of at least the Exhaust gas flowing through the return line 7 can flow. In the case of the first Pulsationsdämpfungselements 11 an equalization of the exhaust gas flow through the exhaust pipe is also carried out 5 in the flow direction 10 behind the first pulsation damping element 11 , The equalization of the exhaust gas flow takes place depending on the design of the pulsation damping elements 11 . 12 in temporal and / or spatial terms. In particular, a homogenization in the return line 7 in terms of the at the return control valve 8th applied pressure of the exhaust gas. Homogenization does not have to mean that a constant pressure in the return line 7 at the return control valve 8th Rather, it means that the range of variation between pressure minima and pressure maxima is reduced, preferably significantly reduced, ie, that the pressure minima are raised and the pressure maxima are lowered, so that essentially a measurable pressure in the return line 7 at the return control valve 8th is applied.

For further compression of the gas mixture, which in return of at least a portion of the exhaust gas through the return line 7 at the gas inlet 2 the internal combustion engine 1 is present, it is also possible, the return control valve 8th in an inflow direction 13 in which the gas supply line 4 is essentially flowed through, even before the turbocharger 9 train, so that too through the return line 7 and the return control valve 8th in the gas supply line 4 recirculated exhaust still a compression in the turbocharger 9 is subjected.

In the flow direction 10 behind the turbocharger 9 are further exhaust gas treatment agents 14 educated. These exhaust treatment agents 14 may consist of a honeycomb body, which may for example be designed as a catalyst carrier body, as a particle filter and / or as an adsorber, in particular as a nitrogen oxide adsorber. In these exhaust aftertreatment agents 14 Thus, alternatively or additionally, an at least partial conversion of at least parts of the exhaust gas and / or of solids contained in it, as well as at least temporary storage of solids and / or at least one gaseous component of the exhaust gas takes place alternatively.

2 schematically shows a possible embodiment of a Pulsationsdämpfungselements 11 . 12 , This is a honeycomb body 15 , which is a honeycomb structure 16 and a jacket tube 17 includes. However, according to the invention are also Wa body 15 without casing pipe 17 possible, for example in spiral-shaped honeycomb bodies 15 , The honeycomb structure 16 is made of substantially smooth metallic layers 18 and at least partially structured metallic layers 19 constructed, which are stacked alternately to three stacks, which are wound together. For the sake of clarity, the at least partially structured metallic layers 19 only in a partial area of the honeycomb structure 16 located. In the present example, the at least partially structured metallic layers 19 corrugated, in particular sinusoidal corrugated. The essentially smooth metallic layers 18 and the at least partially structured metallic layers 19 limit channels 20 extending in the direction of flow through the honeycomb body 15 extend. The channels 20 represent for a fluid durchströmbare cavities.

The formation of honeycomb body 15 Also as an extruded structure, such as ceramic and / or metal, is possible and according to the invention. A honeycomb body 15 can in addition to the in 2 shown possibility of construction, for example, as a spirally wound honeycomb body 15 be constructed, wherein at least one at least partially structured metallic layer 19 and optionally at least one substantially smooth metallic layer 18 be spirally wound up. Here, too, canals are formed 20 out, passing through the honeycomb body 15 extend and for a fluid, such as an exhaust gas, are flowed through. It is also possible to twist another number of stacks, for example two stacks.

Under metallic position 18 . 19 are in addition to conventional sheet metal layers, preferably made of aluminum or corrosion and high temperature resistant steel, preferably a thickness of less than 80 .mu.m, more preferably less than 50 .mu.m, in particular less than 30 microns, to understand at least partially for a fluid durchströmmare metallic layers. This can be in particular layers 18 . 19 be made of a metallic nonwoven, in particular a nonwoven fabric, for example, a sintered nonwoven fabric or layers, which are created by sintering powder or chips. In particular, the term is a metallic layer 18 . 19 in the context of this invention also a location 18 . 19 from a composite material, which is reinforced, for example, from a metallic fiber material reinforced with metal strips or combined with a sheet metal layer or made of a ceramic fiber material reinforced with sheet metal layers or strips held, or even from a particular porous or highly porous sheet metal layer is, preferably substantially captive. According to the invention for the construction of a honeycomb body 15 different types of metallic layers 18 . 19 be used in all possible combinations.

• – Mikrostrukturierungen, die eine Strukturierungsamplitude aufweisen, die wesentlich kleiner ist als die der zumindest teilweise strukturierten Lagen und die sich bevorzugt im wesentlichen quer zur Durchströmungsrichtung des Wabenkörpers 15 erstrecken;
• – Umstülpungen, die sich im wesentlichen in Durchströmungsrichtung des Wabenkörpers 15 erstrecken und die gegebenenfalls eine Durchbrechung der metallischen Lage 18, 19 umfassen;
• – Löcher in den metallischen Lagen 18, 19, die zumindest eine Abmessung aufweisen, die größer als eine Strukturierungsamplitude und/oder Strukturwiederhollänge der zumindest teilweise strukturierten Lage ist; und
• – Strömungsleitflächen, die zur Umlenkung und/oder Verwirbelung der Strömung dienen können.

In or on the metallic layers 18 . 19 or from the metallic layers 18 . 19 may comprise means for influencing the flow formed be. These include in particular

• - Microstructures having a structuring amplitude which is substantially smaller than that of the at least partially structured layers and preferably substantially transversely to the flow direction of the honeycomb body 15 extend;
• - Inversions, which are substantially in the direction of flow through the honeycomb body 15 extend and optionally an opening of the metallic layer 18 . 19 include;
• - holes in the metallic layers 18 . 19 having at least a dimension which is greater than a structuring amplitude and / or structure repeat length of the at least partially structured layer; and
• - Flow, which can serve to deflect and / or turbulence of the flow.

The metallic layers 18 . 19 can be joined together by joining technology, in particular brazed and / or welded. The formation of the technical joining connection at least in axial and / or radial portions of the honeycomb body 15 is possible according to the invention. The honeycomb structure 16 Can be joined with the jacket pipe 17 be connected, in particular brazed and / or welded. This connection can at least in axial and / or radial portions of the honeycomb body 15 and / or the jacket tube 17 be educated. Also the connection of the honeycomb structure 16 with the jacket tube 17 Via an intermediate element is possible and according to the invention, for example, a structured sleeve, which preferably has a different patterning amplitude, structure repeat length and / or material thickness than the at least partially structured metallic layer 19 , wherein the compound of the honeycomb structure 16 with the intermediate element and / or the connection between the intermediate element and the jacket tube 17 is possible at least in radial and / or axial portions, in particular the subregions in which the intermediate element with the casing tube 17 and the subregions in which the intermediate piece with the honeycomb structure 16 Although it can be superposed in the radial direction, it is also possible for these subregions to overlap only partially or not at all in this direction.

The formation of at least one of the Pulsationsdämpfungelemente 11 . 12 as a honeycomb body 15 advantageously allows the combination of Pulsationsdämpfungsfunktion with other functions, in particular for exhaust aftertreatment. So can the honeycomb body 15 be designed in an advantageous manner so that it serves as a catalyst carrier body, particulate filter and / or adsorber for at least one component of the exhaust gas. For the rest, reference is made to the above details.

3 shows a further embodiment of an exhaust system according to the invention. The same components are provided here with the same reference numerals. The exhaust gases of an internal combustion engine 1 with a gas inlet 2 and a gas outlet 3 flow through an exhaust pipe 5 , With a coupling agent 6 is the exhaust pipe 5 with a return line 7 connectable, by the 0 to 100% of the exhaust gas of the internal combustion engine 1 in the gas supply line 4 and above it into the gas inlet 2 the internal combustion engine 1 are traceable. The coupling agent 6 is in the flow direction 10 the exhaust gas in front of a turbocharger 9 formed by the through the Gaszuführleitung 4 flowing fresh air is compressed. In the flow direction 10 behind the turbocharger 9 are further exhaust gas treatment agents 14 educated. These may alternatively or additionally also in the flow direction 10 in front of the turbocharger 9 be educated.

In the return line 7 is a pulsation damping element 21 educated. This includes a honeycomb body 15 which is in an outer housing 22 is held. The honeycomb body 15 may be as stated above. The exhaust gas flows through the return line 7 and then through a gas supply line 23 in the honeycomb body 15 , In the honeycomb body 15 the exhaust gas flows in a first direction 24 , After flowing through the honeycomb body 15 there is a diversion 25 after which the exhaust gas is the outer casing 22 in a second direction 26 flows through. The second direction 26 is substantially opposite to the first direction 24 , The outer case 22 is essentially free to flow through, that is, in particular, that no honeycomb structure in the outer housing 22 is trained. After flowing through the outer housing 22 the exhaust gas flows through outflow 28 continue into the return line 7 , The outflow means 27 are formed in the present embodiment as a dome-shaped component with a derivative, however, all other forms of outflow are possible and according to the invention. In particular, it is also possible and according to the invention not to divert the exhaust gases at the end but in the central region of the outer housing 22 , That is, effluent 28 and gas supply 12 do not have to be in the range of a single end face 29 of the honeycomb body 15 be educated.

The form of Pulsationsdämpfungselements shown here 21 in the form of an outer housing 22 held honeycomb body 15 allows a construction in which the Pulsationsdämpfungselement 21 in relation to the return line 7 and (in the formation of Pulsationsdämpfungselementes 21 in the exhaust pipe 5 in terms of flow direction 10 upstream of the coupling means 6 ) in Reference to the exhaust pipe 5 is formed at any angle, which makes it possible to take advantage of very small gaps in the engine compartment of a motor vehicle. So is a very flexible design of Pulsationsdämpfungselementes 21 , the return line 7 and the exhaust pipe 5 possible.

The pulsation damping element 21 - as well as the Pulsationsdämpfungselemente 11 . 12 - leads to a homogenization of the flow of the exhaust gas in temporal and / or spatial terms. Considering the timing of the pressure PR as in 4 shown, it can be seen that the temporal pressure curve 30 before the pulsation damping element 21 (shown as a solid line) is significantly more pulsatile than the temporal pressure curve 31 after the pulsation damping element 21 (shown as a dotted line). In particular, the pulsation damping element leads 11 . 12 . 21 to increase the full width at half height (FWHM, full width half maximum) by a factor of at least 1.5, preferably at least 2, more preferably at least 3. In particular, this applies to pressure values PR, which over a cross section of the exhaust pipe 5 or the return line 7 integrated and / or averaged.

5 shows propagators of the flow before the Pulsationsdämpfungselement 11 . 12 . 21 and after the pulsation damping element 11 . 12 . 21 , A propagator gives the probability distribution P (v) of a velocity v or also the frequency distribution of the velocity, which differ only by a normalization factor. If there is a data record in which spatially resolved at each point x, y of a plane the velocity v present there or also an intensity of this velocity v is known, which for example is present on the integration over a finitely thick "slice", then it is possible The value of a propagator P (v) of a certain velocity v indicates the probability that a particle in the flow has the velocity v. As a frequency distribution P (v) it gives one In this case, the expected value of the velocity upstream of the pulsation damping element according to the invention can be different from the expected value thereafter.

In the 5 exemplified frequency distribution 32 before the pulsation damping element 11 . 12 . 21 (drawn as a solid line) has a significantly greater full width at half height (FWHM) than the frequency distribution 33 after the pulsation damping element 11 . 12 . 21 , The ratio of the full width at half height (FWHM) of the frequency distribution is preferred 33 after the pulsation damping element 11 . 12 . 21 to the full width at half height (FWHM) of the frequency distribution 32 before the pulsation damping element 11 . 12 . 21 less than 0.5, preferably less than 0.35, more preferably less than 0.25.

6 schematically shows a cross section through the Pulsationsdämpfungselement 21 out 3 , A honeycomb body 15 is in an outer case 22 with holding elements 27 held. The honeycomb body 15 is designed as an extruded component that channel walls 34 has, the channels 20 limit. The channels are drawn only by way of example, it can also according to the invention in such honeycomb bodies 15 high cell densities are present, preferably more than 100 cpsi (cells per square inch), more preferably more than 400 cpsi, in particular up to about 600 cpsi. In this example, the cross sections of the channels 20 mostly square, except at the edge of the honeycomb body 15 located channels 20 , The outer case 22 and the honeycomb body 15 , optionally the honeycomb body 15 surrounding jacket pipe 17 , form a return flow space 35 , Any other honeycomb body can be used in such a pulsation damping element 15 be educated.

7 shows the flow conditions in a Pulsationsdämpfungselement 21 schematically in detail. The exhaust gas flows in a first direction 24 through the honeycomb body 15 , After leaving the honeycomb body 15 there is a diversion 25 , whereupon the exhaust gas in the second direction 26 the return flow space 35 flows through.

In training the Pulsationsdämpfungselemente 11 . 12 . 21 as a honeycomb body 15 Honeycomb preferably come 15 used, which have a high cell density. In particular, such high cell densities have the property of being opaque.

8th shows a section of another embodiment of a honeycomb body 5 , This has a first subset of channels 36 and a second subset of channels 37 on. The channels of the first subset channels 36 each have a first input cross section 38 and a first output cross section 39 on. The channels of the second channels 37 each have a second input cross section 40 and a second output section 41 on. Here is the ratio of the first input cross section 38 to the first output cross-section 38 other than that of the second input section 40 to the second output cross-section 41 , The channels of the first subset channels 36 narrow, while the channels of the second subset channels 37 expand. This leads to the fact that the partial flow of the exhaust gas flow, which by the first subset channels 36 flows, accelerates, while the partial flow of the exhaust gas flow, which channels through the second subset 37 flows, slows down. In the mixing room 42 The partial quantities of exhaust gases are mixed together again. With appropriate design of subsets channels 36 . 37 Due to the differences in transit time, which arise between the partial flows due to the acceleration or deceleration of the partial flows, at least partial destructive interference between the partial flows, which leads to a sound attenuation.

In this case, the first subset is preferably channels 36 formed substantially conically tapered, while the second subset channels 37 is designed to widen substantially conically. This can be achieved by the fact that the honeycomb body 15 from substantially smooth metallic layers and structured metallic layers 43 be formed, the patterning amplitude over the length of the metallic layers 43 changes.

9 is a section of the third embodiment of a honeycomb body 15 to take as gas inlet side view. The honeycomb body 15 is made of substantially smooth metallic layers 44 and structured metallic layers 43 constructed, with adjacent structured metallic layers 43 each rotated by 180 ° from each other. This forms a first subset of channels 36 with first input cross sections 38 and a second subset of channels 37 with second input cross sections 40 , The in 8th and 9 honeycomb body shown and described here 15 can advantageously as Pulsationsdämpfungselement 11 . 12 or in a pulsation damping element 21 also in combination with other honeycomb bodies 15 be used.

10 shows an example of a structured metallic layer 43 for building the honeycomb body 15 in the 8th and 9 is shown. The metallic situation 43 has different structuring amplitudes over the length, which interact with the adjacent smooth layers 44 (not shown) the first output cross-section 39 and on the other side the second input section 40 , When building the honeycomb body 15 become adjacent structured metallic layers 43 each 180 ° about the axis 45 turned trained.

The exhaust system according to the invention with a pulsation damping element 11 . 12 . 21 advantageously allows the return of a temporally and / or spatially uniformed exhaust gas flow, so that a simplified control of the exhaust gas recirculation is possible. As or in pulsation damping elements (s) 11 . 12 . 21 can be honeycomb body advantageously 15 deploy.

1

Internal combustion engine

2

gas inlet

3

gas outlet

4

gas supply

5

exhaust pipe

6

coupling agent

7

Return line

8th

Recirculation control valve

9

turbocharger

10

flow direction

11

first Pulsationsdämpfungselement

12

second Pulsationsdämpfungselement

13

inflow

14

Exhaust gas treatment agents

15

honeycombs

16

honeycomb structure

17

casing pipe

18

in the substantially smooth metallic layer

19

at least partially structured metallic layer

20

channel

21

Pulsationsdämpfungselement

22

outer casing

23

gas supply

24

first direction

25

redirection

26

second direction

27

retaining element

28

Abströmmittel

29

front

30

time Pressure curve before a Pulsationsdämpfungselement

31

time Pressure curve after a Pulsationsdämpfungselement

32

frequency distribution in front of a pulsation damping element

33

frequency distribution after a Pulsationsdämpfungselement

34

channel wall

35

return flow

36

first Subset channels

37

second Subset channels

38

first Input section

39

first Output section

40

second Input section

41

second Output section

42

mixing room

43

structured metallic position

44

in the substantially smooth metallic layer

45

axis

Claims (20)

Exhaust system of an internal combustion engine ( 1 ), in particular in an automobile, wherein the internal combustion engine ( 1 ) at least one Gas inlet ( 2 ) and at least one gas outlet ( 3 ), with at least one substantially in a flow direction ( 10 ) throughflowable exhaust pipe ( 5 ), which for discharging the exhaust gases of the internal combustion engine ( 1 ) with the at least one gas outlet ( 3 ), with a turbine ( 9 ), which at least partially in the exhaust pipe ( 5 ) is formed, with at least one Pulsationsdämpfungselement ( 11 . 12 . 21 ) for temporal and / or local homogenization of an exhaust gas flow, with at least one return line ( 7 ) for returning the exhaust gas of the internal combustion engine ( 1 ) from the gas outlet ( 3 ) to the gas inlet ( 2 ), the return line ( 7 ) between gas outlet ( 3 ) and turbine ( 9 ) via coupling agents ( 6 ) so with the exhaust pipe ( 5 ) is connectable that between 0 and 100% of the exhaust gas through the return line ( 7 ), characterized in that the at least one pulsation damping element ( 11 . 12 . 21 ) in the exhaust pipe ( 5 ) between internal combustion engine ( 1 ) and the turbine ( 9 ) in the flow direction ( 10 ) before the coupling agent ( 6 ) and / or in the return line ( 7 ) is trained. Exhaust system according to claim 1, characterized in that the pulsation damping element ( 11 . 12 . 21 ) a honeycomb body ( 15 ). Exhaust system according to claim 1 or 2, characterized that a temporal homogenization of the Pressure (PR) takes place. Exhaust system according to claim 3, characterized in that the ratio of the full width at half height (FWHM, full width half maximum) of the time course ( 31 ) of a pressure pulse after the pulsation damping element ( 11 . 12 . 21 ) to the full width at half height (FWHM) of the time course ( 30 ) of the pressure pulse before the Pulsationsdämpfungselement ( 11 . 12 . 21 ) is greater than one. Exhaust system according to claim 4, characterized in that the ratio of the full width at half height (FWHM, full width half maximum) of the time course ( 31 ) of a pressure pulse after the pulsation damping element ( 11 . 12 . 21 ) to the full width at half height (FWHM) of the time course ( 30 ) of the pressure pulse before the Pulsationsdämpfungselement ( 11 . 12 . 21 ) is at least 1.5. Exhaust system according to one of the preceding claims, characterized characterized in that a spatial Equalization of flow rate (tracked. Exhaust system according to claim 6, characterized in that the ratio of the full width at half height (FWHM) of the frequency distribution ( 33 ) of the flow velocities (v) after the pulsation damping element ( 11 . 12 . 21 ) to the full width at half height (FWHM) of the frequency distribution ( 32 ) of the flow velocities (v) in front of the pulsation damping element ( 11 . 12 . 21 ) is less than one. Exhaust system according to claim 7, characterized in that the ratio of the full width at half height (FWHM) of the frequency distribution ( 33 ) of the flow velocities (v) after the pulsation damping element ( 11 . 12 . 21 ) to the full width at half height (FWHM) of the frequency distribution ( 32 ) of the flow velocities (v) in front of the pulsation damping element ( 11 . 12 . 21 ) is less than 0.5. Exhaust system according to one of the preceding claims, characterized in that the turbine ( 9 ) is designed as a turbocharger. Exhaust system according to one of claims 2 to 9, characterized in that the honeycomb body ( 15 ) is formed of ceramic material and / or metal. Exhaust system according to one of claims 2 to 10, wherein the honeycomb body ( 15 ) Cavities ( 20 ), characterized in that the cavities ( 20 ) are configured so that the honeycomb body ( 15 ) is substantially opaque. Exhaust system according to one of claims 2 to 11, characterized in that a density of the cavities ( 20 ) per unit area of the honeycomb body ( 15 ) is more than 100 cpsi. Exhaust system according to one of the preceding claims, characterized in that the amount of exhaust gas passing through the return line ( 7 ) can flow through a return control valve ( 8th ) is controllable. Exhaust system according to claim 13, characterized in that the pulsation damping element ( 11 . 12 . 21 ) in the flow direction ( 10 ) in front of the return control valve ( 7 ) is trained. Exhaust system according to one of claims 2 to 14, characterized in that the honeycomb body ( 15 ) in an outer housing ( 22 ), which is substantially freely permeable, wherein the exhaust gas is the honeycomb body ( 15 ) in a first Direction ( 24 ) and then a diversion ( 25 ) of the exhaust gas in a second direction ( 26 ), in which the outer housing ( 22 ) is flowed through. Exhaust system according to claim 15, characterized in that the honeycomb body ( 15 ) has a diameter of 20 to 100 mm. Exhaust system according to claim 15 or 16, characterized in that the substantially freely flowable volume of the outer housing ( 22 ) more than 20%, preferably more than 40%, of the volume of the honeycomb body ( 15 ) is. Exhaust system according to one of claims 15 to 17, characterized in that the outer housing ( 22 ) has a substantially annular cross-section whose radius difference is at least 4 now. Exhaust system according to one of claims 2 to 18, characterized in that the honeycomb body ( 15 ) at least two subsets of channels ( 20 ), the first subset being channels ( 20 ) each have a first input cross section and a first output cross section and the second subset of channels ( 20 ) has in each case a second input cross section and a second output cross section and the ratio of the first input cross section to the first output cross section is different from that of the second input cross section to the second output cross section. Exhaust system according to one of claims 2 to 19, characterized in that the honeycomb body ( 15 ) is formed as a catalyst carrier body, particulate filter and / or adsorber for at least one component of the exhaust gas.