EP3325783A1

EP3325783A1 - Method for metering a reactant into an exhaust gas path of an internal combustion engine, and internal combustion engine

Info

Publication number: EP3325783A1
Application number: EP16741234.5A
Authority: EP
Inventors: Joachim Schwarte; Samuel Vogel; Alexander Kovacevic; Marc Hehle
Original assignee: MTU Friedrichshafen GmbH
Current assignee: Rolls Royce Solutions GmbH
Priority date: 2015-07-24
Filing date: 2016-07-15
Publication date: 2018-05-30
Also published as: US20180209315A1; CN108026811A; HK1255051A1; WO2017016649A1

Abstract

The invention relates to a method for metering a reactant into an exhaust gas path (5) of an internal combustion engine (3), wherein the reactant is introduced into an area of the exhaust gas path (5) in which pressure surges in the exhaust gas stream, generated by a charge exchange of the internal combustion engine (1), contribute to breakdown of droplets of the reactant, wherein a metering device (7) for metering the reactant is activated at a variable metering frequency, depending on an operating point of the internal combustion engine (1).

Description

DESCRIPTION Method for metering a reagent into an exhaust path of a

Internal combustion engine and internal combustion engine

The invention relates to a method for metering a reagent in an exhaust path of an internal combustion engine and an internal combustion engine.

As a rule, a metering release for metering in a reaction agent, especially if the reaction agent is a reducing agent in the form of a urea-water solution, is given above an exhaust gas temperature of 250 ° C., because otherwise deposits of the reaction medium can occur. This means that map ranges of an internal combustion engine, in which lower exhaust gas temperatures are achieved, can not be covered by metered addition of the reagent. This applies in particular map areas with high speed and low load. This, in turn, is followed in particular by an improvement in the cycle turnover of nitrogen oxides on a catalyst for the selective catalytic reduction of nitrogen oxides in a test cycle for the internal combustion engine. It also shows that reactants in an exhaust path of an internal combustion engine typically with a constant metering frequency, for example with a constant

Dosing frequency of 1 Hz, be metered. A quantity control is carried out in particular by pulse width modulated control of a metering valve. The disadvantage here is that the flow conditions in the exhaust path dependent on an operating point of the

Internal combustion engine can be very different. Due to the constant metering frequency depending operating point depending different boundary conditions for the treatment and mixing of the reaction medium with the exhaust gas and thus in particular a high

Fluctuation width of a uniform distribution of the reaction agent in the exhaust gas. This, in turn, adversely affects the efficiency of the selective catalytic reduction of nitrogen oxides (SCR) depending on the operating point.

The invention has for its object to provide a method and an internal combustion engine, said disadvantages do not occur. The object is achieved by providing the subject matters of the independent claims. Advantageous embodiments will be apparent from the dependent claims and the

Description. The object is achieved in particular by providing a method for metering a

Reactant is provided in an exhaust path of an internal combustion engine, wherein the reactant is introduced into a region of the exhaust path, in which by a charge exchange, in particular by at least one exhaust valve, the engine generated pressure surges in the exhaust stream to a disintegration of droplets of the reagent contribute, that is this are suitable, wherein a metering device for metering the reagent is controlled depending on an operating point of the internal combustion engine with variable metering frequency. Characterized in that the metering of the reaction medium takes place in a region of the exhaust gas path, in which in particular in the exhaust stroke, which also as

Exhaust stroke is called, the internal combustion engine generated pressure surges to a decay, in particular a secondary decay, the reagent droplets contribute, it is vaporized faster and more efficient, resulting in the downstream of a more homogeneous mixture in the gas phase. Furthermore, it is found that a region of the exhaust gas path in which the said condition is met is arranged comparatively close to the combustion chamber so that increased exhaust gas temperatures are present here in the entire engine map. Therefore, the metering release can take place in a significantly broader map range, so that in particular the cycle conversion can be increased to an SCR catalyst. Due to the variable

Metering frequency, with which the metering device is controlled, it can - especially depending on a current operating point of the internal combustion engine - be adapted to different flow conditions in the exhaust path. Thus, the fluctuation range for the uniform distribution of the reaction agent in the exhaust gas can be significantly reduced, and preferably, a conversion to an SCR catalytic converter can be made uniform over a significantly widened engine map range of the internal combustion engine. An area of the exhaust path where the im

Outlet stroke of the engine generated pressure surges in the exhaust stream to the

Contributing secondary decay of the reagent droplets is particularly an area in which an amplitude of these pressure surges is high enough to cause droplet decay.

A reaction agent is here and in the following generally understood to mean a reagent which is injected into the exhaust gas path and for reaction with the exhaust gas, in particular a catalyst designed for this purpose is provided. The reagent is preferably metered in the liquid phase. Preferably, the reactant is a reducing agent, in particular for use as a reducing agent for the selective catalytic reduction of nitrogen oxides in a catalyst designed for this purpose (SCR catalyst), more preferably a urea-water solution. Alternatively or additionally, it is also possible that in the exhaust path, a reactant for another

Exhaust gas aftertreatment reaction is introduced. In particular, it is possible that as

Reactant is introduced a hydrocarbon or a hydrocarbon mixture for the reaction of an oxidation catalyst.

The metering device is preferably speed-dependent, that is dependent on a speed of the internal combustion engine, with variable metering frequency, in particular with speed-dependent metering frequency, controlled. This allows a vote of the dosing of the

Reactant in particular to the pressure surges in the exhaust stream, so that they can be optimally used to disintegrate the reagent droplets and thus to a distribution of the reagent in the exhaust gas.

A development of the invention provides that the metering device is controlled synchronously to a specific cycle of the internal combustion engine - in particular pulsed. In this case, activation of the metering device here means in particular a control for opening, that is to say an activation or opening of the metering device. The coupling of

Control of the metering device to a specific cycle of the internal combustion engine allows in a special way a vote of the dosage of the reagent on the flow in the exhaust path downstream of the combustion chambers of the engine, so that pressure surges in the exhaust stream can be used optimally for the distribution of the reagent.

The term "synchronous" means in particular that the activation of the

Dosing device temporally coupled to another event, in particular the specific clock of the internal combustion engine. This may mean that the metering device is driven simultaneously with the beginning of a cycle of the internal combustion engine, which is a

Phase shift of 0 ° corresponds. Preferably, however, a certain, different from 0 ° phase shift is used. This allows the preparation of the

Reactant in the exhaust stream to further optimize, especially with regard to dead times with respect to the exhaust gas flow depending on an actual arrangement of

Metering device in the exhaust path.

The particular phase shift is preferably variably selectable, in particular depending on an operating point of the internal combustion engine, ie operating point dependent. Preferably, the specific phase shift is stored in a map dependent operating point.

A development of the invention provides that the reactant is metered into the exhaust gas path upstream of a turbine of an exhaust gas turbocharger. The arrangement of

Dosing device upstream of the turbine of the exhaust gas turbocharger represents in particular a possibility of realizing a metering of the reaction agent in a region of the exhaust path, in which are generated by a charge change of the engine generated pressure surges in the exhaust stream to a secondary decomposition of droplets of the reagent. Typically, such pressure surges prevail downstream of the turbine, namely only in a clearly damped form, in which case they can in particular cause no further decay. In contrast, an amplitude of the pressure surges upstream of the turbine of the exhaust gas turbocharger for the purpose is still high enough. Another advantage of metering in the reaction medium upstream of the turbine results from the fact that it can be used as a very efficient mixing device for mixing the reaction medium with the exhaust gas. This results in a significantly reduced space requirement for the mixing section of the reaction medium, in particular additional mixing elements can be saved or designed smaller than when the reagent is injected downstream of the turbine in the exhaust path. By the omission or the smaller interpretation of such

Mixing elements, a pressure drop across the mixing elements can be reduced or minimized, which has a favorable effect on the exhaust gas back pressure for the internal combustion engine and thus on the fuel consumption of the same. At the same time the turbine causes a very good uniform distribution of the reagent in the exhaust gas. Furthermore, it can be seen that a higher exhaust gas temperature prevails upstream of the turbine of the exhaust gas turbocharger than downstream of the turbine, which in turn leads to a metering release in a significantly expanded

Map area of the internal combustion engine contributes. Furthermore, a housing of the turbine can be used as an evaporator, in particular because this typically has high temperatures. A development of the invention provides that the reaction medium into a - preferably immediately - adjoining at least one combustion chamber of the internal combustion engine

Flue gas collection area is metered. This is advantageous because here are particularly high

Exhaust gas temperatures prevail, so that the dosage release over a particularly wide

Map area can be done. An exhaust gas collection area is in particular a region of the exhaust gas path, in which exhaust gas from a plurality of combustion chambers of the internal combustion engine

is merged. The exhaust gas collecting region can be designed in particular as an exhaust manifold. Preferably, the metering of the reagent is at least as close to at least one combustion chamber and / or adjusted to the arrangement of at least one combustion chamber relative to the exhaust gas collecting that pressure surges can be used from the at least one combustion chamber for secondary decay. Preferably, the metering of the reagent is centered in the exhaust gas collection area. By doing

In the exhaust gas collection area, by the way, particularly high flow impulses, in particular pressure surges in the exhaust gas flow, result with each charge change of a combustion chamber. Will that be

Reaction medium metered into the center of the exhaust gas collection area, such pressure surges can be used very efficiently from all combustion chambers of the internal combustion engine. One

Dropping of the reaction agent is by the intermittently varying

Relative speed between the exhaust gas and the reaction means, in particular in addition to the high exhaust gas temperature in the exhaust gas collecting area significantly improved. In this case, in particular each exhaust stroke of a combustion chamber of the internal combustion engine for secondary drip decay is made usable by pulses of the exhaust gas flow. Thus, an arrangement of the metering device in the exhaust gas collecting region is in particular an arrangement in which a pressure change, in particular by at least one exhaust valve, the engine generated pressure surges in the exhaust stream to a disintegration of droplets of the reagent are suitable and contribute. At the same time, it is also apparent that the exhaust gas collecting region is arranged upstream of a turbine of an exhaust gas turbocharger when the internal combustion engine has an exhaust gas turbocharger.

A further development of the invention provides that the reaction medium is metered in synchronously with a firing sequence, in particular synchronously with a specific cycle of at least one combustion chamber of the internal combustion engine, preferably with a certain phase shift. This allows a particularly efficient coordination of the metering of the reagent to the pressure surges in the exhaust stream. It is possible that the control of the metering device is coupled to exactly one specific clock exactly one combustion chamber of the internal combustion engine. Within a firing order of an internal combustion engine which has a plurality of combustion chambers, then only once the metering device is driven. But it is also possible that the metering device is driven with a certain - preferably the same - cycle of a plurality of combustion chambers. In this case, the metering device is repeatedly actuated within a firing order of the internal combustion engine. In particular, it is also possible for the internal combustion engine to be actuated within the ignition sequence in a specific cycle of each combustion chamber.

A development of the invention provides that the metering device is driven in synchronism with an exhaust stroke of at least one combustion chamber of the internal combustion engine, preferably with a certain phase shift. Again, it is possible that the

Dosing device synchronously with an exhaust stroke of exactly one combustion chamber, or synchronously with exhaust strokes of a plurality of combustion chambers, in particular also synchronously with

Output cycles of all combustion chambers of the internal combustion engine is controlled. The synchronization of the control of the metering device with an exhaust stroke causes in a particularly efficient manner a coupling of the metering of the reagent with the pressure surges resulting in the exhaust gas path during the charge change of the combustion chambers.

It is preferably provided that the control of the metering device to a

Opening time of the combustion chamber associated exhaust valve is coupled, particularly preferably with a certain phase shift, which may be 0 ° or have a non-zero, finite value. Preferably, the phase shift is variable, in particular operating point-dependent, selectable. Preferred is the particular

Phase shift stored in a map depending on operating point.

A development of the invention provides that the metering device is controlled pulse-width modulated in order to set a metered amount of reagent. In this way, a very accurate and sensitive metering of the reagent in the exhaust path is possible, the pulse width modulated control can be adjusted in particular operating point-dependent on the current metering frequency. It can thus be avoided that only due to an increased metering frequency a larger and possibly too large an amount

Is metered reactant, in turn, it can be avoided that due to a reduced speed and thus a reduced metering frequency, a smaller or too small amount of reagent is metered into the exhaust path. The object is also achieved by providing an internal combustion engine which has at least one combustion chamber and an exhaust gas path, in which a metering device for metering a reaction agent into the exhaust gas path is arranged such that the

Reactive agent is introduced into a region of the exhaust path, in which by a

Charge change, in particular by at least one exhaust valve, the pressure generated in the exhaust gas flow in the exhaust stream to a disintegration of droplets of the reaction agent, that is suitable for this purpose, the internal combustion engine having a control device which is adapted to the metering device depending on an operating point of the internal combustion engine with to control variable dosing frequency. Particularly preferably, the internal combustion engine is set up for carrying out a method according to one of the previously described embodiments. In particular, the advantages that have already been explained in connection with the method are realized. The internal combustion engine preferably has a catalyst along the exhaust path which is set up for the selective catalytic reduction of nitrogen oxides, in particular a so-called SCR catalyst.

Additionally or alternatively, it is possible that the internal combustion engine along the exhaust path has a catalyst which is set up and designed as an oxidation catalyst. At this example, a hydrocarbon or a hydrocarbon mixture can be reacted as a reactant. Incidentally, a "reaction with the exhaust gas" is also understood as meaning a reaction with residual oxygen encompassed by the exhaust gas

Hydrocarbon mixture, in particular on an oxidation catalyst to a reaction with exhaust gas.

The metering device is preferably arranged upstream of a turbine of an exhaust gas turbocharger of the internal combustion engine.

In a preferred embodiment, it is provided that the metering device is arranged at an exhaust gas collecting area, in particular centrally on the exhaust gas collecting area, in particular an exhaust manifold, such that the reagent can be metered into the exhaust gas collecting area, in particular centrally into the exhaust gas collecting area. Alternatively or additionally the metering device at least as close to at least one combustion chamber and / or tuned to the arrangement of at least one combustion chamber relative to the

Positioned exhaust gas collection that pressure surges can be used from the at least one combustion chamber for secondary decay.

It is also preferred an embodiment of the internal combustion engine, which is characterized in that the internal combustion engine is designed as a slow-speed, medium-speed or high-speed. The advantages of the invention are realized

In particular, regardless of the actual achieved speeds of the internal combustion engine, especially in all speed ranges.

The internal combustion engine is preferably designed as a reciprocating engine. It is possible that the internal combustion engine is arranged to drive a passenger car, a truck or a commercial vehicle. In a preferred embodiment, the internal combustion engine is the drive in particular heavy land or water vehicles, such as mine vehicles, trains, the internal combustion engine in a

Locomotive or a railcar is used, or by ships. It is also possible to use the internal combustion engine to drive a defense vehicle, for example a tank. An exemplary embodiment of the internal combustion engine is preferably also stationary, for example, for stationary power supply in emergency operation,

Permanent load operation or peak load operation used, the internal combustion engine in this case preferably drives a generator. Also a stationary application of

Internal combustion engine for driving auxiliary equipment, such as fire pumps on oil rigs, is possible. Furthermore, an application of the internal combustion engine in the field of promoting fossil raw materials and in particular fuels, for example oil and / or gas, possible. It is also possible to use the internal combustion engine in the industrial sector or in the field of construction, for example in a construction or construction machine, for example in a crane or an excavator. The internal combustion engine is preferably designed as a diesel engine, as a gasoline engine, as a gas engine for operation with natural gas, biogas, special gas or another suitable gas. In particular, when the internal combustion engine is designed as a gas engine, it is suitable for use in a cogeneration plant for stationary power generation. Overall, it turns out that the invention provides, in particular, an integration of the evaporation and mixing section upstream of a turbine of an exhaust gas turbocharger, wherein a higher exhaust gas temperature and a higher exhaust gas pressure are used for the preparation of the reactant, wherein the turbine is used in particular as a mixer and the turbine housing as an evaporator can be. Furthermore, a metering valve which can be activated with a variable frequency is used, wherein a suitable operating point-dependent metering of the reagent into the exhaust gas line is provided by adaptation of the metering frequency. Thus, a

Coordination of the dosing process with the gas dynamics, in particular with an exhaust stroke for use for the secondary dropping of the reactant.

Advantageously, this results in an extension of the evaporation and mixing section with the same space. It can be provided a sufficiently high uniform distribution of the reaction medium in the entire map of the internal combustion engine, in particular, an application-independent treatment of the reagent is possible. Due to the higher temperature level at the point of metering, metering release can be wider

Kennfeldbereich take place, which preferably results in an increase in the SCR cycle conversion while avoiding deposits of the reagent in the exhaust path.

A close to the engine application of the dosing system is possible, resulting in a

Application independence results. The space of the exhaust aftertreatment system can be reduced. At the same time pressure losses can be reduced for an improved exhaust gas back pressure, which also has a favorable effect on the fuel consumption of the internal combustion engine. Overall, also reduce the manufacturing and operating costs of

Exhaust after-treatment, because, for example, mixing elements can be saved.

The description of the method on the one hand and the internal combustion engine on the other hand are to be understood as complementary to one another. Characteristics of the internal combustion engine, which have been explained explicitly or implicitly in connection with the method are preferably individually or combined with each other features of a preferred exemplary embodiment of

Internal combustion engine. Method steps which have been explained explicitly or implicitly in connection with the internal combustion engine are preferably individually or combined with one another Steps of a preferred embodiment of the method. This is preferably characterized by at least one method step, which is caused by at least one feature of an inventive or preferred embodiment of the internal combustion engine. The internal combustion engine is preferably characterized by at least one feature, which is due to at least one step of an inventive or preferred embodiment of the method. The invention will be explained in more detail below with reference to the drawing. Showing:

Figure 1 is a schematic representation of an embodiment of an internal combustion engine, and Figure 2 is a schematic representation of an embodiment of the method.

Fig. 1 shows a schematic representation of an embodiment of an internal combustion engine 1. The internal combustion engine has at least one combustion chamber 3, here four combustion chambers, of which for better clarity, only one is designated by the reference numeral 3, on. In addition, the internal combustion engine 1 to an exhaust path 5, in which a

Dosing device 7 is arranged for metering a reagent in the exhaust path 5.

The reactant is preferably a reducing agent, in particular for use as a reducing agent for the selective catalytic reduction of nitrogen oxides, more preferably a urea-water solution. Alternatively or additionally, it is also possible that in the exhaust path 5, a reactant for another

The metering device 7 is here arranged so that the reagent is introduced into a region of the exhaust path 5, in which by a charge exchange of

Internal combustion engine 1 generated pressure surges in the exhaust stream to contribute to a disintegration of droplets of the reagent. In this case, it is particularly evident here that the metering device 7 is arranged upstream of a turbine 9 of an exhaust-gas turbocharger 11. In particular, the metering device 7 at a directly to the at least one combustion chamber 3 of

Internal combustion engine 1 subsequent exhaust gas collection area 13, which may be formed as exhaust manifold arranged. In this case, it is preferably centered on the exhaust gas collecting area 13, so that the reaction agent is preferably metered into the center of the exhaust gas collection area 13.

Downstream of the exhaust gas turbocharger 11, the exhaust gas path 5 preferably has a catalyst 15, on which the reaction medium with the exhaust gas can be converted. The catalyst 15 is particularly preferably designed as an SCR catalyst.

The internal combustion engine 1 has a control device 17, which is set up to control the metering device as a function of an operating point of the internal combustion engine 1 with a variable metering frequency. For this purpose, the control device 17 is preferably on the one hand with an engine block 19 of the internal combustion engine 1, in particular with a speed sensor, not shown, for detecting the rotational speed thereof, and operatively connected to the metering device 7. The control device 17 is in particular set up to the metering device 7

speed-dependent, that is dependent on a speed of the internal combustion engine 1, to control. Furthermore, the control device 17 is preferably designed to control the metering device synchronously with a specific cycle of the internal combustion engine - in particular pulsed, preferably with a certain phase shift - preferably synchronously with a

Firing order of the internal combustion engine 1, in particular with a certain clock at least one combustion chamber 3. Particularly preferably, the control device 17 is adapted to the

Dosing 7 synchronously with an exhaust stroke of at least one combustion chamber of

To drive internal combustion engine. The internal combustion engine 1 is preferably designed as a four-stroke reciprocating engine, wherein a sequence of four cycles of each combustion chamber 3 has an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. The corresponding mode of operation of an internal combustion engine 1 is basically known, so that will not be discussed further. The metering of the reagent in a region close to the combustion chamber and in particular in a region in which pressure surges in the exhaust gas flow, which are generated by a charge change of the internal combustion engine 1, to a secondary decay of droplets of the

Contribute a reaction agent, due to a dosing at elevated exhaust gas temperature, so that a Dosierfreigabe can be done in a wider map area. At the same time they work Pressure surges in favor of a rapid and homogeneous distribution of the reactant in the exhaust gas, so that - in particular compared to a control of the metering device 7 with a constant frequency - one on the map of the internal combustion engine 1 improved

Homogeneity of the distribution of the reagent in the exhaust stream is possible. An arrangement of the metering device 7 upstream of the turbine 9 also leads to their efficient use as a mixing device, so possibly further, additional

Saving mixing elements or at least be designed smaller. This in turn leads to a space-saving design of the exhaust path 5 and to a reduction of the exhaust backpressure for the internal combustion engine 1 and thus also to a reduction in fuel consumption.

The control device 17 is preferably set up for the pulse-width-modulated actuation of the metering device 7, in particular by an amount metered into the exhaust gas path 5

To adjust the reaction agent.

Fig. 2 shows a schematic representation of an exemplary embodiment of the method. FIG. 2a) shows a schematic, diagrammatic representation of a firing order of a

Internal combustion engine 1 with four combustion chambers, which are marked with the letters A, B, C, D reproduced. In the diagram, an exhaust gas mass flow rh _{A is} plotted against the time t in the exhaust gas path 5, wherein the individual mass flow distributions are respectively assigned to the exhaust strokes of the different combustion chambers A, B, C, D.

FIG. 2 b) schematically shows in a diagram a mass flow rh _{R of} the reaction medium in the exhaust gas path 5 as a function of the time t, as it results from activation of the metering device 7. It turns out that here the control of the metering device 7 and thus the mass flow of the reaction medium with the exhaust stroke of the combustion chamber B is synchronized - preferably with a certain phase shift. This results in a speed-dependent dosing To, resulting in a corresponding speed-dependent dosing.

Overall, it turns out that by means of the method according to the invention and the

Internal combustion engine 1, an improved distribution of a reagent in an exhaust gas flow over a wide map range of an internal combustion engine 1 can be realized.

Claims

1. A method for metering a reagent in an exhaust path (5) of a

Internal combustion engine (1), wherein

- The reactant is introduced into a region of the exhaust path (5), contribute in the by a charge change of the internal combustion engine (1) generated pressure surges in the exhaust stream to a disintegration of droplets of the reagent, wherein

- A metering device (7) for metering the reagent is controlled depending on an operating point of the internal combustion engine (1) with a variable metering frequency.

2. The method according to claim 1, characterized in that the metering device (7) is controlled synchronously, in particular with a certain phase shift, to a specific clock of the internal combustion engine (1).

3. The method according to any one of the preceding claims, characterized in that the reactant upstream of a turbine (9) of an exhaust gas turbocharger (11) is metered into the exhaust path (5).

4. The method according to any one of the preceding claims, characterized in that the reaction agent is introduced into a at least one combustion chamber (3) of the internal combustion engine (1) subsequent exhaust gas collection area (13).

5. The method according to any one of the preceding claims, characterized in that the metering device (7) is controlled synchronously with a firing order, in particular with a certain clock at least one combustion chamber (3) of the internal combustion engine (1), in particular with a certain phase shift.

6. The method according to any one of the preceding claims, characterized in that the metering device (7) is controlled synchronously with an exhaust stroke of at least one combustion chamber (3) of the internal combustion engine (1), in particular with a certain phase shift.

7. The method according to any one of the preceding claims, characterized in that the metering device (7) is controlled pulse width modulated to adjust a metered amount of reagent.

8. Internal combustion engine (1) with

- At least one combustion chamber (3) and

- An exhaust gas path (5), in which a metering device for metering a

Reactant in the exhaust path (5) is arranged such that by a

Charge changes of the internal combustion engine (1) generated pressure surges in the exhaust stream to contribute to a disintegration of droplets of the reagent, wherein

- The internal combustion engine (1) comprises a control device (17) which is adapted to control the metering device (7) depending on an operating point of the internal combustion engine (1) with a variable metering frequency.

9. Internal combustion engine (1) according to claim 8, characterized in that the

Dosing device (7) upstream of a turbine (9) of an exhaust gas turbocharger (11) is arranged.

10. Internal combustion engine (1) according to any one of claims 8 and 9, characterized in that the internal combustion engine is designed as a low-speed, as a medium-speed or high-speed.